Hammarlund HQ-160 (+E) Tech-Spec Page

1st ed., old-style painted letters.

2nd ed., modern-style painted letters.

3rd ed., molded plastic cursive letters.
Specification HQ-160 Comments + (AGC/S-Meter & 6BZ6 mods)
       .54 - 1.32 Mcs Band No bandspread Very Good sensitivity
     1.32 - 3.2 Mcs Band No bandspread Very Good sensitivity
     3.2 - 5.7 Mcs Band   3.4 to 4.0 bandspread Very Good sensitivity
     5.7 - 10 Mcs Band   6.970 to 7.300 bandspread Very Good sensitivity
   10 - 18 Mcs Band (Double Conversion) 13.880 to 14.400 bandspread Very Good sensitivity
   18 - 31 Mcs Band (Double Conversion) 20.930 to 21.600 bandspread
27.600 to 29.700 bandspread		 Very Good sensitivity
MAIN TUNING / dial Dial has Ham bands high frequency markers for combined use with the BAND SPREAD. Smooth operation, adjustable hairline (excellent for accurate dial calibration combined with fine tuning).
BAND SPREAD / dial Fine tuning and Ham-band tuning when MAIN TUNING is set to the respective Ham-band high frequency marker. Smooth operation, adjustable hairline.
Single Conversion
(0.54 to 10 Mcs range)		 VFO (LO, 455 Kc above signal frecuency)
455 Kc IF		 3 IF (455 Kc) amplification stages
Double Conversion
(10 to 31 Mcs range)		 VFO (LO, 3035 Kc above signal frecuency)
3035 Kc IF
3490 Kc XtalFO (455 Kc above input IF)
455 Kc IF		 2 IF (455 Kc) amplification stages
LO drift after 20 min warm-up at 20ºC.

Related to VLO frequency & conversion range. Depends on: frequency, tandem opening(a), and environmental temperature.

HQ-160 is a pure Armstrong type design (VLO on high frequency stages). Due to the high coverage design, stability is more impacted by the oscillator tank's L/C ratio at frequency in use than by how high the frequency is.		 AM test:
.54 - 31 Mcs: Unnoticeable, full ranges.

SSB test:
1.32 - 3.2 Mcs: Negligible, full range.
3.2 - 5.7 Mcs: Negligible, full range.
5.7 - 10 Mcs: Negligible to slight.
10 - 18 Mcs: Slight to noticeable(b).
18 - 31 Mcs: Slight to noticeable(b).		 (a) e.g. Drift at 21 Mcs (18 - 31 range) is much lower than at 28 Mcs, not only because frequency is lower, but also because tandem is more closed at 21 than at 28 ('less coil' and 'more capacitor' would be needed, but not possible due to long-excursion coverage).
(b) The upper end of these ranges usually require much more than 20 min of warm-up due to the explained above, but HQ-160 is more consistent in frequency stability than HQ-180/170 due to the use of the classic Hammarlund RF block (big coils and thick wire), LO tube runs cooler too.
AM detection by... Diode Connected to T7
FM detection by... Diode, slope detection, resonance skirt detection. Processed by the 455 Kc IF stage. To know how this system works click to Home→ES_list and link to page "El radio '5+1' de AM/FM", reading "Detección de la FM por la pendiente de la respuesta de FI".
FM operation AM mode
SELECTIVITY OFF
Tune less vertical skirt of the incoming signal		 Audio quality depends of a less vertical skirt of the response curve (the FM detection by signal slope processes very good voice frequencies when the resonance slope is ± 60 degrees).
SSB/CW detection by... Plate (pentode demodulator) CW PITCH (BFO) knob on SSB position
S-Meter S/0-9, dB up to 60.
60 mV, 1 mA end scale, 60 ohms.		 Classic circuit that compares a static voltage source with a variable voltage source affected by AGC; modified, see (*)↓
S-Meter on SSB/CW NO / YES, see (*)↓ AGC disconnected / connected, see (*)↓
Stages under AGC 1 RF + 1 IF stages / 1 RF + 2 IF, see (*)↓ Delayed AGC in RF, fast in IF.
AGC on SSB/CW NO / YES, see (*)↓ Manual SSB operation / AUTO, see (*)↓
Slow AGC NO / YES, see (*)↓ Manual SSB operation / AUTO, see (*)↓
Product Detector YES, pentode type Very good performance
CW PITCH, BFO adjust (PTO). Frequency at center = current adjusted IF
Range: ±1,800 cs center,
(± 350 cs in 5 divisions).		 Always rotated to (-) for Ham Bands.
Adjusted 3 to 4 divs off center (1200 to 1500 cs).
BFO freq-test : C39 to PD tube pin-2.
CW Pitch position on SSB
Single conversion range (.54-10 Mcs) ...→
Double conversion range (10-31 Mcs) ...→		 Panel position
(+) for USB, (-) for LSB (Ham radio).
(+) for LSB, (-) for USB (Ham radio).		 SSB carrier insertion: ±1500 cs off IF center
(+): BFO frecuency is above IF
(-): BFO frecuency is below IF
Phase reversal before the IF chain Reversed ONCE below 10 Mcs and TWICE above 10 Mcs (phase inversion zero above 10 Mcs). As Local Oscillators work above input signal frequency sidebands results always inverted. Below 10 Mcs the 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. Above 10 Mcs sidebands inverts again, so in this range IF sidebands matches antenna input sidebands.
Input to IF chain : T3, green dot lug.
IF output (RCA connector on the rear) Medium impedance. SSB output is always on lower sideband for Ham bands. Weakly coupled to primary of T8 (T8 provides exclusive SSB/CW signal for the product detector). The HC-10 converter works very well connected to the IF OUT plug (RCA to RCA) and selecting LOWER for SSB.
SELECTIVITY, Q Multiplier gain adjust. -Increases signal decreasing bandwith.
-Permits bandwidth selection on all modes.
-Bandwidth range ± 3 Kc to 100 cs.
-ON/OFF, adjustable regenerative circuit, sharp operation only.		 Clockwise rotation narrows bandwidth until the circuit starts oscillating. The minimum usable bandwidth is achieved just below the peak oscillation of the circuit by adjusting FREQ. Very important circuit, it rises the HQ-160 from a SW receiver to a true communications receiver.
FREQ (PTO), Q Multiplier frequency adjust. -Frequency at center = current adjusted IF.
-Range: ±1,800 cs center (±350 cs in 5 div).
-Gives sharp peak to the selectivity curve.		 Adjust must coincide with optimal tuning of received signal in order to reach optimal Q resonance. Adjusted around center arrow.
Usage: SELECTIVITY ON and set knob at center, FREQ at center, tune signal with MAIN or BANDSPREAD, increase SELECTIVITY, retune FREQ to peak signal gain.
SLOT FREQ KCS Range ± 5 kc IF center, adj max slot at '0'.
OFF position: 5 kc off center (e.g. fully clockwise → capacitor fully meshed).		 Very narrow null slot for CW (carrier signals). Adjusted to max slot depth and tuned on the sides can also attenuate modulated signals.
SLOT DEPTH IF slot null level. Maximum depth ~25% clockwise depending on frequency. This control adjusts a balanced position at one point. Set it to max rejection by default using the calibrator.
Noise LIMITER ON/OFF AM only
SENSITIVITY AGC separated, cathode mode on:
V1 and V5 + V6 / V1 and V5, see (*)↓		 In presence of strong signals, it is recommended to turn this control counterclockwise to prevent overloading.
Operation with transmitter Via two contact power receptacle SEND position opens contacts of the power receptacle on the rear
Operation modes
SENDing (standby/transmit)
RECeiving		 SEND opens the two contact power receptacle on the rear for connecting to a set of normally closed relay contacts (equivalent to external REC switch position / remote standby option). SEND position removes regulated fixed voltage to VI and V5 screen grids. Also removes 2 volt bias from the cathode of the delayed AGC rectifier (V7 pin 7)
ANTENNA RF Amplifier sharp tuning Optimal adjust for a tuned frequency
CALIBRATOR ON/OFF 100 KC.
AUDIO GAIN Adjusts audio level up to 2 W. Hammarlund auto-response circuit
FUNCTION switch
AVC .....................................
MAN ....................................
CW/SSB ..............................
AM operation only (AVC ON)
AM operation only (AVC OFF)
CW/SSB operation only (AVC OFF)
AGC voltage to V1 (delayed) and V5 (fast)
AGC lines to chassis
BFO and SSB detector (V8) ON
Line voltage 115, 125, 140, 220, 250 VAC options HQ-160-E model only! (Export model)
Design values
The actual Intermediate Frequency values may vary based on actual values of fixed frequency components.
Conversion chart sequence
18 to 31 Mcs RF amp High-OUT Mixer (LO=signal+3035 Kcs) 3035 Kcs IF Converter module, 3490 Kcs XLO 455 Kcs IF
10 to 18 Mcs RF amp High-OUT Mixer (LO=signal+3035 Kcs) 3035 Kcs IF Converter module, 3490 Kcs XLO 455 Kcs IF
  5.7 to 10 Mcs RF amp Low-OUT Mixer (LO=signal+455 Kcs)     455 Kcs IF
  3.2 to 5.7 Mcs RF amp Low-OUT Mixer (LO=signal+455 Kcs)     455 Kcs IF
  1.32 to 3.2 Mcs RF amp Low-OUT Mixer (LO=signal+455 Kcs)     455 Kcs IF
    .54 to 1.32 Mcs RF amp Low-OUT Mixer (LO=signal+455 Kcs)     455 Kcs IF

Intermediate Frequencies
 

RF input to High-OUT: 10 to 31 Mcs (a mixer + Xtal converter followed by 455 Kc IF STAGES).

  • Mixer: 3035 Kc output. Frequency Received by the antenna - Frequency of the Local Oscillator (FR + 3035 Kcs).
    This mixer reverses sideband positioning.
  • Xtal converter module: 455 Kcs output = 3035 Kcs (mixer IF output) - 3490 Kcs (Local Xtal Oscillator).
    This converter reverses sideband positioning.

RF input to Low-OUT: .54 to 10 Mcs (a mixer followed by 455 Kc IF STAGES).

  • Mixer: 455 Kcs output. Frequency Received by the antenna - Frequency of Local Oscillator (FR + 455 Kcs).
    This mixer reverses sideband positioning.
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".

IF output characteristic on rear RCA connector: 455 Kc (adjusted IF value, may not be exactly 455 Kc).

  • 10 to 30 Mcs range: No sideband inversion at this output, sideband positioning is equal to the sideband positioning at the input (antenna RF amp).
  • .54 to 10 Mcs range: Sideband inversion; a lower/upper configuration at the input will now become upper/lower at this output.

The SSB reception in the HQ-160 is carried out via the classic system of bringing the BFO frequency closer to the signal by the appropriate side; detailed info about this classic SSB demodulation system on the HC-10 Test page.
Tube List and Associated Functions
Function(s) Tube(s), 13 total Comments
RF Amplifier. 6BA6 tube (V1) / 6BZ6 see (**)↓ Delayed AGC.
Sensitivity control.
Screen grid voltage from VR line.
6BZ6 improves sensitivity on 18-31 high-end.
1st Mixer (455 Kcs & 3035 Kcs output) 6BE6 tube (V2) Sensitivity on 10-31 Mcs (double conversión) may be adjusted by changing the value of the coupling capacitor located in the link that interconnects T1 to T2, see (**)↓
Dual screen grid voltage from VR line.
Local Oscillator (above signal frecuency) 6C4 tube (V3) Plate voltage from VR line.
IF amplifier 455 Kcs
2nd Mixer 3035 - 3490 XLO = 455 Kcs out		 6BE6 tube (V4) IF amplifier on single Conversion.
Mixer on double C - Good conversion gain.
IF Amplifier 455 Kcs 6BA6 tube (V5) Fast AGC.
S-meter variable ref / deleted, see (*)↓
Sensitivity control.
Screen grid voltage from VR line.
IF Amplifier 455 Kcs 6BA6 tube (V6) S-meter base ref / variable ref, see (*)↓
Sensitivity control.
Fast AGC stage added, see (*)↓
Screen grid voltage from VR line.
AM detector & main AGC source. 1/3 6BJ7 tube (V7) Detector, AM signal rectifier, pins 1-2.
Delayed AGC source 1/3 6BJ7 tube (V7) AM signal rectifier, pins 6-7.
Noise Limiter, associated to AM detector. 1/3 6BJ7 tube (V7) Series type, pins 8-9.
BFO 6U8 tube (V8 triode section) 455 Kc VFO (CW/SSB)
Product Detector 6U8 tube (V8 pentode section) CW/SSB plate detector
Q Multiplier 1/2 12AX7 tube (V9) 455 Kc pre-regenerative circuit
Audio Amplifier 1/2 12AX7 tube (V9) Triode audio preamplifier
Audio Power Output 6AQ5 tube (V10) Pentode audio power amplifier
Power AC Rectifier 5U4 tube (V11) AC full wave rectifier
Calibrator 6BZ6 tube (V12) 100 Kc Xtal oscillator
Voltage Regulator 0B2 tube (V13) 108 volts, VR line source
Overview, overhaul processes, conclusion.
Pics & Review (*)  AGC + S-Meter Operation on SSB (**)  6BZ6 F-E, Schematics & Overhaul
600x350
The HQ-160 is a great receiver for everybody who likes combining selectivity with audio performances. This model is the latest evolution of the classic Hammarlund superheterodyne design just before the "SSB revolution". Excellent audio dynamic range combined with very good selectivity, good signal to noise ratio (very good with Q Multiplier ON), and amazing stability after a short warm-up time (inasmuch as the best tube receivers are capable). Very good performance both on single and double conversion ranges, and in all bands including the highest (the latter cannot be said for many receivers). HQ-160 has better dial accuracy than HQ-170 and HQ-180 due it uses the same RF/MIXER/LO coil block used in the HQ-120/129/140/150 models, thus HQ-160's dial marking and frequency stability benefits from the use of proven and reliable coils (the classic large block-type coils of thicker wire), but this design has the disadvantage of taking up more space and determining component distribution on the chassis. HQ-160 allows effective and direct adjustment of dial calibration in any frequency range, and this cannot be said for many Hammarlund models either. An important issue in the 18-31 Mcs range was fixed: tendency to distorted sound on SSB towards the high-end due to parasitic oscillations in the antenna amplifier (the procedures to solve this and to improve high frequency performance by means of a front-end stage redesign are explained in the overhaul page). The HQ-160 has product detector but does not have AGC operation on SSB. In order to demodulate SSB signals it is more important to have an strong BFO "carrier" combined with a long AGC chain than to have a product detector installed. A product detector permits to use weak (to a certain extent) BFO "carrier" and it usually gives better demodulation quality, but a long AGC chain is essential. As AGC operation is very useful in order to get comfortable reception on all modes, and mandatory for modern use of a communications tube receiver, this unit has been modified accordingly to the principles explained in the homepage.