Batboard

What would be the best antenna to boost the signal strength on a 45W CDM1250.

To provide an intelligent answer we need to know:

1. What band the radio operates on?
2. If you're running the radio in a fixed or mobile station?
3. If it's fixed how high can you put the antenna?
4. If it's fixed how long the feedline would have to be?

And anything else you can think of that would help.

Tom in D.C. wrote:To provide an intelligent answer we need to know:

1. What band the radio operates on?
2. If you're running the radio in a fixed or mobile station?
3. If it's fixed how high can you put the antenna?
4. If it's fixed how long the feedline would have to be?

And anything else you can think of that would help.

The band is VHF High - 136-174MHz
It is a mobile install.
Primary operating frequecy range is from 150-160MHz.

A 19" 1/4 wave whip provides no gain. It radiates in a nice donut shaped pattern. 45 watts in = 45 watts out.

Every 3dB of gain doubles your effective radiated power. However it also squishes your radiation pattern to do that. It focuses more power straight out as opposed to up. So if you get a 3dB gain antenna, 45 watts in = 90 watts out. These are about 52" high with a base coil. I've never seen anything beyond 3dB gain for VHF. I just checked antenex, comtelco, and Larsen. 3dB is the most you will get.

And honestly, it isn't going to make that much of a difference. some weak areas might sound a little better but thats it. Height of the base station is the big thing.

The CDM Series mobiles actually have a Pre-Amp installed in them, which makes them generically recieve so well, so an antenna with some decent gain should provide for a nice signal - but as nmfire10 stated, not much more than 3db exists. I've seen some hammy-grade antennas (ie comet, diamond, etc) claim up to 5/6 db, but I wouldn't recommend using those.