|[AMRadio] Re: AMRadio Digest, Vol 28, Issue 47|
jtml at losalamos.com
Tue May 30 01:22:44 EDT 2006
I agree that modifying a broadcast transmitter to move it up to amateur service is a worthy goal and aspiration for most of us. Leaving it stock, and being unable to, or marginally able to crank power out of it at 160 or 75 isn't where it should stop. If it takes a new tank circuit, or injecting a signal from an external VFO, or using a Hi fi amplifier to provide audio drive, then so be it. However, modifying and basterdizing it with a dull drill bit, marking the panel with a Sharpie, putting out spurs and high distortion, or leaving it limping along at low power while the plates glow orange, is just not good engineering practice. So many of these beasts have been abandoned from 1 kW stations that have either gone dark, or are going solid state, and it is a shame for them to just be scrap metal, going into one of those metal bailer machines.
I would recommend that K5IZ or anyone else adopting one, to take out a pencil and calculator and figure out those networks, scale them for the frequency change. And remember that the final may need neutralization, near the new operating frequency. You don't have much to loose, those beasts wer pretty reliable and built with some headroom, esp the 833 rigs. Most have overload relays to protect the tubes or power supplies.
There has been an execellent series of articles on just this, in Electric Radio magazine.
73 and get those finals glowing again- not only on 160 but higher if feasible.
> Thanks so much for the insight and advice. I think first hand
> experience and advise from that experience is most valuable. Larry
> Will, another fine engineer, has also given me some great advice and
> help. Hopefully, with the things I've learned thus far and the help and
> advice from you guys who have "been there and done that", I'll be able
> to get this old gal back on the air. I really don't want to make any
> major modifications in the layout or circuitry if I can help it. I have
> always thought it a great challenge to retain the original design and
> layout while achieving my goals. Whether it will be possible in this
> case remains to be seen. I'll keep you guys posted on my progress and
> I'm sure I'll be tapping into your vast experience for help and advice.
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