One of my co-workers, who unfortunately is out of the office on vacation right now, once told me that KBPS-AM used to have a Bauer transmitter with the tubes accessible from the front. Was the old KBPS transmitter a Bauer 707?

Yup.

I am looking at a picture of the transmitter that a friend snapped several years ago... most of the details of the front seem to match up with the rear view shown in the link above, EXCEPT there are 3 small tubes visible to the right of the 5 meters that are in a vertical row in the center of the transmitter. Was this a special KBPS engineering mod, or factory provided?

I looked more closely...perhaps the sockets for 2 of the 3 are under the "shield" cover?

I worked on a few Bauer 707 transmitters back in the day. The smaller tubes that were in the lower part of the transmitter were audio and rf drive tubes.

What kind of transmitter is the mighty 1450 using now?

Yes, KBPS-AM has a Bauer 707 transmitter. The original records have been lost, but recently when I spoke with Bauer company owner Paul Gregg he thinks he helped install the transmitter in 1967 or '68. It has been our backup transmitter for the past 15 years or so. We currently use a 1kw Nautel. We just purchased a new 1kw Broadcast Electronics transmitter and will be intstalling in in a few weeks. The Nautel will become our backup and Kent Randles and Randy Pugsley will be finding a new home for the Bauer. The last time we had the Bauer on the air was last year when a module in the Nautel blew out from a lightning strike cause power surge.

Will the BE do AM stereo as well as the Nautel Ampfet does?

I received a photo of the KBPS Bauer yesterday. I did a Google image search on the Bauer 707, and I found that at least two different versions of the transmitter's front panel were made during its production run. In one of the older versions, the meters the vertical column had slightly rounded faces and protruded from the panel's surface. In the newer version found at KBPS, the meters have rectangular faces that are flush with the panel, and the arrangement of the front panel tube sockets is slightly different. All 707s had the vertical column of meters, but in some photos, they are not visible because the transmitter's front cover is closed.

When I saw the schematic to this transmitter, I was taken by how simple it is. All of it fits on one page. The audio section consists of only four tubes: a push-pull voltage amplifier made up of two 6SJ7s and a push-pull output stage made up of two 4-400As. The RF chain consists of a 6AG7 oscillator, a 6AG7 buffer/voltage amplifier, a 6CA7 driver, and two parallel 4-400As for the output.

The 1960s Bauer literature lists the 707 at $4495.00 fully assembled or $3495.00 in kit form.

Is the Bauer going to another broadcast station, or is it going to a HAM.

I predict someone involved with the W7DTV group will probably use it for hamming it up...

Cool. The Mighty Bauer will live on!! May the tubes never give up their friendly warm glow....

Alfredo,
That pretty much sums up the circuitry of most transmitters of that era.
Simple.

Can you imagine an all tube IBOC AM transmitter!

That would be an awful lotta tubes!!

It would have to be sold with it's own hydro electric and cooling plant.

Something like this?

http://www.ominous-valve.com/tour.html

You can see some more Bauer 707 pictures at http://www.oldradio.com/archives/hardware/707.htm

The KBPS Bauer will probably go to James Boyd, who was once the Chief Engineer of KBPS.

I have a pretty good picture of the KBZY 707.