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

[AC0FP]

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

73,

fp

[WB2WIK]

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.

[AF6LJ]

Someone slap me if I ever buy one of those.

[K8ERV]

I bot one, works well.

$5 at a yard sale.

TOM K8ERV Montrose Colo

[KD8DEY]

I bot one, works well.

$5 at a yard sale.

TOM K8ERV Montrose Colo

I got a workman....

[WB2WIK]

I got a workman....

I got two of them! They cut the grass, clean the yard, take care of the pool...

[W3WN]

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.

[AC0FP]

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

[WB2WIK]

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]

[AC0FP]

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