Dave Brown wrote:
Laurie,
I think you will find that you need to remove the 300 footer before trying
the low height antenna- otherwise mutual coupling effects will surely stuff
things up.
And at 300 feet you will be getting out of 'very short vertical' territory
anyway, even on 136.
At this frequency with both antennas resonant on 136 khz on the same site, the
induced rf from the small vertical into the larger one would distort any
meaningful tests. The antennas would need to be sited several kilometres apart,
when co located one would need to be dismantled while the other one is tested.
I have already tested this by starting off with a 60 ft vertical and progressing
to 120 ft and it certainly made a big difference for the same given rf power
output. Signal reports all over europe confirm this.
G3KEV
73
Dave, ZL3FJ
----- Original Message -----
From: LAWRENCE MAYHEAD
To: rsgb lf group
Sent: Wednesday, March 29, 2000 7:32 AM
Subject: LF: Re. DECCA Tx
The possibility of transmitting from an ex Decca site is very intresting I
would like to put foreward a suggestion for an experiment.Theory has it that
the radiation pattern for a much shortened vertical is not dependant on
height! Some on this reflector disagree.Would it be possible to radiate say
1w erp from the 300 foot antenna and the same power from a co-sited very
short vert similar to those being used by many people, if they used the same
ground system all the better.Then by transmitting alternately from each
station we could gather signal reports from many recieving stations both
near and far,for various times of the day.
Perhaps then we could settle this argument once and for all.. 73s Laurie.
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