BAUER 707 Broadcast TX

[W4RFM]

Has anyone converted a Bauer 707 to 80 meters? I am getting one and I wonder if anyone can walk me thru the changes in the osc and final stages.

[W6DRZ]

Bob,

There are a number of them in use here on the West Coast.  Contact either Rick, K6FMB, or Shorty, K6JSI.

Craig
W6DRZ

[W4RFM]

Thank you Craig, I will do that. Have a good day. BM

[W3GMS]

Has anyone converted a Bauer 707 to 80 meters? I am getting one and I wonder if anyone can walk me thru the changes in the osc and final stages.

I believe Dave, K2DK documented many BC rig conversion in Electric Radio some years back.  Not sure if he did a Bauer 707, but I believe he did.  You may also send him an email to get the details.   

Joe, W3GMS

[W7TFO]

If SCMS reps the Dorrough meters, you know where to ask.

          -or-

KO6NM has done a boatlaod of 75m conversions on them.

73DG

[N8UH]

Another one over here on the left coast with a Bauer is Ron, W6OM. I've had a few QSOs with him. Great guy to talk to.

[W4RFM]

Thank you guys, I will give all these great leads a shout.  What a great Forum!.
BM

[KL7OF]

Was the Bauer 707 available in kit form?

[W7TFO]

That is the one.  Fritz even had one assembled at a NAB show to demonstrate how easy it was to do.

the earliest ones were June bug green, then they went to tan/brown.

The 707 turned into the Sparta brand clone, then died away.

73DG

[flintstone mop]

I am not familiar with the RF design of the Bauer 707. If it's like most B'cast TX follow manufacturer's instructions to move it to the top of the B'Cast band and it will be fine for 160M.
I had a Gates BC1-H that was on 570khz and had to buy those large door knob caps in the tank circuit and I was set. I connected a common VFO to the crystal socket and slightly modified the RF driver to give me 150ma drive for the 833's.
Fred

[kb3ouk]

http://bama.edebris.com/manuals/bauer/707

Looks pretty simple to me, 6AG7 oscillator --> 6AG7 buffer --> 6CA7 driver --> 2x 4-400A finals, then the modulator is just simply a pair of 6SJ7s driving a pair of 4-400As.

[W4RFM]

It is very simple and straight forward in design.  I was just looking for the approximate values for 75/80 meters.  When I pick it up I will determine the PA voltage and current at 500 watts and figure it out with one of the Pi network calculators I guess. There is plenty of room to add a couple of variables or vacuum caps.

[flintstone mop]

It is very simple and straight forward in design.  I was just looking for the approximate values for 75/80 meters.  When I pick it up I will determine the PA voltage and current at 500 watts and figure it out with one of the Pi network calculators I guess. There is plenty of room to add a couple of variables or vacuum caps.

Good approach with (TWO) vac variables in the plate tank circuit. I did that for a McMartin BA1-K and it was very happy 160-40M. The drive was from my Kenwood TS440 and an antenna tuner to the grids of the 4-500's. (About 10watts drive) 4-400's same thing. I kept it simple. Maybe not perfect pretty lash-up, but worked good.
The final tuning (intial set-up and pre-check) was done with power removed, B+ discharged. A carbon resistor with the ohmic value equal to the two finals, (?) 3800 ohms???(DISCONNECT the plate caps of the final tubes!! CONNECT resistor from plate cap to ground) connect the MFJ 259 connected LOOKING INTO the P.A. tank circuit.
Adjust the MFJ for the band/freq and tune the P.A. tank elements for min SWR on the MFJ.
You will be playing with the tap of the coil and the two VAC VARIABLES. Don't be cheap and use bread slicers. The only thing to mark was the tank coil. The capacitors, you will tune in the low power setting to quickly get the PA to resonance, when you are ready for the high voltage part of testing.
Basically I changed the tank to a pi and removed the harmonic filter.
W3BV, Alan, bought the McMartin from me and may still have it.........dunno.
Fred

[W3GMS]

Has anyone converted a Bauer 707 to 80 meters? I am getting one and I wonder if anyone can walk me thru the changes in the osc and final stages.

I believe Dave, K2DK documented many BC rig conversion in Electric Radio some years back.  Not sure if he did a Bauer 707, but I believe he did.  You may also send him an email to get the details.   

Joe, W3GMS

Bob,
Contact Ray out at ER and request a copy of ER number 196 which is the September 2005 issue.  Dave, K2DK goes into great detail how he did his Bauer 707 conversion. 
73,
Joe, W3GMS
 

[W4RFM]

I was able to secure copies of the September 2005 and the October 2007 issue with the Bauer info. Thanks folks.

BTW I picked it up today. I think this is going to be a fun ride.
BM

[flintstone mop]

Has anyone converted a Bauer 707 to 80 meters? I am getting one and I wonder if anyone can walk me thru the changes in the osc and final stages.

I believe Dave, K2DK documented many BC rig conversion in Electric Radio some years back.  Not sure if he did a Bauer 707, but I believe he did.  You may also send him an email to get the details.   

Joe, W3GMS

Hey Joe
That may be the article where I found out the trick to "Pre-Tune" The P.A. without stressing the circuits in new unknown territory.
Fred

Bob,
Contact Ray out at ER and request a copy of ER number 196 which is the September 2005 issue.  Dave, K2DK goes into great detail how he did his Bauer 707 conversion. 
73,
Joe, W3GMS
 

[John K5PRO]

For a BC kW rig, its more compact than many, esp Gates tin boxes. Plus having tetrodes is a bonus (for lack of neutralization). I almost caught one but it got away. Would gladly trade my BC1H1 for it.

Paul Gregg still runs a company in El Paso to refurbish and sell them (mostly third world I imagine).
 
http://www.bauertx.com/about.htm

[flintstone mop]

For a BC kW rig, its more compact than many, esp Gates tin boxes. Plus having tetrodes is a bonus (for lack of neutralization). I almost caught one but it got away. Would gladly trade my BC1H1 for it.

Paul Gregg still runs a company in El Paso to refurbish and sell them (mostly third world I imagine).
 
http://www.bauertx.com/about.htm

I would love a BC1-H just for having it.
For multiband and reasonable TX audio a McMartin BA-1K was fun. I made many very bad decisions moving from Maryland 7 yrs ago. BAD decisions. Prolly another $1,000 moving costs and all of my heavy Ham TX's could be here with me.
Somewhat regret getting rid of the Raytheon ...RA250..
Fred

[John K5PRO]

Fred,
You're probably a long way off to pick up my BC1H1. I have a fellow in the southeast interested, actually a broadcaster needing it as a spare for his. If he doesn't come through (trucking it being ~$500) I might sell off mine. Its taking too much space in garage with the Power pebble and RCA 250L there.