What's the VHF/UHF channel spacing where you live?

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KF5YDR

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Here in Texas we're on 20kHz channel spacing on 2m, but 25kHz on the rest of the bands. Having never operated FM in another state I had never given it much thought, but apparently a lot of places use 25kHz channels for everything, which is weird because 146.52 is not a valid 25kHz channel.

Some places are apparently on 15kHz channels, which doesn't seem like it offers enough of a guard band for a 10kHz-wide signal coming from equipment which requires no type acceptance and has usually not been tested or aligned since the factory (but I guess it works or they wouldn't do so).

What's it like where you live?
 
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zz0468

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Here in Texas we're on 20kHz channel spacing on 2m, but 25kHz on the rest of the bands. Having never operated FM in another state I had never given it much thought, but apparently a lot of places use 25kHz channels for everything, which is weird because 146.52 is not a valid 25kHz channel.
I don't think anywhere is using 25 KHz spacing on 2 meters. In Southern California it's 20 KHz below 146, and 15 KHz above 146. The 440 band is 20 KHz spacing.

Some places are apparently on 15kHz channels, which doesn't seem like it offers enough of a guard band for a 10kHz-wide signal coming from equipment which requires no type acceptance and has usually not been tested or aligned since the factory
The original ARRL bandplan for 2 meters called for 60 KHz, and then 30 KHz spacing. In the mid to late 70's, that was again split to 15 KHz. This was all before repeater operation was legal below 146. When the 144-146 channels were implemented, I know the S. Calif people decided on 20 KHz because of that very problem.

(but I guess it works or they wouldn't do so).
In my area, the technical requirements for a repeater (and it's users) calls for 4.2 KHz maximum deviation, and a 3 KHz maximum audio frequency to the transmitter. Per Carson's Rule, that creates an occupied bandwidth of less than 15 KHz so, in theory, it would work.

The 440 band was changed about 15 years ago from 25 KHz to 20 KHz spacing. The reason for that was because most radios out there at the time were incapable of peaceful coexistence with adjacent channels only 12.5 KHz away. The full 5 KHz deviation can be used and still stay within the assigned channel slot.
 
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DaveNF2G

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I am unaware of any 20 kHz spaced repeaters on 440 in or near New York. 25 kHz is still the standard here.

On two meters, it's 15 kHz above 146 (roughly) and 20 kHz below.
 

nd5y

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Here in Texas we're on 20kHz channel spacing on 2m, but 25kHz on the rest of the bands.
Assuming you are talking about repeater coordination you are wrong about Texas.
6m is 20 kHz spacing.
2m is 20 kHz with a few in between on 10 kHz channels. The simplex parts of 2m are not channelized.
220 is 20 kHz
70 cm (440-450) is mostly 25 kHz with a few narrowband and digital repeaters in between on 12.5 kHz channels.
 
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KF5YDR

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I mean, simplex isn't "channelized" anywhere, but we tend to use frequencies that are multiples of a given channel step. No one is using 146.4025, for example.

You're absolutely right about the rest of it, of course. I don't own gear for anything but 2m and 70cm, so I didn't look too closely at the rest of the band plans.
 

zz0468

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I am unaware of any 20 kHz spaced repeaters on 440 in or near New York. 25 kHz is still the standard here.
Just to clarify, my remarks about 20 KHz spacing on 440 were in reference to Southern California, not nationwide.
 

zz0468

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I mean, simplex isn't "channelized" anywhere...
This is incorrect. Within the various band plans, particularly within the repeater sub-bands, there are channelized unpaired frequencies set aside for FM simplex use.

Below the repeater sub-bands is un- channelized spectrum that is generally mixed mode, including FM. SSB and AM are not usually referred to as "simplex".
 

KF5YDR

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California's way different, then. Our bandplans keep FM and weak-signal modes separate, don't define steps or channels for simplex, and with the exception of 6m, don't have any FM simplex allocations in our repeater sub-bands. The only exception is 146.40, for repeaters on 147.00 with a negative offset, and I suppose technically the allocations for experimental transmissions.

Looks like there is WAY more regional variation than I thought. Glad I started this thread!
 
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DaveNF2G

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...don't have any FM simplex allocations in our repeater sub-bands. The only exception is 146.40, for repeaters on 147.00 with a negative offset,...
I'm not sure I understand what you mean here. 146.40 is a repeater input channel, not a simplex channel. Simplex refers to non-repeaterized allocations. Duplex pairs are allocated for repeater and other 2-frequency operations.
 

Token

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I'm not sure I understand what you mean here. 146.40 is a repeater input channel, not a simplex channel. Simplex refers to non-repeaterized allocations. Duplex pairs are allocated for repeater and other 2-frequency operations.
In the ARRL band plan for 2 meters 146.400 is a simplex channel. I know that in many areas (including here locally) it is a repeater input.

T!
 

KF5YDR

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I'm not sure I understand what you mean here. 146.40 is a repeater input channel, not a simplex channel. Simplex refers to non-repeaterized allocations.
*laugh* I know what simplex is. The Texas band plan allocates 146.40 as a simplex channel, but as an alternate repeater input for the 147.00 output on a case-by-case basis. The 147.00 output channel uses a positive offset in most of Texas.
 

KB1VAI

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channel spacing 25khz?

I'm not sure how this can work. my rig can use 25 khz 20 khz 12.5khz.

How would you use 15 khz?

Thanks in advance,

KB1VAI
 

kayn1n32008

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I'm not sure how this can work. my rig can use 25 khz 20 khz 12.5khz.



How would you use 15 khz?



Thanks in advance,



KB1VAI

What radio are you referring to? Check in settings, most ham rigs also have 5KHz, 10KHz, 15KHz, and some also have 30KHz steps.

My V71 does 5, 6.25, 10, 15, 20, 25, 30, 50 and 100KHz step sizes.


Sent from my iPad using Tapatalk
 

KB1VAI

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channel bandwith

I do have all the settings from 2.5 khz to 50 khz.that part i think i understand.
Iguess my question is when i program a frequency like 156.862 iwould be able to use 2.5 step
to get on the right frequency but if the frequency is 12.5 khz bandwith should i try to use 12.5
step to get the channel? I thought that we only use step size to acess a frequencys or to scan?
mr rig has 25 khz 20 and 12.5 for bandwith .Ithink i am confussed about this as much as i am with
computor skills.
thanks again.
Kb1vai.
 

KF5YDR

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Let's go over some basics.

Bandwidth is how much spectrum a signal takes up. On FM that is measured as deviation, the maximum amount above and below the center frequency the transmitter or receiver detector will skew. Valid current/historic options for FM deviation are 2.5, 5, 15 kHz deviation for two-way, 75 kHz for stereo broadcast.

Now, these are expressions of bandwidth, but they don't tell us channel width (interchangeable with step size even though they are technically different, more later). Some spectrum above and below the maximum bandwidth (deviation) of a signal is set aside in what is called a guard band, to make sure signals on adjacent channels don't interfere with each other. There's math to determine how wide the guard band has to be, but what is boils down to is 2.5 kHz deviation uses a 12.5 kHz channel, 5 kHz dev/25 kHz channel, 75 kHz Dev/200 kHz channel.

Step size is just the space between channel center frequencies. Since a 2.5 kHz narrowband FM signal lives in a 12.5 kHz channel, we use a 12.5 kHz step to tune from one to the next. It gets a little more complicated when you add splinter frequencies to the mix, but that's the gist of the whole thing.

Your 156.862 frequency is not a valid channel in any of those steps, so how you get to it is moot (and you'd have to use a 2 or 1 kHz step to get there, which almost no transceiver/receiver with a stepped VFO will do).

Clear as mud? :p
 

AK9R

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First off, bandwidth is a function of deviation and the maximum frequency of the audio used to modulate the RF signal. This is defined by Carson's rule which states:

Bandwidth = 2 x (Deviation frequency + Maximum audio frequency)

Therefore, if you assume that the maximum audio frequency is 3 kHz, which is standard for communications-grade audio, and the deviation is +/- 5 kHz, the bandwidth is:

BW = 2 (5 kHz + 3 kHz) = 16 kHz

If you reduce the deviation to +/- 2.5 kHz, the bandwidth is:

BW = 2 (2.5 kHz + 3 kHz) = 11 kHz

This is reflected in the FCC emission designator which appears in the license grant. That is, 16K0F3E is 16 kHz bandwidth frequency modulation single analog channel telephony. Likewise, 11K0F3E is 11 kHz bandwidth, yadda, yadda.

This is the technical description of the bandwidth of the transmitted signal and it has nothing to do with regulatory dictates which say the bandwidth may be no more than X or radio design decisions which say the channel step size is Y.

That said, FCC rules which require "narrowband", i.e. no more than 12.5 kHz bandwidth, do not apply to amateur radio. Consequently, most amateur radio manufacturers see no need to make provisions for "narrowband" in the radios they market to amateur radio, though some amateur radios do have a narrowband setting.

Additionally, standards for step size which apply to Land Mobile Radio (FCC Part 90) in the UHF band do not necessarily apply to LMR in the VHF band. Specifically, prior to "narrowbanding" the standard channel spacing in VHF was 15 kHz. With "narrowbanding", the standard channel spacing is 7.5 kHz while in the UHF band it was 25 kHz before and 12.5 kHz after.

A channel spacing of 7.5 kHz is not always compatible with the 5, 6.25, 10, 12.5, 15, 20, 25, 30, 50, and 100 kHz spacing that many amateur radios provide. For example, let's take the old AAR (railroad) channel 46, aka 160.800 MHz. Before "narrowbanding", the adjacent channels were 160.785 and 160.815 MHz. A radio with a 5 or 15 kHz step size will tune those channels just fine. However, now with "narrowbanding", the adjacent channels are 160.7925 and 160.8075 MHz. Most amateur radios simply do not have a step size that will tune those frequencies. They are not evenly divisible by 0.005, 0.00625, 0.010, 0.0125, 0.015, 0.020, 0.025 MHz, etc. You can get close, but you can't get right on. However, if your radio has 2.5 or 7.5 kHz as an available step size, you can tune in the exact frequency.
 

KF5YDR

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I didn't know narrowbanding meant a 7.5 kHz step. What's the rationale for the different channel widths on different bands?
 

nd5y

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The FCC allocates frequencies that are generally spaced at fixed steps.
See the frequency tables at Public Safety Pool and Industrial/Business Pool
On low band most channels are spaced at 20 kHz.
On high band most are 7.5 kHz.
On UHF most are now 6.25 kHz.

The NTIA does the same thing for federal users but most federal channels on both high band and UHF are spaced at 12.5 kHz steps.
Marine, aviation and other stuff can be the same way or different.

I don't know exactly how present day ham radio repeater channel spacing came about since it varies in different areas.
In Texas there was an uproar in the mid 1980's when the frequency coordinator decided to go from 15 kHz to 20 kHz spacing on 2 meters.
Many repeater owners were not happy about being forced to change frequencies which meant they had to buy new crystals and retune duplexers.
 
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