On Aug 30, 2004, at 3:16 AM, Pete Smith wrote:
I've been toying with the idea of adding a modern amp to my SB-220 for
SO2R operation. One of the things I really like about the SB-220 is
that its pi network has sufficient matching range on the low bands so
that, for example, I can run my 40M yagi, which is cut for the CW end,
up well into the phone band, or run my 80m K3LR array, which is cut
for 80CW, up to at least 3900 kHz.
Does the AL-1500 have similar matching range, or will I find myself
more restricted?
Pete -- The Pi output is similar. However, before taking an AL-1500 on
a trip, it might be a good idea to install a VHF parasitic suppressor
in the anode circuit. I would also add a glitch R in the HV+ lead,
for which I would use 2, 10-ohm 10w, glass-coated resistors in series.
As for the suppressor, if it does not get infernally hot on 28MHz, the
Q is too high. If the AL-1500 has a "neutralization circuit", I would
remove it. /// - note 1 - there is no way to neutralize a HF
amplifier at the always-present VHF resonance in the anode circuit.
note 2 - This (RCA Transmitting Tube Manual) "neutralization circuit"
adds a feedback path between the anode/output and the cathode/input,
however, in a g-g amplifier, this is not a very good idea, unless the
plan is to make it into a VHF osc.
-cheers-
73, Pete N4ZR
The World HF Contest Station Database
was updated on August 2, 2004
2753 contest stations at
www.pvrc.org/WCSD/WCSDsearch.htm
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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