My secret homebrew heartbreak.....

Discussion in 'Homebrew and Kit Projects' started by KC2SIZ, Feb 15, 2017.

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  1. KC2SIZ

    KC2SIZ Ham Member QRZ Page

    I've got a reasonably decent record with my homebrew builds. Most of the things I've built have worked....sooner or later. However, I've probably built 6 or 7 cheapo frequency counters over the years and NONE of them have worked for me, despite the fact that (1) they're good circuits that I know to have worked for others and (2) they're really very simple circuits. I've taken into account the capacitance of the counter leads, "damping" effects, etc., and I have tried picking up the signal with coils or via direct contact at the oscillator output. Doesn't matter. I just can't get these little guys to work.

    In my own defense, I built the Oak Hills Research DD-1 counter and it works okay. It certainly wasn't cheap though. Unfortunately I need more than one counter and can't resist the allure of these cheapo counters on Ebay.

    I should resist though. I cannot make 'em work. Sigh.
     
  2. VK4FFAB

    VK4FFAB Subscriber QRZ Page

    I found with the ones i tried off ebay you need to give them quite a lot of drive to work or be accurate. Like in the 3v p-p range. On the small signals we often deal with in homebrew receivers etc, 7dbm and lower, you needed to have a pretty substantial wideband preamp to measure things.
     
  3. W1VT

    W1VT Ham Member QRZ Page

    Yes, I was just thinking that too. More than likely the digital stuff works just fine. But, you need a good circuit to convert the analog circuitry to digital. You might focus your experimentation on finding a good preamp and input circuit for your counters. Once you do that you can probably get all those cheap counters working pretty easily. You might look at some sort of FET or MOSFET preamp that has the high impedance input you want. Those really wideband preamps often have an impedance around 50 ohms which is too low for a lot of counter applications.

    Zack W1VT
     
  4. N8DAH

    N8DAH Ham Member QRZ Page

    I just made the http://qrpkits.com/freqcounter.html that works as a counter or a digital dial. I like it but surface mount is not my best skill. Its about 100$ cheaper than the ohr dd-1 mind you no memories or fancy code for anti-jitter but it works. If you get one make a T connector like it explains for calibration. I don't know if it was the IFR I was using but couldn't get a reading from it, once I used my rig into a dummy load all was well.

    input lvl is 50mv to 100 mv p-p min, max 2 V p-p.

    Best of luck and happy building
    David
    N8DAH
     
  5. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    There are a few ways to make a high frequency comparator, which is what you need as a front end. How high of a frequency do you want to count?
     
    Last edited: Feb 24, 2017

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