Got my 2m/220/440 Compactenna today and did a quick check of receive levels using an Icom R8600 in dBm meter mode. I used an Austin Metropolitan tri band as a reference, which is simply a resonant 1/4 wave on 2m, 220 and 70cm and about 19" tall.
The antennas were used on the same NMO mount at the rear bed toprail of a pickup truck, which has very poor ground plane. A reading was made on various repeater output freqs on 2m, 220 and 79cm and antennas were quickly swapped while receiving the same repeater. Repeaters were coming in from various directions, some line of sight and some blocked by hills.
The numbers below are how much better or worse in dB the Compactenna is over the Austin. -2 would be the Compactenna being 2dB worse at that frequency and a +2 would be the Compactenna is 2dB better than the Austin.
2m,
0
+1
0
0
220MHz
-3
-4
-2
-8
70cm
-7
+3
+8
0
-2
-8
+2
-12
I find this very interesting. On 2m it looks almost a wash with a slight edge to the Compactenna, otherwise both antennas were performing about the same. On 220 the Compactenna was consistently worse than the Austin by 2 to 8dB. On UHF its all over the place with slightly more stations coming in weaker and to a greater depth of weaker than the Austin, but overall they might actually be close with an edge going to the Austin.
Did I mention this is very interesting? Especially comparing a 7 1/2" tall antenna to a 19" tall antenna. All this testing was done within minutes of receiving the new Compactenna. I need to do more testing with a mount that is centered on my roof and in an area clear of hills, etc, but at least I have some initial info that is fairly positive for this expensive little (and fat) antenna.
I'm also a little concerned with the aluminum threaded portion that mates with the NMO mount. I fear it will corrode over time if left on the vehicle and in the rain. Handling the very lightweight antenna doesn't give you the warm feeling that you spent your money well, but time will tell on the performance.