Date: Fri, 26 Oct 2012 09:42:01 -0400
From: "Carl" <km1h@jeremy.mv.com>
To: "Jim Garland" <4cx250b@muohio.edu>, "'Leigh Turner'"
<invertech@frontierisp.net.au>, <amps@contesting.com>
Subject: Re: [Amps] Additional comments, re GU-74B/4CX800A
Sell them for a nice profit and start over (-;
Carl
KM1H
## absolutely brilliant idea Carl ! Then buy a real tube, like a 3CX-3000A7.
Where 100-150 ma of idle current will net you –59db pep of IMD3..and that’s
at 5+ kw pep out.
.
50w in= 1.5 kw out. 100w in= 2.5 kw out 150w in = 3.5 kw out
200w in = 5.2 kw out.
What more do you want ? The 225 watt CCS grid diss is actually way more,
once the grid
is bonded to the chassis in GG. You can use it as a dummy load for your xcvr.
The grid in that
tube is impossible to blow up, can’t be done. A simple, fast 1A 3agc fuse on
rear panel, wired between
chassis and neg terminal of grid meter is all you need for grid protection.
Fuse blows , and no more path
for dc grid current. Amp can’t be driven. PO drops to zero..asap. Input swr
rises to infinity. Xcvr shuts down
real simple, why over complicate things, with ebs, neutralization, screen
supplies, and having to cancel out the
xc of the tube on each band, pita.
EBS will work, sorta....and esp if PTT is used. On SSB VOX, it really buys you
nothing. None of em are fast
enough to cut off between syllables. They are fast enough to cut off between
words though..which saves a little bit of
power. Once the vox drops out, its cut off anyway. Ebs won’t work at all in
ESSB mode.. unless you slow down the
decay on the ebs... which then renders it useless.
If you could pick any tube u wanted.... nobody would pick a GU-74B. Other
than its cheap price, 15 yrs ago,
it has nothing going for it.
Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|