A-A TACAN

Had some MP tests going on today and figured out, that A-A TACAN seems to be messed up atm. Both aircraft were set A-A-TR, and Channels had been set 63 apart from each other (as supposed). We recieved distance-information, but the bearing needle was rotating all the time, independent from our relative positions.

Are we doing something wrong or is it still WIP? Both aircraft were connected as clients btw.

this may be a long shot but I think in RL tacan in A-A mode does only give distance and not bearing, or the other way around, I cant remember which exactly but im putting my money on distance only

* therefore it may not be a WIP, thats just the way it works :)

Why should it be that way? It would be completely useless then. How would you fly an TACAN IMC trail-formation?

A squad mate is flying the german airforce A-330 tanker. He said it should provide range and bearing.

beacause tankers will have a slightly different system as they need it for you to be able to find them, AFAIK a fighters TACAN only transmits pulse for range, and doesnt have a TX of putting out a rotating wave which would give you bearing, I could be mistaken, or it could just be more modern systems that include this. The aircraft I work on cant provide bearing but they are quite old!

As you may know, TACAN, like VOR/DME, consists of two components: the bearing component (called "REC" [receive-only] in the A-10) and the distance component (called "TR" [transmit-receive] in the A-10). The reason bearing information is available in receive-only mode is because a TACAN station continually transmits bearing information. An airplane does not need to send a radio signal to calculate its bearing from a TACAN station; it merely needs to listen to the signal and perform some analysis on it.

In order to receive distance information, however, a TACAN station must be able to listen to incoming interrogations as well as transmit replies. The A-10 sends out a series of radio pulses which the station retransmits; the Doppler shift then can be used to calculate the distance.

As everyone knows, you can't transmit and receive simultaneously on the same frequency; thus, two frequencies are needed in order for a TACAN to provide both range and bearing information. Rather than make pilots memorize two frequencies for each TACAN station, the engineers just decided to make both frequencies a set distance apart. When you tune in one, the jet will automatically tune in the other for you.

In MIL-STD-291C they establish that distance as 63 MHz. One channel corresponds to 1 MHz in TACAN, hence, 63 channels apart. When you tune in, say, 126Y on your TACAN, your airplane's DME transceiver is automatically tuned to channel 189.

So, how does this work A-10 to A-10? Well imagine you're designing the A-10's radio navigation system. To do TACAN ranging, you've installed in the jet the capability to transmit a series of pulses, then listen for a reply, subtract out the Doppler shift, and calculate a distance. You're a bona fide DME receiver. Now what do you need to be a DME transmitter? Well, what does the station do? When it hears a series of pulses, it retransmits them. Your jet can do this too, easily. So it's almost zero additional effort to turn your jet from a DME receiver to a source of DME information for other jets -- and no additional hardware.

So how come you only get distance, no bearing, when using this air-to-air mode? Well, let's look at how TACAN range is calculated. A TACAN station, like a VOR station, transmits two radio pulses. One is a very narrow beam, less than 1 degree wide, pointed away from the station, that rotates through the compass rose once each second. There's a second omnidirectional pulse that's transmitted every time the first pulse sweeps through magnetic north.

So, to calculate your bearing from the station, you just subtract the time between when you receive the two pulses. Let's say you're 90 degrees bearing from the station. You'll get both pulses once per second, but the narrow pulse will come one-quarter second after the omnidirectional pulse, because that's how long it takes the narrow beam to sweep from magnetic north to 90 degrees east (when it's pointed directly at you).

So if we wanted to add this functionality to an A-10, we'd need to be able to make an omnidirectional radio pulse (which the A-10 can do), as well as a sweeping narrow-beam pulse (which would require additional hardware). Additional hardware, additional weight, no-go. They install this equipment onto tankers, fine, but not attack jets.

As boycey said above A/A TACAN in the Hog (and all fighters IIRC) supports range only. So it is working as intended, and as per the real aircraft.

And it's not useless at all, it provides range which is something you can't provide your wingmen over the radio if you can't see them (without the aid of radar or datalink). You can however tell them your heading/position, and with a bit of SA you can work out which way to fly to rejoin/maintain formation.

EDIT: Sniped again. Really need to type faster.

TY for this really detailed explanation gentlemen! Much appreciated!

The Hog uses the ARN-118 tacan set. In A-A mode it only will support distance and bearing. However here are the specifics. A-A between two ARN-118's is distance only. A-A between an ARN-118 and ARN-84, ARN-52 or ARN-21 will give both bearing and range. other wise the bearing needle will indeed spin clockwise with no bearing input for A-A mode between two ARN-118's (I.E. 2 hogs)

As you may know, TACAN, like VOR/DME, consists of two components: the bearing component (called "REC" [receive-only] in the A-10) and the distance component (called "TR" [transmit-receive] in the A-10). The reason bearing information is available in receive-only mode is because a TACAN station continually transmits bearing information. An airplane does not need to send a radio signal to calculate its bearing from a TACAN station; it merely needs to listen to the signal and perform some analysis on it.

 

In order to receive distance information, however, a TACAN station must be able to listen to incoming interrogations as well as transmit replies. The A-10 sends out a series of radio pulses which the station retransmits; the Doppler shift then can be used to calculate the distance.

 

As everyone knows, you can't transmit and receive simultaneously on the same frequency; thus, two frequencies are needed in order for a TACAN to provide both range and bearing information. Rather than make pilots memorize two frequencies for each TACAN station, the engineers just decided to make both frequencies a set distance apart. When you tune in one, the jet will automatically tune in the other for you.

 

In MIL-STD-291C they establish that distance as 63 MHz. One channel corresponds to 1 MHz in TACAN, hence, 63 channels apart. When you tune in, say, 126Y on your TACAN, your airplane's DME transceiver is automatically tuned to channel 189.

 

So, how does this work A-10 to A-10? Well imagine you're designing the A-10's radio navigation system. To do TACAN ranging, you've installed in the jet the capability to transmit a series of pulses, then listen for a reply, subtract out the Doppler shift, and calculate a distance. You're a bona fide DME receiver. Now what do you need to be a DME transmitter? Well, what does the station do? When it hears a series of pulses, it retransmits them. Your jet can do this too, easily. So it's almost zero additional effort to turn your jet from a DME receiver to a source of DME information for other jets -- and no additional hardware.

 

So how come you only get distance, no bearing, when using this air-to-air mode? Well, let's look at how TACAN range is calculated. A TACAN station, like a VOR station, transmits two radio pulses. One is a very narrow beam, less than 1 degree wide, pointed away from the station, that rotates through the compass rose once each second. There's a second omnidirectional pulse that's transmitted every time the first pulse sweeps through magnetic north.

 

So, to calculate your bearing from the station, you just subtract the time between when you receive the two pulses. Let's say you're 90 degrees bearing from the station. You'll get both pulses once per second, but the narrow pulse will come one-quarter second after the omnidirectional pulse, because that's how long it takes the narrow beam to sweep from magnetic north to 90 degrees east (when it's pointed directly at you).

 

So if we wanted to add this functionality to an A-10, we'd need to be able to make an omnidirectional radio pulse (which the A-10 can do), as well as a sweeping narrow-beam pulse (which would require additional hardware). Additional hardware, additional weight, no-go. They install this equipment onto tankers, fine, but not attack jets.

Thats not entirely accurate but close enough :) +rep from me

Hey I'm eager to learn Scabbers ... lay it on me!

I noticed tonight that I could tune in the tacan of a kc135 tanker and got distance and bearing to it as the host of a mp server, but the client playing with me had the spinning dial and neither distance or bearing, even though he'd done exactly the same as me. We were using AA TR mode, tacan 11x on the tanker. Havent tried it with him as the host and myself as client to see if we can replicate this in reverse yet, but I will.

:thumbup: On a side note, we had a blast doing MP aerial refueling tonight..:pilotfly:

After a whole page of theory I still can not figure what is the bottom line. In B4 I was getting the bearing to the tanker. Can someone from ED Team (only) confirm what shall we expect from the A-A TACAN with two simple words: Bearing, Distance or Both.

Thanks.

As far as I understood:

Tanker - A-10C = Range + Bearing

A-10C - A-10C = Range

Both due to the different hardware mounted on the aircraft.

My question is.. can MP clients use tacan now ?? I saw range and bearing to the tanker as host. that works.

Oh, I see. Have yet to test it myself with my squad. Our Game-Server is running DCS:A-10C since yesterday evening. So we can begin to test things without having a flying host.

I'll let you know as soon as we figure stuff out.

noone but the host seems able to see tanker tacan at this point. Hoping that's fixed in the next patch.

Is anyone else getting runtime errors when switching on AA TCN modes ?? Will post screens soon as i get one that sticks.

I dont get run time errors but I dont get range or bearing info either as a client :(

As you may know, TACAN, like VOR/DME, consists of two components: the bearing component (called "REC" [receive-only] in the A-10) and the distance component (called "TR" [transmit-receive] in the A-10). The reason bearing information is available in receive-only mode is because a TACAN station continually transmits bearing information. An airplane does not need to send a radio signal to calculate its bearing from a TACAN station; it merely needs to listen to the signal and perform some analysis on it.

 

In order to receive distance information, however, a TACAN station must be able to listen to incoming interrogations as well as transmit replies. The A-10 sends out a series of radio pulses which the station retransmits; the Doppler shift then can be used to calculate the distance.

 

As everyone knows, you can't transmit and receive simultaneously on the same frequency; thus, two frequencies are needed in order for a TACAN to provide both range and bearing information. Rather than make pilots memorize two frequencies for each TACAN station, the engineers just decided to make both frequencies a set distance apart. When you tune in one, the jet will automatically tune in the other for you.

 

In MIL-STD-291C they establish that distance as 63 MHz. One channel corresponds to 1 MHz in TACAN, hence, 63 channels apart. When you tune in, say, 126Y on your TACAN, your airplane's DME transceiver is automatically tuned to channel 189.

 

So, how does this work A-10 to A-10? Well imagine you're designing the A-10's radio navigation system. To do TACAN ranging, you've installed in the jet the capability to transmit a series of pulses, then listen for a reply, subtract out the Doppler shift, and calculate a distance. You're a bona fide DME receiver. Now what do you need to be a DME transmitter? Well, what does the station do? When it hears a series of pulses, it retransmits them. Your jet can do this too, easily. So it's almost zero additional effort to turn your jet from a DME receiver to a source of DME information for other jets -- and no additional hardware.

 

So how come you only get distance, no bearing, when using this air-to-air mode? Well, let's look at how TACAN range is calculated. A TACAN station, like a VOR station, transmits two radio pulses. One is a very narrow beam, less than 1 degree wide, pointed away from the station, that rotates through the compass rose once each second. There's a second omnidirectional pulse that's transmitted every time the first pulse sweeps through magnetic north.

 

So, to calculate your bearing from the station, you just subtract the time between when you receive the two pulses. Let's say you're 90 degrees bearing from the station. You'll get both pulses once per second, but the narrow pulse will come one-quarter second after the omnidirectional pulse, because that's how long it takes the narrow beam to sweep from magnetic north to 90 degrees east (when it's pointed directly at you).

 

So if we wanted to add this functionality to an A-10, we'd need to be able to make an omnidirectional radio pulse (which the A-10 can do), as well as a sweeping narrow-beam pulse (which would require additional hardware). Additional hardware, additional weight, no-go. They install this equipment onto tankers, fine, but not attack jets.

ok well Tacan is a full dulplex receiver transmitter. it can transmit and recieve simultaniously.

The ground station or air station equipped with an ARN-84, 52 or 21 generates 1 Main Reference Burst and 8 Auxiliary reference bursts. The phase between the MRB and the ARB's gives the bearing to the receiving tacan set. your analysis was very close.

The channels are indeed set 63 Mhz apart to provide one channel for bearing and one channel for distance. so a ground station set at channel 1 is transmitting distance info on channel 64.

This is a little nit picky but to use an airplane tuned to 189 is wrong. the top channel on the set is 126. so the airplane would actually tune to channel 63.

I am not sure if there is a doppler shift in air to air but i cant confirm it right now.

I will look into it :)

There is no doppler shift in any of this, just two different phased signals being compared.