Dear Roger,
please don't give up too soon! If you were willing to go to longer symbol
durations (say a minute or more), you could certainly cover several hundred
kilometers.
A rewarding target would be to reach the F1AFJ grabber, about 600 km south of
you. It is remarkably sensitive, and I believe that the noisefloor in the 24
mHz
FFT bandwidth.may sometimes be as low as 10 nV/m. Across a nighttime single-hop
path, 20 uW ERP from you could theoretically produce about 30 nV/m there - ie.
a
comfortable 10 dB SNR.
Good luck, and thanks for sharing your good work.
73, Markus (DF6NM)
----- Original Message -----
From: Roger Lapthorn
To: [email protected] ; G6ALB
Sent: Friday, September 03, 2010 10:54 AM
Subject: LF: 137kHz activity
My QRPp 137kHz experiments are now on hold until next week as we've our younger
grandson and his mum and dad with us for a few days, so I lose the shack as it
doubles as a bedroom. Thank you for your reports thus far to my QRSS3 and WSPR
tests.
>From the tests this last couple of weeks I'm beginning to think Mal G3KEV was
right.
On 137kHz QRP just does not "do the business", unless one is prepared to erect
a
much beefier antenna, run more power than 5W from the PA, and be very patient
with slower QRSS and DFCW modes. My "sphere of influence" would seem to be out
to about 75km maximum with the system I currently have. Going up in ERP
requires
me to look more carefully at higher output PAs, heatsinking, rating of
capacitors, thicker antenna wire (more obvious in the air to neighbours). It
moves me away from my, self-imposed, QRP ethos in which I wanted to explore the
limits of a truly simple QRP station on 136kHz. It has been a great learning
experience for me though and there are still a few more dBs to squeeze out yet.
I'll be on again next week from Monday, probably giving 137.5kHz WSPR a good
go,
before drawing the tests to a natural close and leaving the band to the big gun
stations.
73s
Roger G3XBM
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
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