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Thread: Is there a way to check the EZUHF transmitter power output w/o a 433MHz power meter

  1. #1
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    Is there a way to check the EZUHF transmitter power output w/o a 433MHz power meter

    I suspect I've got a faulty EZUHF transmitter which is not providing enough power. Failsafes occuring only 1Km out; its been like this since I've had it but its only recently I've been venturing further out. I'm quite confident its not noisy electrics. Is there a way to check the power output. I've been playing around with the ImmersionRC tools scanning software which is really useful for checking antennae & for interference. Can I use this to check the health of my transmitter. I don't have another one to compare it to. I'm planning on sending it out to be serviced but wondered if anyone had any ideas how I could do a check myself without a power meter. I'd be interested in any readings any one has which I can use for comparison. Is there a low cost 433MHz power/SWR meter?
    Last edited by stewjw; 4th October 2013 at 08:58 PM.

  2. #2
    Ouwe Zeikerd Carbon's Avatar
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    First check your environment. What antennas are you using?
    Use the spectrum analyzer and post up some screenshots. We'll get this figured out.

  3. #3
    Navigator jacq's Avatar
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    You can also use an fluorescentlamp/tube. (like often used in the kitchen or garage).

    1 Switch the UHF to high power.
    2 Switch on the fluorescentlamp/tube.
    3 Hold the antenna-tip (UHF powered) against (very close) the fluorescentlamp/tube. (keep it there).
    4 Switch off the fluorescentlamp/tube.

    When it is OK, there should be a part of the fluorescentlamp/tube still produce light.
    If you switch to low power, also some (but smaller) part of the fluorescentlamp/tube is possible to emit light.

    But this is depending on firmware and setting (extreme hopping) if the low power is strong enough to show some light.
    In v1.48 and 433-455 it will also emit light on low power. (ok my one is doing).
    When set to extreme hopping it will not ( the big steps creates radiation loss for this test)
    But in high power you will see the more pulsing/steps light again.

    If you see this, your UHF is OK.

    You can use this as reference/impression... checking your UHF is emitting HF power.
    Last edited by jacq; 5th October 2013 at 03:51 AM.

  4. #4
    ^^ well I learn something new everyday! Makes me wonder what it is doing to my head when i hold it up to it. Think i am going to have to start wrapping my head in tin foil or copper tape and ground my ass

  5. #5
    I can't breathe Hans's Avatar
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    I have one of these at work and know how to use it: http://www.flukebiomedical.com/biome....htm?PID=56636
    I wonder if it could be used to measure outputpower of an EzUHF?

  6. #6
    His Royal Sassiness ssassen's Avatar
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    Quote Originally Posted by Hans View Post
    I wonder if it could be used to measure outputpower of an EzUHF?
    RMS bandwidth: 30 Hz to 10 MHz (-3 dB), not a chance in hell
    Purveyor of the FPV secret sauce at ImmersionRC

  7. #7
    I can't breathe Hans's Avatar
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    Ah, you're right. I read the specs wrong. :P

    i don't have an ezuhf either so, nevermind.

  8. #8
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    Thanks for the quick replies. The fluorescent light was an interesting idea. I have smothered the receiver so I can make the power change more noticeable. So the power switch appears to be working. Changes in dB are not huge as you'd expect using the scanning software. I don't have a portable PC so I can't take scans in the field but that would be interesting to see. I know I have some noisy locations including a cell phone mast a couple of miles away. I'm going to have another flight this weekend and see how I get on.

  9. #9
    ImmersionRC Support Guru swillhide's Avatar
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    Post some scans , we all love nice little pictures of wavy lines.
    AMA # 1015480 HAM Callsign # Procrastinating..
    Futaba 9c w/Ezuhf /Skywalker 1880 or anything else that I can Lawn Dart.
    Retired: Disco(Sold), Skywalker 1900(Dirt Nap), Qav540g/Nazav2/Iosd mk2

  10. #10
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    Using the latest 1.48(6) software.

    Electrics
    Plush 60A Esc
    Corona CBC-5 5A UBEC
    SK3 35-42, 1000KV with the APC 11x4.7 SFP slow flyer pusher prop
    EZOSD
    HK Video Switcher
    Turnigy 700TVL camera
    Fatshark 420TVL camera
    Lawmate 500mA 2.4GHz (TBS Tuned)
    Hitec HS-65MG servos (2)
    Fx-6i wing

    I also use a Mobius ActionCam HD Camera 1080P but its not switched on for this test. Note I have a noisy PC.


    With the electrics powered up it was a short scan time since my motor kept intermittently starting with the Rx connected to my PC which was unnerving. Using standard antenna on Rx & I have a Diamond SRH771 SMA 433MHz Antenna on my Tx.
    Last edited by stewjw; 5th October 2013 at 02:10 PM.

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