Small Wonder Labs
PSK-20 Transceiver Kit 03/09/10
2000
24
Receiver Alignment is now complete
.
•
To copy PSK31 signals, click the mouse
cursor on the center of the signals and copy
should appear shortly thereafter in the upper
text window.
•
It may be necessary to readjust the soundcard
microphone gain settings to prevent overloading
the soundcard.
Transmitter Alignment:
Remove DC power from the PSK-20
Connect the serial port cable (see 'Hooking
Up')
Reinstall DC power to the PSK-20.
Remove the antenna from J6 and connect a
dummy load in its place.
Double-click on the Speaker icon (Windows
task bar) and Set the soundcard 'Wave' or 'All
Waves', etc., slider level to maximum and
close that dialog box. Set the slider level on
the master volume slider to half- scale.
Click on 'TX' on the DigiPan menu bar. Using
a multimeter set on 'DC Volts', (return lead to
board ground) verify that the voltage on the
case of Q10 (TX driver) jumps up to ~12V.
This confirms that the transmitter bias is
being switched on by the serial port
connection .
No Joy?
Make sure that DigiPan is configured to the
correct serial port setting. Click on 'Configure'
on DigiPan's menu bar and select 'Serial Port'.
Make sure that 'RTS as PTT' is checked and
experiment with the COM port selection until
you find the one which works (typically
COM1 or COM2). The serial port signal
(RTS) should be at approximately -10V during
'Receive' and +10V during 'Transmit'.
Connect the multimeter , (return lead to board
ground) to TP1 in the lower right corner of
the board. Using the plastic tuning tool, adjust
inductor L8 for a maximum meter indication.
If the PA is getting hot due to prolonged key-
downs, you may return to receive by clicking
on 'SET' and 'RX' on the DigiPan menu bar.
Connect the multimeter , (return lead to board
ground) to TP2's rightmost pad, left of the
BNC jack. Adjust inductor L9 for maximum
meter indication.
Adjust the master volume slider (Speaker
icon) for a DC voltage reading of 5 to 8
volts
at TP2.
Readjust inductor L8s and L9 - in that order-
for maximum indication.
Note: L8, L9 adjustment procedure may
alternatively be performed using a wattmeter
and dummy load:
Adjust L8, L9 alternately for max output on
wattmeter. Reduce audio output level in
DigiPan as necessary to keep wattmeter at
less than one watt.
Transmitter Operational Adjustment:
If you have a wattmeter available
:
Click on 'TX' and adjust the master volume slider for
1.5 Watts of indicated power output. As you type on
the computer keyboard, you should see the output
power flicker upward by about 25
%. There is a brief
burst of full-power carrier from DigiPan at the end of
each transmission, this meter indication will be about
50% higher.
If no wattmeter:
Install a T1-3/4 LED at TP2.
The 'flat' edge of the
LED body should face to the left
. When transmitting,
this diode should glow steadily when idling and will
flicker noticeably brighter when you're typing. Adjust
the master volume slider as needed to achieve this
indication. Note that this diode may be installed
remotely on a front panel to serve as a rough power
indication.
If you have an oscilloscope:
Click on TX and set the output envelope just below
the level where flat-topping becomes noticeable. This
will be on the order of 40V p-p, depending on power
supply voltage.
