FPVLAB

image
Results 1 to 10 of 10

Thread: RF Interference around RailRoad tracks

  1. #1
    Forum Member
    Join Date
    Jul 2012
    Location
    Yuma, Az
    Posts
    667

    RF Interference around RailRoad tracks

    Just wondering if I am experiencing RF interference due to the trains or what. Here's my short story.

    Recently flew over, around, and along a train passing nearby. Almost as soon as I got close (not below 100ft) I experienced degraded video and upon reviewing the HD video with audio it seems I was going into failsafe a few times, just for a second or so.. This is only based on the pitch of the motor changing to what sounded like the RTH throttle position, there was no change in aircraft direction. My OSD did not report a RTH mode, but my guess is this was a quick "pop" into RTH and back out and did not trigger the OSD to display and change in modes...

    Some time ago a friend complained about losing control over some RR tracks with his Hex, FrSky control, 900mhz telem (I think) and 5.8 Vtx.

    I am using 900Mhz Vtx (500mw) and EzUHF control.

    I know trains have some type of transmitter on the last car called a "End of train" device (former caboose employees have another name for it) and assume this may have something to do with any interference I was getting, but just wondering if this is actually the case. Anyone else experiencing this?
    ________________
    Self Proclaimed world record holder for longest un-powered RTH duration assisted "flight":
    11 months and about 12-16 miles
    We're still working out the details, but, yeah..

  2. #2
    Forum Member
    Join Date
    Jul 2012
    Location
    Yuma, Az
    Posts
    667
    Just found this... May explain the video interference, but not sure about the Control


    http://www.dpdproductions.com/page_rrfreqs_nonaar.html
    ________________
    Self Proclaimed world record holder for longest un-powered RTH duration assisted "flight":
    11 months and about 12-16 miles
    We're still working out the details, but, yeah..

  3. #3
    Forum Member
    Join Date
    Aug 2011
    Location
    SE Michigan
    Posts
    2,695
    Railroads knock out 910 for sure. I was driving around with the RFE on a 900mhz sweep, and crossing over a railroad crossing spiked the noise floor considerably. It's very directional, though, as it was relatively quiet on either side of the tracks, but peaked up as i drove across.

    around here, traffic signals also use 910 - possibly for light synchronization, but not really sure. I just know the noise floor sucks around any areas of town that have 'smart' traffic lights (that also usually have 900mhz yagis on the poles).
    Far better is it to dare mighty things, even though checkered by failure; than to take rank with those who neither enjoy much or suffer much, because they live in the gray twilight that knows not victory nor defeat.

  4. #4
    Forum Member
    Join Date
    Jun 2013
    Location
    Hillsboro, OR
    Posts
    310
    I had this happen over the weekend before the 4th of July at Beacon Rock State Park in Washington.. Flying my quad fine and then all of a sudden it goes into RTH about the same time a train goes by.. right into a tree.. I suspect it was due to the DPU control- Distributed Power Unit -the engine at the end of the train that pushes is radio controlled. There is the EOD- End of Train Devices, along with hot box detectors - sensors on the track to count axles and to detect dragging equipment or hot axles. And also the radio communication for the crew. There is a lot of radio use for your typical train.

  5. #5
    Ouwe Zeikerd Carbon's Avatar
    Join Date
    Aug 2012
    Location
    In philthyy's backyard
    Posts
    3,573

    Re: RF Interference around RailRoad tracks

    I heard Alex mention that 5.8ghz doesn't play nicely with very ferrous soil or rocks. It could be that the gravel they use is very iron-rich...or maybe that's a stretch.

  6. #6
    Forum Member
    Join Date
    Jun 2012
    Posts
    1,623
    A powerful signal around 450Mhz could certainly step on 433Mhz control. I've seen issues with DTV
    broadcast towers who's signals start around 470Mhz, using several different UHF control systems, including ezUHF.

  7. #7
    Forum Member
    Join Date
    Dec 2012
    Location
    Utrecht
    Posts
    455

    Re: RF Interference around RailRoad tracks

    Does the powerlines create a electro magnetic field which could interfere with your plane?

  8. #8
    Forum Member
    Join Date
    Aug 2011
    Location
    SE Michigan
    Posts
    2,695
    Quote Originally Posted by DaKluit View Post
    Does the powerlines create a electro magnetic field which could interfere with your plane?
    Possibly, but the effect may only be in close proximity to the lines. One field I fly at has high voltage transmission lines that comprise the north edge of the field - I've flown over them several times, and have never noticed any image degradation on 910mhz or changes to RSSI, however i am always at least 100' above them and within 2500' of my launch point. Different video frequencies may have different results, however.
    Far better is it to dare mighty things, even though checkered by failure; than to take rank with those who neither enjoy much or suffer much, because they live in the gray twilight that knows not victory nor defeat.

  9. #9
    Forum Member
    Join Date
    Apr 2011
    Location
    Niagara Region, Ontario, Canada
    Posts
    380
    What likely is getting you is a railroad data system called ATCS:


    It uses frequency pairs in the 896, 897 Mhz area paired with 935, 936 Mhz.


    This willl definitely knock out 900 video. It a burstly packet type data system that is usually quiet until a train approaches, then tends to get busy reporting status, etc.

    The other type of system just starting to deploy on US railroads is Positive Train Control (PTC).


    It predominatly uses 220 Mhz (2nd harmonic is 440 Mhz right near 430 Mhz LRS type control), but other frequencies may be used depending on the railroad:

    Reading this part of the wikipedia article, it looks like railroads should be avoided like cell phone towers:

    To be sure, other bands besides 220 MHz will support PTC and in fact have been used to win approvals from the FRA for PTC. When Amtrak received their initial approval, Amtrak initially planned to use 900 MHz frequencies for ACSES. BNSF won their first FRA PTC approvals for an early version of ETMS using a multi-band radio which included 45 MHz frequencies, 160 MHz frequencies, 900 MHz frequencies and WiFi. A small freight or commuter that selects one or more of these bands, or another one such as 450 MHz, may find it easier to acquire spectrum. However, they will need to research spectrum issues, radio equipment, antennas and protocol compatibility issues to successfully deploy PTC.
    Regards,[INDENT][INDENT] Bryan VE3OYN
    "Technoweenie"
    [/INDENT][/INDENT]If it ain't broke, don't fix it.
    If it is broke, deny everything.

  10. #10
    Forum Member
    Join Date
    Jul 2012
    Location
    Yuma, Az
    Posts
    667
    Well, fairly certain the train is the cause of at least my video degradation. Flew again today at a AMA field which is 1/4 mile from the train tracks. I was flying when a train passed. My plane was not close to the train, it was further away from the tracks (if the tracks were to my left, my plane was to my right) and I was getting pretty severe video link interference. This continued until the train left. So, it's not messing with my plane s much as it's messing with my ground station I think.

    So, maybe the AMA field is not the best spot for me to fly fpv after all.
    ________________
    Self Proclaimed world record holder for longest un-powered RTH duration assisted "flight":
    11 months and about 12-16 miles
    We're still working out the details, but, yeah..

Similar Threads

  1. Odd interference
    By glacier51 in forum ImmersionRC
    Replies: 0
    Last Post: 14th May 2013, 12:33 PM
  2. What is that interference?
    By Juan in forum IFR - Video Link Discussion
    Replies: 5
    Last Post: 11th August 2012, 08:45 PM
  3. RTH the only way against interference
    By citi888 in forum IFR - Video Link Discussion
    Replies: 36
    Last Post: 17th February 2012, 12:20 PM
  4. Looking for interference
    By Reverand Blue Chip in forum IFR - Video Link Discussion
    Replies: 6
    Last Post: 24th January 2012, 08:12 PM
  5. Help with interference.
    By theailer in forum RC TECH
    Replies: 9
    Last Post: 24th January 2012, 12:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •