Re: QRN and Loops

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From: Kevin Purcell (xenolith@halcyon.com)
Date: Fri Oct 07 1994 - 20:09:27 EDT


>> I have a situation of VERY high electrical noise from dimmers and other
>> really nasty, terrible, horrible, no-good, very-bad QRN. I also do not

>Well, you could try a magnetic loop antenna.

I don't have the details here but perhaps someone who has a copy of T5W or
G-QRP Antenna (Aerial :-) Handbook could post details of the Rock Loop,
probably the simplest and easy to make small loop. You can make it up from
heavy gauge house wire and a small capacitor plus a small toroid
transformer to match to the low feedpoint impedence. Works well the higher
you go, but recent reports from Rocky indicate a dismal failure to work 80
or 40 with a modified version (more turns).

Another alternative is to make your own from plumbers copper pipe. You need
not even have a variable high voltage capacitor. N7RVD and myself spent
some time fiddling with a hone built loop that used two parallel pieces of
copper as a capacitor. We varied the capacitance by inserting a dialetric
between the plates (thin plastic or even paper!). We fed it via a gamma
match but a single turn inductive coupling would have worked too. Worked
well and had a pretty high Q. You could also find your favorite spot and
use a high voltage fixed capacitor from the junkbox.

I recommend having an noise bridge to find the reasonance, this made
operating really easy. TenTec have a noise bridge kit for on $10 or $15!
Did anyone build one of these noise bridge kits? I heard they redesigned
them.

Post your results and experiences!

Kevin Purcell N7WIM / G8UDP xenolith@halcyon.com 206/649-6489
Seattle dBug Mac Developers SIG organiser kevinpu@atm.com


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