What is the actual dB/S unit differential of the band noise when you AB switch?
Other things to consider……time of day……gain of dipole versus vertical…….dipole height above ground……difference of angle of radiation of the major lobes on both antennas on 20 Mx……direction of dipole’s the major lobes on 20 MX – 80 meter antenna on 20 meters (4 half waves) has selective gain.……”domestic” close-in contacts(compared with DX) -- leaning toward NVIS, but not quite there…compared to noise source location. So, map the “domestic” stations you have worked to test this…..maybe they fall within a certain range where the dipole is better and the vertical either skips over them. Model both and get a big picture view of the differentials. Your note promotes one of my main philosophies of owning an antenna farm….it is good to have one, but much better to have 2 of different characteristics so you can switch – “diversity trans-ceiving”. JM $.02……Rick – W5RH From: BVARC [mailto:[email protected]] On Behalf Of Michael Rapp via BVARC Sent: Monday, January 11, 2016 9:52 AM To: BRAZOS VALLEY AMATEUR RADIO CLUB <[email protected]> Cc: Michael Rapp <[email protected]> Subject: [BVARC] Why is my dipole quieter than my vertical? Hey all, Now that I have multiple antennas up, it is interesting to compare them. For nearly four years now, my wire vertical (30 radials) has been my workhorse antenna. This past July I also put up an inverted-V multi-band dipole, cut for 80 meters and fed with 450 ohm line. The apex is about 20 feet up. One thing that I've noticed is that, especially on 20 meters, my dipole is quieter than my vertical (which is cut for that band). When I say quieter I mean that when using an A-B switch the volume of the background noise is quieter on the dipole. I began to wonder is it just the noise or is it the noise and the signals being attenuated on the dipole? With the little equipment and knowledge that I have, doing an objective test is challenging. I've been using JT65 as it gives fairly objective signal reports. Being very careful to keep the net sound card level input the same between antennas, it appears that for domestic signals on the dipole I can consistently decode down to about -27 dB whereas on the vertical I seem to be only able to consistently decode down to -22 dB. This seems to suggest that the signal-to-noise ratio of the dipole is better than that of the vertical, which suggests that the dipole is less sensitive to noise -- unwanted signals -- than the vertical. Why would this be? What I've been able to research/Google has been confusing. Some suggest that it is because most noise sources are vertical polarized. (Are they?) Others suggest that because half of my vertical antenna is in the ground (the radials) this does...something... to make it more susceptible to noise. And others point to the dipole having a little bit of directivity contributing to its nulling out, probably by coincidence, some of my noise sources. 73, -- /*/-=[Michael / KT5MR]-=/*/
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