Well Oggy, when I first started comparing my GM I noticed when it was mounted close to the house and only 18' high it showed to be sluggish. I raised up to 24' and the signals seemed to show a little improvement. I have another mount further out back that is more in the open and I may mount it out there and do more comparisons with two antennas on a switch box. I told the guys I was going to start using just one mount and coax to compare, but yesterday I put up an A99 w/o GPK where my GM had been and I started taking comparisons with my list of contacts at 18'.
Right off I didn't notice the sluggishness I had noticed with the GM, although I do caution A99 owners not to set the base of their A99 too close to stuff as well. I think the GM is just too sensitive to be set low or close to anything. I think that Scott (007) will also suggest the same idea. At first he an I discussed the antennas being to close together at 35' feet, and subsequent testing with the GM in the air by itself I think proved that to be possible. However, I believe that problem can also show up when the GM is too close in height as well. I PM'ed Mr. Penn asking this question regarding his report. I can't tell what would happen if I could raise the A99 higher to match the height of the GM, but I believe it might show a little better even though the increase is less than 5' feet.
My A99 testing so far is pretty much what Penn is seeing compared to the GM, and that really surprised me. However, I've said for a long time that my old A99 really works great, and it has even shown better signals in the past compared to my Imax...with both at the same 40' tip height. Previously my testing here showed me every time I compared two antennas that were mounted at the same tip height...the shorter antenna always showed better signals. I have such a report posted in my album supporting what I saw with the A99 vs. Imax.
That said however, I note the height of the Imax base was at 17' in that report and it may have experienced the same sluggish fate as note above, being too low to the Earth and not quite above the peak of my roof at my location. At my location these verticals may show similar result (sluggishness) in all cases. Avanti called it "shadow" and that was a factor in the AstroPlane design, but in that case they were referring to building being in the way of a portion of the antenna not necessarily the height above the Earth.
BTW, I commend CTStallion on his nice comments above being easy to read, well written, and I think pretty much hits the mark in my opinion.
Good work CT.
Guys, my A99 thus-far is showing just a bit better signals than my GM in most cases. I believe the A99 is much nosier however, so tomorrow I'll consider to put the GM back up on the mast I use to have my AstroPlane on. Then compare the two. If I see a reversal of the A99 showing better signals, then I'll truly be convinced that doing comparisons, using a switch box, is of little value at all...except maybe for comparing the finer nuances, like clarity of audio in performance. It may also indicate that my range of working heights, close to the house, is too low and maybe too small to be considered being well in the clear. My house is noted by me in the past to seemingly suck the life out of my antennas.
This is my second antenna to compare to my new Gain Master, and soon I'll start adding GP radials to the A99, first 4 x 72" horizontally, and then adding 3 x 102" whips slanted down, and finally removing the 4 horizontals. My previous work of this nature showed me improved signals with more radials added using two GPK hubs.
HomerBB here is a better depiction of the internals for the GM with critical dimensions that you might be interested in.
View attachment Gain Master circuit.pdf
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