Page 1 of 29 12311 ... LastLast
Results 1 to 10 of 285

Thread: TBS CROSSFIRE with 1.2GHz Video

  1. #1

    TBS CROSSFIRE with 1.2GHz Video

    As many people are having video range issues with the TBS Crossfire and 1.3GHz video we are working hard on a simple solution to solve this issue. There has been plenty of potential sources, so finding the true culprit was a bit of a search for a needle in the haystack. Right now, it looks like we found the problem.

    Here is the reason why it does not work properly out of the box: Most receiver use a COMTECH (company) receiver module which is made to receive a wide range of frequencies. Due this wide range and other reasons there is no proper filtering on the antenna input, as we would expect from any common receiver module. Because of this the module receives both signals (video and crossfire) and mixes them into an intermediate frequency. The demodulator is not able to properly see the video signal due to blocking or AGC (Automatic Gain Control) that is going all over the place.

    During our tests we could prove that the issue is on the VRX side. We also verified this by sending random Crossfire TX samples to a (very expensive) measurement lab and ensuring that there are no stray emissions also in a lab environment and not just our development environment.

    The solution is simple: Because the frequencies are relatively close to each other the VRX needs better filtering. We are making notch filters and proceeding with further testing. We opened this thread to keep this issue and the discussions separated from the main thread.



    Setup:
    RX: RMRC - 900MHz-1.3Ghz Receiver w/1258 with RMRC Comtech Tuner (Stock SAW)
    TX: RMRC - 1.3GHz 1500mW Transmitte
    Antennas TX and RX: SPW12 (1200-1360MHz)
    Frequency: 1280MHz

  2. #2
    Navigator
    Join Date
    Aug 2014
    Posts
    526
    I see a Tuned TBS 1.3 VRX on the horizon

  3. #3
    Whatever the solution I'm happy to see progress is being made. Thanks guys.

  4. #4
    Navigator
    Join Date
    Aug 2014
    Posts
    526
    I'm sure they will improve it but if those VRX's are that bad it won't totally fix it. with selectivity that bad the AGC is always going to back down and reduce overall sensitivity/range.
    Maybe with the filter and some separation performance will be acceptable for the 1.3 guys

  5. #5
    Using a 5.8 repeater with the VRx/antenna 10-15 feet away from ground station does work but I haven't ventured out past 5-6 miles. Right now separation appears to be the only real option.

  6. #6
    the notch filter currently rejects at about 36dBm, which is a lot. but yes, separation is key, and it confirms what I've always found to be true for 1.2GHz ... it's very low-tech-y and not that resilient to "external forces". I mean, your mobile phone is right about that frequency as well and it can transmit easily at 2W too. I'd hate to have to turn off my phone while flying long range

  7. #7
    Navigator
    Join Date
    Aug 2014
    Posts
    526
    Always, any receiver at full stretch will be upset with a couple of watts of RF screaming in it ear

  8. #8
    Navigator
    Join Date
    Aug 2014
    Posts
    526
    Quote Originally Posted by Trappy View Post
    the notch filter currently rejects at about 36dBm, which is a lot. but yes, separation is key, and it confirms what I've always found to be true for 1.2GHz ... it's very low-tech-y and not that resilient to "external forces". I mean, your mobile phone is right about that frequency as well and it can transmit easily at 2W too. I'd hate to have to turn off my phone while flying long range
    It's gonna be, no one can afford to develop a fancy TX/RX for a little used band, the 2.4 stuff has to be better so modules will be cleaner and tighter just to function in the busy band.

    You would be best to turn your phone off with any RC

  9. #9
    Thanks Trappy. According to your findings, could you say with reasonable confidence upgrading to a properly filtered VRX, such as the YellowJacket (http://www.rcgroups.com/forums/showthread.php?t=2398907) would solve the issue?

    Many thanks again,
    Hein

  10. #10
    Quote Originally Posted by heinduplessis View Post
    Thanks Trappy. According to your findings, could you say with reasonable confidence upgrading to a properly filtered VRX, such as the YellowJacket (http://www.rcgroups.com/forums/showthread.php?t=2398907) would solve the issue?

    Many thanks again,
    Hein
    They specify a range from 900 to 1500MHz. Not sure if this receiver will solve the problem out of the box. Some other people did some tests with this receiver but I don't know the exact results.
    It's quite expensive tho so I would try the filter first.

Similar Threads

  1. So what's a TBS Crossfire?
    By Toy4trax in forum Team-Black Sheep
    Replies: 416
    Last Post: 9th October 2016, 06:54 PM
  2. EzUhf vs TBS crossfire
    By lookoutbelow in forum ImmersionRC
    Replies: 39
    Last Post: 11th September 2016, 11:59 PM
  3. CrossFire and what we don't know
    By alex26i in forum Team-Black Sheep
    Replies: 10
    Last Post: 13th May 2016, 02:59 PM
  4. how to use gps puck with crossfire?
    By hjscm in forum TBS Support
    Replies: 0
    Last Post: 22nd November 2015, 11:03 AM

Posting Permissions

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