Tree,
You may want to check for any in-band resonances if you haven't already. In
my 77Dx, I've also added additional C from +HV to ground. For the upcoming
77D project, the plan is to discard the B&W 801 choke and replace it with an
RF Parts RFC-3. This choke should provide ample 160m inductance and is
stagger-wound to minimize or eliminate in-band resonance but needs to be
validated after installation. Specs are: 1.5A, 225 uH, 4 KV max.
Paul, W9AC
---- Original Message -----
From: "Tree" <tree@kkn.net>
To: <amps@contesting.com>
Sent: Monday, March 24, 2014 2:17 PM
Subject: [Amps] Alpha 77 160 meter plate choke
All -
I have made a mod to my Alpha 77 to add about 60 uH to the RF plate choke
when on 160 meters. I originally was going to mount a switch to control a
HV relay - but came up with a better solution. If you are interested in
knowing more - check out the pictures here:
http://www.kkn.net/n6tr/directories.html
Look under Alpha 77Dx. The relay was purchased from Henry Radio. It has
a
26.5 volt coil which seems to work just fine off of the +24 volt regulated
power in the amp.
I added a 4700 pf 6KV cap from the HV to ground which you can see in the
pictures.
I am not sure this makes a big difference - but I certainly feel better
about using the amp on 160 with this mod.
73 Tree N6TR
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|