With respect Kevin the 'culprit' responsible for this birdie in my K2 is the
(LO + IF) / 2 spurious response of the receiver which can 'hear' the PLL
reference oscillator. When the receiver is tuned to 14.360 MHz the frequency
of this particular response, assuming a 4.914 MHz IF, is (19.274 + 4.914) /
2 = 12.094 MHz, moving down to 11.914 MHz as the receiver is tuned down to
14.000 MHz.
73,
Geoff
GM4ESD
Kevin W9CF wrote on Friday, October 17, 2008 at 8:29 AM
Mine does that too. The VCO for a frequency around 14.360 MHz should
be running aabout 19.274 MHz and the reference oscillator runs at about
12.096 MHz. 2*19.274-2*12.096 = 14.356 MHz, so that seems to be the
culprit. It pops in because of the way the VCO is tuned. When you get
to the edge of the fine tuning, the U4 tunes the VCO to the next 5KHz
coarse step and U5 changes the reference oscillator back to the beginning
of
a fine step. For the previous coarse step the birdie is not heard, but for
this coarse step the two
oscillators are tuned so that it is. On my K2, with the way I have RTTY
set up, I can hear it pop in on RTTY at 14361.5 and then it pops out at
the next coarse step at 14366.5
73 Kevin w9cf
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