Maker Pro
Maker Pro

AM transmitter question


Eric Sears

Jan 1, 1970
Just a brief comment - you MAY still have a drift problem; or perhaps
I should say "hand capacity" problem - which is shifting the
frequency of the transmitter when you are touching the aerial.
You may need to try tuning receiver when you are NOT touching the
If that doesn't help, you could use a "counterpoise" in place of an
earth - ie connect an 8 foot wire to the earth side of the circuit and
drape it along the floor (this will probably mean just connecting it
the the -ve side of the battery).

Something else that may help is to use the HIGH end of the band (near
1500 kHz) - the short aerial will be more efficient.

Otherwise simply use 20 feet of wire for an aerial as high around the
wall in the room as possible. (Very THIN wire will be fine).

It is also possible that the polarisation is incorrect. Try turning
the radio so that the rod aerial is vertical. It may be that when you
touch the aerial you are adding a horizontal component to the

Well that's enough to try!

Eric (ZL2BMI)

Eric Sears

Jan 1, 1970
Make sure you are tuned to the fundemental frequency!
I have built many trasmitters in my time - and often you may actually
be tuned to a weak harmonic. Tune up and down the band with the
receiver only a few feet away from the TX - and make sure you are
listening to the strongest signal.

Good Music

Jan 1, 1970

I've purchased a pre-assembled inexpensive AM radio transmitter, connected
directly to an 8-foot whip antenna, and find that as long as I'm touching
the antenna, i can pick up music from the CD player through my radios fine.
But when I let go of the antenna, the sound goes away almost completely.

The manual says I can put certain values of inductors in series with the
whip antenna lead to "improve performance" but I have no idea if that has
anything to do with fixing the problem of the antenna only working when I'm
holding it.

The andtenna is 8 feet long oriented vertically, and the readios are about 8
feet from the antenna. This is to be used as a household broadcaster (only
need a range of about 30 feet).

This is the transmitter: I've read many don't like it because it drifts but
that's not the issue for me, it's just getting it to work at all, I think I
might still have this problem if I bought the more expensive AM transmitter
with microprocessor to prevent drifting:

Thanks greatly for suggestions on how to correct this problem.

- Goodmusic