Dear LF Group,
M0BMU is now transmitting WSPR again - also currently logging G4JNT and
G4WGT
Re: the question of a WSPR centre frequency, 503.9kHz +/-100Hz would seem
sensible - it should be possible to allow a guard band of say 10 or 20Hz to
the band edge within that bandwidth. There would not be much point in trying
to transmit a WSPR signal if your TX could not maintain that kind of
accuracy. With that range, the maximum contiguous spectrum would be
available for other things in the amateur band. The only problem would be
for locations where there is a lot of noise around 504kHz - I believe Finbar
has this problem with harmonics of 252kHz, but I don't know how widespread a
problem that is. If it is a problem, 501.1kHz +/-100Hz would be more
suitable...
Re: ERP vs TX power. There seems to be an assumption for the HF users of
WSPR that you should specify the TX power. I think this is partly because
many people are unfamiliar with the concept of ERP. Some others have the
idea that you could deduce information on antenna performance by looking at
the TX power of the transmitting stations and SNR, distances and directions
reported by receiving stations. I don't think that is feasible; to do so you
would also need to have fairly accuate knowledge of the directional pattern
of the transmitting antenna, the path loss (including the effects of ground
loss, fading, ionospheric conditions at that particular time), the
directional pattern of the receiving antenna, and the band noise level at
the receiving antenna at that particular time. These variables would be
different for every receiving station, and also vary a lot over time. As
others have said, an intelligent estimate of ERP will usually be within a
few dBs, which implies the antenna performance will be usually already be
known with much better accuracy than all these other variables. So I think
it would be a much better idea to specify ERP, and use WSPR reports as a
tool to analyse propagation, rather than try to do it the other way round.
As Graham says, on HF the ERP will be within not-many-dBs of the TX power
anyway, unless the antenna is very big or very small. At LF/MF there are
wide variations. G4WGT running 5W is quite QRP with his home antenna, but
would probably be well over the 1W ERP limit if he were using G3KEV's
antenna. So really you have to state ERP in order to give a realistic
measure of how strong the signal is at source.
In answer to:
Of course 2mW ERP from a small antenna won't go as far as 2mW ERP from a
large one.
Of course it will! ERP is a measure of how much field strength is produced
at a given distance, so if both stations have the same ERP, the signals will
go equally far - that is the point of ERP, it is a measure of the actual
radiated signal, after losses and so forth are accounted for. If the small
antenna is producing 2mW ERP, it implies that more TX power is being used to
get that figure than is required by the presumably more efficient big
antenna. Not many people believe it though! I actually did the experiment
back in 2000 on 136kHz, setting up a small inverted L next to the 100m high
Decca Navigator mast at Puckeridge, and adjusting the power levels until the
radiated signal levels were roughly similar (about 1W TX for the 100m mast,
350W for the inv L as I recall...). The signal reports I got indicated the
same relative levels from the two antennas, at distances between about 2km
and 1000km.
Cheers, Jim Moritz
73 de M0BMU
----- Original Message -----
From: "Gary - G4WGT" <[email protected]>
To: <[email protected]>
Sent: Sunday, January 25, 2009 8:45 PM
Subject: RE: LF: Re: WSPR 503.5
Graham, LF,
I do agree that ERP is more meaningful & as Mal & Andy stated it is the
criteria with which the licence is approved.
My comment was to follow the WSPR recommended method as adopting ERP would
mean there are two "standards".
I ERP is adopted for LF then it should be international & not just UK, so
an
official announcement by the main WSPR group would be required.
Comments please.
Gary - G4WGT.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: 25 January 2009 20:29
To: [email protected]
Subject: Re: LF: Re: WSPR 503.5
Gary,
I don't think a guard band is really needed as if you set the centre
carrier
frequency to 503.9 , then operating at the extreme edges is not really
possible, you're right on the edge of the waterfall. the deviation is
only
round 6 hz
Re power .. I would say, the erp is the most meaningful, actual power
supplied to the antenna without the performance data of the array doesn't
really mean too much ?
G ..
--------------------------------------------------
From: "Gary - G4WGT" <[email protected]>
Sent: Sunday, January 25, 2009 7:11 PM
To: <[email protected]>
Subject: RE: LF: Re: WSPR 503.5
Hi All,
In agreement with John & Graham, I believe that makes sense. The top part
of
the band is probably the least used area so we just need to agree on a
200Hz
slot of either 503.800 to 504.000KHz with no guard band or 503.700 to
503.900KHz with a 100Hz guard band.
My WSPR beacon is now active using dial frequency 502.000KHz & 503.550KHz
data.
Looks like Andy just beat me to the announcement.
73
Gary - G4WGT
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: 25 January 2009 18:32
To: [email protected]
Subject: Re: LF: Re: WSPR 503.5
John,
Looks close to my post , just, as wspr is such a narrow mode, could move
to
the band edge without problems
clear of the occasional qrss slightly lower down
With a move to vfo/exciter control, defining the wspr slot is a
reasonable
concept as it will allow other 'casual'
monitor stations to be established .. and negate the number of post
needed
to announce a test !
What of the beacons that used this area of the band , are they qrt or
just
sleeping ?
G ..
--------------------------------------------------
From: "John P-G" <[email protected]>
Sent: Sunday, January 25, 2009 6:04 PM
To: <[email protected]>
Subject: Re: LF: Re: WSPR 503.5
On Sun, 25 Jan 2009 17:40:27 +0000
Andy Talbot <[email protected]> wrote:
Is there some sort of unofficial bandplan on this band?
Oh no!
Please let's not get into this again....
At the moment there is no bandplan, but general concensus would
indicate "beacons at the band edges - real QSOs in the middle".
The current WSPR activity around 503.5 (502.0 dial) seems reasonable,
although moving up a few hundred Hz wouldn't hurt, say to 502.3 dial
which gives a 200Hz window at 503.7 - 503.9
There are often CW mode beacons near the bottom of the band - GI4DPE,
GW3UEP and others, and it's convenient to have them there - it allows
monitoring them and SK6RUD concurrently.
That's just my view on how things have evolved.
"Real Man's CW" seems to live around 502.63
John
GM4SLV
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