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Reviews Categories | Transmitters: Commercial/Military/Marine adaptable to ham use | Bauer 707 Commerical Transmitter Help


Reviews Summary for Bauer 707 Commerical Transmitter
Bauer 707 Commerical Transmitter Reviews: 3 Average rating: 5.0/5 MSRP: $(missing—add MSRP)
Description: Originally manufactured for, and currently still used in the AM broadcast service around the world. 500W - 1KW switchable with late models bearing the "Sparta" logo which used a TTL circuit to establish the operating frequency.
Product is not in production.
More info: http://www.bauertx.com
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K1MH Rating: 5/5 Jun 3, 2010 12:25 Send this review to a friend
Great rig!  Time owned: 0 to 3 months
I have never used one of these in the ham bands but was responsible for one in a radio station in NH.

You couldn't kill it.

Mike- K1MH
 
KE6PID Rating: 5/5 Sep 23, 2008 10:34 Send this review to a friend
Impress your friends!  Time owned: more than 12 months
The Bauer 707 is designed for commercial AM broadcast radio service. Due to it's low initial price and availability as a kit in the day the 707 proved to be a very popular transmitter for many AM broadcasters around the globe. Many of them are still on the air today. Modification for 160/80 meter use is fairly simple, to move it to 40/20 is more difficult. Modification details are readily available on line. To effect these modifications you will need a good working knowledge of electronics and have good fabrications skills. In my case I opted to make as few 'Black & Decker” modifications as possible and keep the rig looking original opting to use vacuum relays and stepper motors to allow for quick precise tuning of the rig from band to band. Originally this transmitter was crystal controlled – after all it would spend it's working life on a single frequency, however I modified the rig to accept the output from an old Kenwood VFO, to reduce complexity you could use a synthesized ham rig as an exciter bypassing the oscillator and driving the buffer stage directly.

When you receive your Bauer 707 from a broadcaster it's pretty typical to find them dirty, modified and in less than perfect working condition, so plan on some serious cleaning and repair. Approach this as a 6 month project, it's not a grab it and go sort of thing, so if you are an instant gratification type don't go this route. You will need a fair amount of space to work on the transmitter as well as a source of 240 volts AC at 20 amps for operation.

In addition to the transmitter you will need some other equipment. Since the transmitter is capable of over 100% modulation (and creating a great deal of splatter on the bands) an effective broadcast grade audio processor is needed. This can be as simple as a classic single band processor from the 50's like a Gates 39 peak limiter/Level Devil combo, a Dorrough 310, Urei BL-40 Modulimiter, PR&E Modumax, CRL 900/950 series AM limiter to something much more modern like an Optimod 9000/9100 AM audio processor. These will provide much more precise modulation control than a “musician grade” compressor/limiter like a Beringer or DBX. I used a Dorrough 310 with mine with excellent results. You will also need some sort of microphone preamp, I went with a small 5 pot Gates “Studioette” console – a cool art deco looking thing that after a complete refurb was great! But something as simple as a small Mackie will work as well.

Once you are getting ready to go on the air – you need to consider that the rig is capable of a frequency response well over 10 KHz which will use well over 20 KHz worth of spectrum bandwidth – although very Hi-Fi it's extreme overkill for ham use – and is useless as most receivers tuned to your signal will only pass a small lower portion of this. Really – be a good ham neighbor and put a sharp cut-off low pass 3 KHz filter in the audio chain . While on audio- the transmitter requires a fairly stout audio signal to drive the modulator – the audio processor will provide this drive with no problem.

So, if you have the space, have the technical ability and don't mind breaking the FCC rules regarding power and emission standards get one today. There are other rigs from RCA, Collins and General Electric which are even classier, but will cost more.
 
W6OM Rating: 5/5 Sep 8, 2007 10:46 Send this review to a friend
Outstanding Transmitter  Time owned: 3 to 6 months
As more commercial stations move to HD radio these big broadcast transmitters are becoming available at a fraction of their original cost. That coupled with the strong resurgence of AM on 160/75 meters at night makes the acquisition of one of these very attractive.

Modification circuits abound on how to move them to 160/80 meters along with switching circuits so it will think its a transceiver.

No, its not the power, its the "presence" and being able to simply speak in a normal conversational voice with the mic a foot away and see 100% modulation peaks on the scope.

After many years of Rangers, valiants, Viking II's, Globe Kings, etc, it would be very hard to go back now. Once you step across the line into the world of big box broadcast transmitters, you are hooked.

 


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