An OpenGeek reader sent me this!

The many discussions on this topic, here and elsewhere, did not meet the burden for AM-IBOC being a clear leader going forward. Personally, I believe any digital solution should also include CQAM - AM Stereo analog support, for the simple reasons:

-many capable radios exist today
-new capable radios are on the market and still being included in cars
-it represents a viable choice for many broadcasters
-would bring digital radios on parity with FM analog support for all modes
-has great sound in primary coverage area.

DRM is very attractive because it's open and aggressive development is happening worldwide. Given the unique additive "everybody needs to get along" nature of AM broadcasts, and the large number of installed and in use radios, a digital solution that does not marginalize this is key to moving the band forward, IMHO.

Discuss?

(Article link and teaser below)

Rethinking AM’s future

http://rwonline.com/pages/s.0044/t.557.html

" Making AM-HD work well as a long-term investment is seen as an expensive and risky challenge for most stations and their owners. With the bulk of successful AMs airing news, talk and sports, the improved fidelity advantage of HD and stereo seem only marginally attractive. There is the significant downside of potential new interference to some of their own AM analog listeners as well as listeners of adjacent-channel stations. And of course we still have no nighttime authority for AM-HD."

The GE Super Radio is now the RCA Super Radio.
Google for "RCA RP7887" and find it an many online dealers. (Note: Mono hifi, not AM Stereo).

Now back to your regularly scheduled topic.

KSKD,

I agree with much of what you have presented here.

I have personnally set up several C-Quam AM Stereo systems on AM stations, and when the system was designed properly using modern day transmission equipment and a wideband antenna system, it sounded suprisingly good on a wideband receiver. Under these ideal conditions, I would say a lot of normal listeners would have a hard time telling an AM Stereo signal from an FM Stereo signal.

The problem is that few, if any listeners have access to a true wideband receiver that has a frequency response that is anything close to what an AM station is capable of transmitting. So as much as I would like to see every AM station in the country running C-Quam AM stereo, I don't think that it would make much difference with the poor quality of the current radios that the average consumer has access to. How many people want to hear a telephone quality radio in stereo?

Needless to say, broadcasters lost control of the quality of receivers a long time ago. It is also unfortunate that the FCC does not regulate the technical specifications of receivers like they do with transmitters. If they did, the AM band might be in far better shape then it is today. Maybe radios should be made to pass a proof-of-performance just like radio stations used to.

My question is: Would AM broadcasters be better served by taking steps to solve the receiver issues, rather then addressing the transmission issue with a complicated digital system? Any thoughts?

If a manufacture tries to implement AM stereo on a "narrow" receiver, they are nuts. That is absured.
It goes without saying that they should be doing wide IF/audio bandwith. Are not most if not all existing AM stereo receivers "wide"?

What you describe (how many people want to hear a telephone quality in stereo) is unfortunatly the false perception by many of what AM stereo is/was.

Obviously there was an attempt to "control" AM receiver sound quality, the AMAX standard (1990's), but it didn't seem to get very far off the ground. If fact, the receiver manufacturers made most of their radios WORSE than they were previously. Worse on both audio quality and RF sensitivity/performance. Who were less interested: the broadcasters? or the receiver manufacturers?
I only remember hearing the word AMAX once on a station in california. Anyone hear mention of it on the air in Oregon?

Others blame the consumers for not seeming to be interested in better sound quality, but that is incorrect assumption because you might have noticed many now listen to FM because of the sound quality. Usually consumers were not given a choice of AM sound quality when they purchase car and other radios.
CCrane and Bose seemed to do well by promoting their "quality" radios, however those radio does not even have wide audio on AM.

It seems a no-brainer that AM broadcasters would want their listeners to be able to hear good sound quality, so that they might listen more often, so yes, they should take steps to fix the receive end. I will take multiple efforts on various fronts. If they think AM is just fading away, that explains the lack of effort.

I went back and re-read a bunch of stuff I've written on OpenGeek about this. Wanted to revisit some of the discussions here, but Dan has that in restoration right now...

IMHO, it's all about setting expectations.

No digital solution on the table today can match the audio quality of an analog AM broadcast --even a low bandwidth one. For talk, accuracy in the human voice range is really key. I find streams tiring for this reason. I'm sure many listeners would think the same of digital AM broadcasts.

So it comes down to either accuracy or some noise. Secondly it comes down to digital degrading analog receivers of all vintage and quality.

I've researched this huge and I've not seen the tradeoff worth it. There are some times when electrical noise gets in the way of AM listening, but really it's only a small percentage of the time. Listening to a program with poor accuracy in the human voice would affect me all the time. No brainer, from where I stand. Analog remains the better choice.

If I were king:

-mandate a move to 20Khz AM channel spacing period.

This is gonna thin the crowd, but will make for a more robust AM band as room for digital and quality analog broadcasts will exist in many areas for a very high percentage of the time.

-mandate CQAM broadcast support in all digital receivers.

This to protect everyone frankly. Should digital on AM prove marginal (and I think it will no matter whose system we use), broadcasters can continue to leverage analog methods and get more out of the band than they can today. Listeners will get radios that are simply better than their old radios and that's all good. Hide the technical stuff and just do it.

They will hear the difference and it will either matter or not.

This does not have to be difficult. A smart DSP today can sharply reduce noise, decode the stereo signal, and can easily couple bandwidth to signal to noise ratio and the user setting on the treble control. All the user hears is a better signal period.

Receiver manufacturers are assured their designs will remain relevant no matter what the marketplace ends up doing with broadcasts.

Frankly, I see a healthy mix of quality mono, analog stereo and IBOC being more viable, given the 20Khz spacing, as being the best overall solution. In each market, there is probably room for an IBOC or two, a fair number of analog stereo stations, with the remainder choosing to broadcast quality analog mono.

There is no one size fits all on AM. That's just how it is. Nature of the beast.

As for those displaced? Given them secondary HD streams, or FM licenses in smaller markets, or something else that is worth it. Or not... But it needs to happen.

It's either that, or carve out a new band, expand this one again and we all know the problems inherent in that --can't leverage existing radios.

As far as the body of existing radios goes. They do vary and there is nothing that can be done. However, I see this problem the same way I see companies with messy databases and part numbering schemes. Going forward is the only fix.

Trying to merge all that mess into one unified plan is doomed to fail. Better to make a solid plan, with a 5 to 10 year goal and let nothing impede that. The end result is worth it, but it takes time and some dollars to achieve.

Doing anything else is just polishing the turd.

The stuff I outlined here would not significantly diminish the utility of existing radios, thus allowing for new ones to slowly repopulate the market over time, while at the same time giving broadcasters something new to add value with.

Barring some of these things happening (like the 20Khz bit!), I'm totally in favor of addressing receiver issues. Again, DSP technology really opens a lot of doors for AM (and FM frankly) analog processing.

Coupla things:

-variable bandwidth mentioned above, key this to signal to noise and user demand on treble knob

-impulse noise blanking

-stereo support

-harmonic bandwidth enhancement

(If we can get just 8Khz of solid audio, some light harmonic additions would easily open up the perception of wider sound enough for a lot of program material to sound more than acceptable)

-beat tone reduction

-dynamic range expansion.

All of these things are possible in DSP, and can be used together in moderation to bring out some quality audio.

The biggie behind this is the lowest common denominator bit. The majority of radios are crap. If we continue to deliver crap, the majority of new radios will also be crap, thus we end up with a lotta crap.

Build the platform, and the programming will come. Don't built it and it will never come.

IMHO, FM IBOC is gonna make it, if we can get some serious content going on the subs. So let's say that happens. People get more choice on the dial, featuring content not easily obtained elsewhere. (and that's the key to the whole nut right there)

They will buy new receivers for the FM, which will drive sales of more new receivers. The right expectations start to become set.

If a solid AM plan arrives with those receivers, which is not happening today and it needs to, then the platform rides on the coat tails of the FM efforts. For a small additional cost, that will be marginalized by scale, AM radio gets a nice boost.

Co-branding, and promotions on the FM secondary streams will drive people to explore their AM options. Early targets would include niche audiences not well served by the FM scene, and talk consumers.

From there, it either will build or it won't.

Slapping IBOC, or DRM onto the mess that is AM right now, really gets us nothing but a warm fuzzy.

We may or may not reach a point where all FM broadcasts are digital. I don't really care. On AM though, we should not be setting that same expectation for public service reasons. The sheer number of AM radios, and the ease with which they are constructed and used makes a strong case for analog AM broadcasts to continue.

If we reach acceptance on this one point, the stuff I wrote above becomes worthy of some greater discussion.

The propagation advantages of the wavelengths in the U.S. AM broadcast band are it's biggest plus. Until such time as the band is either re-bandwidth/channel adjusted, or simply put to sleep in favor of an emerging technology solution, nothing is going to happen. The receiver manufacturers aren't about to increase the cost of new units to pay for better AM sound, when they are trying to integrate satellite and iPod options and remain competitively priced.

The government dropped the ball back when AM stereo first came around and the FCC just let Motorola and Kahn fight it out. What a joke that was. "Let the market self direct and regulate itself" is obviously a failure. Of course, it is terribly overshadowed by the failure of ownership deregulation, but we've beat that one to death already.

The engineer in me would love to see killer digital AM stereo hi fi clear channel broadcast for hundreds of miles capability, but the consumer in me goes "what the fu*& for?" Who really cares? It is not enough of a demographic anymore. It just isn't. Period.

The former FCC broadcast applicant 10 years in court in me knows better than to think the government will ever do the right thing with respect to RF management.

The former DJ in me would like to see the AM band become a delivery band for IP.

Have a nice day.

62: Most of the Chrysler AM Stereo radios were ~5Khz or so... Very listenable compared to the ~3 or so (or less!) we see on many non-stereo radios today.

My particular tuner hits 6Khz, with serious rolloff after that.

The GE is the same, with less rolloff, but no stereo. On a wideband station, it's a great sound. All the musical elements that really matter to people, exist below 8Khz.

Very few are wideband beyond these numbers. I've only been able to hear samples, not actually own a unit!

However, non-scientific listening tests I've done over the years suggest that 6 to 8 khz of solid audio is more than listenable to a fairly large segment of potential listeners.

I did AM Stereo installations for a number of KBBT listeners, who appeared more than happy to deal with ~5-6Khz of stereo sound.

Ideally we would get 10, with some harmonic enhancement, but I would easily take anything in the 6-8Khz effective range. The filtering alone, not messing up voices, would be worth the trouble!

At that range, a lot of program material is listenable. If it's accurate and processed with a DSP, as I described above, it would be competetive with digital broadcasts, IMHO.

Having more geographic spacing (thus fewer stations) would do pretty much the same thing as 20Khz spacings. But there are still too many on at night. Anyhow, thinning them out using whatever method is big problem.
Does anyone know how many AM HD's have been turned off nationwide? Would be curious how many had technical difficulties (like 620) and how many were just turned off because there just wasn't any benifit in having it on.

I just had to put this here (copied from another site):
"...about twenty-five percent of the population can't tell a studio master recording played on JBL studio monitors from a 56 k download of music.

This especially applies to the younger generation that have never heard correctly reproduced audio on a sound system. Their only sense of audio benchmark comes from three inch computer speakers." ...and/or earbuds!

DRM replacing IBOC? possibly if the FCC would allow it to even be tested between 530 and 1700 KHz but for this there is a thing to bring up, an analog component other wise all most listeners will hear is a hiss but DRM can both fit in 10 KHz of bandwidth without spiling over and a French broadcaster TDF has come up with DRM Shaping to allow analog AM to be transmitted along with digital AM but I do not know of any tests of this being done. But if DRM with DRM shaping is used here in the US both the DRM and analog AM signals could both fit in the 10 KHz limit and provide higher quality than the existing IBOC digital AM system but it will require recievers to either be replaced or have their software demodulators updated.

missing KSKD wrote

"mandate CQAM broadcast support in all digital receivers."

believe it or not C-QUAM is already in basically all IBOC recievers! although some perform better with C-QUAM analog AM stereo than others the Accurian IBOC reciever sold at Radio Shack actually performs very nicely with analog AM stereo I have one of those and have successfuly recieved both KDZR 1640 and CKMX 1060 in full analog AM stereo using it.

Are you saying that the Accurian HD Radio receives analog AM Stereo?

yes I am surprised me at first too

Say what?

How about trying some of that new-fangled punctuation and grammar?

;=)

SAGP

The new Sangean HDT-1 tuner also decodes C-QUAM. These new HD Radios are the best thing to happen to AM stereo in years. You can actually buy an AM stereo receiver at Radio Shack now.

Nice!

Does anyone here have an in-car model to test?

I know the first gen radios didn't do this. There was significant discussion about the DSP issues at that time. The consensus was that it was totally doable. Appears those discussions were valid.

No excuses now. When are we gonna get KISN in stereo! The oldies format is totally perfect for this.

I wonder if this was planned? or is it a case of some devious design engineers "don't tell upper management what we did last week - hehehe"?

yuf: if you got a patch cord yet? or can you desiribe what it sounds like when locking into to AM Stereo? [Someone on the other site said it takes like 10 or 15 seconds befor the AM stereo kicks in]. Is it "wide", good amount of treble? or does it sound like 2 speaker telephone? How does it sound when tuned to a AM mono (KISN? 1550?)? Can you get HD on 1330, 1190 up there with that radio?

I don't have a patch cord when it does kick into stereo it sounds about as good as the car tuners that have this capability takes a while after a DSP kicks in to get the stereo. I can get KEX in HD up here but it is kind of hit or miss also KHHO 850 from Seattle unfortunately the HD carriers from KEX are only 500 watts so it is tricky to get the radio to lock on even with a Radio Shack tunable loop. when tuned into an AM mono station it sounds a little better than what it out there now but there is an EQ which can improve the treble cannot get HD on 1330 too much interference from other stations

I just tried the Boston Acoustics Receptor on 1640 and 1450 and could not detect stereo sound. The receptor does NOT have a stereo indicator (only a HD indicator)... but my ear sez no stereo on C-QUAM stations. Both 1450 and 1640 are fairly weak at my location (North of Hillsboro), so that might be a factor. Anybody know if the BA receptor has a C-QUAM decoder?
The Receptor DOES have RDS on FM, which is an extra feature that is not mentioned in the specs or instructions.

I don't think it does never tried it but if it is software defined then C-QUAM capability could have been added easily with a little bit of code added to the firmware

I'm not hearing any AM Stereo on my Accurian unit.

1450 is mono at night (kpsu). Try again during daytime? Also I think you need to wait 10 or 15 sec for it to go into AM stereo mode.

Actually, AM 1450 KBPS broadcasts in stereo 24/7...even when KPSU is on we are broadcasting in stereo, even tho they have decided they only want to send us a mono feed. So, regardless of what time you listen, if you have an AM stereo receiver, it should sense the stereo signal and the indicator should light up.

Billcooper,
The reports on various web sites are that the Accurian and also the Sangean unit go into AM stereo mode WITHOUT any indication on the display that it did. So if the you are transmitting mono audio, but have the 20 hz pilot on, a listener using one of these new units would have no way of knowing (unless the program has stero content) Also, some are reporting no AM stereo, (radioexpret, and others), so its possible that some individual units have it while others don't.
Yikes!? Perhaps there is another variable?

Well, is there a known time of day when there is stereo programming?

The Boston Recepter doesn't do C-QUAM unfortuantely. That's what we get for being the earliest adopters I guess. It does sound like some engineers just added it to the software decoder in the receivers. Do they still have to pay royalties for that?

This is (alledgedly) a AM Stereo recording made off an Accurian (Radio Shank) in Boston:
http://www.theproductionroom.net/accurianstereo.mp3

KBPS-AM is Stereo from 2:00am till 5:00pm Monday - Friday, and from 2:00am - Noon on weekends, specialty programs excluded.

The bandwidth of that recording is about 4.5Khz, BTW.

That's right in line with the Ibiquity analog AM receiver spec.

Older AM Stereo capable car radios, like the ones found in Chrysler cars, average ~5 - 6Khz or so, with a rolloff happening at the lower part of that range. Just by way of comparison.

Thats a bit disappointing KSKD, (presuming the recording doesn't introduce the filtering), as it did sound like there wasn't much high end, although it is clearly better than many recent AM tuners. They could probably fix it easy in software to open it up to 10KHz.

Yep. Would be no biggie to key overall bandwidth to signal to noise and end up with better than that. It's all in the DSP.

My other point was that it's not a bad signal as it stands though!

The recording was not the issue. It was done at a more than adequate sample rate. 44.1, I believe. IMHO, it's representative of the actual audio from the radio.

Do you think it would be easy for the dsp to look at carrier levels at + and minus 10Khz relative to the carrier you are tuned to, and then adjust bandwidth accordingly?

62: (sorry it's long)

I'm tinkering with a little chip, that has a lot of DSP potential. Let's just say it can broadcast a graphics screen, right on channel 3, without even breaking a sweat. Some time next year, I'm gonna try to make it do software radio reception and transmission. Just mono, as I just want to tinker with software radio some.

(IMHO, it could generate a CQUAM signal right on chip, given a guru to program it.)

I don't know that much about the low level code in these things, especially the dedicated DSP solutions used in an HD radio, or to process your home theatre audio.

Having said that, from what I read, determining the ideal bandwidth for an AM signal is not all that easy. Signal to noise works somewhat, but that really varies. CQUAM signals might be easier, because both modulations would be present, making it easier to differentate from just noise, but I could be completely wrong on that.

I do know some of the premium sound systems, produced for Ford, adjust bandwidth based on signal. I've not gotten my hands on one though to see how it behaves, nor how far they will go. (I would be shocked to see them reach 10Khz)

The DSP will sample a given segment of spectrum, after having it converted to a known baseline by an RF tuner. Technically the things see 30Khz or so, because they need it for IBOC. Would be no biggie to deviate from the 4.5Khz or so, currently defined by the Ibiquity reference specifications for analog AM. It's the adjusting accordingly part that's a real pickle.

Honestly, given our current AM channel spacing is 10Khz, I'm not a big fan of very wide AM's. 10Khz, being very wide. There are simply too many AM's for this to be viable right now.

At night, that kind of bandwidth is just crazy, during the day, it's a mixed bad that depends on a lot of things --so many things as to be very tough to justify, again in my humble lay persons opinion.

If stations ran 5Khz with really great filters to preserve as much of the clarity below as is possible, night time reception for a lot of people would improve significantly. As much as I hate it, this is the right thing to do given the current bandplan.

Running the AMAX spec, during the day is a solid comprimise that would work for a lot of scenarios. That gives us about 8Khz tops right? (been a while since I last read that spec)

I've taken program material and bandwidth limited it by various amounts. 5Khz is a bummer, but 8Khz is actually decent. In the car, it would be very good IMHO. Remember, a lot of people are jazzed about the clarity of the GE. It's an 8Khz radio tops and that's with significant rolloff.

Also, IMHO, as I wrote recently elsewhere, setting expectations that are consistant and realistic for a very high percentage of conditions is key to getting better receivers. Warranty returns just kill those guys, which is why they make a ton of narrow radios. People have shown they prefer consistant sound over better overall sound, in general, over and over. Make the radio 2.5 and it will sound like crap, but it's consistant crap and they will keep the radio. It's a brutal metric, but it's easily justified in terms of dollars, which is really what this whole mess is about.

Conservative is better all around on AM.

This too is one area where Ibiquity could really show some leadership and help everyone out. Going forward, there are two kinds of radios: ordinary analog radios that lie all over the map where AM is concerned, and digital radios that will be consistant as far as AM is concerned.

If Ibiquity would focus on the analog aspects of the AM portion of an HD radio, and make it part of their license specifications, it would then be possible to engage people with some branding and some expectations for AM that would raise the lowest common denominator, thus dragging ordinary radios upward over time.

As I've written before, an HD Radio, would then simply be a better radio, no matter what the broadcaster chooses to do, than other radios are. This can sell on all levels, and that's as fundemental as content issues are going forward.

Broadcasters can target the radios, encouraging content creators to do the same. Over time, the bar is raised in that a stereo program would be a value add throughout the chain from creator to listener.

The beauty of the whole thing is that stereo analog broadcasts are viable today. The tech is known good, has few issues, etc... If digital AM ends up not being viable (and I think this will be the case) for a majority of broadcasters, there is a fallback for everyone involved in the chain, in the form of CQUAM.

Anyway, sorry to expound this morning. You and I and many others enjoy AM radio. If that is to continue, it is my belief that completely realistic, defensible and solid advocacy is the only way forward. Shooting the moon will just marginalize the dial, for what that's all worth.

One thing I noticed is there doesn't seem to be distortion like many cheapo AM radios have.

Another thing, there are some clicks/pops during the first 15 seconds approx. Do you think that is from LP record?

When playing that recording thru the windows media player (with graphic equlizer), if I raise the 3 rightmost contols (treble) it helps somewhat (unlike what happens when you try that with 3khz radio).

How did you determine 4.5 kHz?

Give me 8 give me 9 give me 10, not much difference. I dont see(hear) problems with that for normal daytime use at all. Maybe back east its a different story. Of course, a little switch or knob that the user can push resolves much IMO. Since there is supposed to be 75uS deemphisis in the receiver, making it a bit wider (i.e from 3-5 to 5-7.5, or better to 7.5-10 does not make noise alot worse, while it does help the listening experience alot). Signal strength of the station you are listening to is the simplist automated way of keying bandwidth adjustments, although it would be annoying (in car) if not done well.

The clicks and pops are from some other noise source. At least that's the result of some discussion on the list.

(Implulse noise blanking would have largely eliminated those, but one thing at a time I guess!)

I ran the audio through an editing program on the computer and asked for a spectrum analysis. You should get one of these to tinker with 62. Lots of fun. The latest release of Audacity (google it) has most of the basics necessary for a lot of audio transforms and analysis and it's free and fast too.

The numbers are roughly:

-60db below ~60Hz, with a sharp ramp up to:
-12db ~60Hz through 1.5Khz, flat followed by some rolloff beginning at the 1.5Khz mark
-25db @ 2khz
-35db @ 3khz
-45db @ 4.5Khz
-60db @ a little more than 5Khz, where it essentially blends into the noise floor from there, which lies at -65db

You can also take material, and filter it to various bandwidths, then listen. IMHO, you will be surprised at the real numbers, vs what your ears and head are telling you!

I don't get it... was the information transmitted level (like white noise)? How did you separate the radio response from the original music spectrum?

I just sampled some audio, recorded from WNMB, myrtle beach. They went AM Stereo last year and had great listener response. People driving newer cars, with premium sound systems called in.

Anyway, there is a sample of some AM Stereo audio recorded from a Carver tuner. It's really bright, compared to the audio received here. The file is found in the yahoo am stereo forum group. You'll have to register to listen to it (WMNB.mp3). It's for all practical purposes, an 9Khz signal.

There are some other files of similar quality to be found here: http://ourworld.compuserve.com/homepages/kevtronics/

(this file has been processed somewhat, leaving just the pure audio as a reference of what an AM Stereo station could sound like.)

The curve is simpler:

-50db below 60Hz
-10 @ 100
-20 @ 300
-30 @ 1200 (hz)
-35 @ 6000
-35 @ 7500
-60 @ 9200

The fun begins when you decide to filter this signal. At 9Khz, it's very bright and crisp. Perhaps too crisp for longer periods of listening. Filtering this to 7.5Khz yields a very listenable signal, with no loss of important musical elements. IMHO, a majority of listeners, given this signal and basic audio contour controls, would bump the bass quite a bit, and roll off the treble for a really nice sound.

If you download a program, grab this file and toy with some audio bandwidths between 5 and 8Khz. Try some real basic EQ as well, putting a nice bump @ 100Hz, and a smooth rolloff beginning at 5K or so, with a sharp drop off starting at 7k or so. Will sound sweeter than you think!

7.5Khz is a real sweet spot, with 6Khz being another for voice overall. It's important to note they got their good response from people running radios that probably don't respond past 6Khz or so!

IMHO, the AMAX guys have it exactly right!

That's it for me on this, just thought you might find some of that fun, based on your posts!

Jr Tech, sorry I was not clear.

These numbers are only about what the receiver output is.

The numbers I posted are what the radio chose to reproduce. My point being that our expectations, in terms of bandwidth numbers, are often not in line with what our ears tell us sound good.

There are some things one can guess at from received audio, particularly when you've got a coupla different radios and the original program material to use for comparison. It's possible to get a rough idea about some of the choices a particular site made for transmission, but that's it.

To get a rough idea of what the radio is doing, take an average of different program segments. Listen for a balance of elements, ideally know the tune in general. (It's really great to grab it's spectrum from a known good source like CD.)

It's not anything like the accuracy of a sweep, particularly in that it's impossible to properly place the numbers in their absolute space. -10db could be -5, for example and I wouldn't know.

But the beauty of it, is that I really don't care that much either. It's the shape of the curve that matters for the most part and that can be deduced with enough precision to be useful.

The shape of the curve really impacts the perception of the sound. Where it is, is all about how good the radio is and the recording device used. Your average computer noise floor lies between -60 and -75db, with really great devices at -80 or so. (my older SGI does this, and it's nearly flat too!) This is low enough to make comparisons valid.

It's easy to sample a few radios, then look the resulting audio over to factor out differences.

I've hooked up my Am Stereo transmitter to get some info as well. Just transmit nothing, tones, then program material. The same can be done with an FM Stereo modulator. That gives a really great curve. (still no absolutes though as the computer outputs for tone generation are still arbitrary. Someday I need to get a scope again --miss that bugger.)

Are your numbers representing average of audio signal voltage at the frequencies specified? or peak/hold/max audio signal voltage at the frequencies specified?
Where is your 0dB reference point?

BTW, I think kd7yuf deserves some kind of award for the discovery of this unadvertized feature of the accurian radio!

Missing_kskd:
Thanks for the clarification, it appears that you factor in experience, and comparision to the original material, plus a background of real measurments with a stereo transmitter/radio under test, to obtain a reasonable estimate of the response of the Radio Shack unit.

62: It's completely arbitrary.

The numbers posted are for shape only, to give one an idea of the overall sound contour and to place that into perspective where subjective, "sounds like or good..." statments are concerned.

Really, it's just about roughly what kind of radio that one is. Does it have a spike in it's response anywhere, does it roll off and where, what's the peak practical bandwidth received, etc...?

It's not possible to get a solid 0db reference without a full chain of calibrated gear. (Which I do not have at this time.)

IMHO, this is not necessary for a whole lot of comparisons and for understanding what real world broadcasts mean to your ear, and why some broadcasts sound "better" than others.

The real engineers, who set this stuff up for the rest of us, get to worry about that!

Jr Tech: That's it exactly.

OdB could have possibly represented 100% AM modulation (which can be determined at the receive end). But OK, its just arbitrary. You didnt answer about average or peaks? I presume its some sort of averaging over time.

First, it's a fourer (however you spell that) transform of a segment of the received audio. This breaks the signal down into frequency / time components, thus allowing for an aggragate graphical plot to be made.

So, it's an average of the various frequencies found, and their intensity over some amount of time, added together and averaged, corralated, etc..

I take a few of these from different segments of the audio sample in question, get the plots, then make some comparisons. I'll also listen to the audio too. This is an average of averages, with some judgment of mine mixed in for good measure.

In this case, a 0db reading would simply indicate the audio output from the receiver reached the absolute maximum permitted by the digital recording device. Has nothing to do with the transmitter.

0db, in the digital domain, essentially means all available bits that are storing the signal are set to the one position. That's the max, there can be nothing more as there are no bits to communicate it. For a CD, this number is 65536 ($ffff), being 16 bit audio.

So, your average digital recording is down 5-10db or so, just in case. (If one is worried about clipping at all, that is) Ideally, one never overdrives a digital recording device because things are just lost, not distorted. Gone. Not part of the recording to be played back later.

With analog stuff, it just gets mangled! (To a point, that is)

So, radio gets what the radio gets, no matter what the transmitter is doing. Less modulation just means a higher noise floor really.

FYI, FFT = Fast Fourier Transform

(whacks head!)

Of course!

Does your setup allow a peak hold analysis? That would be more representative of the bandwidth curve I think?

Not sure.

Really, I know what I need to know. The overall bandwidth number is solid. Easy to determine. Rough rolloff numbers are essentially broken down to flat, gentle rolloff @ some number, hard roll off @ some number. If they are even close to sane, that sizes up the radio well enough to make reasonable judgements. Once all of that has been related to overall sonic impact, then some real world conclusions can be made.

More detail than that really does not contribute anything of serious value for me at this time.

Sorry, maybe some day in the future when I have time and a workbench and no kids!

The one nice thing about that accurian is that the AM Stereo decoding sounds like it is very low distortion. But in my opinion, that is it, as the radio obviously doesn't meet the AMAX bandwidth specs. I wholeheartedly agree with Missing_KSKD's point about it being a very significant engineering challenge to design a radio that can select the right bandwidth automatically. Consider the following: You could design an algorithm that looks for adjacent channel carriers at +/-10 kHz from the nominal IF frequency. But, how do you design this algorithm so that it can tell the difference between adjacent carriers and normal high frequency audio content?

I think that the slightly brittle sound of the Carver aircheck is due to distortion rather than the tuner's bandwidth. I am not sure whether this distortion was created in the tuner's AM Stereo decoder IC (which was most likely the classic MC13020P) or whether the audio was transmitted that way.

I like the sound of AMAX compliant radios, but one just has to accept that if this is the only bandwidth available on a radio, then that's not a DXing radio. It is too bad that radios today don't have Local/Distant switches because that would be a convenient place for the AM bandwidth selector. Consumers don't understand what "bandwidth" is, but "Local/Distant," on the other hand, would be pretty intuitive.

I think that in the early 1970s, before 6 kHz became the standard IF banwidth on AM (3 kHz audio), a number of manufacturers were experimenting with wide bandwidths on AM. I have an old Panasonic solid state table radio on which the AM sounds surprisingly good, though still noticeably duller than FM. I've also listened to an old "CBS/Masterwork" stereo system (not in my possesion) with even an even wider AM section. You can tell that this is a wide radio because when you tune across a signal, you don't hear the characteristic splatter sound that you would get on a narrowband radio if it is tuned far enough off the carrier. Instead, when you tune across a signal, it gets stronger as you get it centered in, and the sibliance goes away. This is NOT a DXing radio because of its wide bandwidth and poor sensitivity. For local stations, though, it sounds really great. There probably is some roll off, but the stations' NRSC pre-emphasis makes up for this. On this radio, the differences in audio between different stations really stand out.

Somewhere back there, it is mentioned that the frequency response on the GE barely extends to 8Khz by factoring in noise. I am way out of my league here but if I remember my Julian Hirsh, frequency response is dependent on signal to noise ratio so if the latter isn't around 70 or above, the former is, for all practical purposes, not as wide as the numbers would appear. Since I find the GE-1s wide-band position impossible to listen to, I submit that the effective range must be far lower than 8Khz.

Yep, it's less. Kent knows with more precision.

He posted here a while back, but I can't find it.

The GE III is better in this regard. Given a good AM, it's better than 6.5 for sure.

Funny too, this range can make a lot of subjective difference. 500Hz matters more than it does at, say 12Khz where nobody notices that amount.

Alfredo, that audio was distorted at the higher end. One of these days, I'll have to just ask about that because it was processed too. Really would have been great to just get the audio raw from the carver... Better samples are to be found on the kevtronics link.

"frequency response is dependent on signal to noise ratio" is not a good statement. Unless you are trying to listen to a weak signal near the noise level. In which case the treble sounds might be weaker than the noise level in your location, while lower audio frequencies are above the noise. Thats part of the reason its better to listen to DX with narrow filtering. Notice the numbers that kskd put above, the treble content on the average is less power than is lower audio frequencies. Somebody else can probably explain that better.
If i recall correctly the GE super #1 does not have the 75us deemphisis (nrsc), so it likely has too much treble for some ears. A very strong signal isnt going to any better frequency response than a medium strength signal, unless your radio has circuit that widens the bandwith based on received signal strength!

...and I'm still wondering how Ford did that. My guess would be coarse signal to noise, but still everything adds together in the end.

Would be interesting to see what one of those radios does in a case where two wideband AM's overlap.

IMHO, the best overall solution to this, given digital radios, would be a dual function treble control. On FM, or digital broadcasts, it just rolls off the audio in the usual way. On an analog AM broadcast, it would act a bit differently:

It changes the audio, leaving bandwidth alone, for a significant fraction of it's range, then opens up bandwidth as a function of the remaining range, perhaps in combination with some additional audio contouring as well.

Done well, this may well end up being intuitive enough for people to use with no worries. Gets rid of a switch and the costs with that. Since modern radios are software defined in this regard, it only takes a bit of code to accomplish as well.

The relative setting would be remembered between bands too, thus permitting the user to fiddle with it only when necessary.

On most all of my radios, save the GE, the treble control --or tone control, really only does something for a portion of it's range anyway. I'm sure it's actually working, but the AM signal does not lie within the area of emphasis.

So, we change that, in a way that users will just understand after turning the knob some and all is golden.

Given the growing complexity of radios in general, and the generations of people willing to deal with that, this seems to be a good middle ground. Older users will turn the knob and just get more sound choices. (Or mash the button --I hate those +-5 coarse settings... )

Newer users won't think twice either because they will have plenty of other functions to occupy their mental bandwidth. Both sets of people will just fiddle until they like it and move on.

Ever notice how you can actually read some radios today? Sheesh.

It isn't the treble that bothers me but rather the overwhelming background noise combined with unpleasant distortion. It's perfectly fine in the narrow position and just great on FM! Someone said the GE-1 only has one speaker. This one has an extra 2 inch speaker at the top left hand corner so it may be a Supertuner II.

GE SR-I on eBay (one speaker):
http://cgi.ebay.com/GE-General-Electric-Original-Superadio-Radio-7-2880B_W0QQite mZ200064237926QQihZ010QQcategoryZ932QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

GE SR-II on eBay (two speakers):
http://cgi.ebay.com/GENERAL-ELECTRIC-GE-SUPERADIO-II-VERY-NICE-CONDITION_W0QQite mZ110074725250QQihZ001QQcategoryZ16702QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I think you have a SR-II.

Mine doesn't look like either one of those! It's almost entirely black and more streamlined. It looks more like the SR-II though. Thanks.

Could it be a III?

Those have two speakers as well, but mine don't have the noise problem, unless you max the treble.

Set somewhere in the middle range, it's a sweet and fairly low noise sound. --that could be just where I am though. (PDX Airport)

Semoochie's unit might be defective? Or too close to the rf triangle for it to handle?

"how do you design this algorithm so that it can tell the difference between adjacent carriers and normal high frequency audio content? "

A sharp 10khz tone detector circuit/algorethm. Presuming the transmitted audio content on the desired station has nothing above 9.x Khz.

GE SR-III on eBay:

http://cgi.ebay.com/GE-Superadio-III-7-2887A-SuperRadio-3-AM-FM-MW-DX-NR_W0QQite mZ290067374746QQihZ019QQcategoryZ146514QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I have in my collection, a precursor to the Superadio series, the P-780, one of these is on eBay:

http://cgi.ebay.com/General-Electric-P-780-8-Transistor-AM-Radio-GE-P780-NR_W0QQ itemZ230069951655QQihZ013QQcategoryZ50595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Not all GE super radios were "Superadios".

> A sharp 10khz tone detector circuit/algorethm.

Yes, this would be a necessary part of it. However, the NRSC "mask" doesn't start until 10.2 kHz, so high-hats, crickets, etc. could fool such a detector. I think that a smart detector would have to look at the average level of +/- 10 kHz energy and the received signal strength.


Automatic bandwidth control in a analog radio can be done several different ways. In the late 1980s/1990s, Motorola had a chip that simultaneously adjusted the IF and audio bandwidth based on received signal strength. The mixer output of this IC had a shunting device (probably a JFET) that was driven by the IF AGC voltage. This simultaneously reduced the mixer gain and swamped out the selectivity of the first IF transformer on strong signals. There was also a voltage controlled audio filter that was a combination low-pass and 10 kHz notch reject circuit. On weak signals, the notch would get deeper, and the low pass cutoff frequency would decrease. I have the datasheet to the first generation of these advanced receiver chips (1988 datasheet book).

Regarding Semoochie's problems with the Super Radio, what kinds of "background noise" are you hearing? Is it hiss, or is it RFI type noise? I would suspect that there is something wrong with the radio itself, because many of the wide radios that I've listened to can achieve a pretty good noise floor; the SRF 42 is a bit on the crummy side in this regard. It has a lot of internally generated hiss. The distortion could be the radio or the station's processing.

It's hiss. I had a good word for the distortion and now can't think of it. The reason I thought it was the original Superadio is because I bought it before hearing about #II, which would pretty much rule out any chance of it being an SR-III.

This hiss has always been there, with that radio?

Yes, it has. "Raspy" is the word I was trying to think of.

Ok. I assume that's on all stations right?

If so, that's an artifact of either your radio or position. Gotta be. Mine behaves a lot differently.

I've listened with the GE III quite a few places and on different stations. Some really work well with the treble opened up, others don't work so well. By and large, it's just a better quality audio output. On narrow (5Khz) stations, cranking the treble ends up with a poor sound, when done in wide mode. On wider stations, it's usually good to push harder, but rarely all the way.

Too crisp usually, though some of the stuff heard on KKAD and KBPS seems to work nicely enough.

Most stations, but for KEX, are better in wide mode than narrow. (That one just emits a steady background hiss when IBOC is running.)

On my radio (actually the father in laws too), I'll get raspy on really strong stations sometimes, or when something like the TV or micro is too close to the radio. Narrow almost never does this. I can orient the radio and have it all work out nicely.

Near the "end of the line" for AM in UK?

http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/12/30/nradio30.xml

Re the above link. Does that UK comm official have a wonderful idea or what? AM spectrum used for community radio!!......Just watch the true fun of DX come alive again. This might be just undeducated speculation from from way outside of the biz,but what about AM broadcasting being endangered by other factors,such as the land value underneath the stations' sticks....

Since I don't know much about the UK market, it's hard to say. Is it really the end of AM or just the end for its current tenants? This is a tad ironic because, as I understood it, pop formats on AM in England far outlasted their counterparts in the US.

I could be way off on this but was thinking there were about 40 million people in Britain. If 6 million are listening to the BBC and 4 million to commercial radio, that's 25% of the market listening to AM! It sounds like the problem with AM in England is only on the commercial side. It must be a programming issue. Greenway, the value of AM transmitter sites has been a strong factor for many years.

Question: How come I see no mention of the accurian cquam AM Stereo feature on professional broadcaster industry radio sites like RWonline? Is it that they using the ignore stratagy, because the big HD players won't like it? Perhaps they don't believe it? or do they not know about it, yet? [Maybe I have not looked in the right places?]

I think the really simple answer is that nobody, outside of a small circle of people, really cares.

We've only a small number of AMS stations nation wide. The success story of WNMB is a good one, but also atypical of many AMs and their markets.

And of course there are a lot of people behind IBOC. The prevaling view is that AMS failed and the biggie is that digital is the way forward. If the latter nut gets cracked, then things might go differently, but it's gonna take a full cycle to see how that all shakes out.

IMHO, FM IBOC, given some solid content efforts, will make it. The biggie then is will it drag AM IBOC with it, or not?

I suspect many are just gonna watch and see, waiting to spend their dollars when they know more for sure.

And finally, I'll bet a whole bunch of them don't know because the issue is below their sightline.

Report here that RS may have dropped the AM stereo decoding on Accurians (at least one made in Sept. does not appear to have the feature):

http://meduci.com/

...sombody bitched to Ibiquity. Somebody else decided to re-read the license agreement for HD Radio receivers.

Shameless speculation on my part, but I see no other reason for them to drop this feature.

Did he say if other RS radios know to do AM stereo have earlier manufactruing dates? MAybe they added the feature after September?
kd7yuf, how is yours marked?

Another data point... A RS Accurian with a code (09A06) marked on the bottom (this could be a date code for Sept 06 ?) appears to do AM stereo.

A Sangean HDT-1 tuner with SW Vers 1.2F 061020 (perhaps Oct 20 2006 ?) appears to do AM stereo.

I have only heard KBPS-AM (1450) in stereo... is radio Disney (KDZR-1640) still broadcasting in stereo?

KDZR will continue to broadcast in stereo until they go HD later this month. They may continue stereo during nighttime hours when the HD is off, but we won't know for sure until they switch...

They were in stereo as of this morning. They were playing a rap song about basketball when I tuned in. KBPS-AM was playing "The Biggest Ball of Twine in Minnesota" by Weird Al Yankovic. "I bet if we unraveled that sucker it would roll all the way down to Fargo, North Dakota."

Now, I generally am deeply opposed to Ibiquity's IBAC (I think the moniker "HD radio" is grossly misleading, even though it refers to the transmission methos--"Hybrid Digital"--some commercials are now falsely advertising it as "High Definition Radio.")

However, I would likely buy an Accurian anyways just for the AM stereo! Even when IBAC on AM fails (and I bet it will, just wait) at least I would still have a pretty decent wideband AM tuner to play around with. And in stereo to boot! (Would certainly make CKMX sound a lot better.)

If they dropped AM stereo from the Accurians tho, then I wouldn't have any reason to buy one......and therefore my CD player would win out over IBAC (again) for my intents and purposes.

Alfredo, I remember you posted some time ago how to convert a regular mono AM rig to stereo, along with a weblink--could you please post that again? I want to try this with my old Panasonic RX-5030 (the old "gettoblasta" boombox!) or maybe even my Marantz Quad............



JR Tech: Yes, the 09A09 means the radio was made in September 2006, during Shift A. Before the 21st Century they used to drop the first digit from the year. So assuming I had a radio from the 90s, coded 8A3, that would be August 1993, Shift A.

Not sure about Sangean coding, but it sounds like your guess likely would be correct.

Motozak: reread the thread. The reports are that the RS accurian only does "narrow" cquam AM Stereo <5khz. Hopefully they (or somebody) will fix it to do wide audio.

That's the first time I've ever heard anyone say that "HD" stands for "Hybrid Digital". I was under the impression that they chose the name because people would associate it with HDTV and think in terms of higher quality audio.

It's a more descriptive term than "High Definition" is. I like it!

It won't work when they eventually drop the analog signal.

It also won't work when they drop the digital.

I'll rephrase: Calling it "Hybrid Digital" won't work when it's no longer a hybrid.

Bet that takes a long while though. Might as well make use of the phrase while it makes sense right?

sorry to be a little late mine is marked 09A06

when IBOC was first called HD it was clearly stated that HD stood for nothing. it was not High Definition or Hybrid Digital. It is simply just HD.

the idea i suppose is that people will infer it to actually stand for something.

It doesn't officially stand for anything.

Yep. I saw that too. Remember thinking at the time, what passive aggressive crap!

Of course people are gonna associate that with all things HD in the television world! IMHO, this is part of the problem now. Those expectations set, and they were set for a lot of folks, are not exactly being met.

In fact, the early expectations were largely off the mark, and had to be scaled back.

Since IBAC radio (particularly Ibiquity's system, haven't heard FMExtra yet) isn't HD in terms of wording or overall quality, couldn't that be considered false advertising? (Especially with those commercials that call it "High Definition HD Radio"?) And ain't false advertising illegal??

Can't remember specifically where I read about the hybrid digital bit though.......might have been on Wikipedia or Radio Info, something like that anyways.

Maybe it might have been here??

In my opinion, tho, I think marketing this system as being something "high definition" is just pure BS.

It's the perception of high definition!

(Yes, I'm serious!)

All the elements of a high definition signal are there, but for the actual definition! It's got a great S/N ratio, when in coverage area a consistant signal, extra bandwidth, etc...

Perhaps I asked this before, but is there an objective definition created by some trade organization of what "high definition" actually means?
I think its just a marketing phrase thats vague and means whatever you want it to mean.
Another is "digital quality".
It would be nice if there were actually some parameters to measure. Lacking that, how could you prove false advertizing?

Someone could create some standardized audio test recording containing several types of complex waveforms, (kind of like the concept of old TV test patterns ) and create an objective way of comparing output with input.

High definition is an example of a relative concept that some people (probably because marketers want them to) consider to be absolute. In other words, in 1941, NTSC would have been considered high definition television because it was a relatively new system that offered higher resolution than what was available before (405 line British TV and a 343 line experimental system that RCA liked). In the early 1950s, the French 819 line system would have been considered high definition television (and until very recently, it still would have been considered as such).

Likewise, FM and APEX would have been considered high definition radio in 1939, magnetic tape would have been considered a high definition recording medium in the late 1940s, and a vinyl LP would have been considered a high definition record in the 1950s.

"Digital quality" is complete marketing caca. Originally, when digital audio referred specifically to CDs, the idea was that the noise and wow&flutter associated with phonograph records and magnetic tapes were eliminated. However, the marketing guys tried to expand the concept beyond this and to apply it to any audiovisual storage medium that is digitized.

So a general metric would be that it is simply better than that which is expected of established means today.

Well, IBOC does do that!

It's better on a whole range of metrics, it just isn't that accurate.

Damn slippery stuff. Just the kind of thing the marketing and sales folks love.

(Note: I was going to post this as a response on the "Theories and Such" thread, but the direction I went with it, made it seem more at home in this thread than the other!)

Now the dedicated Wifi channel sounds interesting......

Similar lines, someone else on Radio Info (Aplolgies to you too, "Tom Wells") also proposed a theoretical digital radio system that would use audio channels on HDTV channels. You would get high fidelity full stereo audio on a portable radio (essentially a stripped-down HDTV set without the video decoder hardware, much like the analogue TV-audio radios that have been on the market for decades are) as well as on your HDTV set or OTA converter box, a standardised broadcast system and--oh yes--it leaves the analogue FM band unscathed. (Something Ibiquity probably couldn't even dream of doing! ;o)

I think this would be even more practical than the Ibiquity system....and at least the "HD" would actually mean something, be more than a marketing gimmick!

On another hand, I think IBAC on FM might work (AM is just nuts), but as I am seeing it the industry is trying to use it to fix a problem that doesn't even exist! Content is king, you know.....introducing a digital broadcast system does nothing to improve the quality of the production, it only adds hash noise into the band.

While it's true that sound quality is part of it, it's not the core problem radio's facing today! In the long run tho, all I can see Ibiquity's system doing is fading into near-obscurity, most likely being used for specialised narrowcasting like SCA tends to be used today. (Perhaps we might see Physician's Radio Net be reborn, or possibly even a renewed interest of Muzak?)

Although if everything fails and alternate programming choices is still a key issue, there's always the option of repopulating analogue SCA as a sort-of "fall back plan"............

ATSC wasn't designed for portable receivers. It's hard enough to get it to work with fixed antennas. A few stations around the country do include the audio of FM stations they own as subchannels, but it's not widespread.

HD Radio on the other hand works very well. For example I've never been able to get any decent FM reception of many stations where I work. I couldn't get KMHD in stereo. KNRK is full of hash. The B.A. Recepter pulls all the HD stations in perfectly and the 96K audio on KMHD is fantastic, better than the analog reception I get at home.

For the first time ever I'm listening to some good stations during the day, so it's solved one problem at least. I don't see this system fading into obscurity any time soon.

Neither was NTSC at first.......possibly as technology and designs improve we might very well see ATSC audio become built in to many digital radio sets. (Think Boston might implement this, or maybe Ibiquity, possibly giving a little actual cred to its "HD Radio" moniker?)

As NTSC improved over time, receivers became more sensitive, other issues were addressed etc. we started seeing analogue TV audio tuners included in regular radios. (I even have a Sony ICF36 that gets SAP channels, and SCA on the FM section to boot!)

But if anything I don't see this happening [with HDTV audio] for a good, long while yet. These things do take time to develop. (Somewhat related, but look how long Satellite TV, in some format or other, has been available to the masses vs. its fairly recent introduction to the mainstream consumers!) But the possibility is there............

The NRSC has released their Phase I AM bandwidth recommendations report.

http://www.nrscstandards.org/AMB/AMSTG%20full%20report.pdf

I think many of you here will find it interesting reading. They include their methodology, results of listener response tests at various combination of bandwidth, noise and program material, and the response curves of some sample radios.

Their rough conclusions regarding bandwidth compare favorably to some of the material I posted here, based on my own listening experience and sample radios.

IMHO, this report does reinforce the idea of there being sweet spot bandwidths and that they vary somewhat for speech, music and sportscasts. ---Interesting stuff.

I would love to see another one of these done with stereo broadcasts...

How much % of listening in real world is with +15 or +6 adjacent channel interference? Were the conclusions weighted to reflect that?
Does Kpdq vs KGO fall into either of those categories?

It seems to me "duh", if there is alot of adjacent interference, then people will pick lower bandwidths. But the study shows the reverse is true also. Seems to me this report is argument for a wide/narrow switch!

I will have to read it again to digest it better.

I found a coupla things very interesting:

The higher bandwidth preference for speech vs music in general! And the 7-8Khz sweet spot.

10Khz is nice, but it seems that 7-8Khz is nice enough. They do invite public commentary. I didn't go and find the link, but I will soon, after I've thought about this a bit.

Frankly, having stereo broadcasts makes a lot of difference, even at the 5Khz range. IMHO, it's a more viable option than people think and this report more or less proves this out.

Why do you think that wide was more prefered for sports broadcasts??
Is it because people like to hear the crowd noises, and sounds effects and atmosphere of the game (Sneakers, bat hitting baseball, whistles, etc?) and those things come thru better with wide, makes it feel more like your at the game? or perhaps wide adds more clarity to the play-by-play annoucer, and clarity is extra important to be able to follow the game in your brain?

Most likely. As a listener I know this would definately be the case for me.

And I am still waiting for "The Fan" to broadcast the AMA Nationals, or maybe the Mountain Dew BMX/Skateboard thing they have at the Rose Garden in August.....hopefully even in stereo!

Even the MX races (AMA Nationals), I think, would definately justify running stereo AM.........

With portable NTSC operation, you simply lost color or you got momentary ghosts or other interference. This is much more tolerable than hearing a radio station's audio go completely dead which is what would happen with portable ATSC operation. Ibiquity has had to throw in a lot of redundancy and error correction into HD Radio to make reception tolerable and it was already fairly immune to multipath before.

For any of you who looked at the receiver performance data in the study that missing_kskd posted, there is a lot of irony there!!

1) All of the home stereos have a lot (>10%) THD at 50 Hz! All of them roll off the low end, too?

2) The radio whose frequency response comes closest to AMAX standards is the Curtis clock radio!!!! It has pretty low distortion, to boot.

So, if you want nice, room-filling sound from AM stations, then you should buy a Curtis clock radio, disconnect the speaker, and run its audio into your hi-fi amp. Better yet, instead of cutting the speaker wires, add an RCA jack to the radio's case, and connect it to the point right before the volume control pot. Then you can use it either as a clock radio or as an AM-wide tuner!

One radio Panasonic on pg 52 had 43% distortion at 50 Hz. Two of the clock radios had 21 db s/n.
Someone needs to tell these manufactures that their products are deplorable.

...they know and don't care.

If they are gonna invest in the radio, there should be a return. That's not gonna be a solid AM section because the expectation for talk and niche programming has long been set.

This is exactly why most receivers start their rolloff at about 2.5Khz. If talk is the primary program material and they are worried about warranty returns, they are best served by reproducing the talk only, and nothing else.

That way, the listener gets a consistant signal, and that's that. Ringing, cross talk, etc... all could lead to a receiver being returned as bad and that's just not worth the investment overall.

They can keep their cheap junky narrowband AM rigs they produce nowdays............

I wouldn't part with my Grampa's '48 Crosley for the world!!

Not exactly a good DXing radio nowdays because of its w-i-i-i-i-i-ide bandwidth, but I bet it was "back in the day" when the band wasn't as heavily populated as it is now, and stations didn't use as much power as today. But KISN [and now Music of Life, I have noticed] did/do sound lovely on it............

Alfredo reminded me of some early experimentation I did. I took a pocket transistor radio (9v battery type) that had cracked case, and connected an rca cord across the volume control, and plugged it into an amplifer & bigger speakers. That gave big sound. I dont think I had any fm then. I probably tried connecting it thru the earphone jack first, but that didn't sound as good (less bass, less treble, more distortion) as connecting from across the volume control (clean audio).

Another time, a friend told me he connented a transistor radio into his dads Klipsch horn speaker. He was boasting about the (top 40 AM) results, loud, lots of bass, etc. I don't recall if he said if his dad found out or not.

By saying "connected across the volume control" and "connected to the point right before the volume" do you mean it was connected along WITH the volume control still in place (and still usable, so if it is plugged in to an Aux amp you would only need to turn the speaker down), or do you have to remove the volume control completely, rendering the speaker pretty much inoperable?

If I don't have to remove the volume control (and otherwise wreck my good radio!) I might just think 'bout doing this to my GH radio in the Truck....because I am currently running it through the Earphone plug with the volume turned way up.

Volume controls usually have 3 terminals.
One is the input signal.
Middle is the wiper (output audio).
Third is ground.
You kind of have to look at the wiring to determine which (1 or 3) is ground. Ground usually has a bunch of other parts connected, but the input signal would usually have just a couple of other components connected to it.

Connect your external amplifer to 1 and 3. Leave the volume control in place. No need to remove it. The volume control thus does not control the external output, but you can leave it in place set at minimum volume and it will still work for the internal speaker.

If you have a AC powered tube "ac-dc" radio, bevare! Don't do it unless you are willing to sacrifice equipment, burn your house down and perhaps be electrocuted.

Thanks 62..........

I will try that with the Sony.....it's 6VDC (4 AA batteries, I need to add a plug-in to the circuit so I can use it on my cigarette lighter, via a 12/6V DC adaptor) so I doubt there's really a lot of chance of getting electrocuted there..............

My Grampa's Crosley is a tube rig, but already has some sort of auxillary out on the back (old corroded brass screw terminals! O joi, O joi!) so that apparently was taken care of some years ago! (Gramps says it was that way when he purchased it used in the early 1960s when he was serving in the Army.)

I don't think it is wired through the volume.....haven't really studied it too closely to be able to tell. Looks professionally done though, maybe the brittle paper "Hergeson Radio Corp., Duluth, MINN. Phone 5-1187" label inside could be a clue.

Haven't ever tried it myself but Gramps says he used to play it through his 1970s Pioneer stereo occasionally, so it must work......

Motozak said, "I wouldn't part with my Grampa's '48 Crosley for the world!!"

We had a big console model Crosley when I was a kid. It was from earlier than that..... around 1942 era, I believe. I agree, though. That was one great radio. It also had a record cutter turntable. My dad and grandfather cut some "homemade" 78's before I was born on that thing.

62kgw said:"Volume controls usually have 3 terminals.
One is the input signal.
Middle is the wiper (output audio).
Third is ground.
You kind of have to look at the wiring to determine which (1 or 3) is ground."

Older sets usually had a tap terminal, also. The input to the volume control and the common(ground) were the two outer of the three grouped terminals. The output of the control to the amp circuit of the amp is usually the middle terminal. You can think of the center terminal as the wiper. Look at the control and think as you turn it that you are turning it from one terminal to the other..... directly. So, turning it counterclockwise (low volume) would move the slider to the ground terminal.... looking at the board from the top, it would be the one on the left. However, usually, those bigger radios did not usually have the volume control mounted to a circuit board. They were mounted on the faceplate with wires going to the board (if there is a board).... sometimes wirewrapped. just look at the control as you turn it and imagine which post the wiper is moving to. That will tell you which one would be ground. The opposite end is the one with the max audio. That is what you would run to your external amplifier in.

62 also said, "If you have a AC powered tube "ac-dc" radio, bevare! Don't do it unless you are willing to sacrifice equipment, burn your house down and perhaps be electrocuted."
This is not entirely true. I suppose it could be half true if you/ve never worked around tubed equipment with high voltages.
However, we are talking about audio portions, not high voltage sections. The volume control would not be across high voltages. The wiper would be going to the grid of the tube which should be very low voltage. If the input came from a tube output(plate), it would have a capacitor between the volume control and the plate voltage. You can test it before you do anything with a voltmeter.

I was doing these types of mods on tube equipment before transistors appeared and have never had any problems. You just need to be careful. The first audio amplifiers/consoles I built were tube models. They were easy to work with. You just needed to build a power supply. Still have some of those pieces out in the garage in my "junk" boxes.

I am talking about the 5 (usually) tubes sets that do not have a power transformer. Those are the ones to watch out for. One side of the AC cord could be wired directly to the chassis "ground", or thru a capacitor. So your radio's "ground" might actually be 120VAC hot [which case you probably might not want to connect it to your external amplifier].
If the set has a power transformer inside, then as Jimbo describes, just watch out for the DC high voltage which would not be connected to the volume control.
It sounds bizarre that someone would mount screw terminals for an amplifier output. I would think that they would have used rca jack, but if it was done in the 40's or 50's, then they might have just used whatever they had handy. I would think it more likely the screw terminals would be more likely for connecting external speaker, or external antenna. Do you have schematic of the set? many are available on the web for free download. 1st step is to look on the back of the radio for a model# or chassis number.

You will want to use a shielded cord for the external amp output modification.

62-- Judging by the corrosion, I would guess it might have been done in the 40s or 50s, possibly when the original owner bought it. (It's a '48.)

(Grampa bought the thing used sometime around the mid-late '60s while he was still serving in Viet Nam.)

The terminals are in fact for a supposedly auxillary port, evidenced by the "AUX HOOKP." scratched into the wooden backboard of the radio cabinet directly above the terminals, as well as the large silver toggle switch next to it above which is scratched "AUX DISCON."

You flip the switch, it kills the speaker and feeds the terminals on the back. The volume control doesn't seem to work through the aux hookup, by the way--what you hear is what comes out of it. I believe it may be hooked up as stated previously--just before the volume stage.

I would have to try and find a schematic somewhere. Model number isn't indicated on the brass nameplate in the front, and the silk-screened label on the back is mostly worn away, there's something looking like a model number there but it's hard to make out....so I hope there's some indication somewhere inside the thing. (I would have to pull my nut driver and pliers out........)

I will try to report what I find.

Oh and Jimbo (and 62, for that matter)~
It's a table-top model. (One of the "old-skool" semi-triangular shaped rigs, and streamlined somewhat as was the fashion trend in the day. Although I would think of streamlining as more of a '30s think but apparently they were doing it sometimes post-WW2 era as well.

I wish I had room for a console rig tho......would certainly make a statement when my "Apple I-Pod cell phone Play Station Portable wielding" friends come over.......................

You might try looking here or google for other old crosley radio web sites.
http://www.crosleyradios.com/
www.nostalgiaair.org has "rider" schematics.
Try to match up pictures.
You might want to count and make list of all of the tubes. Some of these sites list which modle # have what tubes. Might be easier to narrow down.
There might be a paper label inside the back showing diagram of the tube locations, and possibly a model #.

Sidenote, regarding where I came across "Hybrid Digital" as the true meaning of Ibiquity's brand name for its IBAC system:

http://en.wikipedia.org/wiki/Ibiquity

Quote:
"The technology is marketed under the term HD Radio. Note the "HD" in HD-Radio stands for "Hybrid Digital" not "High Definition" in more popular usage."

Funny how it took me almost two months to remember this........

Also I remember a couple years ago the C ran an article in its "Life" section about IBAC; came as a surprise to me that even an engineer from Ibiquity openly admitted in the article it ain't really High Definition outside of marketing!!

(It was either an AP or Knight-Ridder syndicated article, something or other......hopefully if I come across it somewhere I will try to post it here.)

And also from wikipedia:

"Although the acronym HD has come to mean "high-definition" in reference to HDTV, the "HD" in HD Radio is a trademark with no meaning "

http://en.wikipedia.org/wiki/Hd_radio

So which is true ?

Oh, and 62--

I was poking around at the crosleyradios web site, in the "Gallery" page and came across the '46 model 46FA.

http://www.crosleyradios.com/46FA.html

Notable differences, however:
-Ours has a wood cabinet (this one appears to be bakelite)
-Is AC/DC powered (this one appears to be a battery-only model by its description) and
-instead of saying "American/Overseas" in the dial (the slash indicating that the two words are on the top and bottom of the dial, respectively) it says "C.R.O.S.L.E.Y" on the top. (The "dots" here representing little "diamond" shapes between the letters.)
-Also the wood case is "sloped" a bit more toward the top, lending it its "somewhat triangular" shape I mentioned above.

So the one linked here is similar, but not the same. It is also an earlier (1946) model. (Grampa and I believe ours to be a 48.)

Ours is a four-tube like the one pictured with a bigass transformer inside (lends it quite a bit of weight!) Not certain if the 46FA is a transformer rig or not.

So, the search continues to pinpoint specifically which rig we have!!

While at the Gallery I also stumbled across the '47 AM/FM/Shortwave/turntable model 1117 console.

Imagine blasting Charlie's or even 95.5 over one of those rigs! Certainly would make a statement to my friends, indeed.........

Jr_tech:

Beats the heck out of me, really. If anything I would be inclined to lean toward the "trademark with no meaning" line.

Although that status even is debatable--
trademarks always *do* theoretically have a meaning regardless if they are just ambiguous abbreviations or not. It's a way of identifying the product amongst others, isn't it?

For example, if I was to market a dirt bike under the hypothetical brand name "QZXYXZQ" that would certainly enable a rider to tell it apart from a Honda or Yamaha!! ;o)

Motozak, The info at the bottom of the page (46FA) shows it as a battery powered radio. So there would not be a "big" power transformer in that radio. There probably would be a smaller audio output transformer connected to the speaker, perhaps even mounted on the back of the speaker's metal frame, on all radios of this vintage.
If you got a big power transformer, then yours probably would not be "ac/dc". Ac/dc radios do not have big power transformer. In the lingo, "ac/dc" the "dc" does not refer to battery powar, but to rare cases where the wall socket voltage was actually approx 110V DC, rather than AC. I suppose an unusual model might have ability of both AC and Battery DC, there would need to be a switch to select which. Could you make list of the tubes in your radio? The tubes have type numbers printed on the glass usually. Usually in the format: "number(s) letter(s) number(s)" like 6AB6, 35L6, 12SK7, etc. Sometimes there are more letters at the end, like 6J5GT. This will help us understand the radio better, help narrow down which model it is. That crosley web site must not list every model.

Looking at the 46FA schematic on the nostolgaair website, its a 4 tube (all tube begin with a 1). There is no power transforment, but there is an audio transforment mounted on the speaker. 4 pin socket for batteries.

Does yours have the shortwave (i.e. overseas) dial numbering like the lower part of the 46FA dial (5.8 to 15)? 3 knobs?

I was only saying it *looks* kind of like the 46FA. It's not, tho. The 46FA was produced two years before ours was and is of a somewhat smaller design.

I don't have the radio with me here right now, so I can't make a list of tubes at the moment. (I'll be going to the Grandfolks' place this weekend, they are down in the Clackamas area and I haven't been over to their place in a month anyways. I will post them here sometime next week.)

It doesn't have a transformer mounted on the speaker. To my knowledge Grampa's rig does not have provisions for a battery, i.e. it only has a cord to plug into the wall (120VAC.)

Regardless, the rig weighs about 10 pounds overall!

"Does yours have the shortwave (i.e. overseas) dial numbering like the lower part of the 46FA dial (5.8 to 15)? 3 knobs?"

Yeah, it does. Also has the "CROSLEY" brand printed where the word "American" would otherwise have been.

Three knobs, left to right-Volume (also has a tone control mounted in the middle), A/B (AM/Shortwave modes) and Tuning.

Just curious, When would 110VDC have been used? Output of an Edison generator, maybe?

When you say triangular, do you mean that its wider at the top than at the bottom (looking straight on from the front)?

I think 110DC was used on ships, maybe also farms, but not sure. I read about that somewhere, but I cant remember details.
The "AC/DC" type design was used by many many manufactures (a.k.a. "All American 5"), I think the main reason they did it that way was the lack of need for power transformers made the radios less expensive (more competetively priced) and lighter weight. Being able to work on 110VDC was a "feature" hardly ever needed.

When counting number of tubes, be sure to include the "metal" tubes. These are painted black (metal, not glass), but have the same type of plug-in base as do the glass tubes.

This might have been brought up on another thread. I'm not monitoring the HD & IBOC threads all the time.

This morning I'm picking up the IBOC hiss on KXL but isn't IBOC only broadcast in the daytime?

It's gone now. Maybe it was an anomaly.

daytime only for now

You can download a free DRM decoder, WinDRM, now at http://n1su.com/windrm/

You connect the audio output of your shortwave radio to your soundcard.