Topband: How to orient the receive antenna?

[Fred Fliss]

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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