Message-ID: <000601bf1de4$a7631220$0c788cd4@dave>
From: "Dave Sergeant" <sergeantd@compuserve.com>
To: rsgb_lf_group@blacksheep.org
References: <002b01bf1ce4$407390e0$92e1abc3@default>
Subject: LF: Re: Technical details of CFH (137kHz)
Date: Sat, 23 Oct 1999 19:44:29 +0100
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>From Dave G3YMC

Many thanks for the information on CFH obtained from VE1FTL by Alan.  Now at least we know a little more about it.  As Jon says it seems off the air at the moment (it would now be quite audible when I listen before breakfast if it were on).

I have done a quick calculation on a 200m loaded vertical using G4FGQ's program and this shows that such an antenna, assuming 50 ohms earth resistance, would have a radiation resistance of 13 ohms and an efficiency of 14.3%.  A top loading umbrella is likely to improve this somewhat (and the earth resistance is likely to be quite a lot lower with a professional earth mat).  Given the typical efficiency of antennas most of us can use, and the limitation to 1W erp I suspect this puts things into perspective!

<By the way, the 73.6 kHz transmitter is also located here in
<Newport Corner.  It may be useful for monitoring openings on that band

Unless Rugby on 73.4 is off the air I think we can safely say the chances of hearing CFH on 73.4 are absolutely zero!

Jon says the TX uses FSK.  I remember noting earlier this year that at one time it was transmitting FAX (clearly identifiable as such to anyone who has heard FAX).  Perhaps Jon has some information on this.

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