[Amps] Alpha 77D anode choke swap?
jim.thom at telus.net
Tue Apr 10 12:23:38 EDT 2018
Date: Tue, 10 Apr 2018 16:03:16 +0700
From: Martin Sole <hs0zed at gmail.com>
To: amps at contesting.com
Subject: [Amps] Alpha 77D anode choke swap?
<About to swap the anode choke in my Alpha 77D for the Ameritron RFC in
<the hope it will work on 12m without issue. Any gotchas or is it pretty
<much plug n play?
## will the new choke fit in there ? The series resonance points could still shift up /down
a bit, depending on how close the new choke is to surrounding stuff. What did alpha use for
a bypass cap at the base of the oem plate choke ? For 160m use, they really should have a
pair of 4700 pf disc ceramic caps. I use the....ceramite brand in the mouser catalog... also
available at henry radio in LA. They come in 10 kv and also 15 kv rated, and I believe a couple
of voltages lower, like 5 kv and 7.5 kv.
## Try it and see if it works on all bands. You might want to go easy and pulse tune it, when
testing. The Ameritron / RF parts choke is supposed to resonate at 12.6 mhz and 27 mhz.
## There should be zero issues on 12m band. Folks have had issues at the bottom end of 10m, when
using a hb version of the ameritron choke. If it will fit in there, it should work. Apparently Alpha uses
the exact same choke on their newer amps, identical. Per W8JI, the 2 bands that dissipate the most heat
when using that choke are 160m...and 10m.
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