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FT-847 birdies



Robson PY1DGV wrote:

Chasing for my signal I have discovered that my FT-847 produces strong
birdies on 145XXX and 123XXX when  transmitting on 435XXX on the AO-40
uplink passband. I disconnected the AIDC-3733, moved the uplink antenna out
of the bird position reduced power and analyzed the birdies. On the 123XXX
it almost make the same conversion rule of the AO-40 U/S2 AIDC-3733 chain,
making some frequencies impossible to use depending of the doppler shift. On
the 145XXX case they are near, but don't match on the AO-40 passband.

Wayne W9AE replies:

I also use the AIDC3733 with 123 MHz IF to a FT-847. I have not encountered
a frequency where I could not copy my downlink because of self-interference
from a birdie (which is not to say that such frequencies don't exist!).
Once you know your downconverter L.O frequency, you don't need to tune all
across the band to find your downlink among the birdies.  Very little tuning
is required to find your downlink after you "calibrate" your satellite
memory for the actual downconverter L.O. frequency and get accustomed to
pre-correcting for Doppler shift.  I actually don't use my satellite
memories.  Instead, I use InstantTune 1.07 software which provides virtual
satellite memories that are automatically corrected for Doppler shift.  That
makes it very easy for me to zero-beat my downlink signal.  I only have to
adjust for slight variations in the downconverter L.O. frequency - about 1
or 2 kHz variation from one day to the next, after the downconverter
temperature is stabilized.

Good luck with AO40 operation.  You are obviously very close.

Wayne Estes W9AE
Mundelein, IL, USA
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