Hi Rick As I told in the webinar it is a measured practical result, not a math calculation.. I have a DDC SRD and several receiving antennas in a very clean environment, only one TX antenna detuned, not other tower or Yagi etc.
I can switch from one receiving antenna to another and see how much the signal is above noise. When you remove noise for every direction due RDF, increasing RDF the noise floor decrease. I can pick up a signal and measure db. above noise listening my TX vertical. Then I switch to my vertical WF and the signal to noise ratio increase average by 10 db., it has nothing to do with gain, just signal level against noise level. Then I switch to my HWF and the SNR increase another 10 db. from the vertical WF , it is average 20 db. better them the same signal against noise on my TX antenna. That is observations and measurements since 2009. Any time I can detect a improvement I stick with it, and try something else to get another new improvement. Looking into my records and associating it with RDF, comparing with 5dB RDF from a vertical TX antenna, I come up with average 1,5 to 2 db. increase on SNR for each dB increase in RDF against a vertical TX. I it a practical empirical result, you can try and check it by yourself. Regards JC -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard (Rick) Karlquist Sent: Friday, March 04, 2016 12:38 AM To: Topband@contesting.com Subject: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) In this webinar, it was asserted (without explanation) that for every 1 dB increase in RDF, you get 1.5 to 2.0 dB improvement in S/N ratio. I've never heard that before and don't even see how it makes sense. Actually, I don't even know how you can make generalizations like that unless you are describing a theoretical QTH with uniform isotropic noise. I'd like to believe this is true. Can someone educate me as to why I should believe this? Rick N6RK _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband