RE: [softrock40] Re: QRP DX with Softrocks - Loop antenna
With such a high-Q devices, I guess that it is a realistic possibility. Where a mag loop can fail is when the Q of the system is too low, owing to problems with surrounding objects, the coupling loop, too small a diameter conductor, etc – ironically, if Jean Claude is getting this kind of problems, it probably that means the Q of his loop is REALLY high and it is very efficient!
From: email@example.com [mailto: firstname.lastname@example.org ] On Behalf Of Brad Thompson
Sent: Wednesday, 27 June 2007 9:46 PM
Subject: RE: [softrock40] Re: QRP DX with Softrocks - Loop antenna
At 08:41 PM 6/26/2007, Steve Ireland wrote:
>G’day Jean-ClaudeHello, Steve and Jean-Claude- -
>I am guessing that PJ2 is pretty humid and the
>level of this humidity will change greatly
>between night and day – and at other times.
>As magnetic loops are such high-Q devices, it
>only takes minute changes in moisture levels
>surrounding the antenna to put it off-tune/require re-tuning.
I wonder whether, along with changes in ambient
humidity, day-to-night thermal contraction of the
loop tubing might exert an equally large effect
on the loop's Q?
>On Behalf Of jabauzit
>From: softrock40@yahoogro ups.com
>Sent: Wednesday, 27 June 2007 8:18 AMantenna
>To: softrock40@yahoogro ups.com
>Subject: [softrock40] Re: QRP DX with Softrocks - Loop
>"Roderick Wall" <rwallmail@. ..> wrote:href="http://www.geocities.com/jabauzit/Magnetic_Loop.html">http://www.geocitie s.com/jabauzit/ Magnetic_ Loop.html
> > Hi Jean,
> > Can you please give us some details on your magnetic loop antenna,
>and is it a home made?
>You can see pictures of it at:
><http://www.geocitie s.com/jabauzit/ Magnetic_ Loop.html>
>It is homemade with soft copper pipe - used for gas lines - the
>diameter is a little small - around 10 mm. I use a dual stator
>variable capacitor plus other capacitors in parallel/series to tune
>just the 40m band. The power is limited to around 10W due to the close
>spacing of the capacitor plates. I tried different types of coupling
>as I experience a very strange phenomenon: the SWR changes between the
>day and the night. The problem is not solved and as I just moved house
>I did not try again.
>73 de Jean-Claude PJ2BVU