Topband: 4SQ vs. 8 circle rcv

[Tom W8JI]

> Based on the RDF metric, which is a very useful way of comparing antennas,
> the differences between the "best" arrays is not that great--maybe 1 to 2
> dB.  I have used Beverages and a number of different receiving arrays, and
> found that in practice it is very hard to discern 1 dB RDF differences
> between antennas.  So yes, in a sense, there is not a huge difference
> between the published numbers for the 4 square and 8 circle.

I initially started that so people would quit using gain, which is almost 
completely useless, and not use the front gain to back hemisphere ratio, 
which is just barely better than using gain. RDF is really just directivity.

For example, a pair of close-spaced Beverages have 3 dB more level (gain) 
than a single Beverage, but the directivity is the same.  They will receive 
with essentially the same S/N ratio.

Not factored into RDF, but important with QRM or QRN from multiple 
directions, are "minor lobe" or spurious lobe levels. Unless ambient noise 
and QRM  is evenly distributed or at least not over a minimum level in minor 
lobe directions, we have to be careful to have minimal sized minor lobes.

The very best rule I can think of is to have maximum RDF without letting 
minor lobes get stronger than ~15 dB below the major lobe. Strong minor lobe 
response can easily kill advantages of tightening up the RDF.

For contests and summer time, a clean pattern is worth more than a few dB 
extra RDF. On quiet empty-band low-noise winter nights, it is all RDF 
(directivity).

This why I have a variety of patterns. The eight circle with BSEF 4 element 
pattern is exceptionally clean in pattern, and does not tighten the "nose" 
too much. It is great with storms or contest QRM. The Beverages have more 
minor lobes and stronger minor lobe response but a little more directivity, 
and are better on quiet nights for real weak things.

One cannot have too many choices, if they are all within a few dB RDF.