Hi Dana and all, I meant to comment on this last year.. hah hah..
The Henry dual band tank circuit was pretty unique. The tubes ran in parallel
on 6M and push pull on 2.. Not hard to believe there were 3rd harmonic issues
when transmitting on 6 though.. The old Johnson 6N2 Thunderbolt came out in the
late 50's and had a pair of 4CX250's in parallel on both bands. It used a band
switched pi-network tank circuit. pretty revolutionary for the day I guess.. I
heard they had band switch reliability problems with a lot of RF current
flowing through the switch. Ernie, W3KKN, in Philly ran the Johnson forever it
seemed.. He was always LOUD..
Today we have the LDMOS SS kilowatt amps that are pretty broad banded. For a
dual band amp I always theorized a broadband circuit could be designed that
worked well on both 6 and 2 (certainly 2 and 222) where all you would need to
do to change bands was switch in band pass filters for each band.. Project way
down the list I guess..
HNY everyone, - bill k1DY
________________________________
From: VHFcontesting <vhfcontesting-bounces@contesting.com> on behalf of Dana
<ve3ds@acanac.net>
Sent: Thursday, December 28, 2017 3:41 AM
To: Michael Clarson
Cc: VHF Contesting
Subject: Re: [VHFcontesting] 6 and 2 meters
I have a Tempo 6N2 here SN 50 bought it in 1980.
Yes it works on both bands, and yes there is some interaction
so tuning initially is tricky but once set up its fine.
Just follow the instructions.
The original had “specially cut” cables for each input … I suspect they
were 1/4 wave multiples…Henry had no info on this when I e mailed them..
I doubt it would work on both bands at once however….(never tried it)
but with separate output relays it works fine, with 1000 + watts out
on 6 or 2.
I don’t think it makes the modern FCC emission requirements, so you need
bandpass filters on each of 6 and 2 m to keep it clean, but otherwise
its an interesting design concept.
I also tried getting some mechanical details from henry but they lost the dwgs.
There was an neat deisgn in QEX about 2008 using a pair of 3cx800’s instead
of 8874’s … the layout and plate arrangement was identical!
Of course today you might just do the same with a single solid state device …
73 Dana VE3DS
FN03
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