Re: LF: 137.5kHz WSPR success

[Roger Lapthorn <rogerlapthorn@gmail.com>]

The attached photo shows the current loop ATU on the bedroom table. It's not exactly complex but tunes the loop effectively on both 136 and 500kHz. The other image shows the TX transverter as it currently stands in its breadboard state and sitting on the shack table!

Who says 136kHz has to be complex eh?

73s
Roger G3XBM

On 18 September 2010 19:06, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

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

-- 
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088

loop_atu_180910web.jpg
Description: JPEG image

wspr_tvtr_170910web.jpg
Description: JPEG image