• SG at 60Kc (*) unmodulated to the grid of V5 (pin7) - chassis.
• VTVM to grid of V13 (pin 7) - chassis, negative reading.
• Set the function switch to "AM".
• Set the SIDE BANDS switch to "L" (internal "U").
• Set the SELECT KCS switch to .5 Kc.
• Peak T6 to T11 transformers to max reading (SG adj -5 V).
• Set the function switch to "CW/SSB".
• Set the BFO KCS control to "0".
• Adjust the BFO transformer T28 for zero beat.
• Adjust SLOT FREQ for maximum rejection at "0".

• Function switch: "CW/SSB".
• BFO KCS: "0" (this means frequency at 60 Kc).
• SIDE BANDS: "U" or "L".
• SELECT KCS: 3 Kcs.

IF is aligned at 60 Kcs on the .5 Kcs position of the SELECT KCS switch with the SIDE BANDS switch on the LOWER position, this includes the BFO setting that it is VERY IMPORTANT regarding how the SSB signal is being tuned due it affects the location of the SSB signal in the passband. If T28 is not accurately adjusted "L" and "U" positions will not select correctly the sideband, switching between these two positions will show the balance between the SSB modes. All adjustments must be checked setting SELEC KCS to ".5".

The BFO at center and VERNIER TUNING at center must process exact frequency in order to achieve very good sideband separation when switching sidebands. If the frequency of the BFO at center does not match the OUTPUT frequency of the VERNIER mixer at center, the "U" and "L" positions will not select with enough separation the sidebands, this system corrupts easily and may fooled you. An unequal response of the SIDE BAND switch at "L" or "U" position (depending on SSB mode of transmission) compared to the response at "BOTH" position, or an equal response of sidebands when the SIDE BAND switch selects "L" and "U" are a common issues in this receiver, and also in other Hammarlund gear that uses the same system, e.g. HC-10, SPC-10, and HQ-180. Note: Equal response on "L" and "U" positions only occurs when SELECT KCS is on the ".5" position.

A verification of correct SSB operation on BOTH/Lower/Upper positions can be: An LSB signal received in "BOTH" should be received OK, on "U" the signal should almost disappear (although it depends on its strength), and on "L" should be heard better than on "BOTH". In a communications receiver 'better' does not mean HI-FI, 'better' means mechanical-filter style: no neighborhood interference and less background noise. Signal peak should not decrease but a slight dip may be acceptable. Same for a USB signal, but there may be some differences due to lack of symmetry. You could also notice lack of signal strength symmetry in the different selectivity positions (3-2-1), but this is normal in this system. The important thing is that the maximun signal strength must remain at the same tuning point (retuning should not be necessary). All this will be true when all the frequency centers of the system are well adjusted; that is, when the sideband is received at the center of the corresponding sideband channel, and the carrier (BFO) is set at the center of the IF passband. The center of the IF passband is the operating IF value, and the center of the sidebands are the frequencies +1.5 Kc and -1.5 Kc (approx.) from the operating IF value. And all without the need to retune in any case (not having to retune shows that the system is well adjusted).

That's why Hammalund says: "The skirt selectivity of this system approaches that of the mechanical filter". The performance is similar to MF's when one sideband is selected combined with a bandwidth of "2" or "3", but of course, the skirt is not vertical. The "mechanical filter effect" (switch positions "L" or "U") performed by this system is due to when on one side of the signal there is the "carrier" introduced by the BFO, on the other side of the signal there is nothing due the skirt of the resonance curve. Analyzing the IF distribution of the Collins 51S-1 can help to understand this system. In fact it is similar, what happens is that Collins does not have to look for a system that mimics mechanical filters because he already uses mechanical filters.

(**) 'Correct IF' does not mean the nominal IF value stated on manuals, correct IF is the mathematical value that results from all previous heterodynations. This value may be seriously affected by actual values of non-adjustable components (e.g. crystal or mechanical filters that are so common in communications receivers), that is, when a receiver is adjusted for the first time, it is being made to the actual values resulting from the previous heterodyne stages, not at the theoretical value stated on the manual. Never must be believed that the actual IF value is, or must be, the standard value stated on manuals, adjusting a receiver to this nominal value by default is the perfect method to transform a properly set IF stage into a poorly set IF stage. Prior to make adjustments in a IF chain is mandatory to check the resulting heterodyne value from the previous mixer/converter.

The HQ-170 series manual has a lot of pages, looks like a collection of factory notes. Schematics do not include latest corrections and some have mistakes on component labeling, mandatory to see addendum changes and errata sheets. This manual has contradictory instructions and looks like unrevised (an easy example of this: On chapter "HQ-170-A Service and Maintenance - IF alignment section", the step 2 says "turn the mode switch from AM to CW", if this is applied to this model the BFO will remain badly adjusted, the frequency shift involved is enough to degrade SSB reception, and when tweaking rest of controls to compensate this, sideband selection will not work correctly; this instruction is only true for the non A model). Best taking note of the explained below, and after consult the non A manual. On the positive side it has more detailed info (simplified schematics to know how a circuit works and exploded views of mechanical operatories).

Model A introduces individualized SSB and CW positions that increases confusion about test and alignment. The BFO is always running in SSB/CW mode, of course, but the BFO knob is inoperative on SSB position, in this model the BFO frequency is a fixed frequency adjustable ONLY by means of T28. CW position with BFO at center gives a beat frequency that is ~500 cycles below regarding frequency of the SSB position. On SSB the BFO KCS variable capacitor connected in parallel to T28 is replaced by a fixed capacitor that has less capacity than the BFO KCS variable capacitor adjusted at center.

The CW position in this model only serves for obtain automatically the CW tone but the BFO control can be rotated in order to obtain a personalized tone, so in this model this control may remain always out of center, it does not be positioned again at center for SSB reception as in the model non A. Alternatively, if the pre-adjusted CW-tone is correct for the operator, the BFO control always can remain at center, never must be retouched, it is not mandatory rotating the BFO control for CW reception. SSB listening on CW position is also possible in model A, but the BFO must be turned to the +0.5 division. An advantage of this model is that SSB and CW reception are automatized, but this also makes the operator a slave to that automatization, non A model gives more versatility.

On this model the correct switch positions to test and align are AM and SSB, not CW. CW position with BFO KCS at "0" shifts BFO frequency 500 cs from the IF operational value, so in model A the CW position should not be used for alignments. On SSB the BFO frequency is internally adjusted, and matches (must match) the IF when SELECT KCS is set to position .5.

The BFO knob is inoperative on SSB position, then T28 must be used to adjust the BFO at the same frequency of the IF chain; this gives a BFO "carrier" of 60,000 Cs because the circuit uses the fixed capacitor C161, not the variable capacitor C129 (BFO KCS) adjusted at center (disconnected on SSB position). The CW position makes operative the BFO knob (C129), then a "carrier" of 59,500 Cs is generated automatically when it is at center, the CW tone of 500 cs can be modified retouching the BFO knob. Thus, the HQ-170A MUST be adjusted setting the function switch to SSB, not CW, and when CW is selected a CW audio tone will be hear automatically with the BFO control positioned at center. The SSB position selects the IF (about 60 Kcs), and the CW position selects a lower frequency (about 59.5 Kcs) that gives automatically the CW tone. If the design is unknown for the user, proximity of these frequencies causes confusion about knowing the exact IF value, being that in the real world a receiver rarely remains adjusted to exact values described on manuals (as pop-up photos show). When the manual says: "For CW reception, never set tone by adjusting main tuning, because this detunes the receiver. Always set BFO to zero first, tune receiver for zero beat, then set BFO for desired tone"; this last sentence is avoidable for model A, it must be: then set mode to CW.

This model includes a bizarre modification: V2 and V12 tubes (1st mixer and its LO) stays burning even when the radio is off. The manufacturer purpose was to increase frequency stability, but it actually this configuration only caused the tubes to wear out, so during the service job the transformer for those tubes was re-routed to go out with the rest of the circuit. It also includes a simplification that affects the antenna RF stage: The main tuning capacitor is a two-section tandem (oscillator and converter) instead of three-section tandem (antenna amplifier, oscillator, and converter). On a precision engineered circuit, if the tandem has a section for the antenna stage, this stage should stay in sync with the converter stage, so ideally it should not be necessary to tune on panel the antenna stage.

The VERNIER TUNING control is not a bandspread control associated to the main tuning control (that drives the 1st conversion) as it might seem, it is the variable capacitor that drives the LO frequency of the 3rd conversion stage that gives the low IF output. The VERNIER TUNING is an Intermediate Frequency Output Changer, it acts like a PASSBAND TUNING. Along with BFO KCS, this control is very important regarding how the SSB signal is being tuned due affects the exact location of the signal in the low IF bandpass, that's why for SSB reception the manual says: "Main tunning: Set for loudest signal, ignore intelligibility. Vernier tuning: Adjust for best intelligibility.".

VERNIER TUNING frequency must match always with the selected SIDE BANDS position, VERNIER TUNING locates the signal in the selected/available IF bandpass. When it is at "0" and SIDE BANDS is NOT on BOTH the exact match to the actual (selected) IF is being lost, and a loss of gain and sideband centering is being produced.

VERNIER TUNING control (PASSBAND TUNING), operational frequency is marked inverted on the panel.

• Arrow on the "+" marks decreases LO frequency increasing output frequency (455 Kc input - 392 Kc LO at 3 = 63 Kc).
• Arrow on the "-" marks increases LO frequency decreasing output frequency (455 Kc input - 398 Kc LO at 3 = 57 Kc).
• Bandwidth is dependent on the SELECT KCS switch position.

The low IF converter can correct for previous stage mismatches by adjusting its LO (the "vernier tuning" circuit) to give the 60 Kc spec heterodyned output. The output frequency of this mixer must be the same than the adjusted frequency of the IF chain and the frequency of the BFO at "0"; these frequencies are controlled by L4 and T28 respectively. Vernier (LO) adjustment to provide an IF output that matches the BFO makes sideband separation possible and effective regarding the "L" or "U" positions.
 

Hammarlund SSB system: HQ-170 & A operation (BFO KCS at center must match the correct IF**)

LSB reception: Select "L" and +1,5 Kcs of "Vernier Tuning".	USB reception: Select "U" and -1,5 Kcs of "Vernier Tuning".
Vernier/Sideband accurate adjust: On SSB the VERNIER TUNING control always must point the center of the selected sideband, which is the +/- 1,5 division of the knob dial. This is respectively coordinated with L/U sideband positions. BFO KCS knob position for SSB reception (standard operation and options). HQ-170: BFO KCS always at center, internal BFO coil adjusted at IF center. HQ-170A in SSB position: BFO KCS in any position, internal BFO coil adjusted at IF center. HQ-170A in CW position: BFO KCS turned to the +0.5 division, internal BFO coil adjusted at IF center. VERNIER TUNING sets location and length (from the IF center) of the "SSB decode area", hence the pitch gradation, that is why precise adjustment of this control is so important. SIDE BANDS selects the "IF decode channel" that must match with the center of the VERNIER TUNING location ("+" for "L", and "-" for "U"; in this case) that has the "SSB decode area". SELECT KCS defines the area (bandwidth) to be considered from the center point defined by the VERNIER TUNING. With these settings the SSB signals can (and must) be tuned very easily using the TUNING control, it should NEVER be necessary to adjust the VERNIER TUNING control to receive an SSB signal. If this configuration cannot be achieved the SSB system very surely is badly adjusted, and this implies difficulty on tuning (narrow heterodyne shifting), off-key audio response on tuning, and also dubious sideband separation to achieve the high selectivity that this system can offer (and all this affects audio response of course). On AM the VERNIER TUNING control must be located always at center "0" and the SIDE BANDS switch on "BOTH", the function of this control is NOT to be a clarifier (although it has that effect). Signals must be tuned and clarified using the TUNING knob, only. It is not correct to use VERNIER TUNING as a clarifier because it is a location selector in the IF bandpass; not a tuning selector. Hammarlund's intention to have a fine tuning knob on panel is a good idea, but it is NOT a good idea to perform fine tuning operations on the IF input of this SSB system.

• Tune the AM signal, VERNIER TUNING to "0" with SIDE BANDS to "BOTH" and SELECT KCS to ".5" until maximum S-Meter deflection is achieved, this should represent that the carrier is in the middle of sidebands.
• Switch to SSB with BFO KCS at center, the result should be zero beat, return to AM.
• When switching SIDE BANDS to "U" and "L", combined with several SELECT KCS positions, the level of modulation and S-Meter indication should show balanced results, but in this system this is hard to achieve due the asymmetric IF peaks that produce absence of a centered flatness.

An easy test to check correct working condition of this system: It's about using the noise floor as if it were a broadband generator, the steps are:

  1) Select the 1.8-2 or the 3.5-4 band (double conversion).

  2) Mode to AM, VERNIER TUNING at "0", SIDE BANDS to BOTH, SELECT KCS to 3 (or best 2).

  3) Rotate VERNIER TUNING from full left and vice versa.

  4) Noise must be weaker at the ends and stronger at the center.

  5) Set SIDE BANDS to "L".

  6) Rotate VERNIER TUNING again from full left and vice versa.

  7) Noise must be weaker at the left end and up to 2/3 of the right way, and stronger at 1/3 of the left way (approx).

  8) Set SIDE BANDS to "U".

  9) Rotate VERNIER TUNING again from full left and vice versa.

10) Noise must be weaker at the right end and up to 2/3 of the left way, and stronger at 1/3 of the right way (approx).

11) Select any band from the 7 to 30 Mcs range (triple conversion), and repeat all steps of above.

Bandpass (sidebands) centering test (checking the accuracy of the noise test). In this type of receivers dial calibration is related to pass band and BFO adjustment:

1) SIDE BANDS: BOTH, SELECT KCS: .5, BFO: 0, VERNIER TUNING: 0, AM, CAL position (ON). SLOT OFF (+/-5Kc).

2) Tune with TUNING the CAL signal at max S deflection, use RF to locate the needle at '3'.

3) Switch to SSB position.

4) Zero beat (silence or a very low tone) must being heard if sideband centering (passband-vernier tuning) and BFO are internally well adjusted.

• Switch to CAL. Voltage to the calibrator circuit is stabilized (VR output is connected to pin 4 of Z1).
• Use a frequency counter capacitively coupled near to pin 2 of the Z1 "integrated circuit", or inside the tube shield using a loop.
• Try to achieve 100.000 cycles slowly adjusting the ceramic trimmer C50 (*).

Accurate dial calibration: A common issue on tube receivers is lack of accuracy on frequency reading, so a calibrator is essential.

1) TUNING: select the main mark that starts a Kc division multiple of 100 Kcs to be adjusted within the desired band.

2) SELECT KCS: .5/1, SIDE BANDS: BOTH, BFO: 0, VERNIER TUNING: 0, switch to SSB (model A) CW/SSB (non A), CAL (ON).

3) TUNING: Tune zero beat.

4) Match hairline with that Kc division mark using the small knob at right.

5) CAL OFF (RECEIVE position) and set the rest of controls as desired.

• After that, you can fine tune this division; subsequent 100 Kc divisions on dial may be checked CALIBRATOR ON and a new zero beat should be heard at the next 100 Kc mark underneath the hairline, if not, adjust the hairline to the 100 Kc dial mark.

• There is a special calibration for SSB when the VERNIER TUNING correction (explained above) is applied; see the next section below.

To understand dial calibration, it is necessary to refer to the effects of the settings stated in the manuals for this unusual SSB system: A BFO is used to create a 60 Kc "carrier", that is exact to the low IF design value; and the VERNIER TUNING converter is by default adjusted at center, thus converting an incoming SSB signal to a 60 Kc IF signal which matches the value of the IF... which ALSO matches the BFO value!!! All this does not make sense, it is clear that the incoming SSB signal must be located in a sideband of the IF passband, beating with the BFO; not in the center of the IF passband, colliding with the BFO. Considering all this, muddy audio, distortion, and critical demodulation are the usual consequences, all caused by sideshifts when tuning the input signal with the BFO "carrier". A botched job.

On a calibrated HQ-170 dial (via the calibrator at 100.000 cs), which is calibrated AM-style as usual (BFO center, VERNIER TUNING center, SIDEBANDS BOTH... and for absolute accuracy SELECT KCS .5/1), when receiving SSB and selecting the center of the sideband via VERNIER TUNING at +/- 1.5 Kc (as I strongly recommend for quality audio and easy tuning), dial frequency "will get wrong" +/- several Kcs depending on the L/U sideband. The combination of BFO at center and VERNIER TUNING selecting the center of a sideband, places the SSB signal into the corresponding IF sideband channel, but we need to extract AF from that sideband. The "BFO" is by design used to insert "a carrier" in the middle of the IF, it is only adjustable in order to match the standard IF value (if it is used for something else operational contradictions will appear). The only solution available is to decode the AF contained in the sideband by adjusting TUNING, but this causes the aforementioned frequency shift on an AM-style calibrated dial. If VERNIER TUNING is located at center, frequency reading will be accurate, but as explained above, tuning will be awkward by having random and narrow pitch changes; the gradual pitch shift, which is key in SSB demodulation, will be lost. Therefore, VERNIER TUNING at +/- 1.5 Kc depending on L/U is the correct operating procedure on this SSB system. But when using a calibrated AM-style dial there will be a side effect, there will be some +/- deviation in frequency reading; this is the consequence of changing the location of the signal from the IF center to the corresponding sideband. Therefore, in SSB mode, the dial must be calibrated in that same mode, INCLUDING the offset +/-, that is, zero beat at +/- 1.5 Kc locations depending on Lower/Upper. SSB needs SSB dial calibration when the recommended VERNIER TUNING correction of +/- 1.5 Kcs is applied (this correction is absolutely necessary when quality audio and ease tuning are required). In SSB mode, zero beat calibration is related to actual knob positions, making dial calibration extremely easy.

1. Set mode switch to AM, VERNIER TUNING to "0", BFO KCS at center, AVC to FAST, and NOISE LIMITER to OFF.
2. Set SIDE BANDS switch to BOTH.
3. Set SELECT KCS to ".5".
4. Set TUNING RANGE MCS to about 1.9 or 3.6 or 7.1 or 14.1 Mcs, this is important only for the amount of harmonic output that affects the S-Meter deflection.
5. Set function switch to CAL and tune CAL signal at maximun S-Meter indication.
6. Adjust RF gain control for a S-Meter reading of 5, retune CAL signal.
7. Set the mode switch to SSB: The result must be zero beat; return to AM.
8. Set SLOT FREQ for a minimum reading on the S-Meter.
9. Rotate SLOT DEPTH in order to decrease the minimum reading, retouch SLOT FREQ checking this.
10. If SLOT FREQ is located at "0" when the S-meter indicates the minimum reading, these controls are OK.
11. If SLOT FREQ is not located at "0", set this control to "0", and then adjust L3 in order to achieve a minimum reading on the S-Meter.

Checking what we have in front is the first step, this should always be done before trying to adjust something. Believing that something is unadjusted, or believing that the real values of adjustment are those of design is the perfect method for making mistakes. Start setting AM, VERNIER TUNING at "0" position, SELEC KCS to ".5" and SIDE BANDS to "L" (internal "U" in the circuit, sidebands are marked inverted on the panel due the phase reversal effect), and mode switch to AM, operation to CAL, and after tuning the CAL signal. Usual signal sources are the internal calibrator or an external signal generator for obtaining maximum S-meter deflection.

• Frequency of oscillation of the 1st mixer (LO) can be tested with a frequency counter capacitively coupled to pin 1 of V2.
• Frequency of oscillation of the of the 1st Converter (XLO) can be tested with a FC capacitively coupled to pin 1 of V3, but only when the TUNING RANGE MCS knob selects frequencies from 7 to 7.3 Mcs and above.
• Tuned frequency of the 455Kc IF chain can be tested selecting any band among the .54 to 7.85 Mcs range, and then injecting a signal capacitively coupled to pin 7 of V2, but only when the TUNING RANGE MCS knob is pointing to the 1.8-2 or 3.5-4 bands, then selecting AM, VERNIER at center, SELECT KCS at 0.5, SIDE BANDS to "Both". Set VERNIER at left and after at right, recheck signal generator frequency, S-Meter movement will be less left/right and maximum when VERNIER is at center or at maximun resonance.
• Tuned frequency of the 60 Kc IF chain can be tested injecting a 60 Kc signal to the pin 7 of V5 and chassis, AM, VERNIER at center, SELECT KCS at 0.5, SIDE BANDS to LOWER. S-Meter will show maximum resonance, then read frequency on the signal generator dial or/and a frequency counter connected to it.
• A better alignment indication will be obtained by placing a VTVM at the 'diode load' checkpoint, which is the junction of L10 (R36 up to SN-3900) and C44.
• Frequency of oscillation of the BFO can be tested (SSB-CW) with a frequency counter capacitively coupled to the stator of the variable capacitor C129 (model A: this capacitor is out of circuit on SSB position, it only works on CW position).
• Frequency of oscillation of the last mixer (LO, VERNIER TUNING) can be tested with a frequency counter capacitively coupled to the lateral lateral lug of the variable capacitor C30.
• AGC level: AVC terminal on the rear. Voltmeter, negative lead to AVC terminal, positive lead to chassis (GND).