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Re: LF: 137.5kHz WSPR success

To: [email protected]
Subject: Re: LF: 137.5kHz WSPR success
From: Roger Lapthorn <[email protected]>
Date: Sat, 18 Sep 2010 19:06:46 +0100
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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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