[AMRadio] Broadcast transmitter

KC8OPP Roger S. kc8opp at yahoo.com
Fri Apr 21 18:38:12 EDT 2006


Here is what I did to bring the RCA to 160/80/40M.

First thing is get a copy of the "Radio Handbook" by
William Orr, W6SAI.  This book has all the answers.

I started by bringing the transmitter up on the freq
the radio station used.  I cleaned and repaired as
required.  I checked all voltages against the book,
swept the audio section and made more repairs.  When
it works as advertised by RCA, then you can start to
have fun.

I removed the master osc board and built a box for the
grid input circuit.  I used link coupled coils that
are switched in for each band and drive the grids with
a Kenwood TS-520.  The same band switch is used to
changed the taps on the final tank coil.  The winding
data for the grid coils was borrowed from the 16th
edition of the Radio Handbook.  I did install a grid
coil for 20M, but have never tried the transmitter on
20M, wishful thing I guess.

The final tank that RCA installed was completely
removed and I used the "L" coil for my tank.  Vac
variable caps were used for Tune and Load.  I put the
circuit together on the bench to find the right taps
on the coil.  Use a non inductive resistor in place of
the tube that is equal to the calculated plate load
and then a antenna analyzer connected to the output. 
This put me in the ball park and just some minor
changes were needed when the tank circuit was
installed in the cabinet.

The cabinet measured 32 inches deep and 34.5 inches
wide when I removed the meters and switches, just
enough room to fit through the doors.  I would guess
that in the stripped down mode the cabinet still came
in around 300 pounds or so.

Hope this helps a bit, I will look forward to hearing
your RCA on the air.

Good Luck and 73's

--- Rick Brashear <rickbras at airmail.net> wrote:

> Wow!  Thanks Roger.  Great pictures documenting the
> move and 
> restoration.  I would be very interested in the
> modifications you made 
> to the tuning circuitry.  At this point I only plan
> on having mine setup 
> for 75 meters, but it is nice to know someone who
> has successfully 
> modified one to accommodate 160, 80, 40 and 20 in
> case I want to expand 
> the coverage.
> Could you tell me exactly how wide the cabinet was
> after you removed the 
> meters, switches, etc.?  I'm afraid I'm going to
> have to back my truck 
> through the side of the house to get mine inside! 
> Also, how much do 
> suppose it weighed when all of the iron, doors and
> everything else 
> removable was removed?
> Thanks for sharing your story, pictures and
> expertise.  I can hardly 
> wait to get started on mine.
> 73,
> Rick/K5IZ
> KC8OPP Roger S. wrote:
> >Rick,
> >
> >I have a BTA-1R that is set up for 160/80/40M. 
> Here
> >is a link to some pictures of the process.
> >
> >http://photos.yahoo.com/kc8opp 
> >
> >If I can help in any way let me know.
> >
> >Good Luck.
> >
> >73's
> >Roger
> >  
> >
> >  
> >
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