RCI 2995DXCF alignment procedure questions

[Crambone]

I am looking at the alignment procedure I attached.
and have a few questions. I’m only checking and not making any adjustments at this time till I can clarify a few procedures.
6.1.1 PLL Alignment
1) USB & LSB OSC Set radio to USB TX mode. Mod off. Connect Frequency Counter to TP5 (is an amplifier required for this reading I can’t read anything with a frequency counter, oscilloscope or spectrum analyzer. I assume because the signal has no carrier?)
6.1.2 TRANSMITTER ALIGNMENT
1) Set radio to 28.000 MHz, AM TX mode. Modulation off .
Set radio to 28.000 MHz, USB TX mode. AF signal 30mV, 1 KHz to microphone. Connect Oscilloscope to TP17.
Set RF PWR Fully Clockwise.
Set Clarifier Control to 12 o’clock.
Shows L18 as an adjustment but that’s already aligned in the AM OSC set to 10.6950Mhz +/- 10Hz
2) SSB APC Set radio to USB TX mode. Connect Multimeter to TP8. 12.5 VDC (I see NO voltage?)
3) BIAS Current Set radio to USB TX mode.Modulation off. Connect current meter to TP7(+) and TP9(-). Connect current meter to TP7(+) andTP8(-). (I have NO VR12, are current readings made with SHORT PCB In Place or Removed? Since I have NO VR12 what should I see for Ma?)

That’s all for now, thanks for any knowledge and help shared.

Drew

 

[Handy Andy]

Per your description...

L18 is AM L19 is LSB while L20 is USB

TP5 is the OUTPUT of the AN612 - The Balanced Modulator
TP6 is the INPUT TO the AN612 - for the Audio side of the Balanced Modulator

L18 provides the Carrier to DECODE the IF signal from the RX side - the TX side L19 and L20 take over.

So you are "correct" to hold and ask, for if you locate L18 - it may be AM but that TP5 is AUDIO OUT (the IF version - peaked onto the ~16MHz PLL generated side of signal to mix at the MIXER.

So with that in mind, L19 and L20 are the ones to "tweak" to center the Audio tone into the IF signal TX'd - remember the issue of that change in IF measured is because you are Summing (Or Subtracting) the tone signal from the IF frequency.

L18 is to remove the CARRIER presence (if any)

So as you "peak" you're messing with the voice-side of this - so you peak the spectrum of voice try to peak for the Tone of voice - not just tone - which is subjective.

Subjective? Yes.

Because not everyone has the same voice patterns or tones (Syllabic) - it's been talked about before but never like this...you may have to "tweak" the IF not for peaks, but for BEST OVERALL TONAL RESPONSE - because of the tone is set too high for the TYPE OF MICROPHONE (It's tonal response) or the persons own tone of voice - it may not sound "right" or even produce the correct envelope of power that can be used by the Mixer.

So L18 is used by AM/FM/CW mode, but also to find the center of the Carrier - so you're not mixing it in along with your tone.

L19 and L20 handle the SSB side of this.

While you're playing around in there - also measure the signal and it's quality at TP3 - this is the side that helps the IF - Diode Balancer Bridge (Locate your RX 10.695 FL3 filter on your schematic) See Diodes D25, D26, D27 and D28, D29? Along with D48 and D31 - these act as an RF switch for the Diode Detector Bridge when in RX mode.

An older PDF - schematic is attached but I hope it works - the notes above are for that in reference - for the Service manual copy you posted seems corrupt.

 

[Crambone]

Per your description...

L18 is AM L19 is LSB while L20 is USB

TP5 is the OUTPUT of the AN612 - The Balanced Modulator
TP6 is the INPUT TO the AN612 - for the Audio side of the Balanced Modulator

L18 provides the Carrier to DECODE the IF signal from the RX side - the TX side L19 and L20 take over.

So you are "correct" to hold and ask, for if you locate L18 - it may be AM but that TP5 is AUDIO OUT (the IF version - peaked onto the ~16MHz PLL generated side of signal to mix at the MIXER.

So with that in mind, L19 and L20 are the ones to "tweak" to center the Audio tone into the IF signal TX'd - remember the issue of that change in IF measured is because you are Summing (Or Subtracting) the tone signal from the IF frequency.

L18 is to remove the CARRIER presence (if any)

So as you "peak" you're messing with the voice-side of this - so you peak the spectrum of voice try to peak for the Tone of voice - not just tone - which is subjective.

Subjective? Yes.

Because not everyone has the same voice patterns or tones (Syllabic) - it's been talked about before but never like this...you may have to "tweak" the IF not for peaks, but for BEST OVERALL TONAL RESPONSE - because of the tone is set too high for the TYPE OF MICROPHONE (It's tonal response) or the persons own tone of voice - it may not sound "right" or even produce the correct envelope of power that can be used by the Mixer.

So L18 is used by AM/FM/CW mode, but also to find the center of the Carrier - so you're not mixing it in along with your tone.

L19 and L20 handle the SSB side of this.

While you're playing around in there - also measure the signal and it's quality at TP3 - this is the side that helps the IF - Diode Balancer Bridge (Locate your RX 10.695 FL3 filter on your schematic) See Diodes D25, D26, D27 and D28, D29? Along with D48 and D31 - these act as an RF switch for the Diode Detector Bridge when in RX mode.

An older PDF - schematic is attached but I hope it works - the notes above are for that in reference - for the Service manual copy you posted seems corrupt.

Thanks that’s some great info! The procedures are horrible!!

 

[Crambone]

The reason I brought this up is the fact I’m seeing a carrier on LSB & USB unmodulated. So If I’m reading and seeing things properly “L18” is the culprit most likely.
Seeing that the Alignment procedure is not that informative what’s the best approach for setting L18? I don’t want to just Willy Nilly adjust it unless it would be as simple as just putting the mode into LSB or USB and moving L18 till I see no carrier on the spectrum analyzer, oscilloscope and wattmeter?

 

[Handy Andy]

This is where "Carrier Balance" comes into play and where the Balance - in Balanced Modulator comes from.

Symmetry.

So if you are seeing a carrier - suspect the L18 is at fault - look carefully at the schematic I provided - there is a spot on there that looks to see the "Mode" selected thru the Mode Selector - and when it is in TX - that is where the L18 mess comes into this - it's needs a carrier signal - but only as a means to "center" the audio pass band both above and below it - equally - the Balance part.

What it should do (Add: FL3), is remove - sharply, the Carrier - but leave the IF part to mix with and heterodyne Audio to change the IF frequency of the MODE you are in - via Audio spectrum. To do that - it has-needs L18 tuned right, and FL3 to accept it "right" so the carrier and the opposite side - is cut off.

IF the Balanced Modulator is not getting the right IF frequency - no matter the effort you put into trying to cut out the carrier, is going to work - except to re-tune the carrier IF that goes to the balanced modulator - to the SAME frequency that FL3 is tuned for - if these two are "off" - then you'll need to replace FL3 with a new one that centers onto what L18 is doing - 10.69~ MHz.

Take a look at Q28 - that "kinda'" helps with this - it works on FM mode to use the FL3 IF filter as a sharp filter - leaving a "hole" behind for Audio IF to fill it with. The filter produces the signal the TX mixer needs in FM mode - as a factor of Deviation - so the Carrier power is present but minimized - and the audio is amplified as an error in the DEVIATION of the signal by audio - from the carrier (the Heterodyne process of sum and subtract - think of a circle or angle of degrees in the circle as a frequency range of deviation from a center).

In AM mode - Q28 does not do much - has no power provided to turn it on, except in cases of the Balance Bridge I mentioned - over by FL3 (D27, thru D31 and D48) where deviation products show up because of L18 fixing it's frequency via a tuned network (D107 Varactor, L18 itself, and C204 1,000pF (102)) and straight bias thru R137 (10K) so if L18 is not perfect, that balanced bridge by FL3 helps to offset the error - at least you hear it.

That carrier problem should only be VR7 - that control "trims" how much of the IF signal mixes into the Audio.

• Back in the CB tricks days, I did up a description of how to look at IF and Audio in a mixer like the AN612 as if your speeding up to or slowing down for - a type of wave interaction so the inception point was not causing an aliasing or alignment issue but more like a peaking and troughs of waves that produce less distortion and artifacts (mixer by-products)

If it don't - or can't get rid of it and you can't null it out - L37, L18 and L17 adjust these along with re-tweaking VR7 to try and balance out and remove this carrier.

To finish this up -

Lets start at TP5 - where the AN612 is...

Q58 (Where L18 does it's thing) outputs to Pin 2 at Balanced Modulator that is the IF - Pin 1 is your Audio applied - both Pin 2 and Pin 1 mix together - with one suppositional over the other - producing Double Balanced output - both upper and lower sides of the IF frequency - as Audio + IF = New IF frequencies (range thereof). This is what you'd find at TP5 - both "halves" a Non-inverted and inverted signal - which is sent to get trimmed at FL3

It is applied to FL3 - using properly applied shift from L19/L20 and L18 - to "null off and out" - Supress - the OPPOSITE Audio + IF and the Carrier - leaving only the Audio + IF of the MODE you selected (USB or LSB) to be applied to the Mixer and the PLL supplies the other IF signal to UPMIX to new range of 27+MHz frequencies.

Why mention TP3? Mixing artifacts - you don't want TOO much signal of one and not enough of the other - so when you mention "carrier" look at TP3 (it's volume or if it's clipping) at L17. It might be supplying too much signal and you're picking up this artifact as a carrier - when it truly is an overabundance of signal that L37 simply passes thru into the mixer.

So, check to see if VR7 can null off that carrier - if it does not, your other options are L18, L17 and FL3 section - which use resistors to attenuate signal and or help with matching impedance to another stage. So if a resistor is gone, out of tolerance or modified, this too affects the balance needed to keep SSB as SSB-envelope and FM and AM as carrier-based signal.

Too much signal in one aspect, will make it impossible to properly tune out what is not needed - it is just as bad as not enough signal to mix with another - which both this post of mine and the above post (#2) - I'm trying to cover with you on.

 

[Crambone]

Well, I did find different alignment procedures that do make more sense than the manuals.
PLL Synthesizer / Oscillator Frequency Alignment:

1. PLL2 - VCO Voltage:
A. Set radio to 24.890 MHz, AM RX mode, connect multimeter to TP10.
Adjust L14 for 1.0 Vdc ± 0.1.
B. Set frequency to 29.699 MHz, AM RX mode, connect multimeter to TP10.
Adjust L14 for 4.5 Vdc ± 0.1.

2. PLL1 - VCO Voltage:
A. Set radio to 24.890 MHz, AM RX mode, connect multimeter to TP10.
Adjust L13 for 1.0 Vdc ± 0.1.
B. Set frequency to 32.000 MHz, AM RX mode, connect multimeter to TP10.
Adjust L13 for 6.5 Vdc ± 0.1.

2. AM Frequency:
Set radio to AM RX mode, clarifier to 12 o'clock,. Connect frequency counter to TP16.
Adjust VC2 to 10.1 MHz ± 10Hz.

3. VCO Output:
Set radio to 28.000 MHz, AM RX mode, connect oscilloscope to TP3.
Adjust L17 to 38.6950 MHz (maximum output).

4. AM OSC:
Set radio to AM TX mode, modulation off, connect frequency counter to TP5.
Adjust L18 to obtain 10.6950 MHz ± 10Hz.

5. USB OSC:
Set radio to USB TX mode, modulation off, short TP6 to ground, connect frequency counter the TP5.
Adjust L20 to 10.6975 MHz ± 10Hz.

6. LSB OSC:
Set radio to LSB TX mode, modulation off, connect frequency counter to TP5.
Adjust L19 to 10.6925 MHz ± 10Hz.


This completes this stage of the alignment procedure.


Receiver Alignment:

1. Receiver Setup: Put the mode selector on AM, the RF gain fully clockwise (maximum gain), squelch to minimum (unsquelched), volume at 2 o'clock, set frequency to 28.295 MHz, and NB/ANL to OFF. Connect signal generator set at RF carrier frequency of 28.295 MHz, AM modulated with a 1 KHz audio tone at 30% modulation level.

2. AM Sensitivity:
Connect a SINAD meter to the external speaker jack.
Adjust L3, L4, L6, L7, L8, L10, L11 and L12 for best SINAD.
Increase the RF generator to 1mV RF carrier level.
Adjust L3, and L4 for minimum distortion.
Verify that the receiver AM sensitivity is better than 0.5µV for 10 db SINAD.

3. FM Distortion:
Change the RF generator to the FM mode, 1mV RF carrier level, FM modulated with a 1 KHz audio tone ± 3 KHz modulation level.
Adjust L5 for minimum distortion.

4. USB Sensitivity:
Turn off the audio modulation of the RF generator, and change it's frequency to 28.296 at an RF carrier level of .5 µV. Set radio to USB RX mode.
Adjust L11 and L12 for audio output greater than 2V.

5. LSB Sensitivity:
Keep the audio modulation of the RF generator off, change frequency to 28.294 at an RF carrier level of 1mV, set radio to LSB mode.
Adjust L11, and L12 for audio output greater then 2V.

6. NB Adjust:
Set radio to 28.305 MHz AM RX mode, NB-ANL/OFF switch to ON, adjust RF generator to 28.305 MHz with an RF carrier level of 1mV, AM modulated with a 1 KHz audio signal at 30% modulation. Connect a digital voltmeter to TP1 (R11).
Adjust L1 and L2 for DC Voltage to max ( 1.3V ).

7. AM Scale Meter:
Turn NB-ANL switch to OFF, SWR/S/RF switch to S/RF position, set radio frequency to 28.305 AM RX mode, RF signal generator setting 28.305 MHz with a carrier level of 100 µV, AM modulated with a 1KHz audio signal at 30%.
Adjust VR1 so that bar graph reads 6 bars.

8. USB Scale Meter:
SWR/S/RF switch to S/RF position, set radio frequency to 28.495 MHz USB RX mode, RF signal generator setting 28.496 MHz with a carrier level of 100 µV, no audio modulation.
Adjust VR2 so that bar graph reads 6 bars.

9. AM Squelch:
Set radio frequency to 28.495 MHz AM RX mode, SQ control fully clockwise, RF signal generator setting to 28.495 MHz , RF carrier level at 1 mV, AM modulated with a 1 KHz audio signal at 30%.
Adjust VR4 very slowly until squelch noise just goes off.

10. SSB Squelch:
Set radio to 28.495 MHz USB RX mode, SQ control fully clockwise, RF signal generator setting to 28.496 MHz , RF carrier level at 1 mV, with audio modulation.
Adjust VR3 very slowly until squelch just goes off.


This completes the Receiver stage of the alignment procedure.


Transmitter Alignment:

1. Driver BIAS:
Remove the "Shorting PCB" from TP7, TP8, and TP9. Set radio to USB mode, connect current meter to TP9 (+) and TP8 (-).
Adjust VR11 to obtain 50 mA.

2. DRIVER BIAS:
Set radio to USB mode, connect current meter to TP9 (-) and TP7 (+).
Adjust VR13 to obtain 10 mA.

3. SSB & AM RF Power:
Reconnect the "Shorting PCB" from TP7, TP8, and TP9. Connect a watt meter and a 50 Ohm load to the antenna connector, set radio to 28.495 MHz, USB mode, mic gain to maximum. Inject 30 milivolts of 1 KHz audio into the audio input pin of the mic jack (pin 2). Set SSB power control (VR12) to full counter clockwise position (maximum power position).
Adjust L18, L33, L40, L42, L43, and L44 to obtain maximum power output.
Adjust SSB power control (VR12) to 21 watts peak RF power output.
Change mode to AM
Adjust VR15 to obtain 10 watts RF power output.

4. Power Meter:
Set radio to 28.495 MHz, AM mode, mic gain control to maximum, meter switch to S/RF and key the transmitter.
Adjust VR10 until the RF meter reads 10 watts

5. TX AM Modulation:
Set radio to 28.495 MHz, AM mode, mic gain control to maximum, key the transmitter. Inject 30 milivolts of 1 KHz audio into the audio input pin of the mic jack (pin 2).
Adjust VR17 to 100% modulation.

6. CW Side-Tone Signal:
Connect a voltmeter directly across the speaker, key the transmitter using the CW jack in the rear of the radio.
Adjust VR9 to obtain 200mV across the speaker.


This completes the Transmitter stage of the alignment procedure.

 

[Handy Andy]

While you're working thru this...

Do you have a "Carrier Balance" trimmer? (VR7)

I don't see any suggested methods to check and reduce any produced carrier.

Because of you do not have a provision for carrier leakage (ref. - Uniden) it becomes solely dependent on the Crystal IF Filter your radio will use for the 10.69MHz

 

[Crambone]

While you're working thru this...

Do you have a "Carrier Balance" trimmer? (VR7)

I don't see any suggested methods to check and reduce any produced carrier.

Because of you do not have a provision for carrier leakage (ref. - Uniden) it becomes solely dependent on the Crystal IF Filter your radio will use for the 10.69MHz

Yes I do have VR7, I am picking up a blown up schematic today so I can take a better look at what’s going on I can’t stand looking at a schematic on my iPad.
I did take a few voltage and frequency readings and all I can say is someone definitely took the turn before you understand rule. It looks like once I have the schematic in hand I’m going to need to start from the beginning and perform an alignment. Time to dig out the Signal Analyzer and do a deep dive.