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Thread: EzUHF TX - bench RSSI testing / comparison

  1. #1
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    EzUHF TX - bench RSSI testing / comparison

    My new EzUHF TX appears to have poor RSSI performance (bench testing only), and wondered if anyone might be able to offer some insight from their experience.

    I used a spare EzUHF TX for comparison, with the spectral analysis tool built into a diversity EzUHF RX.

    Old TX is the model without instructions written on the case
    New TX was purchased very recently with instructions written on the case

    Antenna (TX): Diamond SRH771
    Antenna (RX): US Robotics 433mhz (x2)

    For both tests:
    * I had each TX in high power mode
    * Distance approx 2ft between TX and RX
    * Antennas orientated appropriately
    * Diamond Antenna swapped over between tests
    * Firmware updated to latest versions on both sets of TX and the RX (both set to default 433-435)

    Results

    It appears the new TX generates much less "background noise", outside of the configured frequency range ~ -100dBm.

    The old tx sits around ~ 85dBm outside of the configured frequency range, and makes my desktop speakers buzz too.

    The old TX has much better (closer to 0) readings than the new TX.

    New TX:


    Old TX:


    Environment noise (no tx powered up):



    During testing my old TX regularly managed to attain single digit RSSI figures, whereas the new one is difficult to get lower than 30. I've seen several video's at launch where people get < 10dBm.

    Low and high power mode made very little difference to RSSI values for my new Tx.

    Questions
    Is around 30dBm normal in high power, at 2-3ft range?
    Do I need to worry about my new TX power output?
    TX's were not bound to RX after flashing; does it make a difference to RSSI?
    Is there an objective way of measuring power output without expensive tools?
    Is there any simple steps I can take to improve range?

    I guess some real world range tests are required before I can make any conclusions, but it would be great to get an idea of what normal figures look like.

    Sadly my EzOSD stopped working today, so will be a couple of days before a newly one arrives to derive link quality figures from range tests - but I'll let you know how I get on.
    Last edited by mrholozip; 20th August 2012 at 04:40 PM.

  2. #2
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    My EzOSD arrived today, so spent another evening tinkering.

    Once bound, I'm only getting around 35-40 RSSI with my new transmitter in high power mode. My old transmitter sits at 0, so the new one definitely seems broken. RMA I think.

  3. #3
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    I think the new one needs calibration, PM me for details.
    Velvety smooth drone pilot for hire

  4. #4
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    Cheers Sanders - PM sent

  5. #5
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    Is this calibration process documented anywhere? I just put together my first FPV system with a EZUHF, only short range flights so far but headed for some range this weekend.

  6. #6
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    Quote Originally Posted by ssassen View Post
    I think the new one needs calibration, PM me for details.
    Sassen,
    Can you please tell us the calibration procedure?
    Alex

  7. #7
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    Quote Originally Posted by amorealex View Post
    Sassen,
    Can you please tell us the calibration procedure?
    No.
    Velvety smooth drone pilot for hire

  8. #8
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    Why not?
    Is it a secret?
    Alex

  9. #9
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    Quote Originally Posted by amorealex View Post
    Why not?
    Is it a secret?
    Because tinkering with it will adversely affect the performance of the EzUHF Tx if not done correctly.
    Velvety smooth drone pilot for hire

  10. #10
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    I believe I have the same problem as mrholozip, without the luxury of having two ezUHFs to test with.

    First I noticed the link quality indicator in the EzOSD display never hits 100 (see http://youtu.be/9_GhTaREL50). Then I started checking the Spectral analyser with Sander's Immersion Tools.

    First I tried checking the noise floor:
    Click image for larger version. 

Name:	test - trans off - first pass - new ant - no band.jpg 
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Size:	79.8 KB 
ID:	14455

    On the first scan pass everything looks good, but after a few more scan passes regularly either I get a "Failed to communicate with EzUHF(2)" error or I start seeing strange single peaks like below. I'm assuming these are measuring errors or software issues, but I mention them in case they might help in the diagnosis.

    Click image for larger version. 

Name:	test - trans off - third pass - new ant - no band.jpg 
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Size:	54.8 KB 
ID:	14456

    When I turn the Tx on on the "low" setting about 3 meters away from the Rx, I get a picture which is very similar to mrholozips. The RSSI values look pretty lousy, which could explain why I never hit 80+ link quality.

    Click image for larger version. 

Name:	test - trans on - fifth pass - new ant - no band.jpg 
Views:	201 
Size:	64.3 KB 
ID:	14457

    mrholozip or Sander, any ideas on what I could do to fix this?

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