Interference, point me in the right direction.

[Josh00333]

This one is strange. 

After my Midland 275 install I tested all the channels (scan) and had no issues, drove around the block to test it. I took a road trip and after being on the freeway a few min (10 maybe) I got interference on 19. Scan would pick it up and just stay. Very annoying. Got worse to 18-20 all stuck. Tried turning up sq to max hoping it would skip it, no joy.

I moved the head a foot just to see if that helped, nada. 

After my trip took my handheld 905 with me, retested. Driving around w a cold truck no interference on the 905 or the 275. But once the truck is warmed up 10 min or so it comes back in on the 275.

I tried turning off/on AC, turning off the hvac, turning up down the hvac fan, turning off/on car play, turning off the stereo head all together. Nada. 

I'm taking a wild guess I have some power or ground interference that is popping up once the car is warmed up/the alternator is not charging from start up. 

I grounded the head on a factory ground in the cab, took power off the factory supplied ign hot lead (part of the auxiliary switch group). Rig is a 2021 Jeep Gladiator JT. I really like coming off the ign hot, but think I need to run a dedicated hot and ground. 

Thoughts? 

[gortex2]

So first where is your antenna for the 275 ? I run the midland in both my JT and JK and have no issues. Do you have after market LED lights (headlights) by chance. on my JK ii bought ebay LED lights and it killed the 2 mtr band completely. 

 

[maddogrecurve]

On 12/19/2021 at 8:03 AM, Josh00333 said:

This one is strange. 

After my Midland 275 install I tested all the channels (scan) and had no issues, drove around the block to test it. I took a road trip and after being on the freeway a few min (10 maybe) I got interference on 19. Scan would pick it up and just stay. Very annoying. Got worse to 18-20 all stuck. Tried turning up sq to max hoping it would skip it, no joy.

I moved the head a foot just to see if that helped, nada. 

After my trip took my handheld 905 with me, retested. Driving around w a cold truck no interference on the 905 or the 275. But once the truck is warmed up 10 min or so it comes back in on the 275.

I tried turning off/on AC, turning off the hvac, turning up down the hvac fan, turning off/on car play, turning off the stereo head all together. Nada. 

I'm taking a wild guess I have some power or ground interference that is popping up once the car is warmed up/the alternator is not charging from start up. 

I grounded the head on a factory ground in the cab, took power off the factory supplied ign hot lead (part of the auxiliary switch group). Rig is a 2021 Jeep Gladiator JT. I really like coming off the ign hot, but think I need to run a dedicated hot and ground. 

Thoughts? 

I always run wire directly from the battery to my rigs unless it is a portable quick install, then I have used lighter plugs (no good!).  I still get interference sometimes, but not too bad.

Is your antenna grounded?

[Josh00333]

I have factory LED’s.

 

Antenna is a midland one. I don’t have a ground wire for it? But it’s installed via a metal plate bolted to the body?

I do have led lights on the hood but not turned on.

 

[Josh00333]

Quick update. 

In the JT there is a dedicated hot in the cabin, vs running a dedicated power line I figured I would try it. 

Problem solved. 

Note, when I went to power the radio on, it would not turn on?!! WTH?! Metered and had power and ground to the plug... then I noticed on the radio side of the midland power plug the round had come out of the plastic housing. Cut the plug off and direct connected the wires.  

[WROZ437]

I see your problem is solved but I’ll add my experience. I have a 2020 Gladiator with an MXT275 . I have a similar (same) antenna mount (Cool Tech) in the same location with the same Midland antenna. To power the radio I originally tapped the dedicated hot under the glove box, which also powers my dash cam, and used a ground in the cabin, again shared with my dash cam. That was no bueno. I had a lot of interference and I was also worried about the size of the factory hot wire. It was certainly a smaller gauge than the leads on the MXT275. My solution was to run dedicated power and ground through the firewall to the battery. Problem solved. My radio is now crystal clear. I ran 12ga. wire, which was way overkill but I figure I am future proof if I ever want to run a higher power mobile in the future.

[Josh00333]

Ya I used that ground stud at first also, as a part of my eliminating things I went to the dedicated ground wire. While it didn't solve the issue I wonder if it helped any? That studs not used by the factory, I wonder why? Was thinking of going back to it just to eliminate a long wire but as I think it over I'll just leave it. It's working now stop fiddling with it! LOL

The factory hot is 10 amp. The 275 pulls less that 5a on high power. My google fu found:

"Midland MXT275 pulls less than 300mA on Rx, less than 1750mA on low transmit power, and less than 3500 mA on high transmit power (per Midland USA)."

3.5a max goes with what others saying under 5a. That's actually why I went with the 275 vs waiting on the 500. That said now I can't use the temp on I may swap out to the 500 later and move the 275 to my trailer. But that's the future. 

[gortex2]

There are many ground studs in vehicles. Just because there is nothing on it from factory doesn't make it a bad ground. Remember all vehicles use the same body with various options. 

As said before I have the 275 in both the JT and JK. Have no issues with interference. I run a standard NMO on the JT on a back rack and a fender style NMO on the JK. I had tried the cooltech and rugged radio NMO mount on the JK and neither showed continuity to ground after installed so I would guess that could be part of your issues. 

I also use the inside B+ from the JT for my radios.  

[WROZ437]

On 1/24/2022 at 6:33 AM, gortex2 said:

There are many ground studs in vehicles. Just because there is nothing on it from factory doesn't make it a bad ground. Remember all vehicles use the same body with various options. 

As said before I have the 275 in both the JT and JK. Have no issues with interference. I run a standard NMO on the JT on a back rack and a fender style NMO on the JK. I had tried the cooltech and rugged radio NMO mount on the JK and neither showed continuity to ground after installed so I would guess that could be part of your issues. 

I also use the inside B+ from the JT for my radios.  

I went on a road trip over the last few days and it seems I still have some interference with m setup. I ran my power and ground all the way to the battery. I have the cooltech cowl mount and a 6db gain whip. I hear a little whine that corresponds to the engine RPM. My radio also opens the squelch for a lot of transmissions that are not discernable. Sounds like just static or a an open mic but I can't hear talking. Could all of this be ground wire or antenna ground related? I like the location of the antenna but can move it to get a better ground. Could I just add a ground braid? I am unsure with how and when to use different strategies.

I do have a bed rack so I could always move the antenna back there, too, and probably even establish an actual ground plane...

[PartsMan]

Does the interference go away if you pull over and turn off your engine?

[WROZ437]

21 hours ago, PartsMan said:

Does the interference go away if you pull over and turn off your engine?

Yes. It’s directly related to the engine RPM. It’s a faint whine in the background that can be heard when the radio breaks the squelch while receiveing a transmission. 

[PACNWComms]

Noise that changes due to engine RPM is a common issue in other types of radio installation as well. Noise suppressors can help, and it was common to use them with AM Citizen's Band radio, think "Convoy" days. This applies now as well, even with FM radio. Here is a link for Crutchfield, the seller of car stereo equipment, which discusses how to mitigate this problem. https://www.crutchfield.com/S-YvooC7Rfvdw/learn/learningcenter/car/noise_suppressors_installation_guide.html

 

[BoxCar]

BINT (Back In The Day) I built a line filter using a bridge rectifier and a feed-through capacitor to cure the engine noise into my CB. Doubt you could find the electrolytic feed-through cap now.

[PartsMan]

We used to have alternator noise in our car stereos back in high school.

I bet that's it. I agree that some kind of noise filter on the power should help.

[WROZ437]

Thanks @PACNWComms, @BoxCar, and @PartsMan. I’m gonna check out that Crutchfield link. I also did some independent research and have 2 other things I need to check on. I ran power and ground directly to the battery. I need to move my ground to the “bonded jumper” grounding point on the chassis. I may have inadvertently created a ground loop. I also need to check to see if my antenna mount is grounded. The radio in question is mounted in a Jeep Gladiator JT and the antenna is mounted to the cowl. The bolt and mount are steel but the cowl is plastic. The steel bolt is affixed to where the cowl is held to the rest of the body. I assumed this would be a good ground but now I wonder if I don’t have good continuity to ground in that location. I can move the antenna to the fender easily enough although it won’t look as clean. 

[BoxCar]

Rather than move the mount, install a jumper wire from the mount to a good ground point. I would recommend nothing smaller than 14 ga wire.

[WRHV695]

My setup is very similar to Josh's up above using the MX275

Connected to battery positive in the aux switch harness under the Jeep gladiator's glove box area.  Ground is to a grounding post in the passenger kick panel. 

 

I am using a similar cowl mount for the 3db and 6db antenna (I swap them out depending on application).  

 

I get a slight whine when ignition is in accessory or run.  It does not appear to be variable with RPM.  Just a slight whine.  Antenna is not grounded

 

I have tried ferrite coils, etc with no luck. 

 

For you jeep guys, what was the ultimate solution?  

[SteveShannon]

59 minutes ago, WRHV695 said:

I get a slight whine when ignition is in accessory or run.

So even with the engine off you get the whine?

I would start by pulling fuses to see when the whine stops. Check your owners manual first to make sure you won’t set some off kind of anti-theft measure.  

Once you know which circuit produces the whine, then maybe you can figure out how to mitigate the problem. The interference is getting into the radio through either power, ground, or the antenna.  The question will be can you stop (maybe reduce is a better word) it at the source or where it enters the radio?

[gortex2]

I run the 275 in both my JK and JT. On the JK its wired direct to battery for 12V+ and Ground goes to stud next to battery on fender. On the JT power goes to the AUX Switch harness in the front kick panel. Ground is on a stud on the kick panel. Antenna on JK is a stainless bracket on front driver fender at hood with 1/4 wave UHF antenna. On JT antenna is on my light mount on the cowl passenger side. I see no noise on either radio. How is your battery ? I did have some issues on the JK with noise and it ended up being the LED headlights I installed from amazon. I swapped them for Holley ones and no noise sine. I'd definitely double check grounds and the antenna mounts for good ground connectivity. When checking the mount disconnect the antenna cable from the radio so your not using it as the ground.