Hi Ray,
All of this is traceable to real causes, and can be repeated in tests and
measurements. This is something I learned through experience in 1970
building homebrew amps, and it repeats in everything from antenna tuners to
amplifiers.
I have burn up two output band switches on my
I have an amplifier with a pair of 3-400Zs I built in the 60s. When I built
it it was for 20, 15 and 10 meters.
I used 3 of the 5 positions of a BC375 tuning unit switch. Everything work
fine. I added 160, 80 and 40 meters.
160 was switched in and out with a RJ-1a vacuum relay. When I went to 20
- Original Message -
From: Tom W8JI w...@w8ji.com
To: Carl k...@jeremy.mv.com; Bill Wichers bi...@waveform.net;
topband@contesting.com
Sent: Tuesday, March 18, 2014 9:55 PM
Subject: Re: Topband: Antenna matching question
If this is only 160-40 you probably won't have a series
Wrong reflector, but I disagree completely with this:
The HV build up was mitigated by the 10pf cap between the 40-20M positions
which also reduces arcing on the SB-220 which is a shorting switch and a
cap can be adapted to some 160-10M amps. The right hand one in that photo
had the 80-40M
I have burn up two output band switches on my Ameritron AL1200 while on
160m. The amp uses a single 3CX1200A7 tube. My swr may have been high, but
less that 3:1.
Could the discussion above be the same for the AL1200 amp? I'm tired of
replacing the band switch. I looked at replacing it with a
I'm working on a new matching network for my vertical. The vertical is a wire
cage of approx. 82 feet high, and I use it on 160, 80 and 40 meters. The
matching network is a low-pass L network. The new matching network is remotely
tunable with 5 different capacitors selected by vacuum relays and
Here's my question: the large inductor is much higher Q on 160 than the
small inductor (large inductor is about 4.5 diameter, small one about 2
diameter). Would it be better to have the large inductor connected to the
antenna and the small one to the feed (the two inductors would still be in
The inductors are homebrew, but beefy. Basically I use 1/8 thick G10 phenolic
with holes drilled in a cross vise (to maintain spacing), 8 gauge wire for the
windings, and three aluminum brackets shaped like this \___/ arranged like a
triangle on each end to hold the G10 in place. It ends up
You mention keeping the highest impedance part clean electrically, which
would make me think putting the small coil nearest the anteanna would be
best. Whichever part of the inductor is shunted out is essentially just
adding stray capacitance, that keeps the shorted turns part of the inductors
- Original Message -
From: Tom W8JI w...@w8ji.com
To: Bill Wichers bi...@waveform.net; topband@contesting.com
Sent: Tuesday, March 18, 2014 5:33 PM
Subject: Re: Topband: Antenna matching question
You mention keeping the highest impedance part clean electrically, which
would make me
If this is only 160-40 you probably won't have a series resonance issue
with unused turns, but if you cover a wide range you will want to
progressively short the large coil taps. This is why band switches that
do not short (like the old National amp) and why large roller inductors
mess up on
Tom,
I have an amplifier with a pair of 3-400Zs I built in the 60s. When I built it
it was for 20, 15 and 10 meters.
I used 3 of the 5 positions of a BC375 tuning unit switch. Everything work
fine. I added 160, 80 and 40 meters.
160 was switched in and out with a RJ-1a vacuum relay. When I
Phil, Could you not remove the 60ft high guys for a test.
Replace them with four copper radials that are then cut to
resonate the whole array at 1830. Having found your new radial
length introduce insulators into your old radials at the correct
length. Leaving your complete system now
Much has been written about matching 160 meter shortened vertical antennas,
but very little about 160 meter antennas that are too long. There were two
great articles in the old Communications Quarterly in 1998 about elevated
ground planes, but I have lost them over the years. My current system was
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