Hi guys,

I've got a computer in my car and I'd like to do a little AWACS style
signal mapping. I bought a BC245XLT because of the serial interface
and the protocol.

My plan is to build a simple circuit to control a directional antenna
with a servo or stepper motor and write a program to rotate it while
constantly querying the radio for signal strength & frequency while the
scanner is flipping through channels. My program will know which
direction the antenna is pointing plus absolute direction (using an I2C
digital compass), so I should be able to build a circular color display
showing which transmitter sources are in which direction.

Right now, I'm learning about what kind of antenna connectors can let
me do what I need. If the antenna will rotate 360, I'm figuring I'll
need a slip ring based on what I've read online. I understand that
antenna rotors do a lot of what I want already, and maybe that's the
way to go, but I enjoy building things myself wherever possible.

Can anyone with more experience give me some insight into which
direction to go? If I can live without 360 scanning, I could rotate
the antenna back and forth with a normal cable, but I'm all ears if
anyone has any thoughts.

Thanks!

"Chairboy" wrote in message
oups.com...
Hi guys,

I've got a computer in my car and I'd like to do a little AWACS style
signal mapping. I bought a BC245XLT because of the serial interface
and the protocol.

My plan is to build a simple circuit to control a directional antenna
with a servo or stepper motor and write a program to rotate it while
constantly querying the radio for signal strength & frequency while the
scanner is flipping through channels. My program will know which
direction the antenna is pointing plus absolute direction (using an I2C
digital compass), so I should be able to build a circular color display
showing which transmitter sources are in which direction.

Right now, I'm learning about what kind of antenna connectors can let
me do what I need. If the antenna will rotate 360, I'm figuring I'll
need a slip ring based on what I've read online. I understand that
antenna rotors do a lot of what I want already, and maybe that's the
way to go, but I enjoy building things myself wherever possible.

Can anyone with more experience give me some insight into which
direction to go? If I can live without 360 scanning, I could rotate
the antenna back and forth with a normal cable, but I'm all ears if
anyone has any thoughts.


Instead of a mechanical rotator system you need to look at the electronic
rotating systems. There is a design out that takes 4 antennas and
electronically rotates them and gives a direction.

"Ralph Mowery" wrote in message
k.net...

"Chairboy" wrote in message
oups.com...
Hi guys,

I've got a computer in my car and I'd like to do a little AWACS style
signal mapping. I bought a BC245XLT because of the serial interface
and the protocol.

My plan is to build a simple circuit to control a directional antenna
with a servo or stepper motor and write a program to rotate it while
constantly querying the radio for signal strength & frequency while the
scanner is flipping through channels. My program will know which
direction the antenna is pointing plus absolute direction (using an I2C
digital compass), so I should be able to build a circular color display
showing which transmitter sources are in which direction.

Right now, I'm learning about what kind of antenna connectors can let
me do what I need. If the antenna will rotate 360, I'm figuring I'll
need a slip ring based on what I've read online. I understand that
antenna rotors do a lot of what I want already, and maybe that's the
way to go, but I enjoy building things myself wherever possible.

Can anyone with more experience give me some insight into which
direction to go? If I can live without 360 scanning, I could rotate
the antenna back and forth with a normal cable, but I'm all ears if
anyone has any thoughts.


Instead of a mechanical rotator system you need to look at the electronic
rotating systems. There is a design out that takes 4 antennas and
electronically rotates them and gives a direction.

I agree- do a search under doppler based direction finding.
Each antenna has a PIN diode switch at its base- the diodes are each turned
on and off by a sequential clock.

Dale

Won't work. The computer is dedicated to engine management.

I should clarify. I have _built_ a computer into my car. It currently
plays MP3s, does GPS navigation, movies, etc. In fact, it's hooked to
the onboard engine management computer as well so I can view real time
engine status and troubleshoot problems.

Regarding using a 4 antenna system as mentioned in an earlier message,
would that really give me fine enough resolution to detect where a
signal was coming from within say 20 degrees? Or would it be in 90
degree increments?

Regarding using a 4 antenna system as mentioned in an earlier message,
would that really give me fine enough resolution to detect where a
signal was coming from within say 20 degrees? Or would it be in 90
degree increments?

YOu can go here to find one design,

http://www.qsl.net/ve2emm/pic-projec.../mtdop2-e.html

It should do around 10 degrees or so.