UK airband monitors, how do you do this? After reading a bunch of webpages, I'm still trying to get it straight. For an upcoming trip to Scotland, I'm trying to program local airband freqs and am getting hung up on the 8.33 KHz transition. For instance, if a frequency is shown as 135.475 in official documentation, will it actually center on 135.475 or the rounded freq of 135.480? Should I adjust all the 25Khz frequencies upward? (My radio supports 8.33 KHz steps). Thanks for any clarification.
Programming 8.33 KHz frequencies
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If they are published that way I would program them exactly to what is published, if you are band scanning for new then make sure to use step 8.33. There are many scanners that have that ability but little discussion about it here in the CONUS.
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135.475 is correct. Note that is a 8.33 kHz channel--why do think it is not? (For example 135.475 = 118.000+2087*0.008333.
And 135.480 is not such a frequency.
All of the old 25 kHz channels remain. They simply added 2 new channels in between them. E.g., between 123.40000 and 123.42500, there are new channels 123.40833 and 123.41666.
I wrote about this here:
forums.radioreference.com
I wrote about this here:
Another 8.33 kHz Scanner table anybody? Here you are!
Original is in Open Document Spreadsheet Format (which is not permitted here). PM me if you want it, newer Excel will probably open it correctly.
Another thought on this the tuning heads in most of the aircraft I work on only have 5 digits in display. Probably again why few of the 8.33 freqs are in use?? We have in Vegas our ops freq is 131.875 but the pilots can only tune 131.87. Showing the complex addition to adding something like 123.40833
So that would mean I just program in freqs as shown in official pubs without any adjustment? Sounds easier than I expected.All of the old 25 kHz channels remain. They simply added 2 new channels in between them. E.g., between 123.40000 and 123.42500, there are new channels 123.40833 and 123.41666.
I wrote about this here:
Another 8.33 kHz Scanner table anybody? Here you are!
Original is in Open Document Spreadsheet Format (which is not permitted here). PM me if you want it, newer Excel will probably open it correctly.
You need to think of this slightly differently.
135.480 is a channel label and NOT a frequency
The frequency which that channel label represents is 135.475 MHz
There are a few exceptions where 25kHz channels remain in use (ACARS, VDL2, SAR Ops, IAD). so, 121.500 would be used as the label AND the frequency (rather than a controller referring to it with the label 121.005)
As for input to aircraft radios - those used in ICAO EUR Region now accpet input by channel name or frequency so you don't have to worry about long strings of numbers. The radio will tune to the correct frequency just as it did before when the third decimal place wasn't shown.
135.480 is a channel label and NOT a frequency
The frequency which that channel label represents is 135.475 MHz
There are a few exceptions where 25kHz channels remain in use (ACARS, VDL2, SAR Ops, IAD). so, 121.500 would be used as the label AND the frequency (rather than a controller referring to it with the label 121.005)
As for input to aircraft radios - those used in ICAO EUR Region now accpet input by channel name or frequency so you don't have to worry about long strings of numbers. The radio will tune to the correct frequency just as it did before when the third decimal place wasn't shown.
What type/model radio are you using ?
I don't see anything in either of the user manuals that talks about using the channelization scheme that's used in avionics, so I'm guessing you just enter the actual frequency: 123.40833 MHz instead of the spoken channel "123.410", 123.43333 instead of "123.435", 123.45000 instead of "123.455" or "123.450", etc.
I found this website to be a good source about the 8.33 tech. Specifically the embedded PDF page. 8.33 is confusing because the frequency used is not necessary the freq displayed.
So to answer the main question from post 1: it depends.
If it's a scanner, for example the Uniden BC125AT, plug in the actual center frequency. Example being that if someone charted 118.035 it would be entered as 118.033.
If it's a pro-level radio, aircraft radio or something similar then plug in the charted frequency the radio will take care of it in the back end.
So to answer the main question from post 1: it depends.
If it's a scanner, for example the Uniden BC125AT, plug in the actual center frequency. Example being that if someone charted 118.035 it would be entered as 118.033.
If it's a pro-level radio, aircraft radio or something similar then plug in the charted frequency the radio will take care of it in the back end.
spanky15805
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ICAO is coming. Wait until you have "climax" on top of 8.33 and trying to program the scanner. Go*gle it.
Read Here: Scan125 Control Program User Manual (nick-bailey.co.uk)
If you have a certified airband transceiver/receiver then the published Airport / ATC called settings will be mapped to the actual frequency that is actually used. Some scanners get this mapping correct. Others do not.
If Airport/ATC say abd.defg then pilots do not give a monkeys if actually a real frequency of hij.klmn is used. Since the introduction of 8.33 then published / called by ATC frequencies are actually just a SETTING to be dialled into the aircraft radio kit. This setting may or may not be an absolute frequency. The only exception to this would be the 25kHz/50kHz ones.
Translation from abd.defg to hij.klmn is done by the radio kit. For proper aircraft radios and pilots "it just happens". For us people with scanners and other non certified for airband radio kit then our kit may or may not get the absolute required frequency correct.
Not sure what else to add
If you have a certified airband transceiver/receiver then the published Airport / ATC called settings will be mapped to the actual frequency that is actually used. Some scanners get this mapping correct. Others do not.
If Airport/ATC say abd.defg then pilots do not give a monkeys if actually a real frequency of hij.klmn is used. Since the introduction of 8.33 then published / called by ATC frequencies are actually just a SETTING to be dialled into the aircraft radio kit. This setting may or may not be an absolute frequency. The only exception to this would be the 25kHz/50kHz ones.
Translation from abd.defg to hij.klmn is done by the radio kit. For proper aircraft radios and pilots "it just happens". For us people with scanners and other non certified for airband radio kit then our kit may or may not get the absolute required frequency correct.
Not sure what else to add
Sort of. I've heard some traffic from Euro airports where they use the +0.005 channel when speaking about the 25 kHz channels; not sure when/why. E.g., LSZH APP tells pilots to switch to TWR on "120.230" instead of "120.225" or "120.22". LiveATC uses them at random, even on the same airport (see 121.855 immediately followed by 121.925 at LSZH).
The exception I of 25kHz / 50kHz still stands. I was trying to say that frequencies of 25kHz / 50kHz are not changed by the radio kit and are the exact "live" frequencies.
In your example (see my referenced table) 120.230 is the called and ACTUAL live frequency used by the radio kit is 120.225. The radio does the translation from 230 to 225.
A reason for calling 120.230 instead of 120.225 is probably due to speech economy and pilot time economy
One Two Zero Decimal Two Three vs One Two Zero Decimal Two Two Five
Also if all the next in transit required frequencies are on xxx.yy0 then 0 can be left set.
LSZH is 8.33kHz channelised.
120.230 is the correct terminology for the 8.33kHz channel they use and that will be reflected in the official publications. There are very few 25kHz channels (see my earlier reply for examples). Just because a frequency is divisible by 25kHz it isn't a 25kHz channel anymore.
LiveATC labelling can be whatever an individual wants to use and has nothing to do with officialdom. One would hope that enthusiasts would use the correct terminology and labelling but many don't really care about proceedcake, just listening to hairband.
Even people professionally engaged in use of the system seem to have problems. An ATCO here thinks the channel labels are the actual frequencies. Quite shocking but much like a pilot he doesn't need to know what happens inside the cream coloured boxes on his desk.
n2nov
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If your radio can program in 8.33 kHz steps, you will see this scheme:
120.00000
120.00833
120.01666
120.02500
120.03333
120.04166
120.05000
120.05833
120.06666
120.07500
120.08333
120.09166
120.10000
120.10833
120.11666
120.12500
120.13333
120.14166
120.15000
120.15833
120.16666
120.17500
120.18333
120.19166
120.20000
120.00000
120.00833
120.01666
120.02500
120.03333
120.04166
120.05000
120.05833
120.06666
120.07500
120.08333
120.09166
120.10000
120.10833
120.11666
120.12500
120.13333
120.14166
120.15000
120.15833
120.16666
120.17500
120.18333
120.19166
120.20000
Exactly but as the radio kit in old and new aircraft can not dial/set to 4 decimal places a scheme (bad in my view) was concocted to allow old legacy and new kit to be able to tune the the new 8.33 frequencies. In simplest terms for the punters the digits just represent a lookup table entry.
Were the authorities to decide to move to 200MHz frequencies then to avoid then all sorts of costs and issues they could just get the radios to remap and leave the dials etc. as they are.
With the 8.33 introduction I gather the "channel" concept was introduced to follow/mimic the like of Marine channels etc. The problem is that the frequency vs channel are inconstant with each other in that in the US and other countries where 8.33 has not been adopted or certainly not used the called/published frequency is the actual frequency.
Another issue is that typical radio and scanner users are used to talking and working on absolute frequencies. It is actually only the civil airband that has stepped sideways. As mentioned before pilots etc. don't care about absolute frequencies. They just read/hear/punch the numbers and hope find someone on the other end. An exception to this would be the limited number of HF frequencies.
n2nov
Active Member
If the radio that can only do 3 decimal places and if it can set the last place to 1 kHz steps, I would set it to:
120.00000
120.008
120.017
120.02500
120.033
120.042
120.05000
120.058
120.067
120.07500
120.083
120.092
120.10000
120.108
120.117
120.12500
etc
The radio should still be able to hear the transmission even if it is up to 2 kHz away from the carrier spot.
Well I have to assume that:
a) 8.33 was chosen as 25 / 3 = 8.333333
b) there was concern about receiver discrimination / reception overlap if 25 was split by 4 i.e. 5 kHz spacing
c) they wanted frequencies to be centred exactly on 8.3333 and not 8 and 16
d) they wanted the last digit to be either 0 or 5
But yes 120.108 and 120.117 would be more logical if one was talking "nearest frequency".
I've not found a explanation of how they decided to arrange things as they are, but they have, and as long as the kit works I don't think ATC, Airports and Pilots care.
a) 8.33 was chosen as 25 / 3 = 8.333333
b) there was concern about receiver discrimination / reception overlap if 25 was split by 4 i.e. 5 kHz spacing
c) they wanted frequencies to be centred exactly on 8.3333 and not 8 and 16
d) they wanted the last digit to be either 0 or 5
But yes 120.108 and 120.117 would be more logical if one was talking "nearest frequency".
I've not found a explanation of how they decided to arrange things as they are, but they have, and as long as the kit works I don't think ATC, Airports and Pilots care.
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