RF question

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.

msw3113

Well-known member
Joined
Aug 9, 2017
Posts
469
Location
New Hampshire
Trying to tidy up the front compartment of our 5er.  There is a matchbook-size transmitter for the Garmin Rear-view camera and another for the EEZ-RV TPMS repeater.  As the all of the fuses for the rig are in the same compartment, I thought to mount a separate box with fuses for these two devices and put the two devices side-by-side on the surface of the 3x5" box.

My comprehension of RF phenomena is nil so here's my question: is it likely that the function of either or both of these transmitters will be affected by their proximity?  Other than trial and error, is there any way to tell before I go to the effort of this project?  Am I worrying needlessly?

Thanks in advance to responders who understand such mysteries.
 

Isaac-1

Well-known member
Joined
Dec 3, 2016
Posts
5,858
Location
SW Louisiana
I would try to separate them by at least a few inches, chances of interference partly depends on the design and operating frequency.
 

Henry J Fate

Well-known member
Joined
Jun 14, 2018
Posts
1,979
Generally it is not a good idea to put transmitting devices near power. It also is not good to put different transmitting devices close together. Today's transmitters use much more friendly frequencies and power output but the basic rules still apply.

If you have not noticed any issues with the devices, They are probably fine. Any rf absorbed by the electrical system won't affect anything.
 

Mark_K5LXP

Well-known member
Joined
Nov 17, 2018
Posts
2,448
Location
Albuquerque, NM
Generally speaking it's not their proximity to each other, it's proximity to any other conductors that can affect their range by effects of shielding.  The power levels are such it would be quite unlikely they'd interfere with each other.  What I would do is before I'd go through the trouble of mounting them in a box is to temporarily place them in the proposed spot and see it they work OK there.  If they do, you're golden.

Mark B.
Albuquerque, NM

 

Chakara

Well-known member
Joined
Aug 13, 2018
Posts
230
Location
Rio Rancho, NM
I agree - plus the TPMS should be in the 300-500 MHZ range and the camera is likely 5.8Ghz.  Way to far apart to hurt each other....


 

Isaac-1

Well-known member
Joined
Dec 3, 2016
Posts
5,858
Location
SW Louisiana
TPMS can be all over the place for frequency depending on brand, anywhere from down around 300-500 mhz, up to the 2.4 Ghz range (I think the TPMS I currently have is in the 800-900 mhz range), wireless cameras depending on brand can be anywhere between 900 mhz - to 5.8 ghz, with most being 2.4 ghz - 5.8 ghz.
 

msw3113

Well-known member
Joined
Aug 9, 2017
Posts
469
Location
New Hampshire
Coulda looked for this first but didn't think of it:  manufacturers' info reveals that the camera operates at 2.4 ghz, the TPMS at 433.92 mhz.

I'm gonna mount everything to a short piece of plywood and test.  If successful I'll put them in/on a box.

I'm grateful for everyone's input and will post results after our next trip.
 

msw3113

Well-known member
Joined
Aug 9, 2017
Posts
469
Location
New Hampshire
I had in mind a plastic box.  But metal (like we used to find at our friendly local Radio Shack) is not recommended? Why's that?
 

Harvard

Well-known member
Joined
Feb 14, 2011
Posts
220
msw3113 said:
I had in mind a plastic box.  But metal (like we used to find at our friendly local Radio Shack) is not recommended? Why's that?

A metal box is a "Faraday Cage". A Faraday Cage is used to keep RF from crossing IN to OUT or crossing OUT to IN
 

msw3113

Well-known member
Joined
Aug 9, 2017
Posts
469
Location
New Hampshire
Following Mark B's suggestion I first mounted the units side-by-side on a piece of board, screwed that to the front bulkhead, and used alligator clips to grab nearby 12v and ground.  (First photo below)

After a couple of trips it appeared that the units weren't going to interfere with each other, so I re-mounted the units to a plastic (non-Faraday!) box; changed from in-line to chassis-mount fuses; then tapped 12v and ground from the exterior pinbox light.  (Second photo below)

These things don't need to be powered up when we're parked so I mounted a wee power switch in the locker that houses the landing gear rocker switch and manual crank grommet.  (Third photo below)

Operation seems fine and the front compartment is tidier.  Thank you to everyone for your input.
 

Attachments

  • rsz_xmtrs_test.jpg
    rsz_xmtrs_test.jpg
    111.9 KB · Views: 21
  • rsz_xmtrs.jpg
    rsz_xmtrs.jpg
    113.1 KB · Views: 19
  • rsz_switch (1).jpg
    rsz_switch (1).jpg
    113.1 KB · Views: 17

John From Detroit

Well-known member
Joined
Apr 12, 2005
Posts
26,281
Location
Davison Michigan
There are several frequency bands that remote devices operate in like 443.92 Mhz.

But that is not the only frequency.. if two devices (For xample the radio next to me on 443.560 and a TPMS on 443.92) are close together yhou are going to have issues..

But if one is on 443.xx and the other on say 135.. No problem
 
Top Bottom