Moto CDM1250 Antenna Wire and Connectors

bigdoggg · Feb 9, 2016

Ok guys,

I have a Motorola VHF CDM1250 that I use for monitor only for a scanner live wed feed. The Antenna for this radio is currently located inside of the metal fire house building due to the cable not being long enough on the radio to make it outside to the roof. This being said, receiving radio traffic is very hit or miss.

I need to know what kind of cable I need to run this antenna approx 150' outside our building and onto the roof, what kind of connector I need to plug this cable into the back of the radio and lastly what kind of adapter do i need to hook this new wire up to the current antenna which is a standard magnetic mount antenna.

Thanks

mmckenna · Feb 9, 2016

The connector on the back of the CDM-1250 is a "mini-UHF".

It's very important that you do not try to connect heavy coaxial cable to this connector, they are notorious for breaking. Use a short jumper of RG-58 with a male mini-UHF on one end and a female N connector on the other. Motorola sells these, but you can either make up your own or order one on line. For a short jumper RG-58 is fine. Make it about a foot long.

For a 150 foot run on VHF, I'd use LDF4-50A 1/2" Heliax with male N connectors on each end. Even though it's for receiving only, you don't want to go through all the trouble of installing that much cable and have it be something you have to change out later on when you decide to use it to transmit. You could also do LMR-600, might save you a fraction on the cost.
If receiving is the only thing you'll ever do, you might get away with LMR-400, but you'd be crippling your system.

I'd design for future transmitting use if I was in your shoes.

mmckenna · Feb 9, 2016

I'll add this....
If I was doing this as a completely new installation, I'd probably be considering 7/8" heliax for a run that long, but it's overkill if you guys have been using an antenna inside the building for this long.
If you do a lot of simplex work, you want lots of good signal. If your dispatch channel is repeated, then you'd get away with 1/2" heliax or even the LMR400, key thing to remember is that the repeater systems are often designed for coverage with a 5 watt hand held radio, so you can get by with a lot less.

vans113 · Feb 9, 2016

mmckenna said:
The connector on the back of the CDM-1250 is a "mini-UHF".

It's very important that you do not try to connect heavy coaxial cable to this connector, they are notorious for breaking. Use a short jumper of RG-58 with a male mini-UHF on one end and a female N connector on the other. Motorola sells these, but you can either make up your own or order one on line. For a short jumper RG-58 is fine. Make it about a foot long.

For a 150 foot run on VHF, I'd use LDF4-50A 1/2" Heliax with male N connectors on each end. Even though it's for receiving only, you don't want to go through all the trouble of installing that much cable and have it be something you have to change out later on when you decide to use it to transmit. You could also do LMR-600, might save you a fraction on the cost.
If receiving is the only thing you'll ever do, you might get away with LMR-400, but you'd be crippling your system.

I'd design for future transmitting use if I was in your shoes.

I back this 110% hit the nail on the head

Moto CDM1250 Antenna Wire and Connectors

bigdoggg

Member

mmckenna

I ♥ Ø

mmckenna

I ♥ Ø

vans113

Member

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