Rogue transmissions at NASCAR race in Dover.

[RFI-EMI-GUY]

Can you elaborate on this a bit? I'm not a DMR technical expert and I've never heard of this before.

It is not limited to DMR.

If you are familiar with software defined radio, SDR, you will note that entire swaths of frequency band can be displayed in a panoramic view on a waterfall display. This is from the I/Q demodulation.

That same swath can be recorded directly to a digital file and replayed at a later time. So lets say I have an unknown transmitter and I key it up repeatedly on a channel, the AM and FM characteristics of that transmitter can be analyzed. The ramp up of the carrier when keyed. The VCO instantaneous lock up can be captured. It is all different between different makes and models. Less different between identical models from same factory run. This fingerprinting technique was originally patented by a company called MOTRON * if I recall correctly. In their design a discriminator tap was used to capture a fingerprint limited to the FM characteristics. With SDR you can capture AM/FM/PM characteristics and any sort of modulation and from not only one channel, but many simultaneously.

*

https://fccid.io/KR6

 

[RFI-EMI-GUY]

I'd like to see that work. Based off cellular TDOA, I'd have a hard time believing they could narrow it down well enough to really pick out an individual in a crowded grandstand area. Maybe with high res. cameras, they might see someone holding a radio.

E911 is supposed to reach 50 meter accuracy for cellular accuracy per FCC guidelines. And this is for large area positioning. Lets say that 50 meters or better is all that is attainable. Add cameras or spotters near the seats where the last signal was logged and you will likely catch "Bubba" and his radio on the next attempt.

 

[mikewazowski]

I test E911 for work on a regular basis. With a Samsung S8, I typically receive 3m or greater accuracy. Lately, I've been getting a 1m accuracy according to the PSAP.

 

[slicerwizard]

I test E911 for work on a regular basis. With a Samsung S8, I typically receive 3m or greater accuracy. Lately, I've been getting a 1m accuracy according to the PSAP.

But is that the cellular receivers triangulating your position or is it just the GPS chipset in your phone reporting your location? I would expect it to be the latter, and if so, not germane?

 

[RFI-EMI-GUY]

But is that the cellular receivers triangulating your position or is it just the GPS chipset in your phone reporting your location? I would expect it to be the latter, and if so, not germane?

That's a good point, though FCC is seeking in building location with an address that is reportable. They also want to know the floor in a high rise. GPS is not good inside many buildings, so a hybrid approach including network determination like TDOA is needed.

 

[KB3KBR]

That's a good point, though FCC is seeking in building location with an address that is reportable. They also want to know the floor in a high rise. GPS is not good inside many buildings, so a hybrid approach including network determination like TDOA is needed.

You should check out RapidSOS PSAP - Additional Data for Emergency Comms Centers from RapidSOS we've been testing it at our center for the last 6 months or so and when it works it works great.