cris at gm4fam.plus.com cris at gm4fam.plus.com
Thu Apr 22 23:45:08 PDT 2010

Not my experience either!  Moreover, occasionally my 1/4 vertical will
outperform the dipole at 60ft.

As for ground conductivity I used a very un-scientific method; when
looking for a new QTH back in 2005 I put the IC706 in the car and hooked
it up to a 40m mobile whip, then compared the Talk Radio MW signal at the
three places for sale - this one was the best by far for signal strength.

Its not ideal though - I had to add considerable attenuation to the radio
at the Eastern end of the Black Isle which is 3/4 surrounded by salt
water; unfortunately its a fenced-off disused WW1 lookout position with
some very deep holes!

73 Cris

> Andy is correct, its NOT a case of the lower the better for NVIS. That's
only true if you have a copper plated back garden and can cope with very
low feedpoint impedance.  Modelling suggests that the optimum for NVIS 
is about 1/4 wave high.  If you go lower then ground losses start to
outweigh theoretical NVIS gain.
> Alex, GM3ZBE
> Andy Cook, G4PIQ wrote:
>> FWIW - that's not my experience. I prefer 60-70ft dipole height for
>> contests on 80. I don't see any reduction in strength of close-in stations
>> (and that's reflected in the models), and your earth losses go down...
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