Hello LF group,

I had another 2-way CW QSO with Finbar last evening at around 11pm Local 
Time. His signals were on the whole a bit better than the previous night 
and I think mine were better too at the start, although the QRN and QSB 
eventually took me down into the noise by the end.

During the day I did some measurements of antenna current vs TX DC input 
power (easier to measure) and based on them (and a knowledge of PA 
efficiency) I have graphed I^2 against Power to come up with a straight 
line, the slope of which should correspond to overall antenna system 
resistance.

This has given me a set of figures from where I can quantify 
improvements. It has also showed me that tne new antenna installation is 
seriously in need of work!

For 50W RF power I get 0.65A RF feed current which implies a resistance 
of 118 ohms!! 

Other data points for powers between 4W and 50W tend to agree with this 
figure. The best fit line is around 115 ohms.


Calculation of likely radiation resistance gives me around 0.14 ohms, 
which might be a tad optimistic, so my EMRP will be around 50mW, for 50W 
TX power. Obviously I need to improve this, if for no other reason than 
that I don't particularly want to run high RF power just to heat up the 
worms.


I will attempt to lay some more radials tonight, and add some more earth 
rods and then remeasure current vs power.

Hopefully the QRN will be lower this evening for another QSO attempt - 
and hopefully make GW this time?

Regards,

John, GM4SLV