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Thread: Aligning a transceiver, question about winding coils

  1. #1

    Default Aligning a transceiver, question about winding coils

    I am aligning a OHR 500 five band qrp transceiver. The 15m bandpass section has never worked, and the capacitors are good. When I measure the two coil inductors, I get readings of about 3.5 - 4 uH. They are wound correctly with 10 windings each on the correct toroid cores. The schematic indicates that they both should be 45uH. The calculations show that to get this value, you need 97 windings on these T-50 cores, which would be impossible.

    Anyone have experience with this radio? I suspect the schematic is wrong, but 30, 40, and 80 meters work fine, although they use bigger cores and the schematic shows reasonable values in ranges under 10uH. I have an email into the company that made these years ago, but haven't received a reply yet.

    My best guess is that the schematic is wrong, and the values should be 4.5uH.

    Thanks for any info
    Daniel

  2. #2

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    With a schematic, one might be able to use a program like SimSmith or Iowa Hills RFFilter to see if the values are reasonable. I cannot find that schematic.

    Do you have the equipment to test the inductance of that coil? Maybe they got the mix wrong. What test equipment to you have?
    Last edited by brandon lind; Thu 12th Nov 2020 at 05:00.

  3. #3

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    Quote Originally Posted by brandon lind View Post
    What test equipment to you have?
    I have a multimeter, freq counter, oscope, induction meter.
    It seems strange that a small toroid with 10 turns of wire would have an inductance of 45uH.
    I removed the coil from the board and wound as many turns as would fit, and it was no where near 45uH. It was much less.
    I tested my induction meter against a known value, and it was correct.

  4. #4

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    Problem solved.

    I looked at the schematic with my magnifier hood on, and I saw very faint decimal points in front of the inductor symbol.
    The values are .45uH, not 45uH. So that solves that mystery!

  5. #5
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    Quote Originally Posted by DanielW999 View Post
    Problem solved.

    I looked at the schematic with my magnifier hood on, and I saw very faint decimal points in front of the inductor symbol.
    The values are .45uH, not 45uH. So that solves that mystery!
    I know what you mean Ive seen more than my fair share of "fuzzy" schematic's that have given me headaches
    luckily my fuzzy kid helps me calm down
    too much blood in my caffeine system.

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