1.8 inch display with Air Player

[Sling]

Problem is, if you use a 25khz radio in an 8.33 environment you will overlap the two neighbouring freq IRL, that is the reason it’s become mandatory in Europe.

Jacques

Can you explain the basis for this statement because that’s not how I understand it. In that scenario the 25khz radio just can’t tune to the extra frequencies. It can still do all the 25k frequencies.

Tony

[JackZ]

Can you explain the basis for this statement because that’s not how I understand it. In that scenario the 25khz radio just can’t tune to the extra frequencies. It can still do all the 25k frequencies.

Sure.
This is related to the precision of the peak signal strength. As with every radio waveform, the broadcasted signal is slighly "overlapping" around the set frequency (peak signal) and the signal strength is weakening around this center position into an inverted U shaped curve. The radio equipement uses electronic filtering so to ensure that the curve is not spreading too far on both sides of the set frequency.

In the old "25Khz frequency step" radios, each radio signal had to be separated every 25 Khz, with the signal strength curve being at its minimum at +/-12.5Khz around the set frequency (0.0125Mhz).
This is the reason why the two nearest frequencies around 121.500Mhz (International distress frequency) are reserved, in order to not interfer with the Distress frequency itself (that remains unchanged by the way).

In the "8.33" mode, the 25 Khz frequency increment is now divided into three more "subfrequencies" (hence the 8.33 name, as 25=3x8.3333), and thanks to modern and more precise electronic filters, the radio signal strength curve is now at its minimum at +/- 4.16Khz (0.00416Mhz) around the set frequency (The inverted U curve is narrower). The number of frequencies available for ATC traffic has tripled.

If you are using an "old" (25Khz) radio in an 8.33 environment, for any "usable" frequency of say 118.050Mhz, the broadcasted signal will be still quite strong up to a frequency of 118.050+/-0.0125=118.0375Mhz and 118.0675Mhz.
Problem is, with the 8.33 increment, just above 118.0500Mhz, the new frequencies 118.0583 and 118.0667Mhz are valid ones and they will likely be jammed by the braoader 25khz signal which will "spread" from 118.0375 until 118.0675Mhz!
The problem is worse above FL 195 where the line of sight for radio signals can be of more than 150Nm, meaning that a 25Khz radio could jam a very distant signal.
That is the reason why the 25khz radios ban occured first for European traffic flying in the upper airspace a few years ago. The 8.33 airspace is now mandatory in Europe at any level ,and even General aviation airplanes had to eventually change their radio equipment at the latest in 2018 i think, if they still wanted to fly in any radio controlled airspace.

As a side note,IRL we never dial in a 8.33 box any radio frequencies such as 118.0583Mhz. It would be a nightmare for pilots and ATC (and error prone) to use and readback decimal frequencies with such odd digits, so the EASA wisely decided to use instead the so-called "frequency channnels", which are rounded up equivalent of the actual frequency, to the nearest .005 increment.

Channels (instead of frequencies) are now mandatory for any ATC communications and are used in all the official documents and charts. The box makes its own internal conversion in order to broadcast and receive on the appropriate 8.33 frequency.
For example when we dial 118.055 on the radio set, the frequency used is in reality 118.0500, when we dial 118.060 the freq is 118.0583 (+8.33Khz), a dialed freq of 118.065 is in reality 118.0667 Mhz and so on....

Obviously this is only an issue in real life, in the sim world, such a problem as frequency spread is non existent!The only thing is thatcontrary to XPlane, both FSX and P3D have not evolved to take this new mandatory requirement and the sim engine is actually unable to take into account the three new intermediate frequencies.

Hope this is clearer.

Jacques

[JackZ]

I found a very informative drawing about what I was trying to explain.
The red curve is the 25Khz inverted U shaped signal. The blue one is the 8.33Khz

Source Eurocontrol.

As ever, "an image is worth a thousand words", wish I had find it earlier!

Jacques

[JackZ]

It's not as easy as you think. For a while there was no type certification from the FCC for radios with dual spacing. This could really have meant that you were not allowed to use your 8.33kHz radio within the US airspace, because it was not certified. The other way around, you were not allowed to use your 25kHz radio in Europe, so you had to have two types of radios for flights between the US and Europe. But it seems they have settled that whole thing. Although it's still forbidden to broadcast at a 8.33kHz frequency within the US.

https://www.fcc.gov/Bureaus/Wireless/Or ... 000660.doc

Ralph, the document you provided dates from 2000. A lot has occured since then, but as I am only flying in Europe at the moment, I am not familiar with what is actually in force across the Ocean nowadays, concerning radiocommunicatiosn.
Russ might be able to elaborate a bit on his side.

Jacques

[Sling]

Sorry Jacques for making you write all that. I should of explained my query clearer. I already understand all of what you posted. I was actually referring to a dual spacing capable radio. You are correct a 25khz only radio is not suitable for 8.33 use. It may work for the 25khz frequencies if it were allowed but pointless the moment you need to tune to a 8.33 frequency.

On the channel v frequency point. I understand why many do refer to the 8.33 ones as frequencies because they are still frequencies it’s just the displayed digits are a sort of rounded version of the frequency. The point being you can still derive the exact frequency from what’s displayed and know where in the band you are. It’s not like tv or uhf channels which are just plain old sequential numbers.

Really nice explanation though. Thanks for taking the time.

Tony

[JackZ]

No problem Tony, this helped me to learn more on this subject as well.

In fact, what I understand is that a 25Khz only radio is even no longer ALLOWED for use in an « all 8.33 airspace » (all Europe since Jan 2019).

This, because any 25khz compatible frequency set on this old  radio box may actually « jam » when emitting at least the two (or even four) +/- nearest adjacent 8.33khz frequencies, mainly due to its less precisely controlled signal power curve.

Anyways, a 25khz only radio would be quasi useless nowadays since most of the newly published frequencies would be unattainable with this kind of equipment. Some temporary exemptions might exist, but with a strict protocol (special code in the FPLN, etc...). As a result, most of the ground/tower/app frequencies in Europe have been recently reallocated, in some cases the old 25Khz frequencies being kept as alternate.

This mandatory change of radios equipment had cost millions of euros Europe wide, both to the the airlines operators and the general aviation sector. Guess that any non European operator had to change its radios as well, if willing to fly to/from Europe.

As for the term « Channel », while initially forecasted to help differentiate between a 8.33 and a 25khz mode, it has officially been dropped from the standard radio phraseology, as the conversion process is completely transparent to the end users. The only modification being that radio frequency changes by ATC and readback by pilots are now expressed with 3 decimals instead of two decimals.

Jacques

[Corjan]

Hi,

It will take a while before I post a new SD image with the fbcp. I still want to implement mouse support before I push another image.
I would recommend you installing fbcp yourself. Cmake seemed to install and run fine.

Corjan

[marcel_felde]

The download worked today and it seemed that I did install that driver. But I cannot test it, because I was too fast in updating Air Manager and now have "version mismatch". I hope there is an installer for an older version somewhere on one of the PCs here.

[SimPassion]

The download worked today and it seemed that I did install that driver. But I cannot test it, because I was too fast in updating Air Manager and now have "version mismatch". I hope there is an installer for an older version somewhere on one of the PCs here.

I have old versions :

- 08.11.2017
- 26.10.2017

i don't know if these two one could be useful ?

Gilles

[marcel_felde]

Very nice Gilles, thanks!

I found a version from 12.12.2018. After installing (in a new folder), Air Manager does hang up on start. I will have to make backup of some files and then try deinstallation and reinstallation.