CDM1550LS+ vs simulcast

[SteveC0625]

Our county has been phasing in multi-site simulcast repeaters for fire and ems operations. It’s all conventional VHF. I just setup a CDM1550LS+ for one of the new channels and for some reason the radio is not hitting the repeater. A CP200XLS hits it just fine. Newer Motorola mobiles also work fine.

A fire chief tells us that they encountered similar issues when updating their CDM1250s. Their radio shop did not give an answer pointing to any specific reason that the Pro series would encounter this problem.

Is anyone aware of an actual cause for this?

 

[mmckenna]

We used them for years locally on simulcast VHF.

Since these radios are pretty old, has anyone put them on a service monitor?

 

[KevinC]

Our county has been phasing in multi-site simulcast repeaters for fire and ems operations. It’s all conventional VHF. I just setup a CDM1550LS+ for one of the new channels and for some reason the radio is not hitting the repeater. A CP200XLS hits it just fine. Newer Motorola mobiles also work fine.

A fire chief tells us that they encountered similar issues when updating their CDM1250s. Their radio shop did not give an answer pointing to any specific reason that the Pro series would encounter this problem.

Is anyone aware of an actual cause for this?

In analog simulcast all the "magic" is done at the sites, I can't think of anything that would keep any radio from working (assuming all the programming is correct). Unless it's a pre-emphasis/de-emphasis issue, even then it would probably still work.

 

[jeepsandradios]

Same here. We use CDM1250's on our SAR system thats simulcast with no issues. What seems to be the issues ? Should not matter if there is 1 site or 10 same TX channel from the subscriber. Possibly the 1550 needs tuned ? I had a 1250 go to the EEPROM last week after years of use.

 

[nhfdcadet]

based on the fact that a portable is working fine and a mobile is not, I'd say its either programmed incorrectly, or the mobile itself is toast. OR it could be an antenna problem. But I'd start with programming and checking power output from the radio.

 

[SteveC0625]

OK, problem solved. I programmed up 3 CDM's; a 1250, a1550, and a 750. They all worked correctly on the bench. Another gent brought a known good XPR to the party. All four radios performed identically, hitting the repeaters just fine on multiple channels. But they all failed to reach the repeater when installed in the car. I was worried that my ignition sense and external speaker wiring for the CDM's was the culprit. Not the case.

The vehicle is a just retired 2019 Tahou that had seen duty with a neighboring county's sheriff's department and then our own local PD. Something must have happened when pulling the PD's gear to both antenna cables. It has a pair of NMO's with a quarter wave VHF spike and a 5/8 wave VHF spike. Both now show either open or short to ground on the center conductor. Our bad for expecting antennas and cables that apparently worked a month ago to still be serviceable.

We grabbed another antenna and cable and hooked it up. The radio immediately hit the repeater on the primary ems channel and on local fire repeaters. We're totally abandoning both original mounts and cables and just weather capping the NMO's.

We're repurposing this car as a short-term ems fly car to expand the ambulance company's response capability in our rural area. If all goes well, it should be replaced with a new vehicle within a year or two.

Lessons learned and I thank all of you for offering potential solutions.

 

[ac4rw]

What are you using now? Magmounts?
It wouldn't be too time-consuming to replace the NMO mounts and cables entirely.

 

[SteveC0625]

The other gent tossed in a fender mount for now and we'll revisit it when there's more time after the car is fully outfitted. We still need to set up the cargo area for ems gear and install a RAM mount for an iPad. We need the car fully in service in a week or two and both of us have limited hours available to finish the work.

I personally am not a fan of fender mounts as they tend to have a lopsided radiation pattern but it's a quick fix until we can install another roof mount NMO and seems to work OK. It's not what younger me would do and there are other opinions and personalities in the mix, but since the car only has to last for a year or so, it's not a hill I want to die on.

 

[mmckenna]

You probably know this, but 5/8th's wave antennas will read a dead short across the coil. I'm assuming you tested with the antennas removed?

But, no, not surprising. We recently had an upfitter remove some Kenwood TK-5710's and replace them with Harris XL's. Out of the 10 vehicles, only one complete radio/cable package survived. There's very little effort made to protect the wiring/cable when they assume the vehicle is going to go to some auction.

 

[Project25_MASTR]

The other gent tossed in a fender mount for now and we'll revisit it when there's more time after the car is fully outfitted. We still need to set up the cargo area for ems gear and install a RAM mount for an iPad. We need the car fully in service in a week or two and both of us have limited hours available to finish the work.

Probably one of those things that should be fixed while the vehicle is in a semi-decommissioned state. Too many times have I had to deal with an upfitter that installed 3/8" mounts or other antenna mount solutions that are unserviceable with the partitions in the vehicle and the options are either abandon in-place or rip everything out just to get to the underside of the antenna mount.

 

[jeepsandradios]

As said it shouldnt' take that long to replace the NMO. Alot of times You can pull the mount and use the cable as a fish for the new cable. Glad you found the issue

 

[12dbsinad]

You probably know this, but 5/8th's wave antennas will read a dead short across the coil. I'm assuming you tested with the antennas removed?

But, no, not surprising. We recently had an upfitter remove some Kenwood TK-5710's and replace them with Harris XL's. Out of the 10 vehicles, only one complete radio/cable package survived. There's very little effort made to protect the wiring/cable when they assume the vehicle is going to go to some auction.

This is my "beef" with upfitters and not professional radio installers. A check of the antenna system after install should always be performed and proper within spec VSWR noted upon completion. However, most have no idea and you get what you get.