Topband: Hairpin Matching Coil Questions

[Charlie Cunningham]

Hi, Jim

I don't see why the "hairpin" matching coil should be adding BCI. The
inverted L above it should be picking much more broadcast signal than the
coil! Sounds like your matching coil may have enough inductance that it's
resonating the inverted L in the broadcast band.

The idea behind the "hairpin" match, is that the antenna is shortened a bit
and the hairpin, or matching inductor is adjusted to bring it back to
resonance at the desired matching frequency in combination with the
capacitive reactance of the shortened antenna element. (Of course, this can
require a bit of "juggling" of antenna length and matching coil inductance
to get to a 1:1 match.)

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Jim GM
Sent: Saturday, September 14, 2013 1:14 AM
To: topband
Subject: Topband: Hairpin Matching Coil Questions

I have an inverted L and using a hairpin coil to match in on 160M.

One coil is 6 inches OD the other is 2 inches OD.  I have been thinking
about making another hairpin with wire wrapped around a toroid donut,

I have noticed with the 6 inch coil I have a higher noise level on 160M and
hear BCI pretty strong on certain frequencies on other bands.

The 2 inch coil has lower noise level on 160M and BCI is reduced on other
bands.

If I use a toroid hairpin What would happen to the noise level and BCI?  My
guess is both will be reduced a bit more.

Also what hairpin matching coil should I use and why?

-- 
Jim K9TF
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Topband Reflector