LF: 73k activity.

[G0MRF@aol.com]

What an exciting weekend that was.

I haven't been on LF for some time as my local noise level here in London has been slowly increasing. LF here is now a lost cause during the daytime. However an invitation to operate from Scotland, albeit a 879 mile return journey, was just too good to miss. 

Simon GM4PLM, XYL Lynn and their family made me very welcome and I must say a big thank you to them all for the hospitality and the incredibly nice "Tunnock's tea cakes" 

All 3 of the 'DX-peditions' (GM3YXM GM0MRF G3GRO/ M0BMU) had problems to overcome. Our Farmhouse QTH suffered from a constant background noise which we were able to reduce to usable levels, but sadly not to eliminate completely. Sorry Mike, G3XDV, a good 'T' but not enough to read the detail, even though we had good copy on the G3YXM Birmingham 'remote receiver.'
I had expected a very poor ground but, to my surprise, the overall system impedance was somewhere near 40 Ohms. This was unexpected as GM3YXM has always found 100+ Ohms typical at his New Galloway QTH.
The antenna at GM0MRF / GM4PLM was 125m of wire supported by Simon's tower near the house abt 50 feet up and at the far end by a 30 foot portable mast. A 20 ft pole in the middle of the run reduced the sag. - Not an exceptional LF antenna, but a good temporary installation. For insulators we used electric fence supports as much recommended over the years by Mal G3KEV. The system earth was the house earth and a single 100m wire which was clipped to one of the farm's perimeter fences.
On 71.9kHz this combination was resonated with a single big variable inductor which I've just measured at 5.81mH.  For most of the weekend we ran about 2.5A of antenna current, but as the noise problems encountered by G3GRO and M0BMU became apparent, Simon and I threw caution to the wind and began turning up the supply voltage to the TX.  When we finally worked Derek and Jim we had gone from 28V @ 10A to 34V@14A  and had 3.4 Amps into the antenna.

Stations worked on 72k

GM3YXM
MI0AYZ
G3LDO     apx 580km
G3AQC     apx 569km
G3GRO           610km

Also had a number of 136kHz QSOs, including Mal at S9+ CW and DL2HRE QRSS.

Now the equipment has had the dust removed, it's good to see Simon operating on 136kHz. 
I understand via e-mail that he now has 30V at 20Amps into the TX. Not bad for a modified 250W linear PCB.
Hopefully people will try to have a QSO with him before summer static makes reception too unpleasant. Maybe this autumn we'll finally see a GM transatlantic QSO.

Thanks all

David  G(M)0MRF