From: "James Cowburn" <james.cowburn@virgin.net>
To: <rsgb_lf_group@blacksheep.org>
References: <01e901ca37ca$72ccdb30$0217aac0@jimdesk> <4AB28EC5.6020509@sighthound.demon.co.uk>
Date: Thu, 17 Sep 2009 20:44:04 +0100
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Subject: RE: LF: G7NKS back on WSPR with new Umbrella ant
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We'll soon see if it works ok/better

I need to work on the transformer a bit and have had some more pointers from
Jim M so that's a project for tomorrow

See you on WSPR

With best regards
 
 
Jim
 
 
Dr. James Cowburn
-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of John P-G
Sent: 17 September 2009 20:32
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: G7NKS back on WSPR with new Umbrella ant

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