Message-ID: <004201c0759e$76a9dca0$57b6073e@dave>
From: "Dave Sergeant" <sergeantd@compuserve.com>
To: rsgb_lf_group@blacksheep.org
References: <22429.200101031458@gemini>
Subject: LF: Re: Frequency stability, loops
Date: Wed, 3 Jan 2001 16:00:43 -0000
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

James Moritz wrote:

>G3LNP's design deliberately degrades
>the Q to give a wider bandwidth, and eliminate the need for remote
>tuning. Another reason why you might not want the highest possible
>Q is that a high Q loop is more easily de-tuned, for example by rain
>or movement.

My loop, which is matched via a capacitor divider network as described on my web
site, has a usable bandwidth of around 300Hz before retuning it is necessary.
But it is not effected by rain or movement (apart from in heavy winds when the
SWR jumps somewhat), the only environmental change is between hot and cold
weather when the value of the tuning caps changes - on a cold frosty morning it
is some 300Hz lower in frequency which rapidly moves the other way when the sun
starts to shine on the matching box!

I also spoke to Mike Underhill after his talk and he is certainly interested
with the work we are doing with loops on lf.  Results some of us have achieved
seem to indicate that conventional theory is too pessimistic and I look forward
to seeing his report in writing.  It seems Mike is not available via email.

Cheers Dave G3YMC
sergeantd@compuserve.com
dsergeant@iee.org
http://ourworld.compuserve.com/homepages/sergeantd