[TowerTalk] Re: [AMPS] Trade roller(s) for roller

[Rich Measures]

>
>I have two military coupler units. No reference desig. on the front panel
>but they both use a Johnson 229-202 roller coil (18uH #12 wire). They each
>also have four ceramic trimmer caps which are fine tuned from the front
>panel in "set and forget" fashion. One of the couplers says "2-3Mhz" and the
>other says "4 - 5.5 mhz". RF Communications, INC apparently is the
>manufacturer as this is the name on the front panels.
>
>I would like to trade both of these units for a Johnson 229-203 roller coil.
>I have a homebrew copy of the MFJ 986 differential-T tuner and the coil that
>was used is TERRIBLE. I think it is on a Delrin core and with higher power
>levels the impedance starts to change which effects the tuning of my hf
>amps. Yuk!!
>
.Not only that, Lane, a Delrin core will assuredly melt and bubble at the 
kw level, as the ARRL Lab discovered with two MFJ "3kW" tuners, and 
apparently failed to report in *QST*.    It seems that the person 
(Elliot?) who designed this roller-coil was clueless about the RF 
properties of plastics.  ABS, G-10, or G-11 would have worked ok, Delrin, 
no way.    .  .  MFJ purchased a large number of Delrin roller-coils, 
which were sold to unsuspecting buyers.    How many pages of MFJ 
advertising are there in the current *QST*?   .    

Hoil toil bubble and boil.  



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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