Help w/ QRM mystery
 

At 29 minutes past the hour on 147.435 simplex
I'm hearing a weak string of 4 DTMF tones. At first
I thought it was someone's remote link but then I
heard this transmission over a much stronger 2m
simplex QSO in progress. There was no hetrodyning
as if 2 signals were coming in at the same freq - the
DTMF string mixed with the S9+60 operator as
if the two signals were mixing with an audio mixer.

I'm convinced that I'm hearing an "image" freq but
from where? My rig is a Kenwood TM-271A with
a 1st IF of 49.95 mhz and a 2nd IF of 450 khz.

I used to know how to rx strong signals outside my
reciever's range by listening to the image but it's
been years and I've forgotten how to do the math.

Is it 2x the 1st IF + the VFO freq? If that's the case,
then the offending signal would be at 247.335 mhz.

Help?

Ken KG0WX