Roger,
This sound very hopefully and enthusiastic :-) What is the area of your
loop? And what is the "gain" compared to the earth antenna? Will you
give up the earth antenna project? And what about your ULF (838 Hz)
tests?
For the IRF510 you can allow 20...25 V supply voltage, if well matched,
so if the voltage is now 12...13.8 V you can double the voltage and get
6 dB more power, so maybe twice the distance :-)
73 and keep us informated!
Stefan/DK7FC
Am 18.09.2010 20:06, schrieb Roger Lapthorn:
Hi Stefan (et al),
Still using the single IRF510 but driving it with a better square wave
now. I hope to change the design tomorrow to run from a higher supply
rail and realise another 3-4dB or so of ERP. The other simple change I
can make (later) is with my loop antenna, which is made from wire only
1mm diameter. Increasing this to 4-5mm wire should reduce the losses
another 3dB or more. I can also try running the lower part nearer the
ground thereby increasing the loop area by another 20%. However this
may introduce other losses.
So far I am pleased with the results: with only around 4-5W from the
PA, a very simple loop antenna with thin wire, tuned with a simple ATU
on the bedroom table using just a standard capacitance decade box, a
simple 3C90 step-down transformer and a current meter, I've now been
heard/seen by 4 different stations in SE England and the WSPR reports
already suggest further is possible.
This autumn is going to be a bundle of fun!
73s
Roger G3XBM
2010/9/18 Stefan Schäfer <[email protected]>
Hello Roger,
Congrats to that distance and to the PA :-) Which FET is in use now?
And how is the driver realised?
73 and GL,
Stefan/DK7FC
Am 18.09.2010 12:54, schrieb Roger Lapthorn:
Some success this morning with my second
ever 137kHz WSPR
report, this time from G3XIZ who got me up to -23dB S/N during
the morning. According to the WSPR database the distance is 46km. BTW,
the PA is running about 5W RF out (ERP about 10-20uW) in class-E with a
nice cool heatsink. Next steps will be to increase the power and ERP.
| 2010-09-18 08:50 |
G3XBM |
0.137534 |
-23 |
-1 |
JO02dg |
0.001 |
G3XIZ |
IO92ub |
46 |
240 |
Many thanks Chris, and everyone else please keep looking!
73s
Roger G3XBM
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
--
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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