N6RK said:
> Minicircuits coats their cores with "Parylene". The cores are conductive
> like FairRite73 and are in fact probably similar material. A long time
> ago, a batch of uncoated cores managed to find their way into a bunch
> of ASK-1 mixers. We had a special application at HP where we put a DC
> bias on one of the windings. Most users do NOT do this. These
> defective mixers caused a devil of a problem because they didn't
> just fail outright. They would get noisy when DC was applied
> and eventually short out the DC. It took us 6 months to get MCL
> to admit the problem.
>
> What I learned from this is that you should not wind ordinary
> enameled wire on conductive cores even if it seems to be OK
> at first. It may be a time bomb.
>
With the "Battle Creek Special" verticals, we need to use a 2:1 UNUN for the
160 m Inv L section. We've been using 61 type material and glass tape the
cores to prevent the sort of problems described by Rick, Tom etal.
No problems so far in a tx or rx mode.
73 George W8UVZ
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