Hello!

I have no experience working with frequencies in the gigahertz range,
but I am working on a project that broadcasts AM signals on 1030 MHZ
and 1090 MHZ. It is the frequencies that airplane transponders
communicate with ground stations on.

Does anyone have practical experience building a receiver for
frequencies in this range? And what are some good suppliers for
components at these frequencies?

I am looking for some example circuit diagrams and pcb layouts or
something like that.

Thanks for any help.

I have no experience working with frequencies in the gigahertz range,
but I am working on a project that broadcasts AM signals on 1030 MHZ
and 1090 MHZ. It is the frequencies that airplane transponders
communicate with ground stations on.

Slight correction: The 1030/1090 MHz frequencies are
an aid to FAA local search radar to help discriminate
targets and to IDENTIFY targets shown on their radar
display screens. That isn't "communication" per se.

The ground station interrogator antenna physically
rides on top of the search radar dish. It has a VERY
narrow horizontal antenna pattern. The interrogation
signal is a repetitive PULSE pair...fairly high power,
usually better than a hundred Watts peak. An aircraft
transponder receives all signals on that frequency and
uses one of several types of "coincidence detectors"
to separate received pulse pairs from single pulse
signals or "fruit" (avionics term, not mine). At a
fixed time delay, the transponder sends out its own
PULSE pair...plus a PULSE ID code (in octal number
arrangement of two 0-7 numbers or four 0-7 numbers).
The ground station receiver processor strips out the
valid aircraft responses and ID from "fruit" and
sends that to the search radar display unit.

Bandwidth is roughly 30 MHz for those two carrier
frequencies so radar receiver techniques apply.

Does anyone have practical experience building a receiver for
frequencies in this range? And what are some good suppliers for
components at these frequencies?

I do. It's the bottom end of L-Band (1 to 2 GHz) and
in a "nasty" transition range of lumped tuned circuits
into distributed tuned circuits. Cellular and cordless
phones ("old" style in the pulse range, not the newer
2.4 GHz cordless variety) fall into that range.

Ain't NO "good suppliers for components" of front ends
since all of those are designed at the factory or sub-
contracted. Front end tuning is probably simplest using
capacitively-loaded coaxial cavities, whether solid-state
or vacuum-state active devices are used. Stripline can
be used there although those get relatively large at
1 GHz. NOS pencil triodes can be used to achieve high
enough peak RF pulses but I've no experience in AM for
those. Radiosondes/rawinsondes used pencil triodes
crimped into sheet metal cavities at 1.6 GHz. A small
boat radar (short range) used to be sold by a company
called Bonzer three decades ago, used those pencil
triodes with an array of helix antennas in what looks
like a large "TV" style pancake radome. I've seen
lots of similar ones around the marinas here.

IF strips are just radar-style, can be 30 to 60 MHz
center, a relative piece of cake to build, plenty of
textbook data on such from the last 6 decades.

I am looking for some example circuit diagrams and pcb layouts or
something like that.

Uh-uh. Good luck when the federal marshalls show up
at your door along with an FCC field engineer, maybe
a ****ed FAA official.

INTERFERING, however slight, with an ATC radar
interrogator system, is NOT A GOOD THING. DO NOT
DO THAT!

You just want some "examples?" Buy an aircraft
transponder. Reverse engineer it. Maybe $2K for a
used unit? DO NOT USE IT FOR "COMMUNICATIONS."

If you want to do "piracy" on UHF, there's plenty of
RF space in unused TV channels. FCC has the listings
of old and new (DTV) channel occupancy by city. FCC
also regulates all U.S. civil radio and they do NOT
take kindly to anyone interfering with FAA ATC ops
and those very reserved bandspaces.

I have no experience working with frequencies in the gigahertz range,
but I am working on a project that broadcasts AM signals on 1030 MHZ
and 1090 MHZ. It is the frequencies that airplane transponders
communicate with ground stations on.

Slight correction: The 1030/1090 MHz frequencies are
an aid to FAA local search radar to help discriminate
targets and to IDENTIFY targets shown on their radar
display screens. That isn't "communication" per se.

The ground station interrogator antenna physically
rides on top of the search radar dish. It has a VERY
narrow horizontal antenna pattern. The interrogation
signal is a repetitive PULSE pair...fairly high power,
usually better than a hundred Watts peak. An aircraft
transponder receives all signals on that frequency and
uses one of several types of "coincidence detectors"
to separate received pulse pairs from single pulse
signals or "fruit" (avionics term, not mine). At a
fixed time delay, the transponder sends out its own
PULSE pair...plus a PULSE ID code (in octal number
arrangement of two 0-7 numbers or four 0-7 numbers).
The ground station receiver processor strips out the
valid aircraft responses and ID from "fruit" and
sends that to the search radar display unit.

Bandwidth is roughly 30 MHz for those two carrier
frequencies so radar receiver techniques apply.

Does anyone have practical experience building a receiver for
frequencies in this range? And what are some good suppliers for
components at these frequencies?

I do. It's the bottom end of L-Band (1 to 2 GHz) and
in a "nasty" transition range of lumped tuned circuits
into distributed tuned circuits. Cellular and cordless
phones ("old" style in the pulse range, not the newer
2.4 GHz cordless variety) fall into that range.

Ain't NO "good suppliers for components" of front ends
since all of those are designed at the factory or sub-
contracted. Front end tuning is probably simplest using
capacitively-loaded coaxial cavities, whether solid-state
or vacuum-state active devices are used. Stripline can
be used there although those get relatively large at
1 GHz. NOS pencil triodes can be used to achieve high
enough peak RF pulses but I've no experience in AM for
those. Radiosondes/rawinsondes used pencil triodes
crimped into sheet metal cavities at 1.6 GHz. A small
boat radar (short range) used to be sold by a company
called Bonzer three decades ago, used those pencil
triodes with an array of helix antennas in what looks
like a large "TV" style pancake radome. I've seen
lots of similar ones around the marinas here.

IF strips are just radar-style, can be 30 to 60 MHz
center, a relative piece of cake to build, plenty of
textbook data on such from the last 6 decades.

I am looking for some example circuit diagrams and pcb layouts or
something like that.

Uh-uh. Good luck when the federal marshalls show up
at your door along with an FCC field engineer, maybe
a ****ed FAA official.

INTERFERING, however slight, with an ATC radar
interrogator system, is NOT A GOOD THING. DO NOT
DO THAT!

You just want some "examples?" Buy an aircraft
transponder. Reverse engineer it. Maybe $2K for a
used unit? DO NOT USE IT FOR "COMMUNICATIONS."

If you want to do "piracy" on UHF, there's plenty of
RF space in unused TV channels. FCC has the listings
of old and new (DTV) channel occupancy by city. FCC
also regulates all U.S. civil radio and they do NOT
take kindly to anyone interfering with FAA ATC ops
and those very reserved bandspaces.

"Stu" wrote in message
ups.com...
Hello!

I have no experience working with frequencies in the gigahertz range,
but I am working on a project that broadcasts AM signals on 1030 MHZ
and 1090 MHZ. It is the frequencies that airplane transponders
communicate with ground stations on.

Does anyone have practical experience building a receiver for
frequencies in this range? And what are some good suppliers for
components at these frequencies?

I am looking for some example circuit diagrams and pcb layouts or
something like that.

Thanks for any help.


They are called transponders.

You can use a generic satellite receiver to pick it up, they tune from about
950 MHz to 1450 MHz, on the cable from the LNA
The old c-band satellite dish stuff, just take off the LNA and put a good
antenna on the end of the cable, you can make one out of a 1 gallon paint
can. You can buy a low end new satellite receiver for $200, or get a used
off ebay.

The band is easy to design in, for receivers.