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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