Message-ID: <4AB28EC5.6020509@sighthound.demon.co.uk>
Date: Thu, 17 Sep 2009 19:32:21 +0000
From: John P-G <gm4slv@sighthound.demon.co.uk>
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Subject: Re: LF: G7NKS back on WSPR with new Umbrella ant
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James Cowburn wrote:
> Dear LF
> 
>  
> 
> G7NKS is back on tonight with a new umbrella antenna under test.  
> 
>  
> 
> 10m vertical element with 4x8m capacity wires sloping down at 45degrees.
> Not ideal but a little better than the old "L".   

James,

This is much the same antenna as I've used on 500kHz. I started with 12m 
height, but Shetland weather saw to that.... I then used 8m, with 
sloping capacity wires of approx 6m, acting as guys (insulators at the 
lower ends ends and nylon rope for the last section to the guying points.)

I tuned it with a variety of fixed and tapped inductors and matched to 
50 ohms with a tapped ferrite transformer, all in a plastic bin at the 
feed point. A run of 50 ohm feeder back to the shack.

I've had reports and QSOs (in-band and cross-band) from at least the 
follwing: G/GW/GM/GI/EI/LA/SM/DL/OH/F/PA/ON and probably others. I've 
had QSOs with powers as low as 100mW TX power and up to 200W TX power.

My estimate of the ERP for 100W TX power is 4-500mW on a good day (very 
dependant on ground losses which affect the antenna current and hence 
the radiated power).

Hope you have success with it.

John
GM4SLV

-- 
http://gm4slv.blogspot.com
Clousta, Shetland
IP90gg