Topband: Hairpin Matching Coil Questions - BTW

[Charlie Cunningham]

BTW, Jim

The fact that you can't get the feed-point resistance above 27 ohms, sounds
like you are just looking at the driving-point resistance of the inverted L
in parallels with the inductance of the matching coil, that is large enough
that it's out of the picture.  Can you use a grid-dip meter to see where the
inverted L is resonant with the matching coil in place?

Also, a toroid core for the matching coil would be a really bad idea for two
reasons:

1. At full power on 160, there would be several amps of RF current flowing
through the matching coil. That makes core saturation rather likely.

2. Even without core saturation, you would be burning power heating  the
toroid core, creating losses that you don't need.

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
_________________
Topband Reflector