repeaters, gap between frequencies?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by K6XRA, May 5, 2019.

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  1. N6PAS

    N6PAS Ham Member QRZ Page

    You could program you radios receive with the same ctcss code as you do on Tx. The radio would then open only if the code is present.
  2. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page


    The problem is that many repeaters do NOT transmit a CTCSS tone even though one is needed to access the repeater.

    Glen, K9STH
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    Some do and some don't.

    Some pass the tones, Some filter them out and some insert them.
  4. WA4ILH

    WA4ILH Subscriber QRZ Page

    I can remember back in 1969 or 1970 when the ARRL suggested that the 2 meter FM channel spacing be reduced from 60 KHz to 30Khz. You should have heard the uproar!
    Tom WA4ILH
  5. ND5Y

    ND5Y Ham Member QRZ Page

    Probably like in the mid 1980's when Texas went from 15 kHz to 20 kHz spacing on 2 meters.
    Some hams were saying "But my radios only do 600 kHz split and I can't afford new radios!!"
  6. AA5CT

    AA5CT Ham Member QRZ Page

    All those old salvaged 2-way radios back then had w-i-d-e IF filters ... things like the Motorola Permakay mechanical filters weren't necessary until the FCC mandated a "narrowbanding" of FM 2-way radios back in the 50's/60's.
  7. K7JEM

    K7JEM Ham Member QRZ Page

    The Permakay filters were used by Motorola going back to around 1950, when "wideband" FM was still being used everywhere. Some government radios were still using wideband into the late 60's, maybe early 70's or so. I remember seeing some Motracs with wideband receivers, built around 1967 or so, down in the 420MHz range. Those wideband RX's made super good point to point link radios, superb SNR and audio quality. Used between 420 and 430MHz to link repeaters.
  8. AA5CT

    AA5CT Ham Member QRZ Page

    I gave an example, not a tutorial. No need for a history lesson.

    Do you know what the "FM Schematic Digest" is? It's an almost inch-thick plastic-ring bindered notebook of schematics printed on 11" x 17" paper stock. I happen to have one a friend ham (Bob) gave me some +25 years ago when I bought an old B91GJB-3100A 300 Watt low band 6 ft tall base station from him. Someday, I should digitize that 'Digest' and get it put on Repeater-Builder dot com, along with full HTML source of my 6m duplexer work.

    Anyway, the Digest contains schematics of Motorola 2-way radios going back from maybe the late 40's (I really don't know how early) through to the (partially) transistorized MOTRACs sold in the early 1960s. I didn't make a survey to see how many radios over the period used Permakays in lieu of the more usual (for that era) double-tuned IF transformers.

    The only wideband FM I noted here in the DFW area starting 1975 was KRLD's "remote broadcast pickup" (mobiles) and they went 5 kHz deviation a few years later. In those early years very few programmable scanners existed (if you recall) and I had preordered a BC101 sometime mid/late 1975 from Fort Wayne Electronics.

    I will note that the state-wide FBI radio network in Michigan was 5 kHz dev. FM early 70's onward. Every morning roll call was heard with "Creek 1" .. "Zoo 1" ... "Rapids 1" etc responding. They sure responded to a lot of bank robbery calls in Detroit in those days ...
  9. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page

    History lesson or not!

    The deviation regulations for +/- 15 kHz regulation started in the late 1940s and by 1950 was in place for low-band, high-band, and UHF (450 MHz to 470 MHz) systems. In 1957, the deviation was immediately dropped to +/- 5 kHz with all transmitters having to be modified for new technical requirements by 1962 for low-band and high-band units for all but public safety. Public safety units all had to be modified by 1967. In 1967 all UHF systems had to have the deviation reduced to +/- 5 kHz with all transmitter modifications, for all units, in place by 1972.

    Motorola introduced the "Permakay" filters in late 1949 and they were installed in all mobile, portable, and base station equipment through the Motrac and Mocom 70-series equipment. Starting with the Micor equipment, Motorola started going to a crystal filter instead of the old coil / capacitor "Permakay". When the +/- 5 kHz deviation became mandated for all but UHF, for those "Permakay" units that were used in all 3-bands of receivers, Motorola started adding the letter "W" to filters for +/- 15 kHz deviation and the letter "S" (for "split") to those for +/- 5 kHz deviation. The TU-540 "Permakay" was the filter that was in the majority of these units but there were other units as well that were especially used in the HHT versions of the Motrac.

    There were 2-versions of Wolf's Motorola schematic digest publications. The early version had a red paper cover and most of the later versions had a tan paper cover or blue paper cover. The later version included units like the early Motrac and Business Dispatcher units. There was also a similar book of schematics for the earlier General Electric FM radios as well.

    Glen, K9STH
    K7JEM likes this.
  10. WA4ILH

    WA4ILH Subscriber QRZ Page

    I used to have one of those Motorola 11” X 17” schematic digests in the early 70s. It was very useful and well- worn after a few years. It’s funny, I can’t remember what I had for lunch yesterday but I can remember the model number of one of my old Motorola receivers from nearly 50 years ago. ( TA-140 BWQN if memory serves) It only had two receive channels until I built a GLB synthesizer sometime in the mid 70s.
    Tom WA4ILH

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