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Motorola HT1250 question

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Skylab

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I'm interested in using this radio for Amateur UHF repeaters. However, in Southern California, the band plan for 70cm repeaters is in 20khz spacing.

For example, I'd want to program in

449.080mhz
448.540
448.060

etc


The spec sheet says it is 12.5/25khz switchable.


Does this mean the radio cannot be programmed for the above frequencies?



motorola_ht1250.jpg
 

xplorer417

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ht1250 programing ham freqs

as of what know i think you can program those freqs in there are they simplex or repeater channels they look like simplex ie talkaround direct channel just wondering on that thanks pm me or email me if you like
 

studgeman

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Narrowband explained

Ok first thing you will need to check is the the capability of the radio to transmit on those frequencies. Motorola makes two different versions of the UHF HT 1250 One is 400->470Mhz and the other is 450-->512MHz. As long as you have the UHF Lo version you will be all set to go. When you run the CPS software to program the radio it will need to put in a TX frequency and an RX frequency. You will need to know your repeater's offset and PL. To answer your question concerning the 12.5/25 switchable. That refers to the occupied bandwith of the signal (close enough for this explaination) Traditional FM LMR systems worked in 20 or 25 Khz Channel spacings. ie 155.100 155.120 155.140 etc. The same is relatively true for Amateur radio. The FCC and NTIA have requied users to narrow their bandwidths to 12.5Khz signals, effectively doubling spectrum efficiency. eventually they will be narrowed again to an effective bandwith of 6.25Khz per voice channel. It is impossible for a manufacturer to get type acceptace of their product (type acceptace is required for part 90 users) without the narrowband option.
For your purposes you will want to set your bandwith to 25Khz (default) for amatuer repeaters. Hope this helped some.
 

northzone

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Traditional FM LMR systems worked in 20 or 25 Khz Channel spacings. ie 155.100 155.120 155.140 etc. The same is relatively true for Amateur radio.

Actually the explaination above is good but the example is wrong. UHF channels were 25khz spacing, VHF were 30 or 15khz. Such as 155.100, 155.115, 155.130, 155.145, 155.160.... 155.120 and 155.140 are not valid channels. Same spacing holds true for amatuer. 25khz uhf, 30 khz vhf.
 

studgeman

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yes you are correct about the channel plans. Its actually a whole seperate topic. I just pulled some quick numbers off for illustration.

I have never heard of a HT1250 that does not have PL capability. It is a newer generation Motorola and as such comes with PL capability and DPL as a standard feature. Of course antennas, batteries, belt clip, keypad, etc. are not standard features, they are part of the Chinese menu when ordering from Motorola. The GSA has the best reference for capabiliites and options and pricing.
 

studgeman

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Ok to make its slightly cleare. three are severral tings we have been discussing in this thread. first is the frequency seperation of the channel centers in the table of channel assignements. This is also known as channel step. ie 155.01, 155.025 155.04. This channel step affects only part 90 users (for this discussion purposes) it does not affect part 97 users (exception: voluntary band plans). Most public safety "channels" are 20Khz wide, which is different than channel step. a 20Khz channel has and emmision designator of 20K0F3E for FM modulated analog voice (most common) There are two portions of the emmission designator 20K0 and F3E. 20K0 refers to the bandwith occupied of the emmission. 20 (whole number) K (multiplier) this case 1000, 0 (decimal). F3E denotes the type of transmission F (Frequency Modulated) 3 (single analog channel) E (Telephony, Voice). You will notice that the wideband channels will overlap in some bands.
Under the narrowband plan channel step is 12.5 Khz emissions designators are 11K2 or 11k3 or 11K0 typically. This actually does leave some guard space between channels.
The audio deviation for a wideband channel is roughly 4.5Khz for a narrowband is 2.5 kHz.
So what happens when you are programming the radio? First you can enter any frequncy requardless of channel step. So some of the frequencies i mentioned in my first post, that do not exist, could be entered into the software. the software also has a dropdown to select channel width. If you select the 12.5Khz designation, the radio will use the narrow front end filters and have a lower transmit audio deviation. If you were to mix modes what you would notice is lower audio volume from the narrowband signal into the wide band recieve (assuming no AGC), the narrow recieve of a wideband singal may have some clipping, the amount of clipping may be insignificant or very noticeable depending on the praticular speach characteristics.

Hope this helps to clear up some confusion, and i hope i didnt confuse anyone more.
 

CCHLLM

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Motorola radios have had PL capability since the 60's, either by adding optional or aftermarket hardware on older radios, or by programming on all software driven radios. Yes, the HT1250 will do the 20 khz channel spacing, or at least the one I have will. It may depend on the firmware version, but if there's even an issue with that in early firmware, I've never seen it and don't have an early one to check.
 
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