Hi people, i designed a pic circuit that reads data from a GPS and
send some information over the air using a high power radio.

    I tested the circuit several times on my table, and it worked ok on
every test, but when i tried to install it on a car, i got many, many
problems.

    As i did not have an antenna on my test table, i used a "dead load"
connected to the radio's antena output in order to not burn the radio
transmitter.

    The problem is that in the car the transmiting antenna seems to feed
interference in the circuit via the GPS.

    I believe this is true because if i disconnect the gps from the
circuit, the transmitted message is perfectly received.

    If i turn the GPS power on the message is also perfectly received.

    But when the tx/rx pins are connected the message gets messed and
the receiving system does not recognize it.

    If i disconnect the car antenna and connect the dead load again, now
inside the car, the system works! Put the antenna back, and nothing works!

    Any hint, as i already tried everything i could.

    Thanks

Rafael.

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