VOR vs. VORTEC
Barry Libenson
a simple VOR?
I am currently working on an application to parse FS5.x BGL files and am
trying to extract the information to determine if a VOR is a VORTEC, VOR,
or VOR-DME. This information is not currently referenced in the FS5STRUCT
document. Mu suspicion is that it is in byte 4 of the 04H and 05H record,
for those of you familiar with the file format.
Regards,
Barry
Robert King
difference is between a VOR and VORTAC.
The VOR is a navigation aid used by civilian a/c utilizing VHF radio
frequencies while a VORTAC is a combined VOR and TACAN broadcasting site.
TACAN is a military-only set of radio frequencies.
--
Zoomie
15 Wing Moose Jaw
Moose Jaw, SK, Canada
Gerald
A VOR provides directional information. Not range from the VOR.
VOR-DME and VORTACs provide range too, but it is slant range meaning
when you are directly over the VORTAC 6000 feet above it your DME will
report 1 nautical mile. VORTACs also provide navigational information
for military aircraft and combine a VOR and a TACAN. I guess there
might be TACANs by themselves, but I can't definitely recall seeing
any.
--
Gerald
g...@ix.netcom.com
Stephen Brooks
a simple VOR?<<
If this is a "real world" question, here's the answer: A Vortac is a
VOR with a TACAN. TACAN is a military navigation system. I don't know
how TACAN works but that's the answer.
Joe Hachem
...
>report 1 nautical mile. VORTACs also provide navigational information
>for military aircraft and combine a VOR and a TACAN. I guess there
>might be TACANs by themselves, but I can't definitely recall seeing
>any.
There are enough of them...one on the airfield I work at, in fact.
They are used the same as VORs, except at military (much higher)
frequencies and with distance measuring "built-in".
Howard Goldstein
: Can someone please tell me what the difference is between a VORTEC and
: a simple VOR?
For civil aircraft, a VORTAC works exactly like a VOR/DME. Treat them
the same.
Howard Goldstein
: If this is a "real world" question, here's the answer: A Vortac is a
: VOR with a TACAN. TACAN is a military navigation system. I don't know
: how TACAN works but that's the answer.
Why don't we ask? I'm curious. How does a TACAN work and why is it more
useful for mil guys than a VOR/DME?
Barry Becher
Bill Huber
>: If this is a "real world" question, here's the answer: A Vortac is a
>: VOR with a TACAN. TACAN is a military navigation system. I don't know
>: how TACAN works but that's the answer.
>Why don't we ask? I'm curious. How does a TACAN work and why is it more
>useful for mil guys than a VOR/DME?
TACAN works similarly to VOR as far as using it is concerned. The
signal format is different but I'm not sure of the details. It also
has a DME (Distance Mearsuring Equipment) set. The airborne unit
interrogates the ground unit and uses the return time for a distance
readout. Thus, you can get both your bearing and distance from the
station. The distance is accurate down to about a quarter mile or so
and is also used for non-precision approaches. Sometimes a VOR station
will have a DME set without the bearing information. The DME can also
be used air-to-air for range only.
In addition. The number of TACAN channels is the same as the number of
VOR frequencies and each TACAN channel is tied to a specific VOR
freq.
Bill Huber
A. Reichert
VOR - uses a fixed antenna transmitting two signals on two different axis
90 degrees apart from each other. These two signals are also changed in
amplitutde WRT each other on a specific phase. Additionally, the
strentght of the composite signal is changed. Combination of these
signals at the receiver allows the receiver to determine azimuth.
TACAN - (old style, anyway) Single antenna, has two cylinders, one
inside the other and attached to each other, that surround the antenna.
One tube has 9 reflector elements around its curcumference, the other has
one. These tube spin about the antenna. This creates a "scalloped
cardoid" pattern...the single element tube produces the cardoid, while
the 9-element tube provides the scallop (best I can do without a drawing).
The transmissions are actually a series of pulses at very close
interval. When the cardoid pattern points north, that particular pulse
is different from the other. This allows the receiver to detemine
"north" in the signal pattern it receives. It can then follow the
cardoid pattern to determine it's azimuth from the station.
DME in a TACAN - The aircraft transmits a query to the TACAN station with
a specific pulse pattern. The TACAN, when it receives it, will process
it for retransmission after a predetermined delay time. The TACAN will
retransmit the pattern in place of one of its pulses described in the
previous pattern. The aircraft, meanwhile, has been "listening" for the
pattern it sent out originally. When it recognizes the pattern, it will
determine the amount of time it took between transmission and reception,
subtract the delay while in the TACAN station, and determine distance
based on the round trip timing.
I'm sure there are more modern versions that don't use mechanical tubes
for the TACAN pattern, but I've not seen the inside of a TACAN for about
12 years.
Clear as mud???
- Alan
Bill Huber (beb...@business.utah.edu) wrote:
Howard Goldstein
: VORTAC has distance measurung - VOR doesn't!!
That's why I said VOR/DME!
Barry Libenson
>For civil aircraft, a VORTAC works exactly like a VOR/DME. Treat them
>the same.
>
BGL files. For example, the VORTAC located in Bitburg Germany at Frequency
111.90 does not appear to have any distance measuring facilities. I have
spent the last three nights working on a program which extracts VOR and ILS
information and thus far have found 4 different type of ILS (two with DME equipment
and two without), and over 7 different types of VOR facilities. Thus far, the simple
VOR and VOR-DME are easy to identify, however, I have found three different types of VORTAC in
the file, all of which show up on a Jeppsen (sp?) chart as the same type of VORTAC. I expect
to solve this puzzle tonight which has now become a fixation!
regards,
Barry
Howard Goldstein
precise. *Why* is TACAN preferred by military over VOR/DME?
To Alan specifically, thank you for the detailed description of the format
and emission pattern. I'd misunderstood the workings of a "classic"
straight VOR as providing its azimuth indication based only the phase
difference between the two signals, didn't realize the amplitude
difference was also measured and a factor in the result.
Howard
Michael Ely
>: VOR with a TACAN. TACAN is a military navigation system. I don't know
>: how TACAN works but that's the answer.
>Why don't we ask? I'm curious. How does a TACAN work and why is it more
>useful for mil guys than a VOR/DME?
I think TACAN uses UHF frequencies, like their comm systems. Otherwise, I
think it does much the same as VORs do. I might be mistaken though, so
don't quote me. TTYL
Mike
tra...@fn1.freenet.edmonton.ab.ca
: >>Can someone please tell me what the difference is between a VORTEC and
: a simple VOR?<<
: If this is a "real world" question, here's the answer: A Vortac is a
: VOR with a TACAN. TACAN is a military navigation system. I don't know
: how TACAN works but that's the answer.
VOR is a navigation aid transmitting VHF navigation signals 360 degrees
in azimuth.
TACAN (Tactical Air Navigation) is an ultrahigh frequency air navigation
aid which gives bearing and distance information to a Tacan station.
Vortac (Vor/Tacan) nav aid that provides VOR azimuth, TACAN azimuth and
TACAN DME (distance measuring equipment) at 1 site.
Tracer1
Kyle B. Russell
Howard Goldstein <hgol...@bbs.mpcs.com> wrote:
>Stephen Brooks (Stephen...@msn.com) wrote:
>
>: If this is a "real world" question, here's the answer: A Vortac is a
>: VOR with a TACAN. TACAN is a military navigation system. I don't know
>: how TACAN works but that's the answer.
>
>useful for mil guys than a VOR/DME?
frequency matched to the VHF VOR where it is co-located. A VOR/DME is
esentially a VORTAC without the military azimuth equipment.
TACAN is more useful to the military as it is far more accurate than VOR
for attack missions such as bombing blind by tactical fighters, etc..
Don't forget, it was developed long before GPS, back when most tactical
aircraft didn't have independent on board navigation systems with the
accuracy to hit specific targets. Remember the days of E6s leading in
flights of F100s and F4s for bombing runs at night or in weather? Also it
did not suffer as much from siteing problems, allowing portable systems
to be set up quickly with tha precision to allow relatively precise
instrument landings in battlefield conditions (but not to full CATI from
what I remember).
TACAN consists of two parts, one for azimuth information, similar to our
VOR, but on a totally different frequency and signal format that is
significantly more accurate than our VHF VOR. The second part is the
previously mentioned DME.
Since TACAN was a U.S. Military system (sound familiar re. GPS?) and, at
the time, did not offer any significant advantage for enroute navigation
it was not adopted by ICAO for international navigation, but rather the
extensive global VOR system was retained. I am unaware of any civil
TACAN receivers, but that is not to say they don't exist.
Gary Sims
might offer something....
First, DME. The DME equipment on the aircraft sends out a pulse to the
ground station. The ground station, upon receipt of the interrogation,
replies on a different frequency and the aircraft's equipment measures the
time difference between the interrogation and reply.
Time Difference - Known Delay in Ground Equipment
Distance = -------------------------------------------------
Speed of Light
The airborne DME equipment only cares about the timing of the pulse to
measure distance, not the amplitude (strength) of the pulse (within
reason, of course).
For each VOR frequency, there is an associated DME interrogate and reply
frequency.
TACAN is an extension of DME. First, it "fills in the blanks" between
replies with a random set of pulses called squitter (DME only may do this,
but I'm not sure). Then it shapes the azimuth radiation pattern in the
manner of an off-center pattern which looks like a flower with nine petals
and rotates this pattern 15 times per second. Finally, it sends reference
pulses out for each rotation and for each ninth of a rotation (each petal
of the flower). The aircraft receiver looks at the amplitude envelope of
the pulse train and compares it with the pattern of reference pulses to
determine the radial.
The beam shaping and rotation is either done by using a physically
rotating parasitic antenna array around an active center element or with
an electronically scanned active phased array.
Finally, I know of one civilian high-end RNAV unit which uses both TACAN and
LORAN to determine position. I believe it's built by Foster.
Hope this helps....
Ref: FAA System Description for TACAN and VOR
FAA Spectrum Management Handbook
ICAO Annex 10, Aeronautical Telecommunications
--
Gary W. Sims, P.E. KC-135 Pilot
Avionics Engineering Center Ohio Air National Guard
Ohio University, Athens, Ohio
Opinions are naturally my own, no one else will claim them....
A. Reichert
:
: TACAN is an extension of DME. First, it "fills in the blanks" between
: replies with a random set of pulses called squitter (DME only may do this,
: but I'm not sure). Then it shapes the azimuth radiation pattern in the
: manner of an off-center pattern which looks like a flower with nine petals
: and rotates this pattern 15 times per second. Finally, it sends reference
: pulses out for each rotation and for each ninth of a rotation (each petal
: of the flower). The aircraft receiver looks at the amplitude envelope of
: the pulse train and compares it with the pattern of reference pulses to
: determine the radial.
...and to make this complete, when this off-centered nine-petalled flower
(nice description!) points north, that particular squitter pulse is a
specially coded pulse to indicate this. This way, the A/C equipment has
a north reference on the envelope it receives.
- Alan
Albert Sykes
: - Alan
Ah-ha....So that's the reason for the 40 degree error warning. 360 degrees
divided by 9 equals 40 degrees....What the h**l am I talking about ? Well,
USAF training on the TACAN system includes a warning about the system's
susceptibility to a 40 degree (or multiple thereof) error in radial reading.
It doesn't happen often, but one should be aware that it *can* happen.
Tallyho !
Alpha Kilo
A. Reichert
:
: Ah-ha....So that's the reason for the 40 degree error warning. 360 degrees
: divided by 9 equals 40 degrees....What the h**l am I talking about ? Well,
: USAF training on the TACAN system includes a warning about the system's
: susceptibility to a 40 degree (or multiple thereof) error in radial reading.
: It doesn't happen often, but one should be aware that it *can* happen.
This occurs when the A/C equipment has trouble discerning the position of
the main lobe of the pattern. Each "petal" of the pattern accounts for
40 degrees azimuth. When the A/C detects the "north" positions, it can
then "count" the number of complete "petals" and the position within the
partial "petal" it needs, then calculate azimuth (not a good
explanation, but OK for now).
Suppose the equipment figures 3 "petals" and 17 degrees of the fourth
"petal", then the display should read (3 x 40) + 17 = 137 degrees
azimuth. If the equipment does get confused and loses track of where
"north" is in the pattern, then the equipment will figure the azimuth
withing a single petal" correctly, but will reference it to the "wrong
petal" (i.e., figures on four full "petals" instead of 3, giving an
erroneous reading of (4 x 40) + 17 = 177 degrees.
Rare, but possible.
- Alan
Jeffrey Austen
>precise. *Why* is TACAN preferred by military over VOR/DME?
TACAN provides higher angular resolution and is less sensitive to
transmitter siting considerations (multipath due to reflections from objects
near the transmitter -- on an aircraft carrier one cannot do much
landscaping). DME
is a part of TACAN. A good reference which covers these systems as well as
just about everything else in avionics is:
Avionics Navigation Systems
Myron Kayton and Walter R. Fried
John Wiley & Sons, 1969
The book is rather old but the systems it describes (VOR, TACAN, ILS,
transponders, etc.) are a lot older so, except for a few things like GPS and
Mode S transponders, it is still current.
Jeff Austen
Tennessee Technological University
Cookeville Tennessee USA
David Lesher
going whole-hog for GPS.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close...........(v)301 56 LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
DubDub001
so. It's still needed in the terminal areas and "bare base" environments.
Got to prove GPS as a safe approach aid first of all.
Walter Wise
WPW...@aol.com
dubd...@aol.com
Reece R. Pollack
In article <418j08$r...@newsbf02.news.aol.com>, dubd...@aol.com (DubDub001) writes:
|>Not so fast, my friend. TACAN will still be around at least until 2005 or
|>so. It's still needed in the terminal areas and "bare base" environments.
|> Got to prove GPS as a safe approach aid first of all.
Huh? The FAA has already certified GPS for non-precision approaches, and
that's without the increased precision the military units have (no SA).
TACAN has no real advantage over GPS that I'm aware of.
I have an article from Flying magazine from 1993 which talks about the
future of GPS in aviation. It proclaims that it will be 10 or more years
before GPS units start becoming available for the GA pilot, and even then
will be prohibitively expensive. It pooh-poohs the idea that it will replace
the VOR system of navigation until several decades into the next century.
It advises the GA pilot to invest in a good LORAN unit.
Last I heard, the Coast Guard is talking about shutting down the LORAN
chains in 5 to 10 years, and the FAA is talking about replacing the VOR
system with a GPS based system in the same time frame. The specs for DGPS
are being firmed up as I speak, and I'm betting that DGPS will begin to
supplant the ILS in a couple of years.
--
Reece R. Pollack
PP-ASEL-IA -- N1707H Piper Arrow III (based GAI)
Frank James
>Huh? The FAA has already certified GPS for non-precision approaches, and
>that's without the increased precision the military units have (no SA).
>TACAN has no real advantage over GPS that I'm aware of.
GPS will never replace anything because a simple television signal can
jam it - In Europe (esp Italy) GPS does not work at all.
>Last I heard, the Coast Guard is talking about shutting down the LORAN
>chains in 5 to 10 years, and the FAA is talking about replacing the VOR
>system with a GPS based system in the same time frame. The specs for DGPS
>are being firmed up as I speak, and I'm betting that DGPS will begin to
>supplant the ILS in a couple of years.
That's news to me, and I work for the airforce - with navigation
avionics ! The best/most expensive navigation systems are INS
systems (inertial navigation systems). Nothing can jam those because
it works by reading gyroscopic changes in movement - no
VOR/TACAN/LORAN/GPS stations needed. LORAN C is on the way
out though...
Unless GPS is totally redesigned, it will never be used for anything
other than a secondary system.
Frank