Version: 13. September 2004
9
In CW mode soldering pin 9 is left at +10V, that is pin 10 of IC13 shifts low
to high in keying rhytm. R106-C127 rounds the attack and decay soft
keying T23 via T25. T26 leads during the high phase of pin 10 (IC13), and
charges C128 via R108 with at very low time constant. Below th triggering
point of pin 6 of IC14, pin 4 goes high and pin 3 goes high, resulting in
blocking T27 and opening T28 (both P channel MOSFETs). The transceiver is
switched to transmission. After releasing the key/PTT, this status is kept as
long as C128 takes to discharge over the delay potentiometer of P12 and
R107 to the triggering point of pin 6 of IC13. Then T28 blocks and T27
opens. The transceiver goes back to reception mode.
During SSB pin 9 is open, that is the gate is blocked and T25-T26 are
inactive. Pin 5 at IC14 is now controlled directly by the PTT button. The T/R
switch now works without decay control.
10. Stabilization stages:
To make the voltage dependent characteristics of the transceiver indepen-
dent of the supply voltage, all critical parts are supplied by a stabilized 10
V derived from the low drop regulator IC15. This concept limits the supply
voltage for the transceiver to 10,8 to 15 Volts. The 5 Volt regulator at IC5
served to feed IC1-IC6-IC7. D2 reduces the effect loss at IC5. The R11-C12
filter reduces regulation noise at the PLL in conjunction with D1, during
the short breaks in the 10 Volt supply during T/R switching (reducing chirp
in the first CW character sent). The 6 Volt regulator IC14 feeds IC16-IC17
and T20.
11. Optional circuits:
The JFET source follower T11 serves as a load free decoupling of the LO
signal. 100 mVeff is found at soldering pins 16 and 17 for feeding an exter-
nal frequency display.
Author: Peter Solf DK1HE
11. 12. 2003
In the mean we designed a 3 digit frequency display for to the Speaky. This
should be used if you use the very small tramp enclosure or a similar small
one. The standard kit with the bigger enclosure as shown on the manual
frontpage will contain an LCD display. This backlight display is counting the
LO frequency.
The number of SMT parts had to be increased to abt. 25 to prevent the
amplifier stages against Meißner oscillation. All SMT parts are premounted
when the kit is shipped.
March 2004, DL2FI
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