Continuing problems seeing ATCRBS transponders with Mode Sinterrogators

[[email protected]]

Continuing problems seeing ATCRBS transponders with Mode S
interrogators

Hey all, I work in, lets call it 'an associated industry' and we are
still seeing ATCRBS transponders that reply to some interrogators, and
not to others.

At one time this was known as the 'P4 problem', sometimes as the
'Terra problem', just want to ask if anyone out there flying with an
ATCRBS xpdr is still having trouble being 'seen' by some
interrogators, but no problem with others.


Thx-

Dave

[Mike]

> wrote in message
...
> Continuing problems seeing ATCRBS transponders with Mode S
> interrogators
>
> Hey all, I work in, lets call it 'an associated industry' and we are
> still seeing ATCRBS transponders that reply to some interrogators, and
> not to others.
>
> At one time this was known as the 'P4 problem', sometimes as the
> 'Terra problem', just want to ask if anyone out there flying with an
> ATCRBS xpdr is still having trouble being 'seen' by some
> interrogators, but no problem with others.

You need to provide more symptoms, locations, interrogator identifiers, etc.

Some types of interrogators have the ability to selectively interrogate
ModeS transponders (although I'm not sure if any of them do in actuality).
Early on in the ModeS program there were sensor problems with side lobe
suppression and reflection rejection, although those problems may have been
addressed with later modifications. This is my best guess as far as to what
you're referring to, although it would actually be more correctly referred
to as a "P2 problem" although I've never heard it called that.

[[email protected]]

On Sep 24, 12:21 am, "Mike" <nospam@ microsoft.com> wrote:
> > wrote in message
>
> ...
>
> > Continuing problems seeing ATCRBS transponders with Mode S
> > interrogators
>
> > Hey all, I work in, lets call it 'an associated industry' and we are
> > still seeing ATCRBS transponders that reply to some interrogators, and
> > not to others.
>
> > At one time this was known as the 'P4 problem', sometimes as the
> > 'Terra problem', just want to ask if anyone out there flying with an
> > ATCRBS xpdr is still having trouble being 'seen' by some
> > interrogators, but no problem with others.
>
> You need to provide more symptoms, locations, interrogator identifiers, etc.
>
> Some types of interrogators have the ability to selectively interrogate
> ModeS transponders (although I'm not sure if any of them do in actuality).
> Early on in the ModeS program there were sensor problems with side lobe
> suppression and reflection rejection, although those problems may have been
> addressed with later modifications. This is my best guess as far as to what
> you're referring to, although it would actually be more correctly referred
> to as a "P2 problem" although I've never heard it called that.


This is a Mode S/ATCRBS interrogator, short P4 pulse on the ATCRBS
interrogations, certain percentage of the ATCRBS transponders are
visible to a nearby ATCRBS-only interrogator but do not reply to the
MODE S interrogators ATCRBS-ONLY ATCRBS interrogations.

The P4 problem was where an ATCRBS transponder would suppress on the
P3-P4 pair, mistaking it for a P1-P2 pair.

Dave

[Mike]

> wrote in message
...
> On Sep 24, 12:21 am, "Mike" <nospam@ microsoft.com> wrote:
>> > wrote in message
>>
>> ...
>>
>> > Continuing problems seeing ATCRBS transponders with Mode S
>> > interrogators
>>
>> > Hey all, I work in, lets call it 'an associated industry' and we are
>> > still seeing ATCRBS transponders that reply to some interrogators, and
>> > not to others.
>>
>> > At one time this was known as the 'P4 problem', sometimes as the
>> > 'Terra problem', just want to ask if anyone out there flying with an
>> > ATCRBS xpdr is still having trouble being 'seen' by some
>> > interrogators, but no problem with others.
>>
>> You need to provide more symptoms, locations, interrogator identifiers,
>> etc.
>>
>> Some types of interrogators have the ability to selectively interrogate
>> ModeS transponders (although I'm not sure if any of them do in
>> actuality).
>> Early on in the ModeS program there were sensor problems with side lobe
>> suppression and reflection rejection, although those problems may have
>> been
>> addressed with later modifications. This is my best guess as far as to
>> what
>> you're referring to, although it would actually be more correctly
>> referred
>> to as a "P2 problem" although I've never heard it called that.
>
>
> This is a Mode S/ATCRBS interrogator, short P4 pulse on the ATCRBS
> interrogations, certain percentage of the ATCRBS transponders are
> visible to a nearby ATCRBS-only interrogator but do not reply to the
> MODE S interrogators ATCRBS-ONLY ATCRBS interrogations.
>
> The P4 problem was where an ATCRBS transponder would suppress on the
> P3-P4 pair, mistaking it for a P1-P2 pair.


Before ModeS systems were commissioned this was a known problem and a ATCRBS
all-call interrogation was added to the ModeS systems (No P4 pulse). That's
why I'm asking you which sensor you are referring to because none of them
should have the problem you are describing, although some transponders may
still not reply to some ModeS all-call interrogations, they should still be
displayed due to the ATCRBS all-call interrogation from the ModeS sensor.
My understanding was the problematic transponders would be subject to an AD
and fixed, but I don't know if this ever happened.

[[email protected]]

On Sep 24, 11:05 am, "Mike" <nospam@ microsoft.com> wrote:
> > wrote in message
>
> ...
>
>
>
> > On Sep 24, 12:21 am, "Mike" <nospam@ microsoft.com> wrote:
> >> > wrote in message
>
> ...
>
> >> > Continuing problems seeing ATCRBS transponders with Mode S
> >> > interrogators
>
> >> > Hey all, I work in, lets call it 'an associated industry' and we are
> >> > still seeing ATCRBS transponders that reply to some interrogators, and
> >> > not to others.
>
> >> > At one time this was known as the 'P4 problem', sometimes as the
> >> > 'Terra problem', just want to ask if anyone out there flying with an
> >> > ATCRBS xpdr is still having trouble being 'seen' by some
> >> > interrogators, but no problem with others.
>
> >> You need to provide more symptoms, locations, interrogator identifiers,
> >> etc.
>
> >> Some types of interrogators have the ability to selectively interrogate
> >> ModeS transponders (although I'm not sure if any of them do in
> >> actuality).
> >> Early on in the ModeS program there were sensor problems with side lobe
> >> suppression and reflection rejection, although those problems may have
> >> been
> >> addressed with later modifications. This is my best guess as far as to
> >> what
> >> you're referring to, although it would actually be more correctly
> >> referred
> >> to as a "P2 problem" although I've never heard it called that.
>
> > This is a Mode S/ATCRBS interrogator, short P4 pulse on the ATCRBS
> > interrogations, certain percentage of the ATCRBS transponders are
> > visible to a nearby ATCRBS-only interrogator but do not reply to the
> > MODE S interrogators ATCRBS-ONLY ATCRBS interrogations.
>
> > The P4 problem was where an ATCRBS transponder would suppress on the
> > P3-P4 pair, mistaking it for a P1-P2 pair.
>
> Before ModeS systems were commissioned this was a known problem and a ATCRBS
> all-call interrogation was added to the ModeS systems (No P4 pulse). That's
> why I'm asking you which sensor you are referring to because none of them
> should have the problem you are describing, although some transponders may
> still not reply to some ModeS all-call interrogations, they should still be
> displayed due to the ATCRBS all-call interrogation from the ModeS sensor.
> My understanding was the problematic transponders would be subject to an AD
> and fixed, but I don't know if this ever happened.


Yes, my understanding also was that any transponders with this
behavior had been purged or fixed.

We are still trying to find the common thread on this one, could be
something completely different, even an excessively low MTL on the
transponder that is picking up the leading S1 pulse (TCAS ATCRBS
Whisper-Shout interrogations).

Thanks-

Dave