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Thread: Does anyone have a schematic for a Daiwa CN-101L

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  1. #1
    Join Date
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    Default Does anyone have a schematic for a Daiwa CN-101L

    I just bought a (used) Daiwa CN-101L Watt/SWR meter, no condolences please, does anyone have a schematic for this meter?

    73,

    fp
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  2. #2

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    I don't, and Daiwa's pretty famous for not providing schematics.

    I did download the 3-page "manual," and found the note about the warranty being valid only in Japan.
    A government which robs Peter to pay Paul can always depend on the support of Paul.

    -- George Bernard Shaw

  3. #3
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    Someone slap me if I ever buy one of those.
    "I would rather be free than rich."
    Dick Gregory

  4. #4
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    I bot one, works well.

    $5 at a yard sale.

    TOM K8ERV Montrose Colo

  5. #5

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    Quote Originally Posted by K8ERV View Post
    I bot one, works well.

    $5 at a yard sale.

    TOM K8ERV Montrose Colo
    I got a workman....
    I thought I could get rich in the stock market by investing in
    Viagra, Geritol, And Ginseng but my stocks didn't rise to the occasion.
    Hell, I figured that there was always somebody somewhere either trying to
    Get it up
    Get it going
    or
    Trying to remember what to do with it.
    73 De Bubba
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  6. #6

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    Quote Originally Posted by KD8DEY View Post
    I got a workman....
    I got two of them! They cut the grass, clean the yard, take care of the pool...
    A government which robs Peter to pay Paul can always depend on the support of Paul.

    -- George Bernard Shaw

  7. #7
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    Quote Originally Posted by KD8DEY View Post
    I got a Workman....
    I picked up one of those a few months back, brand new from a dealer. Thought I was getting a nice bargain on a dual meter bridge. Hah!

    Frequency range is ~26 - 30 MHz, and they ain't kidding. The meters won't read SWR too well below about 15 MHz, and it was totally useless on it's intended band (dedicated 160 station).

    At least I moved it at the next hamfest for what I paid for it.
    WASHFest 2015, 28 Feb 2015, CSVFD Memorial Hall, SR 88, PGH PA

  8. #8
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    Default

    The meter I bought works just fine but the peak reading scale is a joke. From reading on the web this is a common problem, probably a design problem. I figured with the schematic I should be able to modify the circuit in short order to get a reasonable working PEP reading circuit. I guess I may have to open it up and see what they have done!

    73,

    fp
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  9. #9

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    Quote Originally Posted by AC0FP View Post
    The meter I bought works just fine but the peak reading scale is a joke. From reading on the web this is a common problem, probably a design problem. I figured with the schematic I should be able to modify the circuit in short order to get a reasonable working PEP reading circuit. I guess I may have to open it up and see what they have done!
    I don't have that particular meter, but I do have a different Daiwa "AVG/PEP" meter which also does not use any active circuitry and it's way off. Actually, it would be almost dead on if the signal envelope was a pure and consistent sine wave. It's far off for any other kind of envelope. If you open it up (I did, lots of times) I think you'll find the "PEP" function is nothing more than a capacitor that charges up with the applied signal from the detector, prolonging the meter decay time.

    That's not "PEP" at all. It just makes the meter slower.

    A real PEP meter has substantial active circuitry and requires DC power from a power source like a battery or power supply.

    Here's a reasonable writeup on this, with schematic and board layout for someone who wishes to "roll their own" PEP adapter for an average reading wattmeter like the Daiwas:

    http://www.n9mw.com/Radio%20Topics/PRWM.html





    73,

    fp[/QUOTE]
    A government which robs Peter to pay Paul can always depend on the support of Paul.

    -- George Bernard Shaw

  10. #10
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    Quote Originally Posted by WB2WIK View Post
    I don't have that particular meter, but I do have a different Daiwa "AVG/PEP" meter which also does not use any active circuitry and it's way off. Actually, it would be almost dead on if the signal envelope was a pure and consistent sine wave. It's far off for any other kind of envelope. If you open it up (I did, lots of times) I think you'll find the "PEP" function is nothing more than a capacitor that charges up with the applied signal from the detector, prolonging the meter decay time.
    Thanks for the circuit help, however, the circuit is just a redundant peak detector. D2 is a diode positive peak detector followed by an Op-Amp positive peak detector. The next Op-Amp is a AC to DC peak detector/filter. The third Op-Amp is a DC voltage follower.

    I was hoping to build a PEP (peak to peak) detector. A good accurate one would use Op-Amp's but in a different arrangement. I think I can build a passive one (no power supply) but diode drops would cause the circuit to read a little low. Of course that could be corrected with a single Op-Amp buffer amplifier, the meter does have a 13.8V input for a lamp.

    73,

    fp
    Last edited by AC0FP; 05-08-2012 at 08:13 PM.
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