This is the first winter season using my broadside phased Beverages pairs.
I have a pair for EU, JA, North and OC. In each case they are about 950’ long
and are spaced 400’ apart. Each wire is fed with equal length RG-6 to the
centre point and are combined in-phase using a zero degree hybrid combiner
(magic-T). I designed each combiner box to include relays so that the wires
can be phased or used individually (I made a YouTube video explaining the
system if anyone is interested).
Using this system, I can instantly switch and compare the performance between a
single wire and the phased pair.
Modelling shows that a phased pair will have about 3 dB more gain and about 2
dB increase in RDF compared to a single wire. I expected to see about 3 dB
increase in the noise floor when the wires were phased compared to the single
wire, but I never saw this. Most of my testing is using the Flex waterfall and
dB measurements so it's pretty easy to see even small changes. At first this
confused me and made me wonder if the wires were working. My QTH is a rural
(farmland) area with very limited local noise sources. (most noise is equally
distributed in all AZ directions). Looking more at the modelling, the improved
RDF of the phased pair is the result of narrowing the forward lobe and
increasing the side rejection. It seems that the increased forward gain is
offset by reduced side-lobe signals, such that with equally distributed noise
there is little change in the noise floor. However, there IS a significant
increase in signals arriving from the front of the array. Weak signals
arriving from the front of the broadside pair show a pronounced increase in
signal strength compared to a single wire (obviously) but the noise does NOT
increase with the pair. This equals the improved RDF. For the very weak
signals, there are many times that copy would not have been possible with a
single wire, but were very readable with the phased pair.
Together with the Beverages I almost always use the 9 circle array in
diversity. In my opinion, this is truly a “game changer” for the weak ones.
There has been some discussion about the need for RX antennas in diversity to
have significant spacial separation but my experience has been that even
closely spaced antennas can perform very well. I will not argue that greater
spacing is best, but my 9 circle array is only about 180m from the EU and JA
pair, and is actually in the middle of the OC pair. Even with the OC pair, the
difference between copy with just the Beverages or just the 9 circle is
amazing. For the weak ones bubbling at the noise, I can switch from just the 9
circle, to just the Beverages and the signals are there but the copy is broken
up and perhaps unreadable. When both antennas are combined in diversity, there
is some magic that happens where the signals pop out and become perfectly
readable. Most of the time this is NOT subtle but quite dramatic. This effect
is not selective fading because of spacial diversity, but it sounds like the
small “missing gaps” between the characters gets filled in? Perhaps the
Beverages are responding to a slightly different wave angle for both the signal
and noise compared to the vertical array. For example, maybe one small QRN
crash or noise on one antenna is muted on the other so that a DIT gets through
to my left ear, but not the other and vis-versa next time. This effect is not
easy to explain, but is very obvious when you hear it. Either way, I truly
can't imagine going back to single RX!
73, de steve ve6wz
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