Thought I'd run a comparison of a few of my NMO antennas. Thanks to the color coding of the signal strength with a SDR it's quite easy to compare antennas against each other.
Digital modulation is key here; analog would show too much variation unless it's a dead carrier. IWN (P25 control channel) and TRBOWest (MotoTRBO control channel) were the two handiest candidates. VHF is 167.6875 and UHF is 454.01875.
Antennas used:
Antenex ABSCANC "All band" scanner antenna
Laird A150/450C VHF/UHF
Maxrad MUF4505 UHF
Motorola HAE4003A UHF
PulseLarsen W-490B VHF
Tram 1150 VHF
VHF:
Click to enlarge
UHF:
Click to enlarge
Note I didn't have the gain turned up as much on the UHF tests. Doesn't really matter though since the point is to compare the antennas against each other; the gain was at the same setting for all antennas.
Not sure what was going on with the Maxrad in the UHF tests. I've had it perform better other times; seems like there's a case for revisitng this.