In reading bits on the web and in the books, it seems the directional
receive antenna is a necessity. ON4UN's book includes anecdotal examples
from several lads, which often include comments such as "I switched to the
40 degree Beverage...". How many Beverages does it take? How do you decide
which way to aim them?
In John's book, he makes it abundantly clear that DX is really not to be
expected along the great circle directions. Signal arrival angles suggest
signals that skirt about the auroral oval predominate. For those of us in
the northern hemisphere, we must, therefore, have antennas 'aimed' to the
east and west of north, and also some aimed southerly.
In my acreage-limited existence (less than 1/20th acre), I shall inevitably
be utilising pennants, ewes, K9AY loops or other such compromise antenna.
They have wide forward lobes, so there seems not much to worry about there.
But the nulls in the reverse direction - ah, that must be what is critical!
I confess that I'm quite challenged here. I really have space for one
receive antenna, and I am beginning to believe that I shall be forced to
make it rotary. How many users of small topband receive antennas out there
find the need to make them rotatable? It occurs to me that will be the only
way for me to be confident that I can null out QRN, QRM or noise overall.
At least, until I determine that there is one (or perhaps two) desired
directions.
Furthermore, has anybody had experience making the various small receiving
loops even smaller than suggested in the articles? My highest point in the
entire antenna farm will be 10 metres high. For me, a receiving antenna
probably needs to fit in 2.5 X 2.5 meters vertically and horizontally.
Given appropriate impedance matching and an at-the-antenna preamplifier, are
they usable at all? Or should I give up and move to Montana where land is
available for responsible money?
Yes, I know if I have said remote preamplifier, I shall need to disable it
during transmit. I rather expect I shall have to detune my transmit antenna
(expected to be a shortened, top-loaded vertical) during receive as well.
Amazing how challenging this technology can be. Not ten years ago I spent
all my days performing analyses on 40GHz + devices and considered anything
below 1 GHz to be DC. To find that there are still challenges to be had at
2 MHz is quite thrilling!
Warm regards,
Fred Fliss (ex-G3FLF and about to be relicensed at an upcoming VE test!)
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