[Amps] Ameritron/MFJ ROLLER INDUCTOR for GS35b amp

[Jim Thomson]

Date: Thu, 29 Sep 2016 18:00:50 -0400
From: nemo zilch <nemozilch at gmail.com>
To: "amps at contesting.com" <amps at contesting.com>
Subject: [Amps] Ameritron/MFJ ROLLER INDUCTOR for GS35b amp


Well, the replies are pretty close to 50/50 yea and nay.  I plan to build a
sort of breadboard of the basic amp to test cooling, rf choke, fil choke
and tank, etc.  So I think I'll chance it and invest in the roller inductor
and give it a try.  If anything weird happens, then I'll go to a switch and
tapped inductor.

As for roller inductors in general not shorting out the unused turns, that
is not necessarily the case.  I have a couple of large ones I bought at
Hamfests and both of them do short out the unused turns.  All that is
necessary is to connect the end of the shaft which the rolling contact
slides on to one end of the coil via a rotary contact.  Then connect
the the opposite end of the rotating coil via another rotary contact to the
plate circuit.   Use the end of the coil which connects to the rolling
contact shaft to connect to the loading capacitor side.  Pretty much
analogous to the tapped inductor/switch setup, perhaps more stray
inductance though.

My present HB amp uses a pair of 4-400's and I am using the roller
inductor/tuning capacitor from an old Johnson Thunderbolt amp and it works
fine all bands through 10M.

Thanks everyone for your replies, I value and appreciate them all.

Bob W4AOS

##  On that ameritron roller inductor.  I looked it up in their catalog, and
it appears to be made of edge would ribbon.   But they dont state what the
dimensions of the edge wound ribbon itself are.   IE:   is it .375 x .082
or perhaps .250  x .092     etc etc. 

##  if we knew what the dimensions of the edge would ribbon were, that
would tell us a lot.    We already know its  2.5 inchs OD  x XXX long,and 
measures  16 uh.  

##  does anybody know, or can measure one ? 

Jim   VE7RF