It would be very very hard to guess what the signal difference would be between two very similat 0Dbd gain antennas at fullwave spacing and similar height with similar coax.
The part of the picture you are missing out is there may be multi signal paths on both antennas, all of varing phases, now depending on different obstacles, natural or man made you also have reflections/refraction all coming into play which give peak spot and blind spots and all sorts of spots inbetween.
Assuming for a minute there is only one path on each antenna and a massive obstacle in the path of one antenna and nothing in path of other it pretty obvious what one will win. But take a look at the double slit experiment and all of a sudden you realise there will be peaks and troughs and allsorts of paths going on, all it takes is for a high sided lorry to move and you've lost or gained on that path depending if it was blocking, reflecting or refracting that path.
All double mast comparisons suffer this flaw and thats before you even consider the changing nature atmospheric conditions add to wave propagation.
I wouldn't say dual mast comparisons are cb bullshit, more they introduce far too many complications for accuracy.
I remember once sitting in hills above Glasgow in qso with a 68 div station late at night line of sight, something I could repeatedly do from that very high location nightly, he had a moonraker 4 pointed right at me, he was giving me s6 and I him s4, we moved the car approx 2 feet as tail end was sticking out a biit on single track road, he jumped to s9 and I to about s6, I ain't suggesting a 2 ft move gave me a 2 s point increase in every direction, justhis, I probably lost signal in many other directions, but it shows how a tiny movement can affect signal path and either reduce multipath cancellation or arrive in phase and give addition, that was only 2 feet, can you imagine the difference in terrain over a 36 ft gap to a statio 30+ miles away, incidently io'm about 30 miles from the coast and then lies the irish sea before I hit 68 div and he was a good 10 mile inland.Inbetween some very rough and high terrain.
the terrain and path changes between those two antennas could be enormous, one antenna could get there easily and too another he lies in a blind spot he can either barely or not hear. Its a total lottery. Put both antennas on same pole you've taken all those factors out instant, signal paths are all the same, especially if you change over fast, coax is the same, mast is the same. Results will be a lot more meaningful.
I ain't seen any antenna tests done like that, nor have i seen any that use a calibrated step attenuator and a digital voltmeter/uv meter to measure accurately the signal difference, all rely on heavily innacurate s meters.
I just look at the bigger picture Eddie.
Jazz 73
