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Thread: Will LawMate RX work with non-LawMate TX?

  1. #1
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    Question Will LawMate RX work with non-LawMate TX?

    Just made my first 'real' fpv purchase after lots of research and helpful e-mail from Tim. I have a troubleshooting e-mail into to Tim, however not expecting a reply for a few days given his other support efforts (received AUTO-Reply e-mail indicating this).

    I have set this up on my bench for testing using standard RCA cables and 12v DC walwarts with the various mA outputs.

    Camera works well directly connected to my test 10" LCD TV.


    TX: 2500mW 1300MHz Transmitter - w/ standard antenna
    I am in the US, expecting it to be locked at 1280 GHz, however the LED read-out shows '9'. Its not clear what that is in ref to. Button on TX does nothing that I can determine. Powered by a DC regulated bench top power supply.

    RX: 1.2GHz Lawmate 8Ch Wireless A/V Receiver - w/ standard antenna
    I have set all switches up except 8 and with mode switch on 'B'. Stated with '8' for the 1280 GHz freq. However during troubleshooting tried all combinations of dip switch settings and mode switch settings.

    Other troubleshooting include trying different cables. Since I am using this in a robot platform, I am using standard cables, not the micro or custom made wire sets. Also tried different power supplies.

    Thanks
    ms - KB0MSR

  2. #2
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    Continued research - ref picture

    Searching online has yielded several pictures of the TX that I brought with what appears to be this RX at RMRC. Here is the reference picture. Given non-brand name its a challenged to find specs.

    Wounding if the LawMate RX that I bought has some kind of encryption or key to the TX?

    Not sure what the real difference is between the LawMate RX for ~$50 vs what appears to be more functional ~$35 no name RX?

    ms

  3. #3
    I Like Waffles... SENTRY's Avatar
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    Ignore the color coding on your cables (in other words - swap them around and report back)
    "I Like Waffles" : FPVLab on Facebook and FPVLab on Twitter

  4. #4
    Navigator Airborne's Avatar
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    There is no encryption. It is just like watching a regular TV broadcast on different frequencies than your regular TV set can receive.

    If you get static on all 8 receiver channels, the transmitter (VTX) isn't transmitting. Check power connections. The VTX will get warm after it has been on for a few minutes; if it's not getting warm, it's not broadcasting. DO NOT power up your VTX without an antenna connected, it will burn out almost instantly.

    If you get seven channels of static and one that's solid black, the transmitter is transmitting "nothing". Check your camera power and connection to the transmitter. The transmitter is running, but not receiving a signal to broadcast.

    If you get 8 channels of solid black or blue, the connection from the receiver to the TV is wrong, or you have your TV on the wrong input. Fiddle with cables/settings until you can get it to show static.
    Last edited by Airborne; 12th December 2011 at 05:01 PM. Reason: clarification

  5. #5
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    Quote Originally Posted by SENTRY View Post
    Ignore the color coding on your cables (in other words - swap them around and report back)
    No change when swapping cables around. Thanks for the suggestion.

  6. #6
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    Quote Originally Posted by Airborne View Post
    There is no encryption. It is just like watching a regular TV broadcast on different frequencies than your regular TV set can receive.

    If you get static on all 8 receiver channels, the transmitter (VTX) isn't transmitting. Check power connections. The VTX will get warm after it has been on for a few minutes; if it's not getting warm, it's not broadcasting. DO NOT power up your VTX without an antenna connected, it will burn out almost instantly.

    If you get seven channels of static and one that's solid black, the transmitter is transmitting "nothing". Check your camera power and connection to the transmitter. The transmitter is running, but not receiving a signal to broadcast.

    If you get 8 channels of solid black or blue, the connection from the receiver to the TV is wrong, or you have your TV on the wrong input. Fiddle with cables/settings until you can get it to show static.
    TV has 'No Signal' blue screen on all channels, tried all combinations of settings on the RX. There was 'No Signal' with TX on and with TX off. Input to TV is through an A/V port. Tried two different TVs, still 8 Channels with 'No Signal'. I have not been able to achieve static as you recommend.

    Before trying anything I hooked up the camera directly to the TV. No issues. Also never applied power to TX w/o Antenna installed.

    TX does warm up and fan within case is operating. Also I performed a continuity test on all cables, no issues.

    Thanks for the suggestions.

  7. #7
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    Picture of my 2500MW1300MHZTX running

    It is still not clear what the 7-segment LED is indicating. Looks like channel '9' if connectors are at the bottom, looks like '6' if at the top.

    The stickers say "1280MHE" and "2500mW".

    Click image for larger version. 

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  8. #8
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    Discovered Audio is TXing, still no video

    Additional troubleshooting:

    Hooked video from camera directly to the TV to get signal. I left the audio from camera hooked to TX and Audio from RX to the TV. I am getting the audio signal through the the TX / RX. When hooking video back up to the TX and RX video back to the TV, still getting 'No Signal'.

    Here are additional pictures of the bench setup. Close up of the RX set to 1280GHz. And finally a picture of that camera/tv working hooked directly to each other.

    Click image for larger version. 

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    Thanks for the suggestions...
    Last edited by stempile; 13th December 2011 at 02:12 AM. Reason: grammar fix

  9. #9
    Navigator Airborne's Avatar
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    You have narrowed the problem down to the receiver itself. Either it's just not working, or your monitor does not accept the video signal from the receiver as 'valid' and is using the video mute function (blue screen) to cover it up while still letting audio through.

    Try connecting it to a different TV, preferably an older one that does not have a video muting function.

    I am not sure what the "mode" switch does on the lawmate RX. Is this possibly a PAL/NTSC selection? Have you tried flipping this while leaving the DIP switches configured for 1280mhz?

    Also, you're putting out a lot of power with that VTX. Make sure you have several feet of separation between the transmitter and receiver, otherwise the strong signal may swamp or overload the receiver, causing an unstable picture that activates the video muting function.

  10. #10
    bonafidepirate Keith's Avatar
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    It definitely sounds like the video level coming out of the receiver is too low to make the TV happy. If you have another device that accepts the video out, try it. (goggles, another TV, recorder, etc.) Some of my receivers don't work with some of my other devices. I bought a splitter/amp and it fixed it all.
    AKA Bonafidepirate

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