[Amps] MFJ-(AMERITRON) ROLLER INDUCTOR?

[Glen Zook]

The Henry / Tempo 2001 linear amplifier uses a roller inductor as the plate tuning instead of the "normal" variable capacitor tuning.  It has fixed capacitors that are band switched instead of switching coil taps.  The antenna loading capacitor is a variable capacitor.  Although built before the WARC bands, the amplifier covers those bands very well.  There is a chart, in the manual, that shows the approximate readings, from the roller inductor tuning vernier, for each band.  What I did was to use these readings for initial tuning and then created my own chart for each band with my antenna for each band in use.  That way, when changing bands, I can come very close to "off the air" tuning and then it only takes a very few seconds to "tweak" the tuning for the specific frequency being used. 

I have had one of these amplifiers since it was new in 1972 and have had absolutely no problems with the tuning and the original 8874 tubes are still putting out full power.  The efficiency is excellent even on the 10-meter band.

 Glen, K9STH 
Website: http://k9sth.net

      From: Dale LeStourgeon <dlestourgeon at cox.net>
 To: 'Jeff AC0C' <keepwalking188 at ac0c.com>; amps at contesting.com 
 Sent: Monday, September 26, 2016 7:25 PM
 Subject: Re: [Amps] MFJ-(AMERITRON) ROLLER INDUCTOR?
   
Bob,
This is a little different response. I built an almost exact copy of the
DX-811A amp from the Sep 82 CQ magazine.  It uses a roller inductor that
only goes to 80M, but it works beautifully--and if you get the exact
resonance point for your freq ( and log it on  a vernier dial) you will have
the optimum  no  compromise  output that band switches can not give.  I
agree with Jeff that on 10M it is touchy, but I am still happy and still use
this amp today. I have a 30L1 but use the HB amp more because I like the
roller inductor. Other hams I have talked to are positive about the roller
inductor. I'm not sure the MFJ would be good for that much power and
voltage. My two cents.