Version: 13. September 2004
39
Adjustments
Adjusting the SSB/CW-Stage requires a constant 8 MHz carrier. Therefore
the following adjustments are done in position CW.
Adjusting the carrier frequency for USB/LSB at SSB-filter bandwidth
Speaky in position CW
1. Using P3, adjust a tension of 4.50 V measured at R102 (results in a filter
bandwidth of 2.4 kHz)
2. Remove the band module and key the transmitter
3. Connect a 10:1 Scope probe or a RF-Probe to R58 on the crystal filter
output (Use slow time deflection)
4. Vary the BFO frequency turning P11 slowly. You will see a RF band on
which amplitude one can see very good the filter edges and the long
drawing roof of the filter shape.
5. Notice the maximum RF-Voltage of the filter shape roof. [ ]
6. Turn P11 left until at R58 will occur a RF-Voltage of one fifth of the
maximum value noticed in step 5 (corresponds to 15 dB under the filter
shape roof) .
7. Measure the DC on the output of IC12 (e. g. Pin 10) using a digital
Voltmeter and notice the value. Value A: [ ]
8. Turn P11 to the right away over the maximum filter roof until a RF-
Voltage of one fifth of the maximum value is reached again.
9. Measure the DC on the output of IC12 using a digital Voltmeter and
notice the value. Value B: [ ]
Should it be impossible to adjust the BFO to the higher frequency filter
edge, turn the core of L7 higher or try a 22 µH coil in parallel to L7 (Re-
peat steps 5 – 6 and 7 – 8).
The lower voltage on the output of IC12 corresponds to the LSB carrier
frequency, the higher one to the USB carrier frequency.
Adjusting the BFO frequency for CW Rx/Tx at CW-filter bandwidth
1. Using P3, adjust a voltage of 2.00 V measured at R102 (results in a filter
bandwidth of 500 Hz)
2. Vary the BFO frequency while turning P11 slowly. You will see at the RF-
Voltage on R58 the much smaller filter shape.
3. Determine the middle of the filter shape exactly and notice the voltage
occurring at the output of IC12. Value C: [ ]
4. Stop keying the transmitter and insert the band module again.
5. Adjust the voltage on the output of IC12 with P10 to exactly that value
you noticed in step 3.
6. Feed the Rx-input with a crystal stable signal and tune the DDS exactly
to ZERO-Beat.
7. Turn P10 as far to the right, that you can hear a pleasant pitch of 400 to
1000 Hz. This tone should meet your favourite audio frequency for recei-
ving CW. To beginners it is recommended to adjust to 650 Hz. The pitch
may be simply controlled by connecting the phone output to the input of
a PC-soundcard and examine the signal by an analyser program, like
GRAM.
8. Switch SPEAKY to SSB
9. Adjust a voltage of 4.50 Volts at R102, using P4
10. Switch to LSB and adjust P9 until at IC12 an output voltage of the
value A occurs, which you noticed above.
11. Switch to USB and adjust P8 until at IC12 an output voltage of the
value B occurs, which you noticed above.
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