17 Feb
2014
17 Feb
'14
3:57 p.m.
Hi,
My name is Allan an I am currently working on my final year project for college. The idea
is to create a radar system that interprets MODE C interrogation signals and replies by
aircraft and SSR and with this information determine where these airplanes are in your
vicinity. The device I am using to receive these transmissions is a DVB-T dongle. I will
have to create an algorithm that will use the ping of the above transmissions which I am
aware of. My problem is that I am having difficulty understanding how I will decode the
signal to read the altitude and differentiate between other aircraft transmitting on the
1090MHz frequency. Could anyone in this forum point me in some direction as to how to
learn this? Also apologies if I am unclear.
Regards
Allan
17 Feb
17 Feb
4:31 p.m.
On Mon, 17 Feb 2014 14:57:44 +0000
Allan Healy <allan.healy121(a)gmail.com> wrote:
My name is Allan an I am currently working on my final
year project
for college. The idea is to create a radar system that interprets
MODE C interrogation signals and replies by aircraft and SSR and
with this information determine where these airplanes are in your vicinity.
I never heard of anyone being able to do that so far. Mode S is easy
and there's any number of 1090 Extended Squitter receivers and decoders
out there, but Mode C relies on the illumination by the radar to
trigger the transmission. Since you cannot know where the radar
is pointing and when the impulse started (and sometimes not where
the radar is located), you cannot link Mode C squitter with the particular
primary target.
You can receive Mode C with rtl_adsb and have a look at 56-bit packets,
but they are completely useless for an independent ground station.
Some people nowadays play with a concept of building a something
like interferometer from 3 or 4 receivers, but nobody has succeeded
thus far, as far as I know.
-- Pete
4:46 p.m.
Hi Pete
Thanks for the reply. Yeah I can see the MODE C transmissions with the rtl_adsb alright
but I don’t know how to see the interrogation transmissions from an SSR. Like you said
there are many decoders available for MODE S. Hopefully my supervisor will understand the
gravitas of the project and will accept MODE S as a suitable solution. Still I will try do
some more research. If I am successful I will provide my solution to this forum. Thanks
again.
Allan
On 17 Feb 2014, at 15:31, Pete Zaitcev <zaitcev(a)kotori.zaitcev.us> wrote:
On Mon, 17 Feb 2014 14:57:44 +0000
Allan Healy <allan.healy121(a)gmail.com> wrote:
My name is Allan an I am currently working on my
final year project
for college. The idea is to create a radar system that interprets
MODE C interrogation signals and replies by aircraft and SSR and
with this information determine where these airplanes are in your vicinity.
I never heard of anyone being able to do that so far. Mode S is easy
and there's any number of 1090 Extended Squitter receivers and decoders
out there, but Mode C relies on the illumination by the radar to
trigger the transmission. Since you cannot know where the radar
is pointing and when the impulse started (and sometimes not where
the radar is located), you cannot link Mode C squitter with the particular
primary target.
You can receive Mode C with rtl_adsb and have a look at 56-bit packets,
but they are completely useless for an independent ground station.
Some people nowadays play with a concept of building a something
like interferometer from 3 or 4 receivers, but nobody has succeeded
thus far, as far as I know.
-- Pete 
5:11 p.m.
Hi ,
just one comment : the interrogation is periodic and stable.. the request
is transmitted by a rotating antenna turning at constant speed. If you can
get the direct path to the interrogation system, you may estimate the
round-trip time and then when the interrogation pulse is sent
sylvain
2014-02-17 16:46 GMT+01:00 Allan Healy <allan.healy121(a)gmail.com>om>:
Hi Pete
Thanks for the reply. Yeah I can see the MODE C transmissions with the
rtl_adsb alright but I don't know how to see the interrogation
transmissions from an SSR. Like you said there are many decoders available
for MODE S. Hopefully my supervisor will understand the gravitas of the
project and will accept MODE S as a suitable solution. Still I will try do
some more research. If I am successful I will provide my solution to this
forum. Thanks again.
Allan
On 17 Feb 2014, at 15:31, Pete Zaitcev <zaitcev(a)kotori.zaitcev.us> wrote:
On Mon, 17 Feb 2014 14:57:44 +0000
Allan Healy <allan.healy121(a)gmail.com> wrote:
> My name is Allan an I am currently working on my final year project
> for college. The idea is to create a radar system that interprets
> MODE C interrogation signals and replies by aircraft and SSR and
> with this information determine where these airplanes are in your
vicinity.
I never heard of anyone being able to do that so far. Mode S is easy
and there's any number of 1090 Extended Squitter receivers and decoders
out there, but Mode C relies on the illumination by the radar to
trigger the transmission. Since you cannot know where the radar
is pointing and when the impulse started (and sometimes not where
the radar is located), you cannot link Mode C squitter with the
particular
primary target.
You can receive Mode C with rtl_adsb and have a look at 56-bit packets,
but they are completely useless for an independent ground station.
Some people nowadays play with a concept of building a something
like interferometer from 3 or 4 receivers, but nobody has succeeded
thus far, as far as I know.
-- Pete
5:22 p.m.
Hi,
as far as I know interrogation requests are send on 1030MHz with a
higher bandwidth and a different modulation scheme.
Stefan
Am 17.02.2014 17:11, schrieb Sylvain AZARIAN:
Hi ,
just one comment : the interrogation is periodic and stable.. the request
is transmitted by a rotating antenna turning at constant speed. If you can
get the direct path to the interrogation system, you may estimate the
round-trip time and then when the interrogation pulse is sent
sylvain
5:38 p.m.
Yes, that's true.. but this does not avoid the round-trip measurement...
2014-02-17 17:22 GMT+01:00 Stefan Sydow <st(a)metafly.info>fo>:
Hi,
as far as I know interrogation requests are send on 1030MHz with a
higher bandwidth and a different modulation scheme.
Stefan
Am 17.02.2014 17:11, schrieb Sylvain AZARIAN:
Hi ,
just one comment : the interrogation is periodic and stable.. the request
is transmitted by a rotating antenna turning at constant speed. If you
can
get the direct path to the interrogation system,
you may estimate the
round-trip time and then when the interrogation pulse is sent
sylvain
5:45 p.m.
Yeah that’s true. I am thinking if I could get the Automatic Gain Control of the
transmission from the plane I might be able to give a really rough guesstimate where the
plane is in a 2D axis.
On 17 Feb 2014, at 16:22, Stefan Sydow <st(a)metafly.info> wrote:
Hi,
as far as I know interrogation requests are send on 1030MHz with a
higher bandwidth and a different modulation scheme.
Stefan
Am 17.02.2014 17:11, schrieb Sylvain AZARIAN:
Hi ,
just one comment : the interrogation is periodic and stable.. the request
is transmitted by a rotating antenna turning at constant speed. If you can
get the direct path to the interrogation system, you may estimate the
round-trip time and then when the interrogation pulse is sent
sylvain
3738
days inactive
3738
days old
6 comments
4 participants
participants (4)
-
Allan Healy -
Pete Zaitcev -
Stefan Sydow -
Sylvain AZARIAN