20.92 to 21.60 bandspread (5 Kcs divs.)
27.89 to 29.70 bandspread (10 Kcs divs.)
Excellent sensitivity
MAIN TUNING control / dial
Dial has Ham bands
high frequency markers for combined use with the BAND SPREAD control.
Very smooth operation, static hairline
(better would have been adjustable).
BAND SPREAD control / dial
Fine tuning. Tunes Ham bands when MAIN
TUNING is adjusted at the Ham band high frequency marker. Better using
this for fine tuning instead Vernier (Passband) Tuning.
Very smooth operation, adjustable hairline.
Double Conversion ranges
VFO (LO, 455 Kc above signal) 455 Kc IF
VFO (VERNIER, 395 Kc below IF) 60 Kc IF
2 IF amplification stages (455 Kc)
3 IF stages (2 amplifier + 1 out driver, 60 Kc)
Triple Conversion ranges
VFO (LO, 3035 Kc above signal) 3035 Kc IF
2580 Kc XtalFO (455 Kc below IF) 455 Kc IF
VFO (VERNIER, 395 Kc below IF) 60 Kc IF
3035 Xtal fiter stage (phasing-type, centered)
1 IF amplification stage (455 Kc)
3 IF stages (2 amplifier + 1 out driver, 60 Kc)
LO drift after 20 min warm-up at 20ºC.
Related to VLO frequency & conversion range. Dependent of frequency, tandem opening(a), and environmental temperature.
HQ-180 is a pure Armstrong type design (VLO on high frequency stages). Due to the high coverage design, stability is more affected by the oscillator tank's L/C ratio at the frequency in use than by how high the frequency is.
AM test: .54 - 7.85 Mcs: Unnoticeable, full ranges.
7.85 - 30 Mcs: Unnoticeable to negligible.
SSB test: 1.05 - 2.05 Mcs: Negligible, full range.
2.05 - 4.04 Mcs: Negligible, full range.
4 - 7.85 Mcs: Negligible to slight.
7.85 - 15.35 Mcs: Slight to noticeable(b).
15.35 - 30 Mcs: Slight to noticeable(b).
(a) e.g. Drift at 21 Mcs (15.35 - 30.00 range) is lower than at 14 Mcs (7.85 - 15.35 range) due tandem is more closed at 21 than at 14. (b)Upper end of these ranges may require more than 1 hour of warm-up depending on ambient temperature (this may explain the filament mod on HQ-180A). Aside from temperature, drift mainly occurs because 'less coil' and 'more capacitor' are needed, but this is not possible due the high excursion coverage.
Phase reversal before last conversion stage
Reversed ONCE (oscillator
of the first mixer works above the input signal frequency, rest of mixers/converters
are below). Lower sideband of the incoming signal is placed on the upper side
of the carrier (center of the passband), and the upper sideband on the
lower side, receiving signal arrives inverted to the 60 Kc converter. The
455 to 60 Kc converter does not reverse sidebands due LO frequency is below
input signal.
As sidebands have been reversed
in previous steps "L" and "U" markings are labeled reversed on panel: "L"
is Upper and "U" is Lower. Hammarlund system always adjusts on the Upper
sideband, but due to the above, manual indicates "L" position
must be selected when this stage is being adjusted at ".5" position: At
"L" this stage processes the sideband with more frecuency (upper,
61,500 center), and at "U" processes the sideband with less frecuency
(lower, 58,500 center). Rest of switch selections lowers Q and expands
frequency response.
AM detection by...
Diode
Connected to 60 Kc IF output driver
FM detection by...
Diode, resonance slope, sideband skirt.
Processed by the 60 Kc IF stage.
To know how this system works go to Home→ES_list, load page
"El radio '5+1' de AM/FM", and see "Detección de la FM por la pendiente de la respuesta de FI".
FM operation
AM mode VERNIER TUNING at center
SELECT KCS on "3" SIDE BANDS on "L" or U" (*)
(*) Audio quality depends of the less
vertical skirt of the response curve (the FM detection by signal slope processes
very well human voice when resonance slope is ± 60 degrees).
SSB/CW detection by...
Plate detector, mixer type (double triode product detector).
BFO and signal are injected separately to grids.
AVC (AGC) stages controlled
5 = 4 fast + 1 delayed
RF amp (delayed) + 455 IF
gate + 455 Kc IF amp + 60 Kc mixer + first 60 Kc IF (fast).
AVC switch
OFF, SLOW, MED, FAST positions.
FAST for AM/CW reception
AGC on SSB/CW
YES
SLOW, MED/FAST positions
S-Meter on SSB/CW
YES
S-Meter is based in the VTVM circuit, so it has sensitive and accurate response;
a much better design than the poor S-Meter circuits found in Collins receivers.
Product Detector
Double triode design type
Excellent performance
Function/Mode switch
→ HQ-180: AM - CW/SSB
→ HQ-180A: AM - SSB - CW
→ AM: BFO OFF. CW/SSB: BFO ON, frequency is
the exact IF when BFO knob is positioned at center. → AM: BFO OFF. SSB: BFO ON, frequency adjusted at
exact IF. CW: BFO ON, frequency is -0.5 Kc off the IF BFO positioned at center, thus rotating to +0.5 the BFO frequency matches again the IF.
BFO KCS
Range ± 1.9 Kc from center "0".
+ range: BFO frecuency INcreases.
- range: BFO frequency DEcreases.
→ HQ-180: Works on the CW/SSB position.
→ HQ-180A: Only works on CW, BFO frequency
on SSB is fixed, adjusted by T28.
BFO receiving SSB
Hammarlund's system requires the BFO frequency must be the same as the IF, externally or internally, this mean carrier insertion at center of the AM bandpass. → HQ-180: Positioned at center. → HQ-180A: Adjusted internally at exact IF.
"AM-carrier" insertion in
the IF 60 KC chain. If the BFO needs to be positioned off center this means the SSB system is disadjusted, but the model A disconnects the BFO control on SSB, it only works on CW.
BFO receiving CW
→ HQ-180: Knob positioned to +0.5 or -0.5 divisions → HQ-180A: Knob at center (auto -0.5 Kcs IF)
CW signal must de tuned
at zero beat (SSB position), after adjust desired tone. Model A has an exclusive
CW switch position that detunes automatically the BFO from center.
SIDE BANDS switch
L (lower) - U (upper) - BOTH
On BOTH the 1 - 2 - 3 bandwidths of SELEC KCS are doubled.
SELEC KCS switch
.5 - 1 - 2 - 3 Kcs
.5 - 1 Kcs (CW - BOTH) 2 - 3 Kcs (SSB - L/U or AM - BOTH)
VERNIER TUNING is the Local
Oscillator of the 60 Kc converter that controls the exact output frequency
to the IF chain. In fact this control is not a vernier tuning, i'ts
a PASSBAND TUNING. Was added on panel since serial # 1335 "for extremely
fine tuning, useful for CW and SSB operation, or for moving the incoming
signal +/- 3Kc from the passband center as indicated on the front panel"
(repeating here Hammarlund's explanation).
Adjustable ± 3 Kcs
IF passband tuning range. Centered at "0" is for AM/CW. Can be used always
at center but not advisable. In order to get accurate reception and centered
SSB tuning this control must be turned to + 1.5 for lower sideband (SIDE
BANDS at "L" or "BOTH") and - 1.5 for upper sideband (SIDE BANDS at "U"
or "BOTH"). This permits coincidence of SSB tuned at peaks on AM position
and instant SSB demodulation on SSB position.
Actual PASSBAND TUNING
that permits centered adjust on sideband when "L" or "U" are selected.
Correct setting of this control is VERY important for the performance of
sideband reception; together with the BFO is the "key" of this peculiar
system. When it is located at +1.5 (or -1.5) the sideband is being selected to be tuned
at center. It can be used for fine tuning, but should not be used this
manner habitually, BAND SPREAD tuning is preferable. Very important control
for understand the Hammarlund´s sideband system that requires an
accurate adjust. Erroneous understanding may fooled you and making go on false paths.
Crystal filter
YES (centered
Xtal phasing IF stage)
Only works on Triple Conversion
ranges.
SLOT FREQ
Range ± 5 Kc IF center.
IF passband null slot when at center (ON), OFF position is at +5 Kcs or -5 Kcs.
This model also has the usual SLOT DEPTH control that adjusts the null level,
but not on front panel, it is behind, accessible by opening the upper gate.
Best location because on front panel is useless, always must remain settled
to max rejection, usually 20% advanced.
NOISE LIMITER
OFF and ajustable clipping effect, full wave.
Useful for random noise
pulses, useless for extremely short duration pulses and hiss-like noise
picked up by the antenna. Works on all modes of reception.
RF (Sensitivity)
AGC separated, cathode mode on: V1, V4 and V18 (455 IF gate)
Includes power switch.
SEND
RECEIVE
CAL
Standby/Muting/Transmit
relay
Standard receiving operation.
100 Kc calibrator ON (adjustment range of 50 cycles by means of C50)
SEND position
removes 0A2 regulated voltage to VI, V4 screen grids, and V3, V13B plates.
REC position provides B+ voltage to all stages except calibrator circuit.
CAL position injects a 100 Kcs signal weakly coupled to antenna connector.
Operation with transmitter by... The relay connector J1
and the AVC connector allows the HQ-180 to be controlled from a transmitter
or vice-versa, but the combined operation must be designed with care
taking in mind a possible injection of RF voltage from transmitter
(an antenna switch is ALWAYS required to avoid BURNING OUT the ANTENNA COILS
in the RF stage).
For combined operation the receiver ALWAYS must remain on
SEND, then J1 is open, but it may be "closed" by external
contacts (external RECEIVE position).
→ Model A: Relay & AVC in system socket.
EXT RELAY
&
AVC MUTING (VOX silencing,
optional)
SEND position
opens the pins of the J1 power plug on the rear to use them
connected to a set of normally closed contacts of a remote relay, these contacts opens as
relay is being energized so muting the receiver. Main relay contacts
switches the antenna to transmitter.
Relay operation for disconnecting antenna to receiver is always mandatory. Also, a terminal on the rear marked AVC is provided to inject in the AVC line an
external DC voltage of -80 to -100 volts to mute the receiver, or to extract AVC
voltage from the receiver to an external accessory.
ANTENNA
RF Amplifier sharp tunning
In parallel with the RF tandem section.
Antenna RF stage tuned via tandem section
YES
Sharp tuning.
Antenna connections
SO-239 and terminal strip
Coaxial or twin lead dipole, long wire antennas.
AF gain
Adjusts audio level up to 2 W.
Hammarlund auto-response circuit (that is a simplified Williamson-type feedback circuit).
Line voltage
115 VAC
115, 230 VAC options in model A, or non A export model ('E' labeled models).
Accessories / Options
SPEAKER on the rear.
PHONES at bottom left of panel.
• IF Noise Silencer(1).
• IF Noise Immunizer = Noise Silencer + AGC operation(1).
But these circuits are not particularly recommended.
Xtals panel(2): It contains
a 6CW4 oscillator that replaces the LO of the 1st mixer. Allows
to use a HQ-180 as a fixed-tuned receiver ('X' in label).
Telechron Clock Timer(2).
Terminals: phones or speaker, 3.2 (4) ohms.
Audio jack: phones or speaker, 3.2 (4) ohms.
(1) Can be installed inside.
(2) Can be installed on panel.
Telechron Clock Timer has 3 positions:
ON: Works all the time with receiver on or off.
OFF: Sets receiver to off.
AUTO: Receiver is turned on at desired preset time in the same manner as an alarm clock.
If the function switch has previously been set to "SEND", HQ-180 will remain
standby, this is the usual operation for pre-warming. The small red clock
hand may be retouched in order to obtain exact turning-on of the receiver
at scheduled time.
Left: a 3"-3.2/4 ohm mid-range speaker may be installed into the panel hole for accessories via custom DIY; but for best copyability under the actual QRM of digital household appliances, a voice-range only speaker is better (see text).
Design values
The actual Intermediate Frequency values may vary based on actual values of fixed frequency components.
Conversion chart sequence
15.35 to 30 Mcs
RF amp
1st mixer High-OUT
3035 Kcs + Xfilter
1st converter
455 Kcs
2nd converter
60 Kcs IF
7.85 to 15.35 Mcs
RF amp
1st mixer High-OUT
3035 Kcs + Xfilter
1st converter
455 Kcs
2nd converter
60 Kcs IF
4.00 to 7.85 Mcs
RF amp
1st mixer Low-OUT
455 Kcs IF gate
455 Kcs
2nd converter
60 Kcs IF
2.05 to 4.04 Mcs
RF amp
1st mixer Low-OUT
455 Kcs IF gate
455 Kcs
2nd converter
60 Kcs IF
1.05 to 2.05 Mcs
RF amp
1st mixer Low-OUT
455 Kcs IF gate
455 Kcs
2nd converter
60 Kcs IF
.54 to 1.05 Mcs
RF amp
1st mixer Low-OUT
455 Kcs IF gate
455 Kcs
2nd converter
60 Kcs IF
Intermediate Frequencies
RF input to High-OUT: 7.85 to 30 Mcs (1st mixer + 1 Xtal converter followed by LOW IF STAGES).
1st mixer: 3035 Kc output, followed by 3035 Kcs Xtal phasing filter.
Frequency Received by the antenna - Frequency of the Local Oscillator (FR
+ 3035 Kcs). This mixer reverses sideband positioning.
RF input to Low-OUT: .54 to 7.85 Mcs (1 Xtal converter followed by LOW IF STAGES).
1st mixer: 455 Kcs output, followed by the 455 Kcs IF amplifier gate.
Frequency Received by the antenna - Frequency of Local Oscillator (FR + 455 Kcs).
This mixer reverses sideband positioning.
455 Kc IF stage followed by +/- 5 Kcs SLOT filter adjustable on panel.
2nd mixer/converter: 60 Kcs output = 455 Kcs (IF stage output) - 395 Kcs (
VERNIER TUNING frequency at "0").
What's a mixer? What's a converter? The same thing, a nonlinear electronic circuit that creates new frequencies from two different signals applied to it. The output frequencies are the sum and difference of the two input frequencies, and they are called intermediate frequencies (IF). Usually, the circuit that heterodinates a signal with another signal coming from a variable oscillator (LO) is called "mixer", but when this signal comes from by a crystal oscillator (XLO) is called "converter". There may be other considerations: when the circuit does not require a separate LO tube the circuit is "a converter", and when a separate LO tube is used "a mixer".
Design basis: SIDE BANDS, centers / SELECT KC flatness
KC
Lower position (peak)
Upper position (peak)
BOTH position (peak)
.5
60.000
±60.000
±60.000
1
60.500
59.500
60.000
2
61.000
59.000
60.000
3
61.500
58.500
60.000
Idealized
(theoretical, hard to find in a real unit) Low IF resonances
on respective positions. The ".5" at "L" resonance is the correct BFO
frequency for the SSB position. Usually actual resonance
peaks do not match with this idealized IF passband response chart
due imperfections of centered flatness and symmetrical response.
Lower (internal Upper) sets main IF location at .5 ONLY.
BOTH decreases plate load resistance allowing wide bandpass.
As this chart shows, the "L" (Lower) panel indication is internally the Upper sideband,
this is due the conversion process. Setting BOTH, the KC offset value is doubled
(except ".5"), and the effective off center shift is less than 1500 Cs due the
system provides overlapping at center. When other combination bandwidth/sideband
is selected the sideband response varies due the action of fixed coupling/tuning
capacitors and loading resistors, if the BFO is adjusted off-center sideband
separation doesn't work correctly. When using the standard model (non A), the BFO
should only be adjusted off-center in order to adjust the CW tone when receiving CW,
ALWAYS must be remembered it needs to be adjusted AGAIN at CENTER for SSB reception.
Model A automatizes this, when SSB is selected, BFO frequency matches the IF
by means the value of a fixed capacitor that replaces the BFO variable capacitor,
therefore the BFO control only works on CW reception, BUT when CW is
selected the BFO frequency is shifted 0.5 Kcs from the IF, so a CW tone is
automatically generated. As the BFO capacitor works on CW only, this tone may be
corrected using the BFO knob, and when the personalized CW tone is adjusted the
BFO knob can be left permanently on this position, that is, model A permits
an static BFO knob (on model non A it must be shifted for CW), always must be
remembered in model A the position of the BFO knob has no effect on SSB reception.
The HQ-180 SSB system is adjusted with the sideband switch at "L" and SELECT KCS at .5 Kc
and it is based on switching different values of capacitors and resistors
that changes sideband bandwidth into the low IF section, thus correct
functioning of the system depends very much on the particular resonance
curve in each sideband. As the sideband switch position "U" (internal
"L" as stated) is tuned-in automatically and corresponds to a circuit
with no previous adjust, this circuit is not optimally adjusted and usually
has less performance than the "L" (internal "U") circuit.
Performance beyond the 0.5 KCS selection depends on the exact values of the capacitors and resistors involved in the selected bandwidth.
Checking the correct operating status of the SSB system:(including VERNIER TUNING corrections, see below)
Select VERNIER TUNING to +/- 1.5 Kc depending sideband,
SIDE BANDS on BOTH, then tune in an SSB signal.
Set selectivity switch at the narrowest bandwidth position (.5), recheck peak setting, and change "L" to "U" and vice-versa:
Tuned signal may be weaker and sounding obscure but should not disappear,
copiable and understandable depending on strength.
Set selectivity switch to 1, 2, and 3 successively selecting sidebands: A LSB signal
on "L" must be received OK, and on "U" must be weak or almost disappear
depending on strength; in like manner, a USB signal on "U" must
be received OK, and on "L" must be heard weaker or almost disappear depending
on its strength.
The Hammarlund HC-10 test page has comparative and expanded info on this SSB receiving system.
Trying to show a simplified view on the Hammarlund SSB system: Clearing up misunderstandings on this system.
• The BFO replaces the AM carrier, which is always centered in the IF and between the two sidebands. But the role of VERNIER TUNING is not defined in the manual, it says to set it to "0" and adjusting the other controls as necessary. This doesn't make sense and is easily provable: As the BFO control must remain always at "0", if the VERNIER TUNING control is also at "0", there will not be enough frequency separation when the "X" receiver tunes a SSB signal; BFO and signal will collide at "0"!
• Thus the incoming SSB signal must move and be processed in the corresponding sideband channel, that's why VERNIER TUNING must also be adjusted at one side, not at center, therefore an exact match of IF frequencies (receiver/converter) is mandatory, so the VERNIER TUNING dial reading should be accurate. To reach this:
a) The VERNIER TUNING control must be adjusted to prepare the sideband receiving channel.
b) The incoming sideband must be selected in the IF chain (L-U).
c) Then the SSB signal from receiver "X" can be processed at a selected selectivity (3-2-1-.5).
• The manual does not mention anything about it; it mistakenly refers that the VERNIER TUNING control is a fine frequency adjustment when in fact is a UPPER ↔ BOTH (center) ↔ LOWER operating frequency area selector(tuning concept vs location concept), an exact adjust on its dial is needed.
• When receiving SSB, the VERNIER TUNING control NEVER must remain at center; and when receiving AM/CW the VERNIER TUNING control ALWAYS must remain at center. This control is NOT a clarifier although it may be used as a clarifier, a lot of HQ-170/180 receivers are badly adjusted due manuals do not explain in detail the particular mode of operation of this system, or/and, give counterproductive info.
Operation:
• When receiving AM or CW VERNIER TUNING must be set at '0'.
• When receiving SSB VERNIER TUNING must be set at '+1.5' or '-1.5' (selecting the center of the sideband channel when SELECTIVITY KCS is at '3').
• When receiving SSB, the BFO must ALWAYS be set to '0', this must result in a 60 Kc signal (it may vary a bit).
• BFO must be set '+0.5' or '-0.5' when receiving CW (HQ-180 non A only).
• These positions are NOT randomly adjustable, the only "adjustment" is the MAIN TUNING (or BAND SPREAD) of the receiver, and MAIN TUNING (or BAND SPREAD) should point to the center of the UPPER, BOTH, or LOWER 'channels'. If the above positions need to be adjusted the SSB system is badly adjusted.
• When a 455 Kc signal enters the converter
a) The VERNIER ADJUSTMENT (L4 coil, the Local Oscillator of the converter) must operate at ±395 Kc (this value may vary depending on the exact IF value resulting from the previous conversions.).
b) SIDE BANDS on BOTH must operate centered at 60 Kc.
c) SELECTIVITY KCS with SIDEBANDS on BOTH must select 3, 2, 1, .5 Kc bandwidths.
d) SIDE BANDS on UPPER or LOWER must select the sideband channel, with SELECTIVITY KCS at '3' it is centered at 1.5 Kc, thus the sideband channels at '3' are 61.5 Kc and 58.5 Kc.
e) If all the above is true HQ-180 will work EXCELLENT.
⇒ KEY INFO: This system works with an UPPER ↔ BOTH (center) ↔ LOWER "template" which is not adjustable in terms of locations, it is only adjustable in terms of width, it is the adjustment of the devices that must adapt to locations.
⇒ The manuals give contradictory or inaccurate information about the system, due this it seems that not even Hammarlund understood it (although it may seem nonsensical and incredible to say).
The best SSB (decoding) setting is the one that matches the MAXIMUM voice movements of the S-Meter needle. SSB decoding with lower movements indicates that the SSB signal is not properly tuned, even though the voice appears to be well decoded and understandable. A different setting will result in differences when making bandwidth selection and sideband selection.
When this system is properly adjusted, the tuning procedure is very similar to tuning an AM signal. If the tuning procedure is critical, or requires adjusting any knob other than MAIN TUNING (or BAND SPREAD), the SSB system is not properly adjusted.
VERNIER TUNING is NOT a tuning operator, it is a sideband area selector.
Tube List and Associated Functions
Function(s)
Tube(s): 17 (model A: 16)
Comments
RF Amplifier
6BZ6 tube (V1)
Delayed AGC
Sensitivity control
Screen grid voltage from VR line
1st Mixer
6BE6 tube (V2)
3035 or 455 Kcs output depending on range
7.85 to 30 Mcs ranges: 3035 Kcs + Xtal filter
.54 to 7.85 Mcs ranges: 455 Kcs + IF gate
Screen grid voltage from VR line
Local Oscillator (LO, see table above)
6C4 tube (V12)
Plate voltage from VR line
1st Converter (XtalLO, see table above)
6BE6 tube (V3)
3035 converter on triple
Conversion only (455 Kcs output, 7.85 to 30 Mcs ranges).
Dual screen grid voltage from VR line
IF amplifier gate 455 Kcs
6BA6 (V18)
455 Kcs IF amplifier gate with fast AGC on double Conversion only (.54 to 7.85 Mcs).
Screen grid voltage from VR line
IF Amplifier 455 Kcs
6BA6 tube (V4)
Fast AGC
Sensitivity control Screen grid voltage from VR line
2nd Converter
6BE6 tube (V5)
Fast AGC VERNIER TUNING
IF Amplifier 60 Kcs
6BA6 tube (V6)
Fast AGC SIDE BANDS selection
SELEC KCS selection
IF Amplifier 60 Kcs
6BA6 tube (V7)
SIDE BANDS selection
SELEC KCS selection
IF Output driver-amplifier 60 Kcs
1/3 6BV8 tube (V8A)
SIDE BANDS selection
SELEC KCS selection
Detector
1/3 6BV8 tube (V8B)
AM diode detector
AGC time constant
1/3 6BV8 tube (V8C)
Diode RF rectifier
Product Detector
Full 12AU7 tube (V9)
CW/SSB mixer plate detector
BFO
1/2 12AU7 tube (V13A)
60 Kc oscillator (CW/SSB)
S-Meter amplifier
1/2 12AU7 tube (V13B)
Tube-voltmeter type (simplified)
Noise Limiter
6AL5 tube (V10)
Adjustable peak clipping (series type)
Delayed AGC
2/3 6AV6 tube (V16A) → (HQ-180A V15)
Paralleled diodes rectifier
Audio Amplifier
1/3 6AV6 tube (V16B) → (HQ-180A V15)
Triode audio preamplifier
Audio Power Output
6AQ5 tube (V17) → (HQ-180A V16)
Pentode audio power amplifier
Power AC Rectifier
5U4GB tube (V15) → 2 silicon diodes (A)
AC full wave rectifier
Calibrator
6BZ6 tube (V11)
100 Kc Xtal oscillator,
hairline setting on dial.
Voltage Regulator
OA2 tube (V14)
VR tube, 148 volts, VR line source
Contents
Concluding overview
Top of the line receiver, excellent performance, sensitivity only a bit less
than the R-390A. This receiver does not require improvements, if something
goes wrong suspect a failure not a design defect, although it has some "peculiarities"
that may be corrected, and there are some surprising factory "bugs" (static hairline
for the main dial as an example). Great sensitivity on all bands and conversion stages,
excellent selectivity when the L and U sideband positions are selected,
very good signal to noise ratio, easy SSB tuning if the BFO is at center and
the "VERNIER" control has been adjusted around the center of the LSB/USB passband
(Vernier Tuning positioned at +1.5 or -1.5 respectively, not at center),
communications quality audio (not HI-FI of course, as it should be), and very good to good
LO stability depending on frecuency range after a short warm-up time. Hammarlund always
says in manuals "we do not claim for frequency accuracy", a honest phrase that can be
applied to all tube receivers, and regarding this, the HQ-180 can have accurate
frequency reading on dial when a limited range of frequencies are adjusted using the calibrator.
Also, in order to get megacycle control in the high band, all shortwave tube receivers that
have the value of the tuning capacitor based on medium wave reception, like the HQ-180,
should have dual frequency calibrator (100 Kc & 1 Mc). The model A includes a bizarre
modification, 1st mixer tubes stays burning even when the radio is off,
so when purchasing model A, the first thing to do is check tubes V2 & V12 in a reliable tube tester, since these tubes are essential in performance of any superheterodyne receiver.
The manufacturer's purpose was to increase frequency stability by eliminating warm-up time,
but this arrangement is only practical if the receiver is used very often.
Model non A has standard filament configuration, which is better. A true classic, but updated,
communications receiver, it can be used routinely today. This receiver has a ham-bands version,
the HQ-170.
These receivers are not suitable for Hams of type "home-appliance users", also not suitable for people liking audio HI-FI performances,
to get this better choose a radio with less operational and selectivity exigencies, the HQ-160 for example.
, and see "Detección de la FM por la pendiente de la respuesta de FI".
