PC-833 PCB

GENERAL ALIGNMENT INFO

All adjustments are made with the radio set radio to CH19 on the FCC or NZ RFS23 band unless otherwise stated. (alignment detials for the NZ band are also included)

Make sure that the clarifier is centered

You will need:

A good frequency counter with a 10Hz resolution

The proper (plastic / ceramic) adjustment tools.

A 50MHz oscilloscope (although a 30MHz will do).

Offset oscillator alignment:

Attach frequency counter to TP3 (bottom leg of R105, to the left of L6)

Double check that the clarifier is centered before starting !

FCC Band alignments

NZ Band alignments

Re check all of the frequencies again at this point, they can alter after adjusting the other points.

Carrier oscillator:

Attach frequency counter to TP5 (right leg of R34) which is located to the right of X2 below TR18

Another method which has been suggested is shown here:

Disconnect the transmitter by removing the vertical PCB connecting the driver and modulator DC supplies (TP6, TP7 & TP8).

Connect the frequency counter to TP9 (D19, beside the SSB Crystal Filter)

Unbalance the Double Balanced Modulator (IC3, AN612) by joining pin 1 to earth (usually by using your multimeter on diode test through the BE junction of TR24, making it conduct to earth).

On AM Transmit, adjust L19 for 10.69500 MHz

On USB Transmit, adjust L20 for 10.69750 MHz

On LSB Transmit, adjust L21 for 10.69250 MHz

Re check all of the frequencies again at this point, they can alter after adjusting the other points.

VCO alignment:

Connect DC Volt meter / oscilloscope to TP2 (top leg of R93, just to the left of L14)

Set radio to channel 40 and adjust L14 for 4.5 VDC.

Set radio to channel 1, check that the voltage is above 1.8VDC, if required adjust L14, go to channel 40, check that the voltage is below 8.0 VDC and that the radio will transmit.

VCO output alignment:

Connect oscilloscope to TP3 (bottom leg of R105, to the left of L6)

Adjust L15 for maximum reading.

Offset oscillator filter (tripler) alignment:

Connect oscilloscope to TP4 (left leg of R34, to the right of L13)

Adjust L13 for maximum reading.

TX mixer alignment:

Carefully align L39 and L40 for maximum transmitter output on AM with the transmitter DC supply reconnected. 

TX alignment:

Carefully adjust L38, L37 and L27 for maximum transmitter output on AM. 

Carrier Balance alignment:

Connect the oscilloscope to the Antenna Socket using a 10x probe.

Set Mike Gain to minimum.

Carefully adjust VR4 on USB transmit with no modulation for minimum transmitter output visible on the oscilloscope. Check on LSB, if noticeably larger, adjust VR4 so that it is at a minimum for both (and relatively equal). 

Driver and final bias adjustments:

To check the driver and final amplifier bias adjustments set the radio to USB without any mod, use an ammeter to check for the correct bias current.

To test remove the shorting PCB at the rear of the radio, test between the points listed above, then replace the PCB.

his reading will vary as the transistors warm up, hence the reading window of 5mA. It is important that there is no modulation applied to the SSB transmitter whilst making these readings, the carrier oscillator and the Carrier Balance (VR4) has been adjusted before adjusting the bias.

TX power alignment:

Attach an RF power meter and dummy load to the radio.

Adjust VR10 for an unmodulated average carrier power of 4 Watts.

Check that the unmodulated average power is equal at each end of the band (CH1, CH40). It should be at least 3.7 Watts.

ALC alignment:

Connect a RF Wattmeter and dummy load to the antenna socket.

Set The Mike Gain Control to Maximum.

Inject a 50mV 1KHz signal into the microphone socket, adjust VR6 for 12 Watts Peak Envelope Power on Ch 19 USB Transmit. 

Confirm on Ch 1 & 40 that the output Power is still between 11 and 12 Watts PEP.

AMC alignment:

Connect a modulation meter (or oscilloscope) and dummy load to the antenna socket.

Set the Mike Gain control to Maximum.

Inject a 30mV 1KHz signal into the microphone socket.

Adjust VR5 for 95% modulation.

Tx Meter Alignment:

On AM Transmit (un-modulated), Adjust VR7 for the 4W marking on the meter. 

RX alignment:

Make sure the signal used is very weak otherwise the AGC will activate and cause problems.

Adjust these metal cans for maximum received signal, take into consideration both the signal displayed on the signal meter and the audio volume, strictly speaking it should be adjusted purely on volume.

Inject a 1 KHz 30% AM modulated RF signal on 27.1850MHz (FCC) / 26.55000 MHz (NZ) into the radios antenna socket.

Set the RF Gain control to maximum.

Adjust L3, L4, L5, L6, L7, L8, L9 and L10 on AM for the highest reading on the radios signal meter. Adjust the signal generator to keep the tuning effect obvious on the meter (as you go through the alignment, reduce the output of the signal generator).

Tip - Detune L9 whilst adjusting L3 to L8 and L10 to make the peaking more obvious, then peak L9 last.

Signal meter alignment:

Increase the RF generator output to 100uV unmodulated.

Ensure the RF Gain control is fully clockwise.

On AM adjust VR1 for a reading of S9 on the signal meter.

Squelch alignment:

Keep the RF generator output at 100uV.

Set the Squelch and RF Gain Controls Fully Clockwise.

On AM adjust VR2 counter clockwise until the squelch opens, then adjust it clockwise until it just closes.

Noise blanker alignment:

Turn on noise blanker switch.

Set RF Gain control fully clockwise.

Connect High Impedance DC Volt Meter to TP1 (bottom leg of D2 to the right of L2)

Adjust L1 and L2 for maximum voltage reading.

List of adjustments:

List of test points: