Date: Wed, 30 Jun 2021 07:34:27 -0500
From: Jim <jimw7ry@gmail.com>
To: amps@contesting.com
Subject: Re: [Amps] Swan Mark 1 on 160 meters
<DO NOT use toriods. I speak from experience. Had a reaction when on 10
<meters with my 8877 amplifier. The 160 meter toroid coils would start
<smoking when on 10 meters. I was using a shorting switch.
<Use a small (wire gauge, #16 is all that is required) coil. 3-4" in
<diameter. The closer the turns are together, the more inductance.
<Measure the current tank inductance with all coils in the circuit, (80
<meters selected) then simply add that much more inductance with your 160
<meter coil.
<Simple.
<Jim W7RY
## Per KM1H, the infamous T-225A-2 is good for 850 watts per toroid, cw
or ssb, contest mode. Carl sez to use 2 of em for 1.5 kw ssb / cw.... and
3 of em if RTTY / data modes used. Marv, WC6W years ago, calculated the
dissipation at 57 watts in total, regardless of qty or toroids used.
## I modified a hb 2 x 4-400 80-10m amp into a monoband 160m amp
several yrs ago. Each of those T-225A-2 cores are 2.25 inch diam..and 1
inch tall. With 3 of em stacked, the entire mess ends up 2.25 inch diam x
3 inch tall..and heavy...and that's before adding the tape and 10-12-14
gauge wire. Those cores are painted red at one end, and are optimized for
the lower bands.
## Went to plan B..and found a ton of airdux in my collection, 12 gauge.
I had 2 x almost identical coils, same 12 gauge, same diameter, and the
only difference was one of em had slightly less spacing between turns.
The closer spaced coil also had higher measured inductance.
## In my case, with 80-10m removed, the airdux coil provided the
entire required uh. IF the coil uh is on the slightly...too small size,
it will still work, but the required tune and load cap values will have to
be increased.
## I designed it for an overall network Q of 10....which results in an
input Q of aprx 8..and aprx an output Q of 2. That relaxes the tune
and load C requirements a bunch, and slightly more broadbanded. Being a
160m mono band amp, I then also had the luxury of optimizing the plate
choke, tune and load caps, and fixed padding on the air variable load cap.
I used a 2200 pf broadcast variable for the load cap. Glass vac cap for
the tune cap, which required no padding.
## The small piece of airdux coil weighs nothing vs the 3 x stacked
toroids.... and zero heat from the 12 ga coil.
## One of my 4 x L4B's is modified for 160m (160-10m), using the ag6k
SB-220 160m mod method..for some of it. I used a small chunk of the
same air-dux for the 160m coil.
Jim VE7RF
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