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