Distorted P25

[WX9EMT]

I have an XTL-5000 running P25 on VHF. I had no issues when this radio was installed in my old truck. What is happening is I will lose reception randomly even if I am near a tower and the audio comes in is heavily distorted at times. Here is an example of what I hear:

I have checked the SWR of the antenna and it is 1.2:1 and made sure all the connections are solid. The old truck was a F150 and this one is a Ram 1500. I put a few ferrite beads on the antenna coax and all the power leads with no change. Shot in the dark so I figured why not. I have new coax coming as well as a new antenna. Any help will be appreciated.

 

[hill]

More than likely something in truck.

Virginia State Police really wanted a car to replace their Fords cars a number of years ago rather then a SUV and tested a Dodge Charger.

Virginia uses a VHF P25 Trunked Radio System for State Police.

The Dodge Chargers tested had terrible interference to their VHF Trunked Radio System and so much that the State nixed the Chargers not being suitable and went with Ford Police SUVs instead. A Google search will most likely be able to provide you with this news item of Virginia Stste Police not being able to use Dodge vehicles.

In closing I would think it's something in Dodge vehicles systems that don't play nice with receive on installed VHF radios.

 

[n7maq-1]

Has Hill said, it sounds like RFI. Do you have the issue with the truck off? Lights on/off? Try the brake also. I know it can be a pain to troubleshoot without a constant signal. Try moving the antenna to see if that helps, I doubt it will if the RFI is local to your truck.

When was the last time you had the radio aligned?

Jim

 

[WX9EMT]

More than likely something in truck.

Virginia State Police really wanted a car to replace their Fords cars a number of years ago rather then a SUV and tested a Dodge Charger.

Virginia uses a VHF P25 Trunked Radio System for State Police.

The Dodge Chargers tested had terrible interference to their VHF Trunked Radio System and so much that the State nixed the Chargers not being suitable and went with Ford Police SUVs instead. A Google search will most likely be able to provide you with this news item of Virginia Stste Police not being able to use Dodge vehicles.

In closing I would think it's something in Dodge vehicles systems that don't play nice with receive on installed VHF radios.

That's what I was worried about. I know the injectors are a big problem as they aren't shielded. Was just hoping it was something else. On analog I can hear a constant ticking. I have not noticed if it does it when the vehicle is off.

Has Hill said, it sounds like RFI. Do you have the issue with the truck off? Lights on/off? Try the brake also. I know it can be a pain to troubleshoot without a constant signal. Try moving the antenna to see if that helps, I doubt it will if the RFI is local to your truck.

When was the last time you had the radio aligned?

Jim

The radio was never been aligned while in my possession. So not in the last 5 years. I reached out to our radio shop to see about having it tuned and aligned. The county isn't very busy even on holidays so I will just have to sit at the station one day and troubleshoot slowly.


Antenna is a fender mount and the coax is probably 6-8 years old. It's a comet RG58/U NMO. Part of me is wondering if it was damaged between the removal and install. I have a rack on the roof that I am moving it to. So new mount, new coax, and new antenna.

 

[n7maq-1]

New Double Shield Coax from Larsen or another brand name.

 

[12dbsinad]

That's what I was worried about. I know the injectors are a big problem as they aren't shielded. Was just hoping it was something else. On analog I can hear a constant ticking. I have not noticed if it does it when the vehicle is off.



The radio was never been aligned while in my possession. So not in the last 5 years. I reached out to our radio shop to see about having it tuned and aligned. The county isn't very busy even on holidays so I will just have to sit at the station one day and troubleshoot slowly.


Antenna is a fender mount and the coax is probably 6-8 years old. It's a comet RG58/U NMO. Part of me is wondering if it was damaged between the removal and install. I have a rack on the roof that I am moving it to. So new mount, new coax, and new antenna.

Kinda answered your on question. The "ticking" you hear on analog doesn't go away on digital. Digital is just how the carrier is modulated. Try shutting the truck off and run the radio by itself. It'll probably be fine.

Welcome to VHF. It sucks nowadays. A fender mounted antenna is the WORST place also.. get it up center mounted right on the roof, drilled in, 1/4 wave. The metal roof helps shield RFI if it's being induced thru the antenna system.

 

[WX9EMT]

Kinda answered your on question. The "ticking" you hear on analog doesn't go away on digital. Digital is just how the carrier is modulated. Try shutting the truck off and run the radio by itself. It'll probably be fine.

Welcome to VHF. It sucks nowadays. A fender mounted antenna is the WORST place also.. get it up center mounted right on the roof, drilled in, 1/4 wave. The metal roof helps shield RFI if it's being induced thru the antenna system.

With a storage rack mounted to the roof I can't install the antenna to the roof as it would get destroyed when cargo is tossed up there. The rack is a powder coated steel rack that is bolted directly to the roof, i.e holes drilled. Where the antenna mount is attaching I will be removing the paint on both the rack and the bracket. Hopefully that gives it a better contact area than just serrated lock washers. I know it isn't ideal as a roof mount would. Any suggestions on how to make the mounting location better let me know. I will be on duty tomorrow so I will park the truck outside and see how it is and report back.

 

[MEDIC135]

I have an XTL-5000 running P25 on VHF. I had no issues when this radio was installed in my old truck. What is happening is I will lose reception randomly even if I am near a tower and the audio comes in is heavily distorted at times. Here is an example of what I hear:

I have checked the SWR of the antenna and it is 1.2:1 and made sure all the connections are solid. The old truck was a F150 and this one is a Ram 1500. I put a few ferrite beads on the antenna coax and all the power leads with no change. Shot in the dark so I figured why not. I have new coax coming as well as a new antenna. Any help will be appreciated.

I have the same issue with my Ram, just an RFI issue with VHF that you probably won’t be able to get rid of as I myself have tried many different things and just live with it now 🤷🏼‍♂️

 

[WB5UOM]

Fyi...Ive got maybe 25 newish (22-25) Dodge Durangos with KENWOOD NX-5700 in P25 conv mode...no known issues.

 

[n3obl]

Seems a lot of vehicles are prone to VHF RFI noise now a days.

 

[12dbsinad]

I have the same issue with my Ram, just an RFI issue with VHF that you probably won’t be able to get rid of as I myself have tried many different things and just live with it now 🤷🏼‍♂️

What year Ram? My 2024 2500 display screen radiates RFI all the way up past 460Mhz. Kills my portable sitting in the cup holder.

 

[MEDIC135]

What year Ram? My 2024 2500 display screen radiates RFI all the way up past 460Mhz. Kills my portable sitting in the cup holder.

2019 Classic

 

[WX9EMT]

The noise is not present when the truck is off. The reception issue, "Out of Range" still remains and is still random. Almost like it isn't switching towers quick enough as after a bit it will get reception again. I did check the preferred sites list and the three towers around me are all set to preferred and listed by proximity. I also added some more ferrite beads to the antenna coax, I have a bag of them so why not. One right by the back of the radio, one at the antenna, and one where the coax appears behind the seat. The distortion isn't as bad and is now more sporadic. Clicking on non p25 still remains.

Also the truck is a 2018 1500 Crewcab with the 5.7 if it matters. The previous truck, that had zero issues, was a 2014 F150.

 

[WB5UOM]

you could also play with a temporary mag mount of quality at different places on truck to see if it goes away

 

[wema628]

I run APX 7500 vhf/800 in my Durango and APX 8500 in my 2017 Ram 1500 with no issues with either unit on P25 vhf.

 

[MTS2000des]

Put it on a bench and do a full PM. As old as these XTLs are, you'd be surprised at how many are off frequency, and even 10-20Hz will make a P25 decode wobbly in the face of even a slight RX noise floor or interfering carrier increase.

 

[KE4ZNR]

Put it on a bench and do a full PM. As old as these XTLs are, you'd be surprised at how many are off frequency, and even 10-20Hz will make a P25 decode wobbly in the face of even a slight RX noise floor or interfering carrier increase.

The above. I bet that reference oscillator is off spec. Align it and your problems will probably go away.

 

[WX9EMT]

Put it on a bench and do a full PM. As old as these XTLs are, you'd be surprised at how many are off frequency, and even 10-20Hz will make a P25 decode wobbly in the face of even a slight RX noise floor or interfering carrier increase.

What all do I need to do this? The radio shop my department uses said they no longer have the software to tune and align it.

The above. I bet that reference oscillator is off spec. Align it and your problems will probably go away.

 

[MTS2000des]

With these radios being 20 years old, it's not surprising many shops shy away from servicing legacy radios. From the service manual:
A watt meter
A service monitor with signal generator
An RLN4460 breakout box
The appropriate service cable (outlined in BSM linked above)
A dummy load of the power level handling
Misc cables/connectors adapters as needed
The Astro 25 Tuner software and a computer to run it on

The tuning procedure is outlined in chapter 6 of the above linked manual.

If a service monitor has auto tune software installed for the Astro 25 portable/mobile, this would also suffice.

There are shop's like Sunny's Communications in Longmont Colorado that still support these radios.

 

[WX9EMT]

With these radios being 20 years old, it's not surprising many shops shy away from servicing legacy radios. From the service manual:
A watt meter
A service monitor with signal generator
An RLN4460 breakout box
The appropriate service cable (outlined in BSM linked above)
A dummy load of the power level handling
Misc cables/connectors adapters as needed
The Astro 25 Tuner software and a computer to run it on

The tuning procedure is outlined in chapter 6 of the above linked manual.

If a service monitor has auto tune software installed for the Astro 25 portable/mobile, this would also suffice.

There are shop's like Sunny's Communications in Longmont Colorado that still support these radios.

Ehh yeah I don't have all that stuff. Well the service monitor specifically.