After a month wait, my ARRL 2006 handbook finally arrived. I have been
looking forward to looking at the 3CX1500D7 amplifier designed and
constructed by K8RA, Jerry Pittenger.
The most original section of the amp was the use of an automatic tuned input
sold by LDG Electronics. Jerry chose the 100W version whereas I would have
opted for the 200W one that LDG offers, which would handle the 200W exciters
that are available from Japan these days (when is TenTec going to wake up?).
Also, why put in any automated tuned input? My exciter already has one. It
may not be as smart as the LDG tuner, not does it have >4000 memory
capability but it will look for a better setting if it senses high SWR. The
LDG costs ± $250.
I don't understand how the step start circuit is supposed to work because
the circuit shown keys both K1 and K2 simultaneously instead of sequenced.
I assume they drew the schematic wrong because K1, which is supposed to get
things going, should have been connected before the time delay relay, not
after it, as is K2. Also, there are far too many errors in the component
labeling. T2 and T3 are identified in one way on the schematic and reversed
in the text. The 4 Crydom solid state relays shown in the picture are
described as Potter/Brumfield in the text and they are shown as 2 relays in
the schematic. The design calls for a 50ohm 50watt glitch resistor in
series with the B+. He says that for example, if 5A is called for from the
RF deck, this will result in 1250 watts needing to be dissipated and the
resistor will quickly fail. I think that a better description would have
been "a deafening explosion causing the power supply to levitate off the
floor with the shrapnel destroying everything nearby" would be more
appropriate, at least that's what mine sounded like during some "debugging"
at my QTH.
All this probably sounds like gibberish if you haven't seen the new
handbook. If so, please excuse the use of bandwidth.
Bob Maser W6TR
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