Dear LF Group,
I greatly enjoyed the friday night activities on 73kHz, being able
to work 4 other stations with 'armchair' copy at one sitting. They
were, starting about 20.20pm: G3XDV (589), G0MRF (569),
G3XTZ (569), and a couple of hours later, a brief QSO with Paul,
G0ONA (559). I have not heard Paul before on LF, is he a member
of the Whitton Club? Thanks also for the listener reports from
G4CNN, G3YMC and G3NYK.
It seems that this does not exhaust the possibilities for 2-way
manual CW QSOs on the band, so we will have to have another go
soon.
Also over the weekend, I finally found a sound card that worked,
and now have Spectrogram 5.0 running on my computer. I was
able to copy G3XTZ, G3LDO, and G3YXM operating QRSS just
after midnight last night. I also installed ON7YD's QRS software,
which is looking good too. My tests so far show that my TX and RX
have adequate frequency stability, in spite of both using free-
running VFO's, for QRSS operation, so I hope to get going using
this mode very shortly.
With regard to antennas, it seems that even quite modest
increases in height lead to worthwhile improvements in
signal strength. Originaly, my inverted L was only 5m high,
I have now raised one end to 8.5m by replacing the TV aerial pole
on my bungalow with a length of scaffold tube, which can take the
extra sideways pull of the wire antenna. Together with two
telescopic fibreglass poles, I can get the average height of the top
part to about 8m. This led to reduced loss on 73kHz (ant current
1.2 amps from 0.9), and my signal report from G3XDV went up by 3
S points. I hope it will produce improvements on 136kHz too,
although I am restricting myself to using the full set-up during
darkness, so as not to upset my neighbors.
Regarding ERP, it seems to me that the text book formulae for
ERP, being based on radiation and loss resistance of the antenna,
can't take into account losses in objects like trees, buildings, phone
wires, which although outside the near field of the antenna, and
therefore not directly affecting the radiated power, must absorb
some of the radiated signal. I would guess that in circumstances
like my own, where nearby trees & buildings are taller than my
antenna, the losses could be quite large. Therefore, the calculated
ERP will always be an optimistic 'theoretical maximum', and the
real value will be less. This won't matter much on receive, since
the QRM and QRN will be attenuated by the same amount as the
signal.
Cheers, Jim Moritz
73 de M0BMU
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