FT901.1

From: LA8AK@LA9K.XND.K.NOR.EU

The values for some resistors were later optimized and more than 10dB variation
was possible for 2N5462, but for J177 almost 30dB. By the way, I believe that
FT-101ZE uses similar speech processor circuit, so it may need the diodes.
Later reports on the air 'are possibly the best RF processor ever heard on the

bands, it is tested on 80m/40m, 6m, 2m, 70cm, 23cm, and some rather critical
persons who too often critisize have said this is good and RF processor may be
left on during local QSO's!

7) CARRIER UNIT PB-1706A. FSK-mode.
The dc input level is limited to +1.5V, which is an impractical
level, so I have inserted a 4k7 resistor in series with base (Q701).
It is now possible to use normal TTL-level input, noise treshold is
improved.

8) PB-1707B FM-unit.(PB-1706A *not cw-ms): Carrier level adjustments.
I believe that it is important to achieve as equal level as possible
for the different operations/modes, ie.(1) Normal SSB, (2) SSB with
RF-processor, (3) AM, (4) CW, and (5) FM. Difficulties arise because
the different units loads the common point, which is NB-unit pin 13.
Diode-switching is therefore used. A diode is inserted at the FM-
input to this point, see 'Overall Circuit for IF signals between the
different boards'. Another diode must be inserted in the other cable
from CARRIER Unit, possibly on this unit, and a similar modification
like the one for FM-unit must be made there. Fig. --- shows the
modification for FM board. In the physical location for TC901 is
mounted a trimpotmeter, a capacitor goes to the output, and resistors
are installed to bias the diode connected at the input to the NB-Unit.
It is now easily possible to adjust the levels from FM-unit, and CW/AM
signals from CARRIER unit) independently without interactions to
occur. When the diode is inserted between CARRIER unit and NB-unit the
capacitor in series with cable must be removed (this has a fixed
value, although it is drawn like a trimmcap). Some interesting details
with the FM-unit is that it is easy to find suitable connection points
for G3RUH 9600 baud modem, but it may be difficult to find some proper
free pins on the connector to wire these to.

CONTINUED IN FT901.4