Thanks for the replies. Like you I don't put much faith in published antenna specs.
Would depend on the vendor. Most of the name brand LMR antenna manufacturer specs can be trusted.
The issue was that the hobby/ham grade antenna manufacturers discovered that people would believe outlandish specs and buy the antennas based on that alone.
When I asked the question I was thinking more along the lines of; most people would expect a vertical antenna at 40' to out perform the same antenna in the same location at 20' and wondering if that applied to mobiles.
For a base station/repeater, yeah, higher antenna gives you more distance to the radio horizon.
But on a vehicle, going from ~40 inches to ~60 inches really isn't going to change enough to be noticeable. The additional flex would reduce the performance even more.
Motorola had some interesting "elevated feed" antennas that extended the radiating element about 20 inches up off the mount. The local PD where I grew up used those and they seemed to work OK, but those antennas took hell hitting tree branches/parking garages.
But knowing there are always gotchas in radio e.g. the effect of deformation at speed. Sounds like for mobiles there's not much practical difference which is fine. I would rather not have to deal with a 60" antenna anyway.
Yeah. A long time ago I decided to start playing around with antennas.
My first 2 meter mobile was hooked up to a 'free' Larsen LM-150 5/8th's wave antenna. It worked well, but it was about 45" tall and it would hit a lot of things. I switched to a 1/4 wave that I bought at a hamfest and didn't notice much reduction in performance. I played around with different types of antennas on 2 meters and UHF, and I kept coming back to 1/4 wave antennas as a nice performing antenna or my area (valley) and less problems with clearance. Low profile (visually) was a bonus.
I knew other hams that got hung up on the gain/ERP numbers and would buy the giant antennas and claim huge improvements, but I never really saw that much difference, plus there was the absolute "dork" factor. As a single 20 something year old, I didn't need the dork factor.
A lot of the stuff that impacts mobile antenna performance is the repeater antenna system design. Consider that most public safety systems are designed for some level of street level/indoor coverage for a portable radio worn on the belt. That usually translates into really great coverage for a mobile with a 1/4 wave properly mounted on the roof.
Usually the limiting factor for mobile radio coverage is not antenna gain/ERP, it's distance to the radio horizon. Usually the horizon runs out before the RF power/ERP does. Sure, a bit of gain can help when you are out on the plains and have a long reach out to the horizon, but most public safety systems are not designed for that. Since most hams use repeaters, a lot of the antenna gain they want goes unused.
In LMR stuff, often the operation area of the license is limited, and sometimes you'll see ERP limits called out on the license. No reason to blast your signal way outside the necessary coverage area.
You can often get some pretty good clues by looking at what the local public safety agencies use. Around me, it's very rare to see anything but 1/4 wave antennas, but this area has a lot of hills/mountains with high repeaters.
If I lived out in Kansas where I could watch my dog run away from home for 3 full days, I might have a different opinion. But here in the hilly/mountainous Western USA, I've been totally happy with a simple 1/4 wave.
