TPMS and radar

**sourdough** · 10-29-2017, 03:50 PM

Just had a weird thing happen today and wondered if anyone had encountered it before. I was driving down the highway and saw a state trooper coming down the access road on my right toward me. He hit the side of the road and pulled into what appeared to be his "sitting spot". Just as he was stopping and I was coming upon him, about the time he would hit his radar (as I witnessed so many times in the many, many miles I drove with a detector) my tpms (tst 507) started squawking and quit monitoring one of the tires. I had to turn it off and let it reboot to get it back. After thinking about it DW and I both figured it was when he hit the radar that the tpms module went bonkers. Since they both work on radio frequency it was the only thing I could figure.

Ken / Claudia · 10-29-2017, 06:06 PM

I do not know if that is what happened but, wanted to add during any of the many radar training classes that I have had. That was never mentioned as something that could happen.

bobbecky · 10-29-2017, 09:44 PM

The only likely thing that might have happened was the radar transmitter accidentally acted as a jamming device to the radio signals from the wheel sensors. I don't think the frequencies are even close between the two systems.

**sourdough** · 10-30-2017, 03:22 PM

Yes, I figured the frequencies weren't close but couldn't figure anything else. It may have been just some sort of fluke. I did pass at least a dozen various LEO vehicles on the highway today and it didn't fail so it may have nothing to do with it. I haven't used a detector in years but may take one when I get back next year and see if there is any correlation. Thanks for the thoughts.

LarrySharon · 10-30-2017, 07:23 PM

If indoor/outdoor thermometers can interfere with unit and tire monitors. I can see where a radar gun could interfere. And not all law enforcement use the latest tech. Call the mfg and see if they could give a correct answer on this. It's crazy.

Ken / Claudia · 10-30-2017, 09:36 PM

Police radar is mostly X band 10.525 GHz or K band 18 to 27 GHz.
Many police radios are now 800 MHz but, could be anything. MDTs around here (computers) 802.11 MHz

I looked up the Tire minder stuff, it says 433 MHz radio freg.

I will say when hitting the transmit button on a police computer, some car alarms nearby go off. Never had that happened with a microphone radio transmission.

Any police radar at those numbers causing problems with TPMS is above my pay grade.

notanlines · 10-31-2017, 02:36 AM

I found this in www.Ferrarichat.com: "Incidentally, I have had police radar cause a TPMS sensor on a Jeep to go ballistic"
Two thoughts here. It certainly seems to be an isolated incident, and two; no I don't hang out with Ferrari owners or their forum.

Dave W · 10-31-2017, 06:38 AM

Why not give TST a call. Their customer service is good. And no, mine have not reacted to any LEOs radar gun ---- yet.

Desert185 · 10-31-2017, 07:13 AM

Remembering from my Army training days, frequency harmonics could explain this. The transmitter and receiver don’t necessarily need to be on the same frequency. The phenomenon is not a constant. All the influences need to align for repeatability.

https://en.m.wikipedia.org/wiki/Harmonic

TheGriz · 11-01-2017, 01:51 PM

Quote:

Originally Posted by Desert185

Remembering from my Army training days, frequency harmonics could explain this. The transmitter and receiver don’t necessarily need to be on the same frequency. The phenomenon is not a constant. All the influences need to align for repeatability.

https://en.m.wikipedia.org/wiki/Harmonic

Yes...harmonic frequencies are a common issue, especially if the transmitter is of a cheaper make, as is the case with many of the Chinese radios being sold today. I speak as a ham radio operator (FCC Extra Class).

A harmonic is a multiple of the intended transmit frequency. For example, if there is a transmission on the 2 meter band (144 to 148 mhz) frequently used in mobile radios on the highway, the second harmonic could occur at or near the frequency previously mentioned (433 mhz).

Also, these Chinese radios are also "very dirty" in their transmissions. What should be a narrow transmit frequency could be a dirty wide transmit frequency near 440mhz (Ham 70cm band), and wipe out the frequency of one of the TPMS monitors.

So, since the police radars are in the gigahertz range vs. the megahertz range (very far apart in frequency spectrum), knocking out the TPMS monitor was not likely the radar. More likely is there was a transmission from one of the cheaper radios on a ham band from a vehicle near you (probably transmitting an alert of a "smokey in middle").

BTW...hams are usually very conscientious to use "Good Operating Practices" which include quality radios (ICOM, Yeasu, TenTec, etc). These cheap radios are being sold to everyone, and therefore the transmission could have been by anyone...without a valid FCC license.

Regards,
Mike

the sodfather · 11-02-2017, 03:09 PM

I have the TST 507 and have never run into that issue. Maybe I’ve never been hit with the radar...

**sourdough** · 11-02-2017, 06:41 PM

Thanks all. I think I'll probably call TST just to see if they have an idea. I figure it is an anomaly caused by harmonics or? Oddly, coming into Mobile a day later one of my sensors beeped loudly and went blank. On the left of my vehicle a sheriff's dept. vehicle went by.....

It only happened twice in about 1500 miles and both times were when we were by LEO vehicles. Strange but a rare occurrence and certainly not a reason to complain about a TPMS system. If I find out anything I'll certainly post.....thanks again for the thoughts.

Ken / Claudia · 11-02-2017, 08:16 PM

On my 1st trip with TMPS about 90 miles of travel I lost a signal on 1 wheel for about a mile or so. I stopped and changed out the battery and continued on about 600 miles without a loss or screw up of any signals. I was in a area without any police parked anywhere do to no place to park. None seen on the road in either direction.

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