> I want to ask you how a k9ay works relatively to 1.8 MHz ,
as the antenna is
> a optimal solution for MW reception as stated in many
literature.
> Does it maintain their carachteristics of nulling,
directivity, quietness
> operation and so on even at higher frequencies than MW ???
The K9AY actually behaves like two imperfect small
verticals. These two verticals are really the bent sides of
the diamond.
The horizontal component of those wires acts as a phase
delay line. Less than perfect phasing, but still a
unidirectional pattern.
This is the same way a flag, EWE, Pennant, and any other
small terminated loop works. (In the Ewe, the ground makes
the closure of the loop).
The ground rod in the K9AY allows us to feed the two
"verticals" differentially, so the ground rod must have a
low impedance compared to the loop termination impedance or
F/B will be needlessly limited.
Quietness ONLY comes from an antenna's directional
properties. Nothing else. The loop has a very broad response
with only two very sharp nulls. If the narrow response holes
align with a very dominant noise source, then the loop will
improve S/N ratio. If the nulls do not align with a dominant
noise source, there will not be a good S/N change. The K9AY
or a 200 acre million dollar antenna all behave the same. If
they have a null on your noise, they help. If they do not
have a directional null on the noise, they do not help.
While you may find exceptions based on where the null is and
where your local noise happens to come from, the basic order
of improvement is at:
http://www.w8ji.com/receiving.htm
A small loop would be like a small vertical or 1/2 wl long
antenna. The chart listing antennas down that page expresses
directivity.
As for which works better, it would depend on your
particular circumstance. If the antenna happens to put a
20dB null on a dominant noise source and not on the signal,
even a loop could be 20dB better. For the large part over
many situations, the order will be followed.
73 Tom
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|