RadioBanter - View Single Post

November 9th 03, 03:08 PM

wrote:

On Sat, 8 Nov 2003 18:16:19 +0000 (UTC), "Reg Edwards"
wrote:

"Roger Adam" wrote -

I don't see any mention of a fixed or variable capacitor. I take it that
there is one fitted!

================================

Neither is there any mention of frequency. Where is the antenna analyser
connected? What parameters are being measured. How long is the feedline,
etc. ?

Does the antenna work when connected to a transmitter or receiver? If it
doesn't what are the symptoms?

A magloop has an extremely high Q and narrow bandwidth. Behaviour
approaches that of a quartz crytal. If you don't get the expected
measurement results then the most likely reason is the limited capabilty of
the analyser. A precision, scientific-grade instrument is needed.

I've read a little about magloops (I'm a total dunce as far as aerials
are concerned). It always mentions the fact that losses should be
minimised on aerials made of copper tube by making sure that all the
joints are well-made. Would it not be better to get a long piece of
pipe and a plumber's pipebender and make the loop out of one piece of
pipe to avoid joints?

You are right, but.....

If we look at the "best" setup, it would probably be one very wide
diameter (not talking about the perimeter of the loop itself) silver
loop. But these things work even with soldered copper pipe.

Plus with the perimeter of my loop (7.3 meters or almost 24 feet!)
getting one solid piece of pipe would be pretty hard, let alone forming
the loop. So I do a few tradeoffs.

- Mike KB3EIA -