Re: LF: RE: New personal QRP DX record on 500kHz: 1733km

[Roger Lapthorn <rogerlapthorn@gmail.com>]

No, the 500kHz TX, ATU and loop antenna are as they were a few weeks ago Rik and I am suprised how well this all works.

The transverter (on my website) TX produces 5W from an IRF510 and this is fed to a vertical wire loop in the garden tuned with a capacitance decade box for maximum loop current. The loop is supported at the house end by the aluminium poll used to support the 28MHz halo (about 9m above ground at highest). The wire runs about 17m down to a tree where the far end is about 4m above ground. Then it runs down to the lawn and runs back along the ground (buried in the long grass that is wet and needs cutting) to the house. The feed is via an upstairs bedroom window with the ATU on the bedroom table. In all, the loop area is about 70 square metres. The wire is PVC covered 1mm diameter wire.

The experts tell me I should raise the bottom of the loop above the ground, but just resting it on the wet grass doesn't seem to be doing too bad. The grass is about 10cm long at the moment as it is too wet to cut and we were away in South Africa for the last few weeks. I can increase the wire diameter soon which will increase the loop current some 3dB.

I'd be interested to know what you believe my ERP is. My last calculation came out around 2mW.

This evening I shall be back on 137.5kHz WSPR with the same antenna and ATU, although the ERP on 137.5kHz is much lower and almost certainly not more than 100uW at very best.

73s
Roger G3XBM

On 21 October 2010 07:47, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote:

Hi Roger,

 

congrats with teh new ODX.

Did you improve the setup ?

I had daytime copy of your signal up to -25dB at at night copy up to -18dB (meaning you could have reduced power by another 13dB).

 

73, Rik  ON7YD - OR7T

 

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Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger Lapthorn [rogerlapthorn@gmail.com]
Verzonden: woensdag 20 oktober 2010 23:24
Aan: rsgb_lf_group@blacksheep.org; GQRP@yahoogroups.com
Onderwerp: LF: New personal QRP DX record on 500kHz: 1733km

This evening, quite unexpectedly, I got a string of reports on 500kHz WSPR from OH1LSQ in KP03sd at an astounding distance of 1733km. To me these are amazing reports pushing my best DX on the band with just a few milliwatts ERP to new levels.  What surprises me is how well a very simple vertical wire loop works as a TX antenna: the wire is just 1mm diameter, with an area of around 70m square with part of the loop laying on the ground buried in wet grass.

Even more than before, I now believe almost anything is possible.

Now I just need to repeat this on 137.5kHz....

73s
Roger G3XBM

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G3XBM   GQRP 1678    ISWL G11088

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