Looking for Pinout of Motorola Permacode Filters

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by AD7I, Jun 29, 2019.

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  1. AD7I

    AD7I Ham Member QRZ Page

    Still looking....

    I'm trying to use some Motorola Permacode filters (those used in Minitor II pagers) to make my own home-brew two-tone decoder. Does anyone happen to have the pinout for the Permacode filters? These are 4 pin devices and I suspect the pins are Ground, Power In, Audio In and Audio Out. I'm sort of groping in the dark a bit here. I'm also looking for the specific voltage used to power the filter. And finally, what's the expected output from the Permacode filter with the proper frequency input tone?: a sine wave at the desired frequency (like a very high Q band pass filter)? or is there a level detector in the Permacode filter so the output is a DC value (i.e, something like low output on correct tone detect and high output otherwise)?

    I've checked the obvious sources (google, repeaterbuilder.com, radioreference.com), but haven't found anything. I'm hoping that someone has an old Minitor II service manual in their files and could take a look at that and let me know.

    I appreciate any information people can provide about these filters.

    Thank you.
  2. ZL1TKL

    ZL1TKL Ham Member QRZ Page

    tried austech forums ???? maybe ????
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    There is a Motorola E-Mail reflector on the "mailman" lists. You can sign up for the list at


    Then, post your inquiry and see if anyone there has the information.

    Glen, K9STH
  4. AD7I

    AD7I Ham Member QRZ Page

    Thank you Glen. I'll give that a try.

    Paul, ad7i
  5. WA8NVW

    WA8NVW Ham Member QRZ Page

    You might also include the model number of the PermaCode filters already in your possession. Several similar but electrically different models were used in portable and paging products over the decades.
  6. KB0MNM

    KB0MNM Ham Member QRZ Page

    This is a very long shot: I worked for a friend in St.Paul Minnesota ( McKnight road near 3M ) who had a few broken pagers and a manual for them. They did have replaceable code elements. Someone might check to see if Denny Mix, owner of United Towing has that manual and wants to sell the book or the entire system. Be aware that it is a long shot because this was before 1991- I moved away and had not visited since at least 2000- about 20 years ago. K0GX may know...
  7. KJ7BZC

    KJ7BZC Ham Member QRZ Page

    Has anyone found this out? I am looking to test several minitor pagers for alert without having to transmit on their frequency.
  8. AD7I

    AD7I Ham Member QRZ Page

    No joy so far. I would have thought it would have been easy for me to find a schematic of something that used these filters, but after looking on and off for a year or so I've found nothing.
  9. NE4EB

    NE4EB XML Subscriber QRZ Page

    I worked at a Motorola MSS for about 11 years and we serviced those pagers. I'll try to stop by there this week and pull a service manual.

    My less trustworthy memory says they are a Hi-Q active audio filter that will only pass the frequency listed on the side. This audio was passed to an IC that measured the duration of the two sequential tones (audio) and if that fit the 'window' the pager would alert. If it had the group call option the second tone alone at twice the normal duration would alert on all the pagers that had the same second tone frequency. I think they ran on 1.5 VDC.
  10. AD7I

    AD7I Ham Member QRZ Page

    Thank you Lowell. Any help would be appreciated. Paul, ad7i

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