SQUELCH ISSUE

[W0RS]

I have run into an issue I have never had before so I need a little more expertise with it. The transceiver is a micro mobile made by Midland in the GMRS radio frequencies. There are two locations where the antenna was tried, both locations are NMO mounts, one is located on the front right fender area, and the other on the right rear top hatchback roof, I say roof because it’s mounted at roofline on the corner of the hatchback.

When the antenna is mounted on the right fender, the squelch on the radio works as it should, but when I put the antenna on the rear hatchback, I get open squelch. The radio is set at the highest setting but does no good. Does anyone have any suggestions what I could try in order to troubleshoot? 🤔🤔

 

[mmckenna]

Sounds like it's picking up noise from something back there.
What sort of vehicle is this?

 

[W0RS]

Sounds like it's picking up noise from something back there.
What sort of vehicle is this?

It’s a Acura RDX, I also have two other antennas back there, one is for
a Yaesu 400XD and the other is a scanner, no issue with either. When it gets warmer I might pull coax and reroute….

 

[Hans13]

It’s a Acura RDX, I also have two other antennas back there, one is for
a Yaesu 400XD and the other is a scanner, no issue with either. When it gets warmer I might pull coax and reroute….

AFAIK, the Midlands are direct sampling receivers, as opposed to heterodyne receivers, which means they are not as selective and are more susceptible to interference/noise. Also, you could move an antenna slightly and change the RF circumstance; the antennae are not occupying the exact same physical space. Same goes for the different coax, different mounts, where the coax runs, etc. While it is diagnostic that the other two don't have issues, it is not definitive.

 

[W0RS]

Well, I found the problem today. I have a remote battery that keeps the dash cam powered up, when I unplug the battery, the open squelch on the midland radio goes away. I now need to find a filter….

 

[mmckenna]

Well, I found the problem today. I have a remote battery that keeps the dash cam powered up, when I unplug the battery, the open squelch on the midland radio goes away. I now need to find a filter….

If it's a 12 volt cigarette lighter to USB adapter, those are notorious for being annoying little noise makers. My son had one that would take out the tire pressure monitoring system on my wife's old car. Didn't impact the Motorola radio in it, however.

 

[W0RS]

If it's a 12 volt cigarette lighter to USB adapter, those are notorious for being annoying little noise makers. My son had one that would take out the tire pressure monitoring system on my wife's old car. Didn't impact the Motorola radio in it, however.

No, this one is hardwired ☹️

 

[mmckenna]

No, this one is hardwired ☹

OK.
But the dash cameras probably don't use 12 volts natively. There's probably a voltage regulator inside the camera that is converting it to 5vdc.
Same circuit, just built in, and apparently making a lot of unwanted noise.

 

[AK9R]

If it's a 12 volt cigarette lighter to USB adapter, those are notorious for being annoying little noise makers.

I had one that wiped out the 2m amateur radio band. On the suggestion of people in this forum, I bought one with the Anker brand. It was a little more expensive than the others, but it seems to be clean RF-wise.

 

[W0RS]

OK.
But the dash cameras probably don't use 12 volts natively. There's probably a voltage regulator inside the camera that is converting it to 5vdc.
Same circuit, just built in, and apparently making a lot of unwanted noise.

What's odd, is if I connect a mag mount antenna and place it on the roof of the car, the radio squelch is fine, but If I have it on the hatchback mount the noise comes back....🤔