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.
However, there are other things to consider here. When the RDF gets large, say more than 12-13 dB, the beamwidths get very narrow. This means that the angular footprint over which the high RDF is actually realized is quite small. Once you are outside the "sweet spot", performance falls off pretty sharply. Unless you can somehow rotate the beam footprint in fine steps, like a rotary Yagi, you will have gaps where the large RDF actually doesn't help you and you may do worse than with a lower RDF antenna with a wider beam footprint. The other point is that RDF is a good predictor of receiving performance only to the extent that external atmospheric noise is more or less uniformly distributed over the entire receiving hemisphere of solid angles. When noise is stronger in one particular direction, then RDF is less accurate at predicting performance. When you beam in a direction of high noise, you just pick up more noise and you won't see the theoretical advantage of RDF. I observe this every morning when I beam SW, where the ambient noise level jumps up typically 5-6 dB compared to other directions. 73, John W1FV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Mike Waters Sent: Wednesday, January 13, 2016 9:56 AM To: Bill Hider Cc: topband Subject: Re: Topband: 4SQ vs. 8 circle rcv According to what I read there, there is little difference between the two. That seems odd. Was some information left out, or did I read the wrong .pptx file? 73, Mike www.w0btu.com _________________ Topband Reflector Archives - http://www.contesting.com/_topband
