Frequency Counter - New $100 model or old HP??

Discussion in 'General Technical Questions and Answers' started by KB5RFT, Feb 12, 2008.

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  1. KB5RFT

    KB5RFT Ham Member QRZ Page

    I'm trying to assemble a work-station that I can use to restore/re-cap old radios. I have some old signal generators that I would like to test as well as the oscillation of circuits in the old radios.

    What kind of frequency counter do I need? There are several models on ebay for around $100, but the maximum input voltage is 30V. Is this going to be a problem?

    Would an older model HP be a better choice? Such as an Agilent HP 5316A?

    Also, none of the ones that I see for sale do not come with probes. Where do I get probes? Any help would be greatly appreciated.

  2. VK2TIL

    VK2TIL Ham Member QRZ Page

    Frequency Counter

    I wanted another counter some time ago to save using my HP5345A system for simple work. I looked at one of the cheap counters; this one (but I think they are all much the same);

    It was OK for the money but it didn't have an air of quality about it (perhaps comparison with my HP5345A system was unfair :) ).

    I settled-on one from AADE;

    There are some examples of housing it on the page; mine is the last one.

    It's a great counter, small & convenient and very accurate; ideal as a general-purpose counter.

    The older HP counters are beautiful instruments (I love my 5345) but they are getting old and you may have to delve into one if it misbehaves; that might be a downside if you aren't really into repairing such instruments.

    On the positive side, they are solidly-made and last a long time; manuals are available, often for nothing on the 'net, and HP manuals are incredibly detailed and walk you through the troubleshooting & repair process if that is required.

    Counters always have a limit on input voltage, often less than the 30 V you mention; this is normal and will not be a hindrance. In the most unlikely event that you will be measuring high-voltage AC/RF, just add an attenuator.

    For instance, you would not normally connect a transmitter to a counter; frequency measurement/adjustment would be done back in the low-level circuits. If you did want to measure 100s of watts you would use a coupler with attenuators.

    If you test a circuit that has DC as well as RF on it, use a blocking capacitor; these are made in a housing like an attenuator and sometimes can be found on ebay & elsewhere as "DC blocks". Just soldering a suitably-rated capacitor at the test point does the job, though.

    But most signals that you will encounter will be in the milliwatt range; it's sometimes necessary to use a small amplifier to get tiny signals to trigger a counter.

    Counters don't have special probes; a BNC patch cable is usual. If you want a probe, get a 1:1 oscilloscope probe; they are cheap on ebay.

    So any of the several types of counter will be OK; you have to decide which one best suits you.

    It's like cars; what suits me probably wouldn't suit you.
  3. KB5RFT

    KB5RFT Ham Member QRZ Page

    Great advice, Thanks!

    Thanks so much for clearing that up for me. Also, attaboy on the nice housing that you made for your counter! It's people like you that have always made QRZ such an awesome resource for hams!

    Thanks again,

  4. AC0FP

    AC0FP Ham Member QRZ Page

    I have a HP5303A and it works great. However the cheap counters can also work just as well. You just have to have a means to check the counters "calibration" plus stability with temperature variations is an issue..
  5. AF7CE

    AF7CE Guest

    I have 2 HP-5328A's, 1 USM-207 nixie tube, and a couple of cheapie newer counters. I prefer to use the HP counters as they provide much higher resolution, so that when I am done working on a rig I KNOW what the accuracy of the display is.

    I added a freq counter "tap" to my MFJ-250 Versaload rf dummy load to feed my freq counter without any worry of overloading the front-end. I can check the the freq output and stability of just about any transmitter up to a kilowatt with resolution down to the hertz level.

    I think for the money you can't beat the precision of old decommissioned lab and military gear.
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