I still feel guilty that I managed to bluff my way on this subject in the
RAE test in 1949 when I was a physics sixth former and ' knew everything '
If a man from Ofcom turns up here and says "demonstrate that you are not
exceeding the 1w ERP specified in your licence" how would I theoretically
dispose the dipole to which ERP refers . Assuming the rx antenna is a dipole
it would make a big difference how I oriented the Tx dipole to compare with
the inverted L and plastic laundry basket former-loading coil.
Is there some way of showing and measuring distant FS without putting an
antenna there? Certainly the FS will be different if the tx dipole is
broadside on or end on .
[ ps enjoyed the talk on Saturday - apology if closing my eyes to
concentrate on loop bandwith gave impression of dropping off ;-) ]
bandwidth gave the impression of sleep in the front row ;-) ]
----- Original Message -----
From: "james moritz" <[email protected]>
To: <[email protected]>
Sent: 09 October 2006 14:46
Subject: LF: Re: erp ierp VY1JA
Dear Bryan, LF Group,
ERP is defined by the field strength at a point distant from the TX. Field
strength is a measure of how much signal is present at a particular point in
space. Of course, if you place a receiving antenna at that point, the signal
level at the antenna terminals will be reduced if its polarisation does not
correspond to that of the signal. But the field strength itself does not
depend on the receiving antenna, or indeed the presence of any antenna at
In practice, to measure field strength, you usually have to use some kind of
calibrated antenna to convert the radio wave into an electrical signal, with
a known relationship between field strength and antenna output signal level.
It is up to you to ensure that any effect of mismatched polarisation (or
directional pattern, mismatch or any other kind of gain or loss)is taken
Cheers, Jim Moritz
73 de M0BMU
From: [email protected]
[mailto:[email protected]] On Behalf Of captbrian
Sent: 08 October 2006 20:01
To: [email protected]
Subject: Re: LF: Re: erp ierp VY1JA
Well I always thought there was a large loss depending on the extent to
which polarisation differed between emitter and recvr.?