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RF Sampler

Discussion in 'Home Brew' started by Moleculo, Jan 21, 2009.

  1. Radio Tech

    Radio Tech Radio Operator

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    Well it is a start. But the data displayed does not really tell you a lot, in theory, I agree with CK you have no trigger, If you really want to get fancy build the circuit I posted above. With it you can look at the rf carrier and demodulated audio imposed on one another. What you are seeing on yours is a modulated carrier less trigger. The scope you have will display X and Y mode so you can see a trapezoid wave form if needed.


     
    Shadetree Mechanic and LeapFrog like this.

  2. LeapFrog

    LeapFrog Wielding Hanlon's Razor

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    I just need to salvage or acquire the required diodes for the detector and order another BNC jumper!
    Thank You Radio Tech
    -Leap
     
    #47 LeapFrog, Jul 30, 2016
    Last edited: Jul 30, 2016
  3. rabbiporkchop

    rabbiporkchop Sr. Member

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    This seems to be the best homebrew sampler I have seen yet. It doesn't pick up noise like some other homebrew samplers I've seen. -20db to -58db attenuation with the variable air gap.
    https://www.briandorey.com/post/variable-rf-signal-sampler
    [​IMG]
    [​IMG]
    [​IMG]

    For someone unable to afford the Bird 4273, it looks like a viable option.
     
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Actually that looks like a very good sampler. I can't remember how many I have seen thrown into a plastic hobby box. I like the capacitive coupling as long as it has GOOD insulation from making direct contact with the thru-line section.
     
  5. Beetle

    Beetle Sr. Member

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    Where do you find the copper pie?
     
  6. nomadradio

    nomadradio Analog Retentive

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    I really prefer an envelope detector.

    All you get is a DC voltage from the carrier and the audio envelope riding on it. Just about any 'scope will display this just fine, whatever the rated bandwidth may be.

    Best advantage for me is that I can trigger the 'scope on the audio envelope this way. A 100 MHz 'scope displaying your RF signal is probaby quite capable of triggering to the 27 MHz carrier wave. But your audio is what we care about. Persuading a 'scope to give you stable trigger from the audio envelope alone is a bit tricky.

    The venerable old Heathkit "cantenna" dummy load has one of these built in, feeding a phono jack. You have to make the RF-bypass ceramic disc cap smaller, and put a 10k resistor across the output to get a good audio waveform.

    Gotta build one to go inline with the coax.

    Oh, wait a minute... I already did.

    [​IMG]

    Never have plugged it into a 'scope. Oughta do that.

    73
     
    Shadetree Mechanic likes this.
  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Really? I mean really Pat? Nine years later and you just caught it? You are slipping my man. :p
     
  8. Beetle

    Beetle Sr. Member

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    I have been busy perfecting my Universal Solvent, and I finally made a batch. Now what can I keep it in? :whistle:

    Actually, I was just skimming through some older threads and "copper pie" jumped off the page and smacked me right across the face. At least that's the way it seemed.
     
    Captain Kilowatt likes this.
  9. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I must have typed that line before I blew the crumbs out of my keyboard. :ROFLMAO:
     

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