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Old September 3rd 11, 07:31 PM posted to rec.radio.amateur.antenna
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Default MFJ-868 SWR/Wattmeter

On Sat, 03 Sep 2011 09:25:31 -0700, Jeff Liebermann
wrote:

The two 47K resitors going to 0.01uf bypass caps make
an effective ground to any fast risetime voltage spike at the antenna.


Hi Jeff,

I'm sure you are perfectly aware of the single point of failure in
that generality.

Few Caps exhibit 0.01uF (when so marked) to transients (where it is
presumed they will exhibit 1/2*pi*f*c reactance to the risetime).

When we (silverbacks) got into this game, (the preferable) mica caps
were available, snipped out of the nearest sacrificial TV or radio.
Trying to read those several styles of color coding was the biggest
hurdle, but I had plenty in my junk-box.

Ceramic is ubiquitous, now, and far from choice in these matters,
unless you do deep research (maybe).

You got any favorites that respond to this?

73's
Richard Clark, KB7QHC


 
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