Re: LF: 137.5kHz WSPR success

[Roger Lapthorn <rogerlapthorn@gmail.com>]

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 <schaefer@iup.uni-heidelberg.de>

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