Re:
mounting to utility pole:
@TheWaterbug 's idea is pretty clever and it's probably true that something like that could last a decade before anyone questioned it lol. That being said, you could probably just plop it on a pole and wait until (if ever) someone notices. Doubtful any lineman is going to get a supervisor involved or call the cops, and even if they were to, there's no way to prove you yourself affixed it to their pole. No utility company is going to come after you for putting a little hole in their log either... I'd just put it on there and spray-paint it brown or whatever color matches.
Distance from road:
You really want to be <50ft maximum away from the vehicle. You don't need to be right up against the street if you're gonna get hit by a plow, but as close as possible. That includes vertical distance as well. Some Pythagorean action might be necessary.
Regarding antennas:
Both 433.95 Mhz and 315 Mhz antennas are needed, as different sensor vendors use different frequencies. It is very important to note that there is a massive difference in quality between antennas you will find on amazon/chinese OEM vs reputable electronics vendors. Antennas (especially for UHF like this) need to be precisely tuned to be resonant at the correct frequency to work properly. Many Chinese vendors and amazon sellers will advertise extremely wide frequency ranges or create multiple listings for the same antenna claiming different frequencies.
For an effective rx element, either purchase from a reputable vendor like the ones linked in #665 or build your own and verify the spec with an antenna tester.
SDRs:
I'm sort of on the fence now about going back to using an RTL-based receiver (which is an SDR) and desoldering the connector, modifying the heatsink, and using a PI zero instead of a full RPI.
Reasoning for this is because it's a bit hard to source good components required the custom solution nowadays. I've only ever built one other embedded solution like this before, and it was extremely basic, so I don't
really know what I'm doing.
If anyone is or knows an actual electrical engineer who actively designs and manufactures circuit boards / components, please chime in!!! It really isn't very complex, but is sort of one of those situations where it will take 10 minutes for someone who knows what they're doing, and will take ages and still end up being wrong for someone who doesn't. Kinda like automotive work or tax preparation....
The other important thing to note about using an SDR is that you will either need 2x SDRs or you will need to tell the SDR to flip-flop between the two frequencies very quickly at all times, listening to both. In this setup, you will also need an adapter to attach two antennas, which can create other complications. The best solution is really to use two separate SDRs, each with their own dedicated frequency.
This just ends up getting so expensive for such a simple system. We're talking something like $170, so nothing crazy compared to a nice camera, but that's still just way more than it needs to be. Especially considering the fact that you can get an RF TPMS checker for 10-20 bucks.
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I've consulted a few different people abt the RF components, looking to get a seal of approval affirming that it will actually work in the configuration that I spec'd out. If I can get that verified, I'm going to order larger quantities of the components anyways because of the price break.
I'm happy to mail them around for anyone who wants a ready-to-go box.
www.tirereview.com
