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[Amps] Alpha 77D anode choke swap?

To: <>
Subject: [Amps] Alpha 77D anode choke swap?
From: "Jim Thomson" <>
Date: Tue, 10 Apr 2018 09:23:38 -0700
List-post: <>
Date: Tue, 10 Apr 2018 16:03:16 +0700
From: Martin Sole <>
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?

<Martin, HS0ZED

##  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.  

Jim  VE7RF        
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