Transponder codes
Phil M
1- I would like to know for a fact if military aircraft are equipped with a
Transponder ?
2- We all know that there are "mode A" and "mode C" Transponders. Are there
any Transponders with a "mode B" or any other modes, if yes, what's a "mode
B" and other modes.
3- Transponder codes "0000" and "7777" are not to be used. I heard that
these are for interception only. In what situation these are used? and where
can I find *detailed" information on 0000 and 7777 code usage ?These codes
are used by whom? (If military a/c are not equiped with a Xponder, then why
its prohitited to civilian use - I'm I missing something here?)
Steven P. McNicoll
"Phil M" <philli...@videoclub.edu> wrote in message
news:BV6U5.261$wE6....@wagner.videotron.net...
>
> 1- I would like to know for a fact if military aircraft are equipped
> with a Transponder ?
>
They are.
>
> 2- We all know that there are "mode A" and "mode C" Transponders.
> Are there any Transponders with a "mode B" or any other modes, if
> yes, what's a "mode B" and other modes.
>
Yes, there are other modes, but I don't remember exactly what they are.
What we commonly refer to as "mode A" and "mode C" are actually "mode 3/A"
and "mode 3/C", civil Mode A is identical to military Mode 3. I believe the
military uses Modes 1 and 2 as well but I don't know their function.
>
> 3- Transponder codes "0000" and "7777" are not to be used. I heard that
> these are for interception only. In what situation these are used? and
> where can I find *detailed" information on 0000 and 7777 code usage ?
> These codes are used by whom?
>
The specific allocation of beacon codes is in FAA Order 7110.66, National
Beacon Code Allocation Plan. Code 7777 is for DOD interceptor aircraft on
active air defense missions and operating without ATC clearance. Code 0000
is not listed at all.
I have a 1974 edition of the AIM that says code 0000 is reserved for
military interceptor operations. The current AIM does not mention code
0000.
Curtis Suter
1, 2, 3/A, C and 4
I've never heard nor know where 1 is used, but we still aligned and
calibrated it. It's a two digit code with the first digit able to be set
from 0-7 and the second digit from 0-3. Mode 2 is a 4-digit code with each
dial able to be set from 0-7. Mode 4 is the Identification Friend of Foe
feature. It's classified.
Curtis
"Phil M" <philli...@videoclub.edu> wrote in message
news:BV6U5.261$wE6....@wagner.videotron.net...
> Hi All, I have 3 basic questions that my flight club couldn't answer:
>
> 1- I would like to know for a fact if military aircraft are equipped with
a
> Transponder ?
>
> 2- We all know that there are "mode A" and "mode C" Transponders. Are
there
> any Transponders with a "mode B" or any other modes, if yes, what's a
"mode
> B" and other modes.
>
> 3- Transponder codes "0000" and "7777" are not to be used. I heard that
> these are for interception only. In what situation these are used? and
where
Steven P. McNicoll
"Curtis Suter" <sut...@earthlink.net> wrote in message
news:NOaU5.4609$II2.5...@newsread2.prod.itd.earthlink.net...
>
> I've never heard nor know where 1 is used, but we still aligned and
> calibrated it. It's a two digit code with the first digit able to be set
> from 0-7 and the second digit from 0-3.
>
Sounds like the old 64-code non-discrete transponders.
Phil M
a/c without ATC crealence. In other words, for example, if a military A/C
enters a class B airspace and lands at O'Hare Int'l without even bothering
contacting ATC or Tower, he must be on a 7777 squack, right?
... and if my Cessna 150 is Intercepted in a ADIZ zone by a F16, then he
must be on 0000. (I know for a fact, that from my side I will dial the
emergency code ModeA 7700).
Are these 0000 and 7777 codes international? (I know for a fact that the
7500, 7600 & 7700 are woldwide standards).
Just making sure that I understand these - not so clear - codes. Back when I
was in ground school, my instructor overstressed that we shall avoid dialing
by mistake codes 7500, 7600 and 7700. Never mentioned anything for 0000 and
7777. I think they should be included in the - do not use list-.
Scott
Happy Flying
Scott Skylane
N92054
Phil M
I totally agree with you, that there I should worry about more pressing
matters in life, but having some general knowedge our bag doesn't hurt.
Bob Gardner
Foe") during WWII, so the military had them before civilians did...and still do.
Insofar as the codes are concerned, I believe you are obsessing about something
that is not all that critical...the ATC system is not going to grind to a halt,
nor are F-16s going to be launched, if you mistakenly select 7777 for a second
or two. Remember that ATC radar sweeps; it it might be five or six seconds
between sweeps depending on the facility....they might never see your faulty
selection before you have caught the error and corrected it.
Bob Gardner
William W. Plummer
signals and sets off an alarm if 77xx is heard. I'll bet there is a
hold-off that ignores hits of less than, say one second. --Bill
"Bob Gardner" <bob...@halcyon.com> wrote in message
news:3A216911...@halcyon.com...
Roy Smith
> ATC radar sweeps are not involved. Electronics monitors the transponder
> signals and sets off an alarm if 77xx is heard.
Of course radar sweeps are involved. Your xponder, regardless of what
code it's got set in the windows, only transmites when interrogated, and
it's only interrogated when the radar antenna sweeps around to its
position (azimuth).
Mike O'Rourke
Transponders are as such (from memory at this late stage)
MODE 1 - military usage
MODE 2 - military usage
MODE 3 - civilian usage
MODE 3/A basic 4,096 code equipment
MODE 3/B not used
MODE 3/C altitude encoder equipment
MODE 4 - military usage
Then there is the occasional older aircraft that will waddle through the
system with the old 64 code MARK "X" or MODE "X" box.
MODE 3A
CODE 12XX upt thru code 1267 are VFR with the vast majority of aircraft
simply using 1200. Codes 1270 thru 1277 are allocated to Govt agencies
for use as a ground/surface based alignment of radar systems. These reply
on the assigned discrete code 3/A and a special 3/C return not associated
with the elevation of the target.
CODE 0000 block has some general usage in the system but nothing official
that I know of.
CODE 01XX thru 07XX are allocated for terminal radar approach control use.
CODE 10XX thru 74XX are allocated from assinment by ARTCC's.
CODE 75XX = hijack
CODE 76XX = radio failure (NORDO)
CODE 77XX = emergency.
MODE 3/C - Altitude encoded signals transmit down to the ground based on
as ALTM of 29.92. Upon receipt of the signal, receiving (processing) ATC
computer converts the 29.92 value to actuls ALTM value for the area that
the
ATC computer is responsible for. Also, transmitts in 100 fot increments
only.
This means that if ATC shows you at 1,500 feet MSL, your aircraft would
continue to transmit that value so long as you operated not lower then 1,450
feet and not higher then 1,549 feet.
Hope this was of some help.
Retired NTSB investigator and former ATC type.
"Phil M" <philli...@videoclub.edu> wrote in message
news:BV6U5.261$wE6....@wagner.videotron.net...
Steven P. McNicoll
"William W. Plummer" <wplu...@mediaone.net> wrote in message
news:ppfU5.24767$M51.7...@typhoon.ne.mediaone.net...
>
> ATC radar sweeps are not involved. Electronics monitors the transponder
> hold-off that ignores hits of less than, say one second.
>
Before it can be heard it must be interrogated, that would certainly involve
a sweep of the radar.
Steven P. McNicoll
>
> I believe transponders will periodically, say once per second, emit a
> "squitter" without being poked by a radar. Is that not true?
>
I'm no expert, but I would say no, it's not true.
Steven P. McNicoll
>
> If I understand, Xponder code 7777 will be dialed on a military
> interceptor a/c without ATC crealence. In other words, for example,
> if a military A/C enters a class B airspace and lands at O'Hare Int'l
> without even bothering contacting ATC or Tower, he must be on a
> 7777 squack, right?
>
Wrong. Code 7777 is for DOD interceptor aircraft on active air defense
missions and operating without ATC clearance. An active air defense mission
would be to intercept some unidentified or known hostile target, such a
mission would not wait for an ATC clearance.
>
> ... and if my Cessna 150 is Intercepted in a ADIZ zone by a F16, then he
> must be on 0000. (I know for a fact, that from my side I will dial the
> emergency code ModeA 7700).
>
Code 0000 is not listed in the National Beacon Code Allocation Plan.
Gene Whitt
I have written some historical information about the
IFF (idenfification friend or foe) as to its origin and the residue that
remains today.
Gene Whitt
Sean McCarney
used as an SSR Interrogater 'Permanent Echo' to ATC units that the radar PPI
is correctly aligned and operating within limits.
Hope that helps
Sean
Scott <sco...@SPAMgci.net> wrote in message
news:3A215501...@SPAMgci.net...
> I think you should worry about more pressing matters in life ;)
>
> Happy Flying
> Scott Skylane
> N92054
>
> Phil M wrote:
> >
> > If I understand, Xponder code 7777 will be dialed on a military
interceptor
> > a/c without ATC crealence. In other words, for example, if a military
A/C
> > enters a class B airspace and lands at O'Hare Int'l without even
bothering
> > contacting ATC or Tower, he must be on a 7777 squack, right?
> >
> > ... and if my Cessna 150 is Intercepted in a ADIZ zone by a F16, then he
> > must be on 0000. (I know for a fact, that from my side I will dial the
> > emergency code ModeA 7700).
> >
Bob Moore
what does the "SIF" as in IFF/SIF mean? :-)
Bob Moore
Dave Hyde
> OK, all of you "smart" IFF types, now that we know all about IFF,
> what does the "SIF" as in IFF/SIF mean? :-)
Selective Identification Feature.
Dave 'NCTR' Hyde
na...@brick.net
Bob Moore
>Bob Moore wrote:
>> OK, all of you "smart" IFF types, now that we know all about IFF,
>> what does the "SIF" as in IFF/SIF mean? :-)
>Selective Identification Feature.
Must be an "old fart"! :-)
Bob Moore
William W. Plummer
"Roy Smith" <r...@panix.com> wrote in message
news:roy-C7C92C.1...@news.panix.com...
> "William W. Plummer" <wplu...@mediaone.net> wrote:
> > ATC radar sweeps are not involved. Electronics monitors the transponder
> > signals and sets off an alarm if 77xx is heard.
>
Stan Prevost
Dave Hyde <na...@brick.net> wrote in message
news:3A21B22A...@brick.net...
> Bob Moore wrote:
>
> > OK, all of you "smart" IFF types, now that we know all about IFF,
> > what does the "SIF" as in IFF/SIF mean? :-)
>
> Selective Identification Feature.
>
Or "Selective Interrogation Feature".
Bob Noel
W. Plummer" <wplu...@mediaone.net> wrote:
> I believe transponders will periodically, say once per second, emit a
> "squitter" without being poked by a radar. Is that not true? --Bill
Mode S will indeed transmit squitter.
I'll check on the bugsmasher transponder action.
--
Bob
(I think people can figure out how to email me...)
(replace ihatessppaamm with my name (rnoel) and hw1 with mediaone)
Bob Moore
>> "squitter" without being poked by a radar. Is that not true?
William.......is it getting late???? Think!
How does the controller determine the bearing to the aircraft if the
emission from the TXPDR is not linked to the sweep of the interogating
RADAR?
I know...... it's been a l o n g weekend. :-)
Bob Moore
Phillip Smith
When in Mode C/Alt, how does the XPonder determine the altitude? Does it
simply read off the altimeter on the panel or does it determine it itself
using the static port?
-Phil
Phil M <philli...@videoclub.edu> wrote in message
Phil M
Mike O'Rourke wrote an interesting responce here and you might want to add
this info to whittsflying's Xponder section.
I'll quote it:
MODE 3A
"
> I have written some historical information about the
Phil M
on this "mistery big brother device"... I'll print it and ammend it to my
Flight Manual.
> Yep, military aircraft "DO" have transponders
Ok, since we all know by now that military a/c do have Xponders and operate
mode 1,2&4, are they capable of mode3?
Bob Noel
<philli...@videoclub.edu> wrote:
> > Yep, military aircraft "DO" have transponders
>
> Ok, since we all know by now that military a/c do have Xponders and
> operate
> mode 1,2&4, are they capable of mode3?
yes.
and also Mode S (which, of course, is of no interest to
most of the US GA pilots).
Mark Boyer
Phil M
> most of the US GA pilots).
Is this a new one? (mode S). What is mode S and used by whom and where?
Dave Holford
interrogation, is only received when the transponder is in the radar
beam. You can squitter all you like (you don't have any control over it
the rate is specified in AIRINC/ICAO specs) but only sites whose
antennas are pointing at you when you transmit will receive the signal.
Dave
highflyer
>
> While we're on the subject (again),
> When in Mode C/Alt, how does the XPonder determine the altitude? Does it
> simply read off the altimeter on the panel or does it determine it itself
> using the static port?
>
> -Phil
>
Yes, more or less. The transponder requires an encoded altitude input
that it sends when it is interrogated. It gets that input from a
separate encoding altimeter. Most of these are called "blind
encoders" because their only output is the encoded one for the
transponder. Some are called "encoding altimeters" because they are
a convention panel instrument with the encoding circuitry built in.
In either case, the encoder ignores the altimeter setting and sends
absolute pressure altitude, which is corrected at the receiving end.
That is why, sometimes, your indicated altitude may be different from
the altitude sent by your transponder.
--
HighFlyer
Highflight Aviation Services
Brian E
BTW, Bob, you only give us 01+29 to answer the question before you give the
answer. My news server service takes longer than that for me to see the
posts, by the time I see the questions all the good answers are taken.
Old enough to have had an SIF in the plane, Not old enough to have used it.
Brian E.
V-31220
Stan Prevost <spre...@nospam.home.com> wrote in message
news:LMjU5.25492$iy3.5...@news1.rdc1.tn.home.com...
Tarver Engineering
"Dave Holford" <hol...@sympatico.ca> wrote in message
news:3A229486...@sympatico.ca...
> Yes, it's true. But the signal, be it squitter or response to an
> interrogation, is only received when the transponder is in the radar
> beam. You can squitter all you like (you don't have any control over it
> the rate is specified in AIRINC/ICAO specs) but only sites whose
> antennas are pointing at you when you transmit will receive the signal.
The once per second requirement is of needed for TCAS.
John
>
> Dave
>
> "William W. Plummer" wrote:
> >
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http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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Tarver Engineering
"Bob Noel" <ihates...@hw1nospam.net.invalid> wrote in message
news:ihatessppaamm-B7B...@news.ne.mediaone.net...
> In article <3erU5.3686$RG4.1...@weber.videotron.net>, "Phil M"
> <philli...@videoclub.edu> wrote:
>
> > > Yep, military aircraft "DO" have transponders
> >
> > Ok, since we all know by now that military a/c do have Xponders and
> > operate
> > mode 1,2&4, are they capable of mode3?
>
> yes.
>
> most of the US GA pilots).
Except those desiring ADS-B.
John
Tarver Engineering
"Gene Whitt" <gwh...@ix.netcom.com> wrote in message
news:8vspka$lom$1...@slb1.atl.mindspring.net...
> All,
> I have written some historical information about the
> IFF (idenfification friend or foe) as to its origin and the residue that
> remains today.
The IFF codes are now passed through the airborne TACAN system.
John
> http://www.whittsflying.com
>
> Gene Whitt
Steven P. McNicoll
"Sean McCarney" <se...@mccarney.demon.co.uk> wrote in message
news:975313640.6690.0...@news.demon.co.uk...
>
> In the UK, 0000 is used to indicate transponder malfunction.
>
A transponder code for transponder malfunction. Interesting.
>
> 7777 is, AFAIR, used as an SSR Interrogater 'Permanent Echo' to ATC
> units that the radar PPI is correctly aligned and operating within limits.
>
In the US, 1273, 1274 and 1275 codes are used for calibration performance
monitoring equipment, or "parrot" transponders.
William W. Plummer
unsolicited squitter? I have no idea of how it figures what the bearing is
to the other craft. Distance is figured by comparing the attenuation of
two different frequencies. --Bill
"Bob Moore" <rmoo...@tampabay.rr.com> wrote in message
news:sekU5.66134$vc3.14...@typhoon.tampabay.rr.com...
Stan
terms are used. This term makes sense given the way Mode 4 works.
One place it shows up is
http://cliffie.nosc.mil/~NAUG/manusr/appendix/acronym-s.html
"Brian E" <som...@microsoft.com> wrote in message
news:3a22...@flexnet239.uunt.net...
> My book just lists "Selective Identification Feature" (AN/APA-89).
>
> BTW, Bob, you only give us 01+29 to answer the question before you give
the
> answer. My news server service takes longer than that for me to see the
> posts, by the time I see the questions all the good answers are taken.
>
> Old enough to have had an SIF in the plane, Not old enough to have used
it.
>
> Brian E.
> V-31220
>
> Stan Prevost <spre...@nospam.home.com> wrote in message
> news:LMjU5.25492$iy3.5...@news1.rdc1.tn.home.com...
> >
Steven P. McNicoll
"William W. Plummer" <wplu...@mediaone.net> wrote in message
news:QmBU5.25882$M51.8...@typhoon.ne.mediaone.net...
>
> Doesn't the Ryan TCAD rely on other aircraft emitting a periodic,
> unsolicited squitter? I have no idea of how it figures what the bearing
is
> to the other craft. Distance is figured by comparing the attenuation of
> two different frequencies.
>
I believe TCAD simply listens for transponder replies to interrogations by
secondary radar or TCAS.
Larry Fransson
> Is this a new one? (mode S). What is mode S and used by whom and where?
Mode S is far from new. I've been flying for 15 years and I've been
hearing about Mode S almost since the beginning. All aircraft were
supposed to have been carrying Mode S transponders starting several
years ago, but that was dropped. We (my employers) have two aircraft
(Lear 31A and Challenger 600) with Mode S transponders.
Larry
Bob Noel
<john_...@juno.com> wrote:
> The once per second requirement is of needed for TCAS.
why? TCAS II actively interrogates.
Bob Noel
<john_...@juno.com> wrote:
> The IFF codes are now passed through the airborne TACAN system.
which TACAN LRUs process IFF codes?
Tarver Engineering
"Bob Noel" <ihates...@hw1nospam.net.invalid> wrote in message
> In article <3a22d...@goliath2.newsfeeds.com>, "Tarver Engineering"
> <john_...@juno.com> wrote:
>
> > The IFF codes are now passed through the airborne TACAN system.
>
> which TACAN LRUs process IFF codes?
Shipboard TACAN have done this for some years and the new air to air TACANS
do the same. You would not want to respond with your distance and direction
to an unfriendly.
John
Tarver Engineering
"Bob Noel" <ihates...@hw1nospam.net.invalid> wrote in message
> In article <3a22d43a$1...@goliath2.newsfeeds.com>, "Tarver Engineering"
> why? TCAS II actively interrogates.
So what?
RW Walker
"Steven P. McNicoll" <ronca...@writeme.com> wrote in message
news:t25qf8q...@corp.supernews.com...
airports, were mountains block secondary radar from the pattern.
TCAD is an aid for, not a replacement for, the eyeball.
BW
Gary Watson
RCAF in Europe in the 60s. You had to dial it up in the R/T whenever you
replaced it in the CF 104
I have also heard that the Russians used Mode 2 connected to their fuel
totalizer so their controllers could tell when they were Bingo fuel.
Gary Watson
"Phil M" <philli...@videoclub.edu> wrote in message
news:2erU5.3685$RG4.1...@weber.videotron.net...
> Hi Gene,
>
> Mike O'Rourke wrote an interesting responce here and you might want to add
> this info to whittsflying's Xponder section.
>
> I'll quote it:
>
> "
> Yep, military aircraft "DO" have transponders
>
> > I have written some historical information about the
> > IFF (idenfification friend or foe) as to its origin and the residue that
> > remains today.
> >
> > http://www.whittsflying.com
> >
> > Gene Whitt
>
>
Gary Watson
SSR (Secondary Surveillance Radar) which interogates transponders. You only
get hit with it once per revolution with a 12 Usec wide interrogation pulse.
If the transponder is adjusted properly on th ebench it should not emit
spurious transmissions unless interogated. DMEs use a squitter action. Mode
S is different in that during the 50 usec or so that the SSR bean is
interogating the aircraft the Mode S with a very narrow pulse width can send
numeous queries tothe transponder which at some point in the future will be
able to downlink a variety of information.If my pulse size descriptions are
not completely accurate it is due tothe fact I haven't worked on an avionics
bench in about 8 years and am not about to go dig up one of my refernec
manuals.
Gary Watson
"Bob Moore" <rmoo...@tampabay.rr.com> wrote in message
news:sekU5.66134$vc3.14...@typhoon.tampabay.rr.com...
>
Bob Noel
<john_...@juno.com> wrote:
> > > The once per second requirement is of needed for TCAS.
>
> > why? TCAS II actively interrogates.
>
> So what?
what purpose does the squitter serve in support of TCAS?
Gary Watson
all existing ATCRCBS (Air Traffic Control Radar Beacon System - better
pronounced as At-Crabs) transponders in the coming decades. The transponder
still works on the same frequencies but is used with TCAS(Traffic Alert and
Collision Avoidance System) to datalink between two TCAS equipped aircraft.
It is also intended toprovide downlink information to ATC in the future when
the ADS-B (Automatic Dependent Surveillance - Broadcast) network becomes
effective. When everything gets up and running in the ATC world then
controllers will be able to Selectively interrogate a particular aircraft as
you are assigned a world-wide descrete code for your registration when
installing Mode S equipment.
Gary Watson
"Phil M" <philli...@videoclub.edu> wrote in message
news:K%vU5.4156$RG4.1...@weber.videotron.net...
> > and also Mode S (which, of course, is of no interest to
> > most of the US GA pilots).
>
Gary Watson
information to the transponder. For North Atlantic and parts of the Pacific,
a new term has crept in - RVSM (Reduced Vertical Seperation Minimums) which
requires tighter tolerence ADCs to allow ATC to reduce the vertical
seperation between aircraft.
Hope this helps, if anything it will ad to your acronym data bank :)
Gary Watson
"highflyer" <high...@alt.net> wrote in message
news:3A22BD57...@alt.net...
Paul Hirose
xponders I've seen have modes 1, 2, 3/A, 4, and C. Selecting both 3/A
and C requires separate switch throws or button pushes.
As for Mode 3 being "civilian", I won't say that's wrong, but my C152
manual and Jepp ground school text both call the civilian mode "A", not
"3". I suspect Mode 3 is the military terminology.
Paul Hirose, student pilot & retired USAF avionics maintainer
Bob Noel
<paulh...@earthlink.net> wrote:
> I don't think there's any such thing as Mode 3/C. All the military
> xponders I've seen have modes 1, 2, 3/A, 4, and C. Selecting both 3/A
> and C requires separate switch throws or button pushes.
>
> As for Mode 3 being "civilian", I won't say that's wrong, but my C152
> manual and Jepp ground school text both call the civilian mode "A", not
> "3". I suspect Mode 3 is the military terminology.
nope. 3/A and 3/C exist and are not military.
It would seem that people drop the "3" because it is understood
when saying Mode A and Mode C. Sort of like being told to contact
ground on "point seven" instead of 121.7.
gross_arrow
"Steven P. McNicoll" <ronca...@writeme.com> wrote:
>
> "Curtis Suter" <sut...@earthlink.net> wrote in message
> news:NOaU5.4609$II2.5...@newsread2.prod.itd.earthlink.net...
> >
> > I've never heard nor know where 1 is used, but we still aligned and
> > calibrated it. It's a two digit code with the first digit able to
be set
> > from 0-7 and the second digit from 0-3.
> >
>
> Sounds like the old 64-code non-discrete transponders.
>
>
'cept that if the second digit only went from 0-3, you could only get
32 codes.
(i always wanted to nitpick a steven mcnicoll post).
:-) :-)
john
Sent via Deja.com http://www.deja.com/
Before you buy.
Chuck
not just a random grouping of pulses. It contains the mode-s address for the
aircraft. A TCAS processor uses the squitter to identify the presence of a
mode-s equipped aircraft. TCAS generally assumes that an aircraft with a
mode-s transponder also has a TCAS processor. Once the address is received
the processor will add the aircraft to its track file and periodically
interrogate it to update its position. The TCAS processor must actively
search out standard mode-a/c transponders but not necessarily mode-s because
this squitter.
Chuck
"Bob Noel" <ihates...@hw1nospam.net.invalid> wrote in message
news:ihatessppaamm-486...@news.ne.mediaone.net...
Dave Holford
Civil modes are identified by letters.
Military mode 3 is the same as civil mode A, hence ATC calls it 3/A.
Mode C has no military equivalent, at least AFAIK.
I have never heard of 3/C, in military or civil aviation documentation
or useage, until this discussion.
Other differences are in the Ident function and Emergency, however
modern civil ground equipment processes the military ones so that they
are displayed the same. I don't know for sure, but it would seem
reasonable to assume that modern military xponders probably transmit
both military and civil responses to ensure everyone gets the ident and
emergency data.
Dave
Bob Noel wrote:
>
> In article <3A23359E...@earthlink.net>, Paul Hirose
> <paulh...@earthlink.net> wrote:
>
> > I don't think there's any such thing as Mode 3/C. All the military
> > xponders I've seen have modes 1, 2, 3/A, 4, and C. Selecting both 3/A
> > and C requires separate switch throws or button pushes.
> >
> > As for Mode 3 being "civilian", I won't say that's wrong, but my C152
> > manual and Jepp ground school text both call the civilian mode "A", not
> > "3". I suspect Mode 3 is the military terminology.
>
> nope. 3/A and 3/C exist and are not military.
>
> It would seem that people drop the "3" because it is understood
> when saying Mode A and Mode C. Sort of like being told to contact
> ground on "point seven" instead of 121.7.
>
Gary Watson
accompanyed by TCAS, as lots of light a/c now have Mode S. I thought that
Modes S or A/C changes the TCAS interogation from whisper to shout?
"Chuck" <Hor...@peoplepc.com> wrote in message
news:3a245...@news3.prserv.net...
> Without going into too much detail the squitter from a mode-s transponder
is
> not just a random grouping of pulses. It contains the mode-s address for
the
> aircraft. A TCAS processor uses the squitter to identify the presence of a
> mode-s equipped aircraft. TCAS generally assumes that an aircraft with a
> mode-s transponder also has a TCAS processor. Once the address is received
> the processor will add the aircraft to its track file and periodically
> interrogate it to update its position. The TCAS processor must actively
> search out standard mode-a/c transponders but not necessarily mode-s
because
> this squitter.
>
> Chuck
>
> "Bob Noel" <ihates...@hw1nospam.net.invalid> wrote in message
> news:ihatessppaamm-486...@news.ne.mediaone.net...