Confused with calculating repeater offsets

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mjz55

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I'm new (2 weeks into ham radio) I'm having a mental block on how to calculate repeater offsets in the VHF and UHF bands. The frequencies shown is the frequency that the repeater transmits on. Your rig receives on that frequency.

I want to contact a repeater with a frequency of
146.640 - (would this be 146.040 for transmit in my radio?)

Also repeaters of
446.925 – (would this be 446.920 transmit in my radio?)
444.200 + (would this be 444.205 transmit in my radio?)
447.575 + (would this be 447.580 transmit in my radio?)
442.950 + (would this be 442.955 transmit in my radio?)

Thanks
 

wx5uif

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I'm new (2 weeks into ham radio) I'm having a mental block on how to calculate repeater offsets in the VHF and UHF bands. The frequencies shown is the frequency that the repeater transmits on. Your rig receives on that frequency.

I want to contact a repeater with a frequency of
146.640 - (would this be 146.040 for transmit in my radio?)

Also repeaters of
446.925 – (would this be 446.920 transmit in my radio?) -- If this is the output.. then the transmit would be in the commercial band (with standard 5mhz offset)
444.200 + (would this be 444.205 transmit in my radio?) -- 449.2 transmit
447.575 + (would this be 447.580 transmit in my radio?) -- If this is the output.. then the transmit would be in the commercial band
442.950 + (would this be 442.955 transmit in my radio?) -- 447.95 transmit

Thanks

Two of these would be traditional repeaters with their inputs 5mhz above their output. The other two, I have no idea.
 

gewecke

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I'm new (2 weeks into ham radio) I'm having a mental block on how to calculate repeater offsets in the VHF and UHF bands. The frequencies shown is the frequency that the repeater transmits on. Your rig receives on that frequency.

I want to contact a repeater with a frequency of
146.640 - (would this be 146.040 for transmit in my radio?)

Also repeaters of
446.925 – (would this be 446.920 transmit in my radio?)
444.200 + (would this be 444.205 transmit in my radio?)
447.575 + (would this be 447.580 transmit in my radio?)
442.950 + (would this be 442.955 transmit in my radio?)

Thanks

Turn on ARS in your radio and you'll be all set! (Auto repeater shift) Sometimes it's known as ARO - auto rptr offset too.

73,
n9zas
 

Jay911

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I'm new (2 weeks into ham radio) I'm having a mental block on how to calculate repeater offsets in the VHF and UHF bands. The frequencies shown is the frequency that the repeater transmits on. Your rig receives on that frequency.

I want to contact a repeater with a frequency of
146.640 - (would this be 146.040 for transmit in my radio?)

Also repeaters of
446.925 – (would this be 446.920 transmit in my radio?)
444.200 + (would this be 444.205 transmit in my radio?)
447.575 + (would this be 447.580 transmit in my radio?)
442.950 + (would this be 442.955 transmit in my radio?)

Thanks

If the repeaters are using standard offsets, you would be looking at the following:

146.040 input

441.925 input
449.200 input
invalid
447.950 input

The offset in the 440 MHz band is 5 MHz. 447.575 with a "positive offset" (add 5 MHz) is invalid as the input would be 452.575 which is outside the ham band. It would actually be 447.575 with "negative offset", also displayed as 447.575-, or input of 442.575.
 

ramal121

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You have the 2 meter correct. Most repeaters have a 600 KHz offset. It could plus or minus. The listed frequency is the repeater output, what your radio will receive. The offset is the shift the radio will do when you transmit. VHF and UHF repeaters are listed in megahertz, and 600 kilohertz is 0.6 MHz, so you add or subtract 0.6 to the repeater frequency as needed to get the transmit frequency.

UHF 70 cm is a little more uniform. Repeater outputs will always be between 440 and 445 MHz and always a plus offset (your radio transmits 445 to 449.975) The UHF offset is 5 MHz. Your error here is that you're using 5 kilohertz which is 0.005 megahertz. Add 5.0 to the output frequency to get your radios transmit frequency. In you example, 444.200 is your receive and 449.200 would be your transmit.

The two you listed above 445 MHz are not valid repeater output frequencies.
 

KB5ILY

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I would think that the 447.575 + should probably be - shift. Check with locals or the Repeater Coordinator in your area and ask if that is a non-standard shift.
 

kayn1n32008

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Why are they not valid, depending on where one lives they could very well be valid repeater pairs. I realize that he is in the US but as an example our Provincial Uhf system here in Alberta has repeaters that Tx on 443.xxx, 444.xxx, 446.xxx, and 447.xxx. What IS valid is what the local coordinating group gives you for pairs.
 

ramal121

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Why are they not valid, depending on where one lives they could very well be valid repeater pairs. I realize that he is in the US but as an example our Provincial Uhf system here in Alberta has repeaters that Tx on 443.xxx, 444.xxx, 446.xxx, and 447.xxx. What IS valid is what the local coordinating group gives you for pairs.

I'm trying to be general here for the sake of a new user. If you want to beat me up, lets step around the corner.

For the northern California listings from NARCC, of 663 listed UHF repeaters only two have a minus offset (both from Bakersfield, mmmmm).

Sure the ham will come across some oddball stuff out there and hopefully understand how to utilize it, but the UHF around here is pretty well written in stone.
 

kayn1n32008

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Not trying to 'beat you up' and I always value your knowlege and insite in the treads you contribute to. With that ramal, considering that he has a '3' call and he may very well see lots of 'oddball' high in, low out repeaters.
 

jaspence

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Offset question

http://www.dummies.com/how-to/content/ham-radio-for-dummies-cheat-sheet.html This link will give you a simple chart to help you understand.

A couple of quick examples:

147.04 + 147.64 is the transmit frequency
146.66 - 146.06 is the transmit frequency
444.500 will be + 449.500 transmit
447.500 will be - 442.500 transmit

147.00 can be either 147.60 or 146.40 transmit
 
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mjz55

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Thanks for all your help. I think I understand it way more now! I double checked the repeater frequencies listed and with the people involved and they said it is a +. This is the repeater website Skywarn.

gewecke, I have to check my radio to see if it has that automatic offset setting. It is not a ham radio. I don't remember seeing it but I could have missed it.
 

Jay911

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If it's a professional radio and not a ham radio, it won't have the automatic offset function, as that comes from amateur radios.

I still 99% guarantee that 447.575+ is a typo on the webpage's part. Ham radios would not be able to tune 452.575 as an input as that's outside the ham band. Either it's 447.575- or the '447' part is wrong.
 

fineshot1

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Mike - you can always look up the info on the ARCC website which is the coordinating council
in your area. The answer to your question is going to be all over the map from these folks on
RR due to it being a local area coordinating council policy.

ARCC - Main Page

but, in general your going to see the standard offsets below

on the 2mtr band - above 147MHz will be a + 600Khz offset
below 147MHz will be a - 600KHz offset
some areas may have some pairs for 1MHz and odd offsets

on 70cm(440-450) the offsets can go in either direction depending
on where you are, but in general if you are on or above 445MHz the
offset will be - 5MHz and if you are below 445MHz the offset will be a
+ 5MHz for the standard offsets.

on the 222 band in general the only standard offset is - 1.6MHz but
some local area councils may have others and pairs for odd offsets.

you can also find some of this info in the ARRL repeater directory.
 

loumaag

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Everyone here is saying basically the same thing. The repeaters above 445 MHz will probably have a - 5 MHz offset. Indeed I feel the page you linked has a several typos on it, but for further evidence on the specific 447.525 repeater you mentioned, according to this site, it has a negative "-" offset, not a positive one.
 

mjz55

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Jay911, I went to the above suggested ARCC page and it does show a -. Thanks fineshot1, that is a very informative page!
 

KB7MIB

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ramal121, per the 2010-11 ARRL Repeater Directory, NorCal has a plus offset, but SoCal has a minus offset. AZ & NM use a mix. CO, NV & UT use minus offsets. OR & TX use a plus offset. So 70cm isn't standardized nationwide. Just throwing that out there.
 
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MountainMike

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This is fine and good for ham radio but I also have a scanner and I discovered a frequency of 458.418MHz which is not a ham band. Does the same rule apply? 5MHz? If so is it + or -?
 

ko6jw_2

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Non-Ham Repeater Offsets

The offset depends on the band. 450-470Mhz is 5Mhz. 470-512Mhz is 3Mhz. 800 Mhz band is 45Mhz.

150-174 Mhz band is locally assigned and don't have a fixed offset. Same for 30-50Mhz, although there are few repeaters on this band. CHP has some and CA State Parks used to.

Some frequencies are not paired and are assigned for tactical use etc.

For scanner users the offsets are usually irrelevant because you want to listen to the repeater output - not the input.

There are exceptions. For example, USFS has many repeaters and you can hear the dispatcher locally on the input even when the repeater is out of range. Also, it can be interesting to listen on the input of a repeater system as a test of a new antenna etc. Weak signals from mobiles can help with testing.
 

ecps92

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458.418 is not a valid Frequency

It could be
458.4125 or 458.4250

And No, if this is the actual Freq this is the input, so the output would be 453.xxxx

UHF Part 90 is
451-453 Mhz Rptrs/Simplex
456-458 Mhz input/simplex
460-464 Mhz Rptrs/Simplex
465-469 Mhz input/simplex



This is fine and good for ham radio but I also have a scanner and I discovered a frequency of 458.418MHz which is not a ham band. Does the same rule apply? 5MHz? If so is it + or -?
 

wtp

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a good book

to read is the arrl repeater directory. i used to carry the pocket edition all the time but now i would like the desktop version.
 
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