De profundis -- out of the trash pile

Steve Harrison ko0u at OS.COM
Wed Nov 24 09:26:28 EST 1999

At 07:59 AM 1999-11-24 -0500, N5AIT  Allan Stephens wrote:
>     Anyway, I had the pair on and they are working.  Still some
>minor things in the Viking, like knowing grid/plate current limits
>(ran it at 60 watts out last night, holding it down until I know)
>(I do have a range sent by BA member, and kept within it - and
>a bit less).

We used to run 829Bs at 90 watts input on 144 MHz a coupla decades ago
:o))) Since they ran in class C, we saw plate efficiencies of 75% to 85%,
CW. They could withstand 750V: but man alive, you wanted to be wearing sun
classes if the SWR went high!! =8-0

A 5894 has 10 watts more plate dissipation and handles up to 900V pretty
easily, but it's taller and may not fit. At 750V, 5894s do a really nice
job and live a fairly long time. Swan used them in the TV-2 2 meter
transverters and I could get 90 watts output when biased into class C. The
currents are just about like a pair of 6146s and you can easily run 120W DC
input on 144 MHz. So, for your Viking, you could take those kinds of
numbers as max-case capabilities.

But the REAL restriction would be the Viking's power transformer and choke
(I presume the HVPS is built in, not separate??). IMO, unless you line up a
spare XFMR and choke, I'd be real reluctant to let the thing run any more
than rated current. In any case, I'd certainly consider hanging a muffin
fan somewhere around the old transformer. If there's very little space (in
a BA?? come on.....), perhaps a bank of those lil tiny 12VDC CPU fans. Some
of those noticeably flow more air than others. It doesn't feel like much,
but even the littlest lil bit can really do wonders. I'm using a pair, one
pushing in air, one pulling out air, on a small cold-fusion heatsink and
they keep the sink temp down to almost ambient now compared to almost
burning before.

Boy, sure wish I could get some kinda HF antler up at this QTH and get a BA
back on the air. The stories of successful resurrection like this that you
guys relate are making me salivate.... :o))

73, Steve K0XP

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