T wrote:
All i want is to be able to pick up the signal from my "transmitter"
with an am-radio across the room.


Hold on guys! T, this is a rarified group here, and sometimes it shows.


Okay, so you have a transmitter that is presumably transmitting somewhere.

You want to be able to receive the signals on an AM radio at some
distance. Let's collect a little data, and I maybe I can help.


If you are using a typical AM radio to pick up the signals, you don't
need to do anything with it. It's already got an antenna.

Now on to your transmitter.

If the transmitter is working, you should be able to pick up a pretty
strong signal when the receiver is sitting next to it. Even if you just
have a short piece of wire on the transmitter.

If you don't, it is possible that the transmitter is not working. It is
also possible that if you have only a weak signal, you might be
transmitting on a "harmonic" frequency. This is pretty much double or
half, but it means that you are getting a much less powerful signal to
the radio.

Assuming that your transmitter can be tuned, set the radio at some
frequency, preferably on the lower part of the band and away from local
stations.

Now, with the radio sitting right beside the transmitter, tune the
tansmitter until you hear the signal you are looking for. Even when you
get a signal, you might try tuning the transmitter all between it's
limits just in case a harmonic signal is what you found at first. Go
with the strongest signal.

Now start moving the radio away from the transmitter. At some point,
the signal will become weaker, eventually going away - and if it
doesn't, your doing great.

If not, you need to lengthen the wire. There are some legal limits to
this, and I think that they are around 5 feet or so. Someone else might
be able to chime in here if they know exactly.

Some misc stuff:

The transmitter circuit may change frequency as you move toward or away
from it. Putting metal between you and the circuit can help, although
with some adjustment, you can predict how much change there will be and
accommodate the problem.

If you aren't getting anything with a short wire antenna and the radio
right beside the transmitter, the transmitter probably isn't working.

- 73 de Mike KB3EIA -