Hi John,
You make some very valid points. I intend fully to proceed more or less
the way you suggested. I've been crunching numbers for some time now
trying to figure out the best way to get to 75 meters with the least
amount of modification. I appreciate all of the input, it has been very
helpful. These old gals were built to last and to withstand years of
full time use. They are equipped with many, many safety devices to
protect the circuitry and jugs, just as you stated, so if care is taken
they can certainly withstand a few tests to see if proper resonance has
been attained. I appreciate your thoughts about not settling for a
partial conversion where you run at a reduced output due to poor
engineering practices, that is certainly not what Amateur Radio is
about. Most of all, I agree with NOT hacking up these beautiful
transmitters. I have restored many, many pieces of equipment and some
that were so hacked it was pitiful. One of my BC-610's fell under the
hatchet at some point in its life and it will be some time before I have
the chassis' and cabinet returned to original.
Thanks again for the insight and if you have any tips or further advice
I would certainly be grateful.
73,
Rick/K5IZ
John Lyles wrote:
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.
John
K5PRO
