How to tell I you broke a crystal filter.

Discussion in 'Radio Circuits, Repair & Performance' started by N1RND, Oct 18, 2019.

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  1. N1RND

    N1RND Ham Member QRZ Page

    I was about to install SSB crystal filter into my Icom ic765 and accidentally dropped the filter onto the concrete floor.
    I yelled an expletive figuring I just blew $98.
    I installed it anyway and it SEEMS to be working as intended.

    How easy is it to break a crystal filter and if I did would it just not work at all and I'd hear no signals through it?

    Dave
     
  2. KL7AJ

    KL7AJ Ham Member QRZ Page

    It's highly unlikely that you would break the actual crystals (there are usually two of them in a typcal lattice filter). They are enclosed in their own hermetically sealed holders. You COULD conceivably break a solder connection in the assembly, but probably not...most of the mass is in the case itself. Bottom line....if it works, you didn't break it.
     
  3. N1RND

    N1RND Ham Member QRZ Page

    Thanks for the encouraging news. I was going to unsolder the case to look inside but decided to leave it alone.
     
  4. NE1U

    NE1U Ham Member QRZ Page

    Expletives in some circles are also known as ham, magic, or golf words. Probably a few others and applies as necessary.
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yes, best to leave it alone.

    If it's passing signal without excessive attenuation then it's likely working. But you can test them in circuit in several ways. Perhaps the easiest is to tune into a carrier signal, calibrators built into older rigs worked nicely for this purpose but any steady carrier like WWV will do. Set your rig for the finest tuning and move the dial frequency back and forth on either side of the carrier and note where it drops off by about 6 dB (approximately 1 S unit) that's a quick down and dirty test to find the 6dB bandwidth with the filter in line.

    The other even quicker way to check out installed filters is to download one of the free audio spectrum analyzer programs you run on a PC or Mac. Tune into band noise and run your rig's audio output to the computer, launch the audio spectrum analyzer and switch the filter in and out. You should be able to easily see the filter's shape on the spectrum analyzer display and note the filter center frequency, cut off frequencies and skirts to see if it's doing what it should.
     
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Sounds like it may have a dent in it. :p
     
    K7TRF likes this.
  7. K8ERV

    K8ERV Ham Member QRZ Page

    Try the rattle test.

    TOM K8ERV Montrose Colo
     
  8. KL7AJ

    KL7AJ Ham Member QRZ Page

    Like this?
    upload_2019-10-18_14-57-32.png
     
    KA0HCP likes this.
  9. KL7AJ

    KL7AJ Ham Member QRZ Page

  10. K8ERV

    K8ERV Ham Member QRZ Page

    Dynamite works better.

    TOM K8ERV Montrose Colo
     

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