KC0QNB
Member
Back in the late '70s early '80s, a lot of radio users had to update their equipment to narrow band, now I read that there is a new narrow band spec from 25kHz down to 12.5kHz, anybody know what the pre 1980 wide band spec was?
I must of missed something
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That change was in the late 50s-early 60s, not the 70s or 80s. Channel spacing was 30 kHz with 60 kHz separation between adjacent assigned frequencies, i.e. 154.310, 154.340, 154.370, 154.400, 154.430, etc. and adjacent assigned frequencies would have been 154.310, 154.370, 154.430, etc.
It became 15 kHz, i.e. 154.310, 154.325, 154.340, 154.355, 154.370, 154.385, 154.400, 154.415, 154.430, etc., with 30 kHz separation between adjacent assigned frequencies.
Soon it will change again to 12.5 kHz spacing and 25 kHz separation for analog, and 6.25 kHz spacing with 12.5 kHz separation where applicable for digital. Check the VA STARS system for the layout of their freqs for their vhf high band trunking. That'll give you an idea where it's all going.
Us old guys remember this kind of thing because we were still wet behind the ears when it was happening.
It became 15 kHz, i.e. 154.310, 154.325, 154.340, 154.355, 154.370, 154.385, 154.400, 154.415, 154.430, etc., with 30 kHz separation between adjacent assigned frequencies.
Soon it will change again to 12.5 kHz spacing and 25 kHz separation for analog, and 6.25 kHz spacing with 12.5 kHz separation where applicable for digital. Check the VA STARS system for the layout of their freqs for their vhf high band trunking. That'll give you an idea where it's all going.
Us old guys remember this kind of thing because we were still wet behind the ears when it was happening.
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A good observation of how the technology has changed how we speak about the subject. Perhaps the most ironic of the labels we give to radio frequencies is "shortwave." When the name was given everything above 2 MHz was considered shortwave as the wavelength of a 15 MHz signal is much shorter than a 1 MHz signal. Shortwave is a popular term that applies to everything above the AM broadcast band and below 30 MHz. The irony is that "shortwave" has some of the longest waves in use currently and this is not likely to change. Shortwave is a term used by people who don't have much radio knowledge and "HF" or high frequency is what is used by those more familiar with radio. We then have VHF (30-300 MHz), UHF (300-3000 MHz, SHF (Super High Frequency), and finally "ISARTRWMIMAOUIRT" or Incredibly Short And Ridiculously Tiny Radio Waves Measured In Microns And Only Used in Radio Telescopes.
KC0QNB
Member
Ok the reason I referenced that time frame, I ran across a radio shop that had a bunch of Motorola trunk mounts, back in 1980-81 I wanted to buy one but he said they were wide band and could not be used any more, they were the green colored enclosure and as I recall they were solid state or maybe a tube/solid state hybrid, they were only about 4-5 inches tall and no ventilation holes for the tubes, see why the time frame? So they weren't from the 50s or 60s.
I remember there were plenty of low band radios still in use in the late 60s-early 70s that were still "wideband", and some probably later than that. Eventually the ones that could be converted to "narrowband" were converted, and the rest were just adjusted for output modulation that conformed to "narrowband". The receive audio of a wideband unit being used on a narrowband channel sounds like it's too low, which it is, by half, but lots of customers just lived with it instead of spending money on new gear. Trust me, adjusting the TX audio isn't the solution to a bandwidth change. That kind of decision comes from decision makers who don't have to use a radio, and it makes things hard on those who do.
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rfradioconsult
Member
In your spare time you would narrow band Twin V's with the conversion kits. I bet there are some wideband Permakey filters still around in some shop.
Ever wonder what Motorola would say if you tried to hold them to their lifetime warranty?
rfradioconsult
Member
Don't forget the nifty little sticker!
Funny you should mention Twin V radios. Behind me, on the bench top shelf, is a working T-power Twin V on the local county fire vhf dispatch frequency. Other than a power failure or two and a tube refreshing or two, it hasn't been turned off in 30 years..... Yes, I remember converting many older vibrator power Twin Vs and attempting to convert pre-Twin V units as well as converting GE Prog Lines and two piece pre-Progs, especially low banders.
Oh, how old I feel .......
Oh, how old I feel .......
Hmmmm!
Quote "Soon it will change again to 12.5 kHz spacing and 25 kHz separation for analog, and 6.25 kHz spacing with 12.5 kHz separation where applicable for digital".
Unless I am mistaken, 6.25 Khz. steps are ALREADY in use. I have towns localy using frequencies in this step and analog as well. Take a look;
Ansonia, City of
Frequency Input License Type Tone Alpha Tag Description Mode Tag
156.18750 154.07750 WQAZ678 RM 431 DPL AnsoFDHiDisp Fire Dispatch FM Fire Dispatch
151.06250 WQAZ678 M 431 DPL AnsoFDHiFG06 Fireground FM Fire-Tac
151.07750 WQAZ678 M 431 DPL AnsoFDHiFG07 Fireground FM Fire-Tac
400 MHZ 7.5 KHZ steps are in use as well;
Madison, Town of
Frequency Input License Type Tone Alpha Tag Description Mode Tag
46.06000 KDE252 BM 141.3 PL Fire Dispatch "Control 2" FM Fire Dispatch
460.58750 465.58750 KDE252 RM 245 DPL Fire Dispatch (linked with 46.06 MHz) FM Fire Dispatch
453.93750 KDE252 M Fire Tactical / Vehicle Repeaters FM Fire-Tac
458.93750 KDE252 M Fire & Police Tactical FM Fire-Tac
453.47500 458.47500 KNBF245 RM 1 Police Dispatch P25 Law Dispatch
155.29500 153.77000 WPTT608 RM 94.8 PL Public Works FM Public Works
Manny
Quote "Soon it will change again to 12.5 kHz spacing and 25 kHz separation for analog, and 6.25 kHz spacing with 12.5 kHz separation where applicable for digital".
Unless I am mistaken, 6.25 Khz. steps are ALREADY in use. I have towns localy using frequencies in this step and analog as well. Take a look;
Ansonia, City of
Frequency Input License Type Tone Alpha Tag Description Mode Tag
156.18750 154.07750 WQAZ678 RM 431 DPL AnsoFDHiDisp Fire Dispatch FM Fire Dispatch
151.06250 WQAZ678 M 431 DPL AnsoFDHiFG06 Fireground FM Fire-Tac
151.07750 WQAZ678 M 431 DPL AnsoFDHiFG07 Fireground FM Fire-Tac
400 MHZ 7.5 KHZ steps are in use as well;
Madison, Town of
Frequency Input License Type Tone Alpha Tag Description Mode Tag
46.06000 KDE252 BM 141.3 PL Fire Dispatch "Control 2" FM Fire Dispatch
460.58750 465.58750 KDE252 RM 245 DPL Fire Dispatch (linked with 46.06 MHz) FM Fire Dispatch
453.93750 KDE252 M Fire Tactical / Vehicle Repeaters FM Fire-Tac
458.93750 KDE252 M Fire & Police Tactical FM Fire-Tac
453.47500 458.47500 KNBF245 RM 1 Police Dispatch P25 Law Dispatch
155.29500 153.77000 WPTT608 RM 94.8 PL Public Works FM Public Works
Manny
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KC0QNB
Member
Does anyone know all of the wide-narrow conversions time frames the current one is easy to find, what about the older attempts? I don't think we are talking only channel spacing it also has to do the audio (modulation) band width, in FM, deviation specs probably have to be considered as well.
You are very correct about 6.25 already being in use, obviously. How I shoulda worded it is that presently we have a mixed bag as things progress, but soon 12.5 and 6.25 will be the only choices, or at least until the next technology leap makes for more changes.
As for modulation changes, reduced channel bandwidth dictates reduced modulation bandwidth, so unless there's some special consideration involved, the affected modulation bandwidth necessarily has to change to comply with separation standards. For years, the UHF 450-470 band had several 12.5 mHz "splinter" frequencies between the 25 kHz "standard" channels. Those were awarded to certain low power licensees in areas where there was no channel crowding. Those required no change to the "normal" plus/minus 5 KHz modulation standard, but now plus/minus 2.5 kHz "narrowband" with 12.5 spacing is a thing of the present. The so-called "splinter" freqs are now "standard" channel assignment and the modulation standards are plus/minus 2.5 mHz and plus/minus 1.25 mHz.
Example: old system was 460.025, 460.050, 460.075, 460.100 etc., standard 0.0250 spacing, with the 12.5 low power "splinter" spacing sequences 460.0125, 460.0375, 460.0625, etc. That 12.5 spacing is now the game plan for "narrowband" with the 6.25 spacing applied between the 12.5 spacing.
As for modulation changes, reduced channel bandwidth dictates reduced modulation bandwidth, so unless there's some special consideration involved, the affected modulation bandwidth necessarily has to change to comply with separation standards. For years, the UHF 450-470 band had several 12.5 mHz "splinter" frequencies between the 25 kHz "standard" channels. Those were awarded to certain low power licensees in areas where there was no channel crowding. Those required no change to the "normal" plus/minus 5 KHz modulation standard, but now plus/minus 2.5 kHz "narrowband" with 12.5 spacing is a thing of the present. The so-called "splinter" freqs are now "standard" channel assignment and the modulation standards are plus/minus 2.5 mHz and plus/minus 1.25 mHz.
Example: old system was 460.025, 460.050, 460.075, 460.100 etc., standard 0.0250 spacing, with the 12.5 low power "splinter" spacing sequences 460.0125, 460.0375, 460.0625, etc. That 12.5 spacing is now the game plan for "narrowband" with the 6.25 spacing applied between the 12.5 spacing.
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KC0QNB
Member
Now I see thank you, the 25khz bandwidth is gone for ever, then soon there will be 12.5 kHz wide band and 6.25 KHz narrow band, it will be tough to squeeze analog audio into that tiny space, but I am sure they have found a way.
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