I'm using a Uniden Bearcat BC-125AT (version 1.06.06) and it will automatically tune to whatever is entered on the keypad to the closest 8.33 khz frequency. This mostly works when the "channel" is entered except for the dual 8.33/25 frequencies where in these cases the "channel" is closer to the next frequency up. For example if the "channel" 120.005 is entered the radio will tune to 120.0083 instead of the correct 120.0000. It works for the rest, for example if "channel" 120.015 is entered the radio will tune to 120.0166.
Programming 8.33 KHz frequencies
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I'm using a Uniden Bearcat BC-125AT (version 1.06.06) and it will automatically tune to whatever is entered on the keypad to the closest 8.33 khz frequency. This mostly works when the "channel" is entered except for the dual 8.33/25 frequencies where in these cases the "channel" is closer to the next frequency up. For example if the "channel" 120.005 is entered the radio will tune to 120.0083 instead of the correct 120.0000. It works for the rest, for example if "channel" 120.015 is entered the radio will tune to 120.0166.
Thanks for this information.
When you have a moment to spare please can you check if your BC125AT responds like the UBC125XLT does in this table HERE.
I only have the UBC125XLT scanner so it may be that the version of the firmware you have in you 125AT scanner may perform better.
However my UBC75XLT scanner get everything correct.
My verification device is a the certified Yaesu FTA-250 Airband Transceiver.
Yes the BC125AT appears to respond as per that table. When a channel is entered the correct 8.33 frequency is tuned except for the channels that end with 05, 30, 55, 80.
Thanks for that AirScan. I had not had until now a direct feedback for the BC125AT scanner tuning on 8.33 so your have now confirmed like the UBC125XLT it is not 100% correct and for me my programs "Airband Correction" is applicable to the BC125AT scanner.
5kHz wide voice transmission centred on 8.33kHz spacing to provide isolation between the transmissions. The naming is to do with limitations on the radio displays and simplifying* the communication
* clearly not enough for airband hobby listeners
5kHz is quite wide for normal voice. That would explain the 8.33kHz step as this give a 3.3kHz inter channel guard band.
Ubbe
Member
When I look at the spectrum in SDR# it seems that radios in VHF airband are limited to a 6KHz bandwidth +/-3KHz. When I look at what filters are used for AM in some Uniden scanners they use +/-9KHz or +/-10KHz filters. SDS100/200 scanners seems to be programmed to use a more narrow 10KHz bandwidth in the DSP, +/-5KHz. If the interference and bleedover issues can be solved by filter selection and IFX then SDS scanners have so far the best sounding AM mode of Uniden scanners.
Ubbe
I found the following to be of help discussing the details of 8.33:
http://www.lightaircraftassociation.co.uk/2013/Magazine/May/radio.pdf
833radio.com
ICAO, in order to stay with AM modulation as a bit of compatibility, went to 8.33 to avoid the bandwidth issues using 5khz which caused heterodyning of adjacent 5khz frequencies, but adding the complexity of 8.33 naming/channelization as already mentioned.
There is a potential modicum of compatibility with the new radios, but it sure seems like it's a hodgepodge. As long as new radios were required to comply with 8.33, why not bite the bullet and migrate a sub-band to digital, e.g., NXDN Very Narrow or even dPMR (look at dPMR446 channels in the EU CEPT countries)? LOTS of frequencies all of the sudden become available. Granted, eventual world-wide coordination, but same goes for 8.33 AM ... 8.33 planning and initial implementation goes back well over 20 years now, but evolving technologies should have been considered. It is what it is, but just adding 2 cents worth of ideas.
http://www.lightaircraftassociation.co.uk/2013/Magazine/May/radio.pdf
8.33kHz Voice Channel Spacing communications
ICAO, in order to stay with AM modulation as a bit of compatibility, went to 8.33 to avoid the bandwidth issues using 5khz which caused heterodyning of adjacent 5khz frequencies, but adding the complexity of 8.33 naming/channelization as already mentioned.
There is a potential modicum of compatibility with the new radios, but it sure seems like it's a hodgepodge. As long as new radios were required to comply with 8.33, why not bite the bullet and migrate a sub-band to digital, e.g., NXDN Very Narrow or even dPMR (look at dPMR446 channels in the EU CEPT countries)? LOTS of frequencies all of the sudden become available. Granted, eventual world-wide coordination, but same goes for 8.33 AM ... 8.33 planning and initial implementation goes back well over 20 years now, but evolving technologies should have been considered. It is what it is, but just adding 2 cents worth of ideas.
Ubbe
Member
AM has an advantage that you often can hear both of the transmissions if two transmit at the same time, and also are easy to hear that it is more than one transmitter operating at the same time. If two digital transmissions manage to start at the same time it will probably be silence from the decoder when it's too much bit error. It has to be a more complicated and costly frequency hopping technology for safety reasons that also need to be able to handle the doppler effect when an aircraft are travelling near Mach 1. Expensive military class radios.
There are different classes of AM aircraft radios depending of what they can handle in narrow bandwidth in both TX and RX and if they have 8.33 channel capability. It also include frequency offset capability, total some 7-8 different classes.
/Ubbe
There are different classes of AM aircraft radios depending of what they can handle in narrow bandwidth in both TX and RX and if they have 8.33 channel capability. It also include frequency offset capability, total some 7-8 different classes.
/Ubbe
Great find and a pleasure to readI found the following to be of help discussing the details of 8.33:
http://www.lightaircraftassociation.co.uk/2013/Magazine/May/radio.pdf
8.33kHz Voice Channel Spacing communications
ICAO, in order to stay with AM modulation as a bit of compatibility, went to 8.33 to avoid the bandwidth issues using 5khz which caused heterodyning of adjacent 5khz frequencies, but adding the complexity of 8.33 naming/channelization as already mentioned.
There is a potential modicum of compatibility with the new radios, but it sure seems like it's a hodgepodge. As long as new radios were required to comply with 8.33, why not bite the bullet and migrate a sub-band to digital, e.g., NXDN Very Narrow or even dPMR (look at dPMR446 channels in the EU CEPT countries)? LOTS of frequencies all of the sudden become available. Granted, eventual world-wide coordination, but same goes for 8.33 AM ... 8.33 planning and initial implementation goes back well over 20 years now, but evolving technologies should have been considered. It is what it is, but just adding 2 cents worth of ideas.
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