Antenna Length

[n4yek]

I am pondering this issue, What, in your opinion, would be the best length to make an antenna for the best reception for mobile installation?
Full wavelength, 1/2 wave, or 1/4 wave (this install would be for 460 MHz and 800 trunk frequencies)

 

[zz0468]

1/4 wave would be best, but that's a 1/4 wave at one band only. I've always had pretty decent luck using a 1/4 high band antenna (18") on all bands. Performance on low band is pretty marginal, but where i am, the signals I've wanted to listen to were strong enough that I didn't need to care.

 

[prcguy]

Only one of your three choices will match to 50ohm coax which is the 1/4 wave. The 1/2 wave and full wave would be very high impedance. A full wave vertical whip would also have a null at the horizon where you want the main lobe. As zz suggests, a 1/4 wave VHF antenna acts as a 3/4 wavelength antenna at UHF and will match ok to 50ohm coax however it will have a slight null at the horizon.
prcguy

 

[N1BHH]

A UHF quarter wave would work quite well, just a six inch spike would work nicely. It would work as a half wave in the 800 range and give you decent coverage.

When people say they want a quarter wave antenna, they need to specify for which band. You want UHF and 800 and what I suggest may be the best for you. I have used a quarter wave on VHF and had excellent UHF and 800 reception mounted on the roof of my van, which is the best place for any antenna.

The formula for a quarter wave is 2808/frequency in MHz. giving you length in inches.