From: "Mike Dennison" <mike.dennison@ntlworld.com>
To: rsgb_lf_group@blacksheep.org
Date: Sun, 04 Mar 2012 09:56:43 -0000
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Subject: Re: LF: Permissible QSY limits for 136
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On 4 Mar 2012 at 2:09, Stefan Sch=E4fer wrote:

> Am 04.03.2012 02:01, schrieb Graham:
> > Permissible QSY limits for 136
> > Q what  is the  average  Q   of  a   136 Khz  Ae  system  ? (back
> > garden  + larger)
> 
> Maybe arround 50.

My very rough tests here suggest that a Q of 50 is about right. My 
current reduces to approx 70% at 1.5kHz off the antenna's tuned 
frequency. This is a Q of 1.5*2/137 =3D 46%. It is raining at the 
moment and I would expect the Q to rise when it is dry. 

The antenna is in a small back garden. It is an inverted-L, with a 
14m vertical wire, and five roughly parallel top wires each 14m long. 
Lots of trees around help to reduce the Q. Inductive loading is 
distributed over several coils, small ones at the bottom and top of 
the vertical section, and most inductance some 3m up.

The original question referred to SWR, which in most cases is 
irrelevant. In practice, my PA makes worrying noises when the antenna 
detunes by only a couple of hundred Hertz.

Mike, G3XDV
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D