Hello AM broadcast engineers!

Discussion in 'Technical' started by BBurns, Sep 16, 2014.

  1. BBurns

    BBurns Member

    Hey Guys,

    I just this afternoon got a quick look at the remains of an old RCA AM broadcast transmitter. The grave robbers have had a go at it, but there is enough left in the way of meters, tube sockets, and transformers to be worth going to the trouble to haul it home. The price is right! My suspicion is that it was powered by 220 three phase, so my question is whether a three phase plate transformer can be wired to work on single phase.

    The rig is in four standard width racks with a couple of spacer bays of perhaps 10 inches wide. If I recognized it correctly, the modulation transformer is still there, though I'm not at all sure it was plate modulated. Any and all info that you might have tucked away would be greatly appreciated.

    Cheers,

    Brian Burns Ex: W5BRO, K6UCD
     
  2. BBurns

    BBurns Member

    Re: Hello AM broadcast engineers! Update

    Hello again,

    As near as I can tell it is a RCA BTA5G AM Broadcast Transmitter, or what's left of it.

    Cheers,

    Brian
     
  3. W5HRO

    W5HRO Administrator

    You have a second house next to your current one to put it in? :razz:

    5G.jpg
     
  4. BBurns

    BBurns Member

    Hello Brian,

    Thanks again for keeping AM Forever going!

    I am the fortunate owner of an 1800 square foot shop! It was derelict when we bought the place, and it took me a year and a half to get it back to a workable shop. After seven years working in a 400 square foot basement (low overhead, both literally and figuratively) it's like I died and went to heaven.

    Since you are a CA resident these days, you should know that Fort Bragg (CA) is a marvelous little town. We are in our 15th year here, and still love it. We are having a heat wave---yesterday it got up to 77° F. Don't think about it, just move here!

    The RCA transmitter is not all there any more, and is way beyond restorable. It will take at least two and maybe four trips to haul it the 10 miles home, and eventually it will be reduced to parts. There are still all the meters, and it looks like the oil filled caps, and several transformers//chokes. It used 807's and 813's in the modulator section, so there are some nice ceramic tube sockets. I'll end up with quite a bit of trading stock for anyone interested in swapping things.

    Cheers,

    Brian
     
  5. W5HRO

    W5HRO Administrator

    If all the meters are there and some of the other stuff like you mentioned then why not just use that and build something out of it. Yeah forget restoring it, but you have the cabinets and the meters to make a killer 4 cabinet wide HB transmitter out of it. Just pick your own tubes and build your own RCA design ;)

    If the cabinets need repainting then just take it all stripped down to one of those appliance painting places and have them repaint it.
     
  6. BBurns

    BBurns Member

    Hello Brian,

    At age 74 I am in excellent health, as certified yesterday by two doctors, but in my most megalomanical fantasies, and I have them, do I imagine that I will live long enough.....

    BTW I attribute my excellent health to the low-carb diet. Details available on request to anyone that's interested. My other hobby is promoting the low-carb diet.

    Cheers,

    Brian B.
     
  7. W5HRO

    W5HRO Administrator

    Well, I have no plans to end AM Forever. I started it as an ordinary website back in 1994 so how many years has it been, around 20 now?

    Anyway, a lot of the guys here in California run the big broadcast transmitters, but most don't have that great high positive peak modulation that cuts through the noise and typical band conditions. I hear a lot of them down south, but their audio is usually so low that it's really hard to hear them at times up here in San Jose. They have the high carrier power, but their audio is usually running through console mixing panels and loads of other processing garbage so you can hardly hear them most of the time. I've been working like a dog to finally get my station back on the air this winter so we will see what happens.

    As for the low carb diet, that would not work for me. My diet has always been mostly carbs/starch. I was raised on meat, potatoes, rice and bread and most everyone in my family has outlived their peers so I don't see any reason to change. I think what it really boils down to is attitude and state of mind ;)
     
  8. Roger

    Roger Member

    Hi Brian:

    Regarding the 3 phase xformer.... I tried using one in a two tube 3-500 amp that I recently finished. It was a 220V input rated 3 phase unit and listed as 1100V output each phase to neutral. I experimented using very low voltage input from a wall wart. Becoming more encouraged I then used a variac into a bridge and with 150Mfd total filter capacitance. By experimentation, paralleling windings, etc I was able to input 120V to get 1600V out of the filter caps and with good smooth DC. Next, I changed the bridge to a doubler ckt and had about 3300V DC output...again nice and smooth. Put the two 3-500's on the air ( SSB), made some contacts, got good reports BUT....regulation was horrible. At 700-800 watts out EP would drop 800 or so volts. Oh well..........I tried. I once accidentally put 240V on one of the input legs and the transformer became a loud buzzer. Got AC removed before it damaged anything. Bit the bullet and paid $400 for a custom built transformer from EPD in North Carolina. Hope you have better results but I just didn't have very good luck.

    73
    Roger