On 22 May 2007 at 15:15, lawrence mayhead wrote:
> I am very encouraged by the response to my comments on our
> erp limit.
> Regarding ground loss, the best way to reduce this is not to bury wire
> in the ground but to put it in the air ! 1 metre of wire in the air
> is worth 10 in the ground, and it does'nt have to be in a straight
> line either just so long as it covers new ground as it were. My 136
> now 500kHz ant has 600 feet of top load in 3 zig zags and I get about
> 30 ohms resistance on 136 and about 15 ohms on 500. So I dont need
> many watts to get 0.5 amps int the vert section. 73 Laurie G3AQC
>
I am not quite sure what you are saying Laurie. I gather you are
using lots of top load to your antenna which results in the radiation
resistance increasing to a more realistic level than the 1 ohm or so
you get with short antennas. This does not surely reduce the ground
resistance per se, only give you higher efficiency because the
radiation resistance is higher.
You are lucky to be able to do this. In a 45x22ft garden I have no
such options. When I used the Butternut on 136 for a short while a
few years ago I did attempt a top loading wire, but it is not really
a good idea as the top section of the Butternut is very flexible, and
it would get in the way of my hf antennas which have to share the
same space.
As I said, the biggest problem is that the ground is sand and so I
have an enormous earth loss resistance which cannot be easily
reduced. I have used the Butternut on 160m in the past couple of
years with the same problems - during the winter I unroll a short
length of chicken wire on top of the lawn which seems to improve
things a bit but cannot at the moment leave it down in the grass
cutting season.
My aims for the 500kHz experiment of course are to prove you can
operate on the band in such an impossible QTH. The intention is to
overcome all these 'little difficulties' I encounter. I did it on 136
(even though you all moaned I was way down in the noise), I am
determined to do the same on 500kHz.
73 Dave G3YMC
http://www.davesergeant.com
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