FT901.4


FM-DEVIATON.
It should be pointed out the difference between FM operation on VHF
and HF. On VHF/UHF 25kHz channel spacing is used, while on 10M 10kHz
channel spacing is employd, this transceiver is built for FM operation
with transverter. For 10M deviation must be reduced, and it is an
advantage to use a narrower FM RX filter. On VHF/UHF deviation is set
to +5kHz, while for 10m it should be adjusted to maximum +2.5kHz
(at voice peaks). This is important otherwise you will cause severe
interference with the adjacent channels on 10M. Using simple tools,
you can just reduce to audio to the varactor diode to about the half
of the setting as adjusted for VHF. You may whistle 'hard' into the
mike and measure at the input to the varactor diode with a sensitive
audio level meter, and adjust the reading to about half of the first
reading.

9) FILTER Unit PB-1995: NOISE-BLANKER-improvement.
I made an ignition noise simulator, this was earlier used to improve
the FT-7 noise-blanker, so it was interesting to compare FT-7 with
FT-902.  The noise-blanker seems not to be too bad, but it seems to be
room for improvement. Without NB, S-meter reading was about S9, with
it was S-3, and after modification, the noise dissapeared almost
totally, the background noise could be heared without antenna.
Change: Add 0.1uF to the capacitor C328 (PB-1995 FILTER Unit),
bead-tantalum may be used.