Topband: K9AY Loop questions

[Maciej Wieczorek]

> Question 1 - I have seen plots on K9AY loops and their relative gain is
way down on 160 compared to 80.  Of course, they work great on 160,
certainly with a preamp.  Does this mean you could make one for 80 that was
half the size and it would still work well?  Is there something magical
about the size that Gary designed them to be?

Mark,

Responding to question 1: in 2006 I played a lot with size, dimensions and
shape of my K9AY loop. I have no space for an array of more than one
antenna, so I wanted to get as much a posible from a single loop. In the
result, since last winter I 'm using 2 different K9AY loops (with 2
different dimensions), switchable from the shack. Here are some of my
observations:

- the original size (abt 85 feet) seems to be an optimum for 160m
- on 80m those dimensions are OK, but I noticed better signal to noise
ratio, while receiving weak DX signals with much smaller loop, about 55
feet, so a bit more than half of the original size
-on 160m  F/B ratio is about the same on both antennas, but I prefer to
listen on the original size, the smaller one is a bit deaf on top band
- on 40m the smaller (55 feet) loop is working definetely better. I had very
surprising result one morning on 40m, when switching from the smaller loop
to the bigger one could not see any signal increase at all, while the noise
flor was going  few db up.
- I work a lot on 30m band (I like this band preety much). Here again the
bigger (85 feet) loop is showing much better performance. The smaller loop
has worse F/B ratio and seems to have not enough signal output.
- by the way, with the original K9AY size there is no need to use any
preamp, on any band, unless the feedline is very long. Smaller loop may
require a preamp on 80m and will certainly need it on 160.

The results are from my own QTH, hasn't already been tested in other places.

73's
Mac SP2XF