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Thread: Service Manual for Nesssi RX-503 SWR/PWR meter

  1. #1
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    Service Manual for Nesssi RX-503 SWR/PWR meter

    Hi, I Have a NESSEI RX-503 SWR/PWR Meter and I think the calibration is not correct. Would anyone have a service manual for his device that explains the re-calibration procedure ? Thanks Rob VK4ALL.
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  2. #2
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    Have you had a look inside it? I can't imagine there would be too much to it. The critical thing would be the accuracy of your 50ohm dummy load.
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  3. #3
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    Many Many Pots

    Originally Posted by werdan
    Have you had a look inside it? I can't imagine there would be too much to it. The critical thing would be the accuracy of your 50ohm dummy load.
    Thanks for the reply Werdan - Unfortunately its not as simple as it looks - There are 12 adjustments inside so I really need an adjustment guide before re-alignment was attempted. Rob VK4ALL.

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  4. The Following User Says Thank You to VK4ALL For the Above Post:

    werdan


  5. #4
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    Yeah, sorry. It makes sense. 2 band settings by 3 power settings by 2 pots (1 each for forward and reverse) gives you 12 pots.

    You could probably reverse engineer it by looking at what everything connects to.
    2 banks of 6 look like the HF and V/UHF groups. The band switch should point to which is which.
    The connections to each needle movement will give you which pots are for FWD and REF.
    That will narrow it down to 3 possible pots for each power level. The value of the series resisters will give you a clue to which is which as the higher power will need higher resisters, but realistically you could just try tweaking the pot at each power setting it applies for.

    As for the actual calibration, you could use the method as stated for my meter. It relies on having access to an already calibrated meter though.


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  6. #5
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    Thats the main problem I dont have another meter - I will try to find one on a loan. Thanks
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