I've recently been looking into getting a CDM1250 and I'd like to make the equivalent of a HAM Go Box, but for a commercial band radio. This would be for public safety and commercial use. I remember seeing a few on eBay a while back that were pre-built but I have been unable to find them since. I'm interested in building my own but I am unsure whether this would even be a feasible option. My hope is to have a unit that could be charged from a standard wall outlet but have its own dedicated power supply. Could anyone point me in the right direction?
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CDM1250 Install in a Pelican Case
- Thread starter alexjusti
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DeoVindice
P25 Underground
You'd be looking for an external battery, probably LiFePo4 for light weight if you're willing to pay the price. Power cords and fuses, battery charger with 110VAC plug, antenna solution, maybe a cooling fan if you anticipate a heavy duty cycle. There are lots of folks out there who have built portable repeaters, this project won't be too different from a support/utility perspective.
mmckenna
I ♥ Ø
This is one I did for our OES.
It's a Motorola power supply and speaker connected to a Kenwood NX-900 800MHz trunking radio. There's no internal battery, but that's not an issue in our EOC. This was intended to be a loud radio that could be set up and used to monitor various groups as needed, as opposed to using a handheld.
Adding a battery would be easy, but you'd want a 12 volt supply with a battery revert circuit.
Depending on what you use it for, you need to consider air flow. Radios won't be happy packed tightly in a Pelican case with no airflow unless you have the RF output turned way down.
It's a Motorola power supply and speaker connected to a Kenwood NX-900 800MHz trunking radio. There's no internal battery, but that's not an issue in our EOC. This was intended to be a loud radio that could be set up and used to monitor various groups as needed, as opposed to using a handheld.
Adding a battery would be easy, but you'd want a 12 volt supply with a battery revert circuit.
Depending on what you use it for, you need to consider air flow. Radios won't be happy packed tightly in a Pelican case with no airflow unless you have the RF output turned way down.
The issue I've been encountering is how I'm going to charge the battery. What kind of setup would I need for a battery backup?
I am looking into drilling into the case to have charging take place without the case being open. I'm assuming this will be more wiring but I'll definitely want to have that ability.
DeoVindice
P25 Underground
Any quality charger for the type of battery you select will do the job. You'll need to match charger and battery charging voltage (12V vs 24V).
As mmckenna posted, a 12V power supply will be a must if you want to run the system directly off of 110VAC without drawing from the battery. Your wiring should allow you to switch between wall power and battery power. Could be a switch, could be alligator clips - that depends on how elegant of a solution you'd like.
DeoVindice
P25 Underground
Look at cable pass-throughs for a cleaner install and some weather resistance.
mmckenna
I ♥ Ø
You can get chassis mount IEC type (computer) connectors. That's pretty standard. Or, you can get a marine on board battery charger socket. It's designed to mount through a fiberglass hull and allow you to plug the female end of a standard extension cord into it.
You can use any standard 12 volt power supply to power the radio directly. Switching power supplies will be smaller and lighter. Get one big enough to power the radio and charge the battery. So, radio current draw at transmit + a few amps extra to feed to the battery. Keeping the RF output low is a good idea, since it reduces heat and means you can run a smaller/lighter power supply and battery. Put the effort into better antennas rather than higher power. A CDM running at 25 watts will pull 7-8 amps when transmitting. That'll leave a few amps to charge your battery.
For connecting to the battery, you can use something like this: Emergency Relay/Charger | 12V DC | 24V DC | Emergency Radio Tie-in to Battery | Newmar Powering the Network
That will charge the battery when your power supply is plugged in, and allow the battery to run the radio when you are not plugged in.
I've been looking into different types of PwrGate options. I found one (PWRgate Battery Backup DC Power Switching System PowerPole Amateur Ham Radio | eBay) and I do know that this doesn't allow the battery to charge like the more expensive systems. Could I add a separate charging circuit?
mmckenna
I ♥ Ø
You could.
But you can do better. Personally I'm not a fan of those small Andersen Power Pole connectors. All the guy is selling is a relay with preinstalled connectors. You could make your own cheaper.
There's a few companies that sell "Battery Revert" power supplies that have it all built in to the box. There are some larger units that even have the battery pack enclosed in the same housing as the power supply.
I have built a system with a lifepo4 battery and a power supply with trickle charging and battery backup capabilities. However my only drawback now is that the radio has to be powered on by AC power before it can be run off of the battery backup. Is there a way to make a switch to turn the radio on from the battery in the event that an AC source is not available?
You should not need 110vac to turn on a CDM under any circumstances. Just press the center of the volume knob to turn it on or off. As long as there is adequate current available from the battery, you should be fine.
If you want a remote on/off capability, run a 12vdc line from battery hot to pin 10 on the accessory connector. Put a simple on/off switch in that line and you’re all set. Fuse it at no more than 3 amps. The main hot to the radio should be fused at 15 or 20 amps depending on the power rating of the radio.
Make sure the radio is programmed for on/off and ignition sense.
You can buy a plug for the accessory connector prewired for ignition sense from seller mre1032 on ebay if that will make it easier for you.
If you want a remote on/off capability, run a 12vdc line from battery hot to pin 10 on the accessory connector. Put a simple on/off switch in that line and you’re all set. Fuse it at no more than 3 amps. The main hot to the radio should be fused at 15 or 20 amps depending on the power rating of the radio.
Make sure the radio is programmed for on/off and ignition sense.
You can buy a plug for the accessory connector prewired for ignition sense from seller mre1032 on ebay if that will make it easier for you.
The radio isn't getting powered directly from the battery. The AC in runs to the PSU and the PSU powers the radio and trickle charges the battery. The PSU then takes battery power and the battery takes over if the AC power fails. Is there a way to bypass the PSU and power the radio with battery power? I'd have to make a switch to bypass the PSU but I'm not sure how.
Buy a commercial "PowerGate-type" switching device. These will allow operation via the AC/DC converter, with auto-switching to the backup battery if no AC power, and trickle charge the backup battery at the same time.
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