For the frequency range you are using, a full length 1/4 wave whip antenna would range from 2.37m at 30MHz to about 81cm at 87.975Mhz. When you shorten an antenna considerably its efficiency goes way down, so a whip closer to its natural full 1/4 wavelength and with no lossy matching circuits would work the best.
Since you are using what sounds like VHF lo band FM military radios with 25KHz channel spacing, antennas for these come in various sizes and have some complex matching circuits in them to cover the wide frequency range and those circuits can be quite lossy, further degrading the antenna performance.
Even though all your antennas are rated for the entire frequency range, for best performance use the longest one (150cm) when your operating frequencies are in the 30-60MHz range, the 80cm long antenna when you are in the 70-90MHz range and if you have one in between size use that around the 50 to 70Mhz range.
I play a lot with similar radios to yours and at 50Mhz where a 1m long antenna on a hand held radio can communicate 30mi to a mountain top, switching to a 33cm long antenna just doesn't work at all.
If you were using radios in the higher VHF band like 136 to 174Mhz where a full 1/4 wave antenna is much smaller and around 41 to 52cm, you can use a full size 1/4 antenna with no lossy matching circuits and get very good performance.
Height is also important in the frequency range you are using and getting the antenna up high in the air will have the most impact on increasing range with your radios.
prcguy
Hello,
During my work I have to use multiple radios in the VHF low band and with each radio we have a combination of antennas, each antenna will work with any of the frequencies used on these radios.
My question is, what are the benefits of using either the shorter or longer antennas that I have available?
(Frequency band is 30mhz to 87.975mhz and antenna size is 80cm to 150cm, power is 0.1, 1, 2 and 5watt)