Why am I not finding any high gain 800 mhz mobile antennas? When comparing vhf to uhf the uhf ones alway have higher gain. The higher the freq the more common the gain but I'm not seeing that in 800 mhz.
3dB are pretty common. Look for the co-linear design, the ones with the coil (either open or closed) about 1/3 of the way up.
5dB are available, also.
Larsen, Laird, MaxRad, Comtelco, etc.
Wait, I thought you were looking for mobile antennas?
If it's base, I've got 9dB base antennas at work. Not cheap, not for most hobbyists, but they are certainly available. Much above that, and you start getting into sector antennas, etc.
I have been using a Laird Technologies TRAB7603 760-870 MHz. 2.7" ABS plastic Phantom Antenna rated at 3dB for years and I couldn't ask for anything better. Many of the cruisers I see have them as well.
the highest gain 800MHz mobile antenna I can think of off the top of my head is a 5/8 over 5/8 over 1/4wave. common back in the day for cellular phones. they can be found in both elevated feed(No ground plane needed) or with out the elevated feed:
In a mobile environment, you should not require more than 5dB gain. There is less than a S-Unit difference between a 1/4 wave antenna and the three section high gain antenna.
Physics and terrain will limit what you can or can not hear more than a low or high gain mobile antenna at 800MHz