At 03:21 PM 6/12/2006, Mike wrote:
>Hello John,
>
>Your warning of having the filter in the line while the ATU is tuning
>is interesting.
>
>The series coupling capacitor on my homemade 40 meter W3NQN filter
>has blown twice and your warning may explain why.
>Fortunately, the W3NQN filters are homemade,
Mike, K4GMH
Mike--
Do your homemade W3NQN filters use the capacitors specified by
Ed in the article, or did you substitute some other type? I know
that the caps specified in the article were somewhat "special"
and a bit difficult to get.
The reason I ask is that I did the power testing for the original article
and ALL six bands were subjected to 200 watts carrier for 30 minutes.
(IC-781 driving an 87A at 200 Watts carrier.)
During development I measured temp rise on all of the components
and there were a couple of filters that had cores getting too warm.
But these filters were redesigned before publication. And at no
time did any capacitors fail the 200 watt test -- or even get very
warm.
So your report of failures at modest powers and SWRs, when added
to the fact that you said they were homemade, made me wonder if
you used identical components or made some substitutions.
73 John W0UN
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