Re: Sweep tubes at VHF
The high output capacitance of sweep tubes make them more suitable for
low Z plate circuits. The operate just fine into the VHF region, but the
efficiency drops off quickly past a certain relative "MHz cutoff point",
depending on the the actual tube(s) used. 6JS6, 6LQ6 etc...
The 6JU6 was a very popular VHF sweep tube, I haven't looked at the specs
for it in some time. The Lafayett and Sonar amps all had them onboard.
There have been numerous sweep tube amplifiers made well into the VHF
region, by Sonar, Lafayette (6&2 meter 2 tube, mobile), Kris and others.
I used a home brew dual 6LQ6/6JE6 amplifier on my Hamtronics 6 meter
repeater strip for years. FM & CW designs were pretty easy...
Linear operation is another animal, super cathode circuits are very
popular. A 10 ohm 5 watt resistor in each of the cathode lead cleans
things up quite a bit.
6146's are a much better animal for VHF operation, much lower output C.
I have an old photo copy somewhere, of a sweep tube dual band (6&2 meter)
amplfier using a knife switch for band changes (Oh-yeah, touch that
one..?) An ariticle in 73 with a 4cx250 also had the knife shorting band
switch. Knife bandswitch often = SK
:But as they didn't give you anything you couldn't get from a 5894 ( and
they
:weren't that expensive over here) or even a surplus 829B, there didn't
sem
:much point.
Yep...
Hey, I still have my 5894 amplfier which I rebuilt from an 829 amplfier I
made in the 70's. What a smoker at 110 watts output on 2 meters FM, but a
pain to neutralize when I first got started with link coupling.
: I'd junk the 572s and go for a 3-500Z.
I'm partial to the 4CX250 on 2 meters...
73's
skipp
nospam4me@juno.com
ps, Wayne Green still alive...?
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