Using a CDM1250 for a repeater

[HRN]

I have been kicking the idea around of setting up a vehicle repeater because of not being in a good area working and having to operate on portable radios. I was thinking I needed to get something like a Pyramid repeater like we have in our Rescue, however, as I was sitting here, I just happened to think that this should be possible to do with 2 CDM1250s. I have a UHF and a low band. My goal is to have the UHF act as the repeater into the low band radio. Three questions: 1. Is this possible? 2. What do the code plugs need to look like? 3. What accessory pins get used on each radio?

Thanks in advance for any help or guidance. I can't see spending money on a repeater if I can do this all with the two radios I have.

Jason

[Jim202]

I have been kicking the idea around of setting up a vehicle repeater because of not being in a good area working and having to operate on portable radios. I was thinking I needed to get something like a Pyramid repeater like we have in our Rescue, however, as I was sitting here, I just happened to think that this should be possible to do with 2 CDM1250s. I have a UHF and a low band. My goal is to have the UHF act as the repeater into the low band radio. Three questions: 1. Is this possible? 2. What do the code plugs need to look like? 3. What accessory pins get used on each radio?

Thanks in advance for any help or guidance. I can't see spending money on a repeater if I can do this all with the two radios I have.

Jason

It sounds like your forward thinking is getting you outside of the technical abilities of the CDM radio. I will state that you COULD use any radio and make a repeater out of it. The problems come up when you start looking at the duty cycle of the transmitter in a repeater service. In some cases, this duty cycle could approach 100% TX time.

The CDM radios will not survive long under this condition. They were never designed for that type of transmitter on time duration. Your looking at over heating and a good chance to burn out the PA and driver stages of the transmitter.

You didn't mention where or in what service this radio idea of yours was going to be used in. You get into the issue of the issue of a radio license for this repeater operation. Need to walk carefully on this idea of yours. It could open up several cans of worms that you might not be thinking about.

Jim

[HRN]

Thanks for the udpate/info. I'm the Assitant EMS Coordinator at an EMS Agency. I'm an autorized radio transmitter on the low band frequency and we currently have 2 UHF repeater frequencies licensed to our EMS Agency. This would be in my response vehicle and would be used for limited, short transmissions, roughly 3-4 seconds at a time. Basically, it would be to provide an incoming unit on where to park, what equipment is needed, etc.

If it would be better just to go with a different route, what would you recommend? I'm doing this at my own expense and not submitting it to the Agency for reimbursement, since this is for my benefit and playing around.

Here is the current equipment I have installed, or access too:
1. Installed - Motorola Maratrac low band with siren driver
2. Not intalled - PM1200 low band that I'm looking to replace the Maratrac, if end up getting a stand-alone siren driver.
3. Not installed - CDM1250 low band
4. Not intalled - CDM1250 UHF

I was going to initially try to use a Pyramid SVR200 (find a cheap, used one) with the PM1200 or CDM1250, but then I saw the Motorola RICK and it looked like it would do the same type of thing with two radios, but I have no experience with them or ever even seen one and am not sure about hooking it up.

If this would work out in a fashion I could do relatively cheaply, I would like to put a seup in our paramedic unit since they respond as a single provider and are on scene prior to any ambulance. This way, if they got to a call and things go south, need police backup, patient crashes, etc, they would have the ability to reach someone with a portable radio. I know we could have a communications company come in and setup us up with what I want for around $1,500, but we have limited funding. We receive no municipal support and rely on 3rd party billing.

Thank you,
Jason

[ard099]

Using a Rick module with 2 CDM's will work great. I have personally done this with numerous vehicles and will be glad to help with you with whatever question you need answered about the setup. The only downside is if you are planning on using multiple vehicles with this setup then you need to be careful and coordinate who will have their Rick module on.

[TreyH]

Not to hijack the thread, but I'd like to do the same thing the op is asking only I need to use a VHF CDM1250 to UHF XPR4550.
VHF Portable <--> VHF CDM1250 <--> UHF XPR4550 <--> MotoTrbo Site Connect System

[Will]

If you want to use a R.I.C.K. I have one here that needs a good home....

Otherwise we use a modified ID-O-Matic II. http://www.hamgadgets.com/index.php?mai ... 0qcvrfaf61

I have the mod and install directions here on .pdf.

[arnu]

This should work without any problems.

The duty cycle is not an issue since this is a crossband repeater and the transmitters will only be on during the timeperiods someone is pushing the PTT on the remote radio (lowband or UHF).

[thebigphish]

Ok, and if it's repeating an active scene, or a long winded diatribe...the duty cycle will absolutely be an issue.

[dbusse]

Simply throttle back the RF output of the UHF radio to 50% or less rated output power and you'll be fine.

I use 2 CDM's as repeaters all the time in VHF and UHF. Works fantastic. We have about 6 of then set up in Pelican cases for SAR ops.

Dan

[ard099]

Well, to answer the original question about the pin assignments etc of the Rick module and radio programming:

Rick module: S2 switch settings- 1,2,6,8,10,11- ON
3,4,5,7,9,12 - OFF
Turn both blue pots fully clockwise.

Low band CDM- Program pin 14 as PL/DPL CSQ detect active level low
pin 3 Ext PTT Active level low
Make sure the time-out timer is active in the radio
plug 16 pin cable from Radio acc port to RX port of Rick


UHF CDM- Program- Program pin 8 as PL/DPL CSQ detect active level low
pin 3 Ext PTT Active level low
Make sure the time-out timer is active in the radio
plug 16 pin cable from Radio acc port to Tx port of Rick.

[ard099]

And to answer your question Trey about the XPR radios- do the same for the Rick settings. Make sure the time-out timer is active. Here are the pin assignments for the XPR, plug 16 pin rick plug to RX port of rick.

Ground Pin 8 of radio to pin 7 of rick plug
Tx Audio Pin 11 of radio to pin 2 of rick plug
PTT Pin 17 of radio to pin 3 of rick plug
Switched B+ Pin 7 of radio to pin13 of rick plug
Rx Audio Pin 14 of radio to pin 11of rick plug
COR Pin 19 of radio to pin 14 of rick



VHF CDM- Program- Program pin 8 as PL/DPL CSQ detect active level low
pin 3 Ext PTT Active level low
Make sure the time-out timer is active in the radio
plug 16 pin cable from Radio acc port to Tx port of Rick.

[HRN]

Thank you ard0999 for taking the time to supply me with this info. I appreciate it, as the repeater side of things are all new to me.