The AM Forum

Received an email query from a friend in VA this morning looking for info on this transmitter, specifically the following:

"I'm trying to locate a manual with schematics for one.   I could probably use one for it's little brother, the BA-1k which is very similar.
 
I have access to one of these transmitters that uses four 4-1000A tubes, two in the RF out and two as modulators.  This is probably way overkill for the hambands, but I won't have much in it so a conversion would seem practical.  They only run about 4 kV on the plates and the output is rated at 2.5 kW.  My question concerns operation on the higher bands, specifically up to 10 meters.  I've heard some horror stories about VHF parasitics with these tubes when trying to get them to run on ten.  This transmitter will be mainly used on 160 and 75 meters, but I'd like to be able to get it on ten, especially since the higher bands are heating up.  For simplification, I think I'd go with an untuned, resistively loaded grid driven circuit and maybe even plug in coils to further simplify the mechanical configuration.
 
I'm looking for advice on how to tame the potential VHF oscillations and what your recommendations would be for the plate choke etc."


I'm not terribly familiar with the McMartin transmitters but I know there are a number of folks here who are. Any help you can offer would certainly be appreciated.

TNX

Todd,

KV4D is parting one out in the for sale section.  Perhaps he has info (or is this the person seeking info?)

Hi Todd,

I ran a BA2.5K on 160M for two years and it was almost stock. When I moved from North Dakota to Montana, it was too big to move, so I gave it to K7YOO and he parted it out. He probably still has the manuals and some of the original parts. Give Skip a call.

There were only a few modifications that I made. The final tank was changed to a standard pi network using the stock parts. I disconnected the oscillator and used a CE 20A as an exciter. I disconnected the blower since it was too noisy and never had a problem with the 4-1000s overheating. Even with both 4-1000 RF tubes in the sockets, I was able to run the rig at about 450 watts carrier output. I don't remember exactly what I used for audio driving, but I have never had any fancy audio gear here, so I guess I just used my Heil mike with the W2IHY equalizer. It worked great, and I got very good reports on the signal and my audio.

I would recommend minimal modification and using it as a single band AM transmitter. Good luck!

73, Ron W8ACR