My C Crane FM transmitter has been
a wonderful work horse for 6 or 7 years.
It has gotten a little beaten up, though, so
I am going to be getting a brand new one
from C Crane.
Before I go on, I have to mention that my
C Crane transmitter has always had an interesting
characteristic. I'm not sure how to describe this,
but if you listen to the transmitter unmodulated,
about 40 dB down you will hear an audio whine.
With my C Crane, the whine consists of a couple
of different audio frequencies. When the unit
is fully modulated, you never hear the whine at
all, although it is still there - again, about 40dB
I have wondered for a long time if turning off the
stereo generator in the transmitter would eliminate
Just for the sake of experimentation and my own
education, I decided to try to do it.
If you look back at the Forums on this board, you
will see various discussions about how to do the
above. I believe the best way is to open a line
that is after the stereo chip. I am mentioning this
in a simple manner - I do not have sufficient eyesight
to accomplish that modification.
That other way that has been mentioned to achieve
mono operation is to disconnect the X1 crystal. I
do not recommend this, because all it does is disable
the stereo pilot signal (I think.) There might still
be other output in the above audio range (such as
left plus right and left minus right audio components.)
However, a stereo radio will receive the signal in the
mono mode, because the pilot is not there for the
receiver stereo circuitry to lock onto.
Anyway, I went with the latter option just for the
sake of experimentation, and because I can't see
well enough to do the correct mod, and also because -
I wondered if the negative 40 dB whine would go
away if the pilot tone was off.
Lacking vision to do it any better, I took a pair of
pliers, and pulled X1 off the circuit board. So for
me, this experiment is not reversible. This transmitter
will not ever deliver a stereo signal again. But that's
OK. I'm getting another C Crane transmitter anyway.
So, did I achieve my objective, which was to eliminate
the negative 40 dB audio whine??
Nope, it's still there.
So, I recommend that you don't try to do what I did.
The whine still exists in the signal and the mod
cannot be reversed.
Still, I'm not sorry I tried it. I really wanted to know
P.S. The transmitter still sounds great and still
goes a couple of hundred feet on the car radio.
The radio in the car just thinks it's hearing a
mono transmission now.