Need a little big help

Questions about deployment and use of Air Manager Instruments

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Keith Baxter
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Re: Need a little big help

#31 Post by Keith Baxter »

Ralph wrote: Mon Sep 20, 2021 7:05 pm The tricky thing is, I think, to make a link between the frequency, distance to the station and the range power.
Then there's of course also physical obstructions, like mountains, those you cannot compensate for with our data :)
:mrgreen: :mrgreen:

Ralph

Range (Range-power) is in nm so that can be filtered in. Declination is also available.

I have obstacle data in .json format that I am using in the G1000 Dev. It is OS and comes from here.
https://www.faa.gov/air_traffic/flight_ ... ducts/dof/
Not found a free "GLOBAL" source yet so restricted to what is available.

Terrain would have to come from the likes of the link.. I think @Sling might have some insight here. He did talk of something when vector maps were the topic.
https://www.ngdc.noaa.gov/mgg/topo/gltiles.html


We can all work on this as a team..

Keith
AMD RYZEN 9 5950X CPU, Corsair H80I cooler, ASUS TUF GAMING B550-PLUS AMD Ryzen Mother Board,  32Gb ram Corsair Vengeance 3000Mh, MSI GTX960 4G graphics card 

JackZ
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Re: Need a little big help

#32 Post by JackZ »

There have been an attempt at modeling the VHF/UHF radio waves transmission/loss properties by implementing an existing atmospheric and ground/obstacle attenuation algorithm (Longley-Rice ITM algorithm) to XPlane with the libradio plugin by siselkov.

It computes the properties of the signal received
0: direct line of sight
5: single horizon, diffraction
6: single horizon, tropospheric scattering
9: double horizon, diffraction
10: double horizon, tropospheric scattering
Not sure if the direct obstacle is taken into account

AFAIK, DME is broadcasting in the UHF range, so it is less subject to attenuation/loss of precision of signal than VHF.

But all in all, I am wondering wether it’s worth the hassle.
This because if you create such an advanced DME receiver that more or less models the real transmission of signal, the other instruments won’t be affected accordingly, and won’t behave like the Dme (loss of signal, errors). This unless you conpletely override the standard radio system of the sim, much simpler for that matter, since the reception range is somewhat limited to the height of the aircraft. That would mean that the Nav radios should implement those algorithms as well.

The algorithm is called ITM irregular terrain model
https://www.its.bldrdoc.gov/media/50676/itm_alg.pdf
Last edited by JackZ on Mon Sep 20, 2021 8:29 pm, edited 1 time in total.
My YouTube Chanel on the A320 (Real SOPs by an Airline Pilot IRL):
https://www.youtube.com/playlist?list=P ... 0Q6SBASRqJ

vangyver
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Joined: Sat Dec 05, 2015 8:30 am

Re: Need a little big help

#33 Post by vangyver »

Thanks again Ralph. I am a license pilot (vfr). Never did get my instrument rating but I love doing ils approaches in flight simulator. I see your point in not needing a 3rd dme frequency. I agree it's not really needed. I do not fly in real life anymore as I am near 70 years old so flight simulator quenches my desire.
Van

JackZ
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Re: Need a little big help

#34 Post by JackZ »

Poor Keith and I, guess we don’t even deserve a “thank you”, we have not reached Ralph’s status and aura yet :lol:
Lesson learned, I will spare my energy and let the big boys talk from now on.
My YouTube Chanel on the A320 (Real SOPs by an Airline Pilot IRL):
https://www.youtube.com/playlist?list=P ... 0Q6SBASRqJ

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jph
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Re: Need a little big help

#35 Post by jph »

JackZ wrote: Mon Sep 20, 2021 8:08 pm

AFAIK, DME is broadcasting in the UHF range, so it is less subject to attenuation/loss of precision of signal than VHF.

But all in all, I am wondering wether it’s worth the hassle.
This because if you create such an advanced DME receiver that more or less models the real transmission of signal, the other instruments won’t be affected accordingly, and won’t behave like the Dme (loss of signal, errors). This unless you conpletely override the standard radio system of the sim, much simpler for that matter, since the reception range is somewhat limited to the height of the aircraft. That would mean that the Nav radios should implement those algorithms as well.
Hi Jacques,
Sticking my 'Ham Radio' hat on for a moment ;) ... UHF is more subject to issues such as attenuation than VHF. UHF, to all intents and purposes can be considered 'line of sight'.
I honestly do not think that any form of complex modelling is necessary at all and would be massively complicated for no real gain - if any - in any of the sims, and also unlikely to give satisfactory results. The 2 most basic issues - as far as I can see - are distance to station and reception distance. Although reception distance can vary with several factors it could be coded into a lookup table if the data is not available (it is probably available I presume ?). Distance to stations will always be distance to station at the bottom line so is just simple trig.
I have actually just been looking into any propagation / degradation issues on the same frequency spectrum area as I am in the process of putting together a ground based ADS-B receive station to feed into the main networks. This is slap in the middle of a range of DME frequencies. It is on 1090MHz. Quite a nice little project and inexpensive. It links up to sites like ADS-B Exchange. Joe (G4XRZ)
Joe. CISSP, MSc.

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Keith Baxter
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Re: Need a little big help

#36 Post by Keith Baxter »

JackZ wrote: Tue Sep 21, 2021 3:59 pm Poor Keith and I, guess we don’t even deserve a “thank you”, we have not reached Ralph’s status and aura yet :lol:
Lesson learned, I will spare my energy and let the big boys talk from now on.
I am not despondent Jacques.

The win here is that @vangyver and many peeps reading and following this, are now better informed and are not locked into sim and AirFrame house data.
AM offers so many "HACKS" in the sim world. This is not the start, but a continuation of sharing different views on how things can be done, a sharing of knowledge and resources before old farts like me kiss the pyre and that knowledge is lost, is important. :mrgreen:

Keith
AMD RYZEN 9 5950X CPU, Corsair H80I cooler, ASUS TUF GAMING B550-PLUS AMD Ryzen Mother Board,  32Gb ram Corsair Vengeance 3000Mh, MSI GTX960 4G graphics card 

vangyver
Posts: 127
Joined: Sat Dec 05, 2015 8:30 am

Re: Need a little big help

#37 Post by vangyver »

First I would like to thank everyone here for their technical input into the DME functions. My apologies if this is a bit off subject: but I wonder how A2A simulations program the Piper Cherokee KN62. It works amazingly well but beyond my current level of programming knowledge. I’ve flown in real life, license pilot (vfr) and numerous flight simulator aircraft and I find the A2A simulated Piper aircraft truly amazing. I am happy to see this is an interesting subject for everyone here and will follow this thread to see where it goes.
Thanks Again to All,
Van
Last edited by vangyver on Wed Sep 22, 2021 7:37 am, edited 1 time in total.

JackZ
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Joined: Mon Feb 22, 2016 1:02 pm

Re: Need a little big help

#38 Post by JackZ »

jph wrote: Tue Sep 21, 2021 5:19 pm
JackZ wrote: Mon Sep 20, 2021 8:08 pm

AFAIK, DME is broadcasting in the UHF range, so it is less subject to attenuation/loss of precision of signal than VHF.

But all in all, I am wondering wether it’s worth the hassle.
This because if you create such an advanced DME receiver that more or less models the real transmission of signal, the other instruments won’t be affected accordingly, and won’t behave like the Dme (loss of signal, errors). This unless you conpletely override the standard radio system of the sim, much simpler for that matter, since the reception range is somewhat limited to the height of the aircraft. That would mean that the Nav radios should implement those algorithms as well.
Hi Jacques,
Sticking my 'Ham Radio' hat on for a moment ;) ... UHF is more subject to issues such as attenuation than VHF. UHF, to all intents and purposes can be considered 'line of sight'.
I honestly do not think that any form of complex modelling is necessary at all and would be massively complicated for no real gain - if any - in any of the sims, and also unlikely to give satisfactory results. The 2 most basic issues - as far as I can see - are distance to station and reception distance. Although reception distance can vary with several factors it could be coded into a lookup table if the data is not available (it is probably available I presume ?). Distance to stations will always be distance to station at the bottom line so is just simple trig.
I have actually just been looking into any propagation / degradation issues on the same frequency spectrum area as I am in the process of putting together a ground based ADS-B receive station to feed into the main networks. This is slap in the middle of a range of DME frequencies. It is on 1090MHz. Quite a nice little project and inexpensive. It links up to sites like ADS-B Exchange. Joe (G4XRZ)
The main issue with VHF/UHF signals is that they are basically as you said “Line of sight » signals, so that obstacles such as mountains should block the signal if you are low enough. Don’t think any sim in the market has implemented this feature, except the XP libradio plugin I discussed previously (as it needs a terrain/obstacle database)
My YouTube Chanel on the A320 (Real SOPs by an Airline Pilot IRL):
https://www.youtube.com/playlist?list=P ... 0Q6SBASRqJ

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