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Re: LF: Re Propagation report

To: [email protected]
Subject: Re: LF: Re Propagation report
From: Peter Dodd <[email protected]>
Date: Wed, 07 Oct 2009 20:21:45 +0100
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There is a whole lot of stuff written about determining ERP involving a lot of maths. The most accurate method is to measure the actual field strength. These methods are described in 'LF Today' and 'The Low Frequency Experimenter's Handbook' available from ARRL Books (look in RSGB section). Also check out QST Nov 1998 and you will see the antenna I am using. My unconventional method of working out ERP is to calculate antenna gain (loss) using EZNEC. Because the radiation R is so low much of the gain is determined by the ground characteristics. This parameter I determine by measuring the RF current on the real antenna which is input into the model. My present antenna has a gain of around -12dBi.
I trust this helps

Peter Dodd, G3LDO

As an interested observer from the other side of the pond, how do you determine that you are close to the ERP limit?? I'd be interested in knowing as I am trying to do some pro-bono work for the ARRL on getting use of 137 kHz here in the USA. Tnx & 73, David Weinreich

*From: *  Peter Dodd <[email protected]>
*To:*     <[email protected]>
*Date: *  10/07/09 3:09 PM
*Subject: *   LF:  Re Propagation report

Hi Jay,
I will be sending a beacon signal QRSS3 on 501.1kHz until 2330z.
I have modified my old PL519 TV sweep tube transmitter which ran about
60 to 70W. It now has two PL519s in parallel running 120W.
I have taken down the HF quad until the sunspots wake up a bit and
reinstalled the antenna used for 73/136kHz so I am now running close to
the new ERP limit.

Peter, G3LDO

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