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#21
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TACAN
Stubby wrote:
Hilton wrote: Bob Moore wrote: A VOR antenna must be permanently aligned to the earth, Why? Why not have a heading indicator (or DG) to drive the 'angles' (i.e. phase) it sends out? An advantage of VORs over TACANs is the VOR antenna does not physically more, whereas it does in a TACAN. Electronic "rotation" of the antenna intuitively makes shipboard use easier, but I might not understand ships enough! Operating frequencies dictate the size of the antenna array. Compare this picture of a TACAN site at http://en.wikipedia.org/wiki/TACAN with this one of a VOR site at http://en.wikipedia.org/wiki/VOR. Other advantages: Range: TACAN DME has a maximum range of 300 NM miles. VOR reception range is limited to 25 - 130 NM, depending on the site's transmitter power. Bearing accuracy: TACAN can provide bearing resolution of +- 1 degree. Typical VOR bearing accuracy is +- 2 degrees. A bearing error of 1 degree at 100 miles isn't likely to be critical on land, but that same error at sea can mean the difference between finding your carrier and a very long swim home. | George Ruch | "Is there life in Clovis after Clovis Man?" |
#22
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TACAN
George Ruch wrote
Operating frequencies dictate the size of the antenna array. Compare this picture of a TACAN site at http://en.wikipedia.org/wiki/TACAN with this one of a VOR site at http://en.wikipedia.org/wiki/VOR. Actually George, the first picture is a VORTAC, a TACAN and VOR installation. The TACAN is just the round cylinder part and that is what makes it so easy to mount onboard a ship. Bob Moore |
#23
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TACAN
Bob Moore wrote:
George Ruch wrote Operating frequencies dictate the size of the antenna array. Compare this picture of a TACAN site at http://en.wikipedia.org/wiki/TACAN with this one of a VOR site at http://en.wikipedia.org/wiki/VOR. Actually George, the first picture is a VORTAC, a TACAN and VOR installation. The TACAN is just the round cylinder part and that is what makes it so easy to mount onboard a ship. Oops. My mistake on that. I was focusing on the size of the VOR antenna ring. | George Ruch | "Is there life in Clovis after Clovis Man?" |
#24
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TACAN
Bob Moore wrote:
George Ruch wrote Operating frequencies dictate the size of the antenna array. Compare this picture of a TACAN site at http://en.wikipedia.org/wiki/TACAN with this one of a VOR site at http://en.wikipedia.org/wiki/VOR. Actually George, the first picture is a VORTAC, a TACAN and VOR installation. The TACAN is just the round cylinder part and that is what makes it so easy to mount onboard a ship. Bob Moore We used to carry a portable TACAN (TRN-41) in a backpack for contingencies in the USAF. Didn't take long to set up and then align so it could be used. http://esc.hanscom.af.mil/esc-ga/Products/trn-41.htm JPH |
#25
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TACAN
I wonder if the TACAN has to move physically. That may be an old
design. Looking at the portable tacan posted later in the threads, it doesn't look very mechanical. Stubby wrote: Hilton wrote: Bob Moore wrote: A VOR antenna must be permanently aligned to the earth, Why? Why not have a heading indicator (or DG) to drive the 'angles' (i.e. phase) it sends out? An advantage of VORs over TACANs is the VOR antenna does not physically more, whereas it does in a TACAN. Electronic "rotation" of the antenna intuitively makes shipboard use easier, but I might not understand ships enough! |
#26
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TACAN
George Ruch wrote:
That's a fine reference. I saved a bookmark there. It looks as if the UK TACAN is the same as the USAF TACAN, but I'm still not clear as to the differences from a VOR. Maybe it's just the frequencies. Or, I believe all TACANs are supposed to have DME built in. I don't know much about how either works, other than TACAN transmits its azimuth signal in the UHF band and DME is an intergal part of the TACAN station. The DME portion of the TACAN is compatible with civil DME avionics. Many of the en route VORs in this country have VOR and TACAN at the same site. The civil users's airborne DME equipment use the DME portion of the TACAN station. The official name of one of these sites is VORTAC. |
#27
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TACAN
M. J. Powell wrote:
Is TACAN still in use? I worked on it briefly in 1956 when I was in the RAF. I remember from a recent history or discovery channel program that air-to-air tacan is still used for aerial refueling operations. Here's a page about it from Rockwell: http://www.rockwellcollins.com/ecat/gs/TCN-550_Tacan.html - Ray |
#28
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TACAN
Ray wrote:
M. J. Powell wrote: Is TACAN still in use? I worked on it briefly in 1956 when I was in the RAF. I remember from a recent history or discovery channel program that air-to-air tacan is still used for aerial refueling operations. Here's a page about it from Rockwell: http://www.rockwellcollins.com/ecat/gs/TCN-550_Tacan.html When I was stationed in Thailand, I also heard about A-A mode being used in a two-ship formation when a major system (attack radar or INS) failed. The aircraft with working systems would lead, and the aircraft with the failed system would follow the leader. As I understand it, buddy bombing was possible, but may not have been all that accurate. | George Ruch | "Is there life in Clovis after Clovis Man?" |
#29
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TACAN
George Ruch wrote:
Other advantages: Range: TACAN DME has a maximum range of 300 NM miles. VOR reception range is limited to 25 - 130 NM, depending on the site's transmitter power. But, civil aircraft use the TACAN's DME, so they should see the same range for DME, shouldn't they Bearing accuracy: TACAN can provide bearing resolution of +- 1 degree. Typical VOR bearing accuracy is +- 2 degrees. A bearing error of 1 degree at 100 miles isn't likely to be critical on land, but that same error at sea can mean the difference between finding your carrier and a very long swim home. Help me with that one. The TACAN ground station is on the ship, right? If so, angular errors diminish as you approach the station and you should end up at the ship, whether you started at 150 miles out with a 1 or 2 degree error. |
#30
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Quote:
Know this is an old thread.. but.. 1 degree sounds like a lot, and would be significant if you were 10 miles away, shot an azimuth and followed that for ten miles.. but with TACAN it's continuous feed of direction and distance so as you get close (picture a funnel) the error becomes less and less, and of course as a plane gets closer to a carrier there are many more control systems that "Capture" the aircraft and provide guidance and landing control. For an idea of current TACAN and future trends (TACAN is not going away) google TRN 47 Marine Man Portable TACAN, URN 32 Shipboard TACAN.. Fernau TACAN 2010, and Moog MM7000 |
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