Adding Frequency Counter to Tube Radios

Discussion in '"Boat Anchor" & Classic Equipment' started by KD2NOM, Apr 1, 2018.

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  1. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I am interested in adding the ability to connect a frequency counter to my older tube radios via a BNC connector. The first one I would like to add this capability is my recently restored Hallicrafters S-85.

    In my research, I found mention of needing to add 'buffer stage' circuit to isolate the frequency counter harmonics from getting back into the receiver. I came across this posting that talks about this as well - http://www.g3ynh.info/digrdout/d_rdout.html.

    I'm interested in knowing if this is require when using a frequency counter such as my HP5334A, or my FeelTech FY-6600.

    Thank you for your thoughtful responses.
     
  2. W6ELH

    W6ELH Ham Member QRZ Page

    Might be worth a look...

     
  3. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I should have known Mr. Carlson would have already covered this! Thanks for the link.
     
  4. N2EY

    N2EY Premium Subscriber QRZ Page

    Be aware that if you do this, the counter will not indicate the received frequency. It will indicate the local oscillator frequency, which is about 455 kHz above or below the received frequency in the S-85.

    You don't need a buffer stage to isolate the frequency counter harmonics from getting back into the receiver. You need a buffer stage so that the connection does not load down the oscillator and cause it to do odd stuff like shift frequency or even stall out.

    There are ways to build a correct-reading digital dial, but they are more involved than just hooking up a frequency counter to a buffer stage.

    73 de Jim, N2EY
     
  5. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page

    Many of those "cheap" (like $10 to $15) Chinese frequency counters have the ability to "offset" the actual frequency reading so that they can be used with single conversion receivers. One can "dial in" any particular i.f. frequency and also program whether or not the injection frequency is on the low side or the high side. Then, the counter reads the "received" frequency instead of the actual oscillator frequency.

    With receivers that have several different frequencies involved, such as the Collins receivers, then that is a "horse of a different color" and differing methods of producing the correct frequency on the readout are involved. The AADE units did such at a very reasonable cost.

    Although the original owner died a couple of years ago, someone has taken over the business and various kits are again available!

    http://www.mtechnologies.com/aade/

    Glen, K9STH
     
    WB1E likes this.

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