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