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8.33 spacing questions

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dave3825

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I was wondering if anyone here has an xls file with the 8.33 spacing from 108.000 to 137.000 that I can compare to what I did.

I tried using something I found online but I am not sure its correct. It did say that with the 8.33 spacing I should get 2280 channels and I did get 2280 channels with the last of 136.9916, like the default band chart says at marks scanners. Does the sample below look correct?

I get
118.0000
118.0083
118.0167
118.0250
118.0333
118.0417
118.0500
and the last is 136.9916 number 2280 which is what’s listed on marks scanners and I think to be correct


This is being done by typing 108.0000 in A1 and typing in A2 =A2+0.0083333 , hitting enter, and dragging it down..

My reference point was Roger-Wilco | 8.33 kHz Channel spacing



I am also having an issue getting sdrsharp to scroll the same freqs with a spacing of 8.33 khz. I start on 108.000 with the spacing set to 8.33khz and on the first scroll I get 108.06780. Scrolling back you would think it would be 108.000 but I get 107.998450. Very confused with that.


Any help would as always be appreciated.

Thanks
 

airwolfbell222

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In the 108-117.95 mhz range you'll only find 50khz steps being used in which you'll find mostly VOR and Localizers. In the US, 8.33khz steps are not in use with ATC.
 

nd5y

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This is being done by typing 108.0000 in A1 and typing in A2 =A2+0.0083333 , hitting enter, and dragging it down..
That doesn't work for some reason.

This isn't an excel spreadsheet but it shows how the actual frequencies are mapped to radio dislpay.
http://www.eurocontrol.int/sites/default/files/article/content/documents/communications/2016-03-frequency table.pdf

See also the paragraph Frequency/channel tables at the bottom of the page http://www.eurocontrol.int/833.
 
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dave3825

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In the 108-117.95 mhz range you'll only find 50khz steps being used in which you'll find mostly VOR and Localizers. In the US, 8.33khz steps are not in use with ATC.

My bad on the 108 to 118 (I had those in as V O R) and I understand that 118 to 136 8.33 are not used in the US with the ATC, but if that's the case, why are some of the newer scanners listing the default step sizes for the airband as 118 - 136 with a 8.33 khz step size, as seen below?

Pro 106 Easier to Read Pro-651/652/106/197 - WS1040/1065 - PSR 500/600 Digital Scanner Manual 108-136.9916 8.33 AM Civilian Air

Bcd436hp Easier to Read BCD436/536HP Digital Scanner Manual 108.0000 136.9916 AM 8.33 Commercial Aircraft


I am interested in the 8.33 freqs that are being used by the following, a quote from a wiki,

"Some channels between 123.100 and 135.950 are available in the US to other users such as government agencies, commercial company advisory, search and rescue, military aircraft, glider and ballooning air-to-ground, flight test and national aviation authority use. "

source https://en.wikipedia.org/wiki/Airband#Spectrum_usage




.
 

nd5y

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All the stations that are authorized to use 8.33 KHz channels in the US are non-FAA and will have FCC licenses that you can easily look up.

Here are the parts of the FCC rules that deal with 8.33 kHz channel operations:
eCFR — Code of Federal Regulations

§87.133 Frequency stability.
(g) Any aeronautical enroute service transmitter operating in U.S. controlled airspace with 8.33 kHz channel spacing (except equipment being tested by avionics equipment manufacturers and flight test stations prior to delivery to their customers for use outside U.S. controlled airspace) must achieve 0.0005% frequency stability when operating in that mode.

§87.137 Types of emission.
Notes:
17 In the band 117.975-137 MHz, the Commission will not authorize any 8.33 kHz channel spaced transmissions or the use of their associated emission designator within the U.S. National Airspace System, except, on an optional basis, by Aeronautical Enroute Stations and Flight Test Stations, or by avionics equipment manufacturers which are required to perform installation and checkout of such radio systems prior to delivery to their customers. For transmitters certificated to tune to 8.33 kHz channel spacing as well as 25 kHz channel spacing, the authorized bandwidth is 8.33 kHz when tuned to an 8.33 kHz channel.

§87.263 Frequencies.
(a) Domestic VHF service. (1) Frequencies in the 128.8125-132.125 MHz and 136.4875-137.00 MHz bands are available to serve domestic routes, except that the frequency 136.750 MHz is available only to aeronautical enroute stations located at least 288 kilometers (180 miles) from the Gulf of Mexico shoreline (outside the Gulf of Mexico region). The frequencies 136.900 MHz, 136.925 MHz, 136.950 MHz and 136.975 MHz are available to serve domestic and international routes. Frequency assignments may be based on either 8.33 kHz or 25 kHz spacing. Use of these frequencies must be compatible with existing operations and must be in accordance with pertinent international treaties and agreements.

(c) International VHF service. Frequencies in the 128.825-132.000 and 136.000-137.000 MHz bands are available to enroute stations serving international flight operations. Frequency assignments are based on either 8.33 kHz or 25 kHz channel spacing. Proposed operations must be compatible with existing operations in the band.

§87.287 Frequencies.
(a) The frequencies assignable to aircraft data link land test stations are 131.450 MHz, 131.550 MHz, 131.725 MHz, 131.825 MHz, 136.850 MHz, 136.900 MHz, 136.925 MHz, 136.950 MHz, and 136.975 MHz. Interstitial frequencies separated by 8.33 kilohertz from these frequencies may also be assigned.

§87.303 Frequencies.
(f) Frequency assignments for Flight Test VHF Stations may be based on either 8.33 kHz or 25 kHz spacing. Assignable frequencies include the interstitial frequencies 8.33 kHz from the VHF frequencies listed in paragraphs (a) and (b) of this section. Each 8.33 kHz interstitial frequency is subject to the same eligibility criteria and limitations as the nearest frequency listed in paragraphs (a) and (b) of this section.

The frequencies listed in paragraphs (a) and (b) are between 123.125 and 123.575.
 
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DaveNF2G

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My bad on the 108 to 118 (I had those in as V O R) and I understand that 118 to 136 8.33 are not used in the US with the ATC, but if that's the case, why are some of the newer scanners listing the default step sizes for the airband as 118 - 136 with a 8.33 khz step size, as seen below?

.
For the same reason many of them don't have 7.5 kHz available on VHF, and the same reason band searches don't land on US channels on VHF. The scanners are designed and the firmware programmed in Asia.
 

dave3825

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For the same reason many of them don't have 7.5 kHz available on VHF, and the same reason band searches don't land on US channels on VHF. The scanners are designed and the firmware programmed in Asia.
So your saying that newer scanners, that are made for use in the United States, don't have 7.5 khz step size or band searches that land on US channels, is because their firmware is programmed in Asia reflecting Asia's scanner defaults?
 
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natedawg1604

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So, what type of company/entity/operation is most likely to use 8.33 kHz within the US? Do people typically re-program or upgrade existing radios for 8.33 spacing?

Also once you buy a 8.33 kHz radio for intra-company channels, could the radio communicate on-the-fly with 25kHz radios if necessary (i.e. without programming changes)?
 

nd5y

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So, what type of company/entity/operation is most likely to use 8.33 kHz within the US?
This was answered in post #6 above.
Do people typically re-program or upgrade existing radios for 8.33 spacing?
I haven't heard of an avionics AM com radio that can be reprogrammed or upgraded.
Also once you buy a 8.33 kHz radio for intra-company channels, could the radio communicate on-the-fly with 25kHz radios if necessary (i.e. without programming changes)?
Some radios automatically select the correct bandwith for the selected frequency, others need the operator to manually select the bandwidth, then the radio only allow 25 or 8.33 kHz frequencies depending on which bandwidth is selected. 8.33 KHz radios don't always display the exact frequency. There is more information about this in the stuff I linked to in post #4 above.

It's still AM. If the max audio frequency is limited to 3 kHz like in most communications quality radios and audio circuits then the transmitted signal should not be more than 6 kHz wide. I don't think you could tell the difference by listening. As far as I know 8.33 kHz only requires tighter transmit frequency tolerance and narrower transmit and receive filtering but I could be wrong. I never worked on com radios when I was in avionics.
 
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natedawg1604

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Lockheed Martin and Bell Helicopter in the DFW area each have one 8.33 kHz frequency licensed.
KA97185 (BELL HELICOPTER TEXTRON INC) FCC Callsign Details
WQGL678 (Lockheed Martin Corporation) FCC Callsign Details
WQGL679 (Lockheed Martin Corporation) FCC Callsign Details
I don't know if they are actually used. I don't know of any others and haven't looked very hard.
So, the Emission Codes have necessary bandwidths of 5.0 kHz, 5.6 kHz and 6.0 kHz. Which of these implies a 25 kHz vs. 8.33 kHz channel spacing?
 

nd5y

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So, the Emission Codes have necessary bandwidths of 5.0 kHz, 5.6 kHz and 6.0 kHz. Which of these implies a 25 kHz vs. 8.33 kHz channel spacing?
Emission designators designate occupied bandwidth, not channel spacing.
You can't always go by emission designators on licenses. Sometimes they don't reflect what is used in real life.
The ones on the licenses in question are all less than or equal to 6 kHz bandwidth.
I assume the 5.0 and 5.6 ones are for 8.33 kHz channels, but I could be wrong.
The table in 87.137 says that at frequencies above 50 MHz, 6 kHz bandwidth AM (6K00A3E) is authorized 50 kHz bandwidth (or 25 kHz if the transmitter was made after 1974) and 5.6 kHz bandwidh AM (5K60A3E) is authorized 8.33 kHz bandwidth.
The FCC rules don't make sense. How can a 6 kHz wide signal be 25 to 50 kHz wide?
 

natedawg1604

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Emission designators designate occupied bandwidth, not channel spacing.
You can't always go by emission designators on licenses. Sometimes they don't reflect what is used in real life.
The ones on the licenses in question are all less than or equal to 6 kHz bandwidth.
I assume the 5.0 and 5.6 ones are for 8.33 kHz channels, but I could be wrong.
The table in 87.137 says that at frequencies above 50 MHz, 6 kHz bandwidth AM (6K00A3E) is authorized 50 kHz bandwidth (or 25 kHz if the transmitter was made after 1974) and 5.6 kHz bandwidh AM (5K60A3E) is authorized 8.33 kHz bandwidth.
The FCC rules don't make sense. How can a 6 kHz wide signal be 25 to 50 kHz wide?
Yeah it's a bit of an odd rule, and it hasn't been amended since 1988. After a bit more reading, I think you are correct. I pulled the spec sheets for several Air Band radios, namely the Rexon RHP-530, ICOM A14, ICOM IC-A24/IC-A6, and ICOM iC-a6e/iC-a24e. The spec sheets all indicate 6K00A3E = 25kHz spacing, and 5K60A3E= 8.33 spacing.
 
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