Air Distress - Now 121.505 MHz ?

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Air Distress - Now 121.505 MHz ?

Postby Mark5R » Fri Oct 12, 2018 12:00 pm

With the new airband steps I noticed the default fireground frequency at airports has changed from 121.600 to 121.605

I can find no notice but I am guessing that the emergency 'Guard' frequency has also changed from 121.500 to 121.505?

Can anyone confirm this?
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Re: Air Distress - Now 121.505 MHz ?

Postby thelad » Fri Oct 12, 2018 12:07 pm

Guard 121.500 should be staying.
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Re: Air Distress - Now 121.505 MHz ?

Postby Mark5R » Fri Oct 12, 2018 2:28 pm

Thanks thelad I am having a hard time figuring this all out

Some airports converting, others not. Some people are saying when ATC says for instance go to 128.855 that you should tune to the original 128.850? Not sure what thats about?

Also these are supposed to be new 8.33kHz steps but they are clearly 5kHz steps.
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Re: Air Distress - Now 121.505 MHz ?

Postby thelad » Fri Oct 12, 2018 3:29 pm

I have no idea myself! Was going to buy a cheap Icom A off Ebay but think i will wait and see what changes.
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Re: Air Distress - Now 121.505 MHz ?

Postby Minus1 » Fri Oct 12, 2018 5:59 pm

121.5 is NOT changing, nor is the SAR frequency of 123.1, nor the NATO common Tower freq of 122.1.
I've not seen any reference to 121.6.

Some common freqs are not yet changing:
http://publicapps.caa.co.uk/docs/33/CAP ... _NOV17.pdf

The numbers given for 8.33 kHz channels are CHANNELS they are NOT frequencies. They are NOT 5 kHz steps.

"128.855" is an 8.33 kHz bandwidth channel using a frequency of 128.85 MHz.
"128.85" is a 25 kHz bandwidth channel also using 128.85 MHz

Read and understand this:
https://www.eurocontrol.int/sites/defau ... 0table.pdf
The convention doesn't initially make a lot of sense to most people, but that's what they decided to do.
Professional airband transceivers are programmed to know this; I've yet to come across any scanner manufacturer that has bothered, I doubt any of them even understand the convention.

More CAA info:
https://www.caa.co.uk/General-aviation/ ... Hz-radios/

I now record 8.33 kHz channels using a semi-colon rather than a dot (like 128:855) to make it clearer.
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.
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Re: Air Distress - Now 121.505 MHz ?

Postby jonnyboyy » Mon Oct 15, 2018 11:01 pm

Listening to LHR UHF heard controller telling flight monitor tower 118.705 used to be 118.7. So do I need to alter this in my scanner to 118.705 or leave it as 118.7?

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Re: Air Distress - Now 121.505 MHz ?

Postby Chris P » Tue Oct 16, 2018 6:20 am

Leave it as it is the channel designation is .705 but the frequency is .700
The channel designation is dialled on an 8.33Khz aircraft transceiver but the actual frequency ( which is transmitted or received ) in each 100Khz segment of the airband is as below . Your scanner should be set to the frequency

Channel Frequency step Khz
118.005 118.0000 25
118.010 118.00833 8.33
118.015 118.0166 8.33
118.030 118.0250 8.33
118.035 118.0333 8.33
118.040 118.04166 8.33
118.055 118.0500 25
118.060 118.05833 8.33
118.065 118.06666 8.33
118.080 118.0750 8.33
118.085 118.08333 8.33
118.090 118.09166 8.33
118.105 118.1000 25

So if a channel designation is XX.005 you set your scanner to XX .0000 and if channel is XX.010 you set your scanner to XX.00833
Regards Chris aka G8FFF nipper or tazmin88
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Re: Air Distress - Now 121.505 MHz ?

Postby Minus1 » Tue Oct 16, 2018 8:33 am

It's already obvious we'll be repeating useful advice about 8.33 for years, yet for some people it will still go in one ear and straight out the other. :rolleyes:
It will take scanner manufacturers to properly implement 8.33 (including channel numbers and narrow AM bandwidth) to resolve this. As far as I am aware no scanner manufacturer does this yet (After all, it's only been 19 YEARS since 8.33 was first introduced!)
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.
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Re: Air Distress - Now 121.505 MHz ?

Postby FreqFreak » Wed Oct 17, 2018 11:15 am

Agreed, it just needs to be understood that frequencies with 3 decimal places are just "names" and don't match up with the actual frequency.

Good luck with getting scanner manufacturers to do simple things to make life easier for us, there's been a number of really obvious things over the years that would have made scanners better but they never bothered. It's as if they never really use them themselves!
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Re: Air Distress - Now 121.505 MHz ?

Postby Scan125 » Wed Oct 17, 2018 11:31 am

Minus1 wrote:It's already obvious we'll be repeating useful advice about 8.33 for years, yet for some people it will still go in one ear and straight out the other. :rolleyes:
It will take scanner manufacturers to properly implement 8.33 (including channel numbers and narrow AM bandwidth) to resolve this. As far as I am aware no scanner manufacturer does this yet (After all, it's only been 19 YEARS since 8.33 was first introduced!)


The Uniden UBC125XLT sort of gets right, however in my Scan125 Control Program I have to add what I call "Air Band Correction" to fix some which the UBC125XLT get wrong.

See: https://www.nick-bailey.co.uk/scan125/Manual/Scan125-Manual.html#48.1 and scroll down a little to Air Band Correction text.
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