The HP-310 is an all transistor design that dates back to 1963. The unit I have works beautifully. This is a true example of fine design. I checked the unit out when I got it and it was still well within factory calibration! For 1963, this is a very sophisticated design. It is an upconverting superhet design (3 MHz IF), with a frequency range of 1000 Hz to 1.5 MHz. The signal level is rated at 10 uV to 100 Volts input (selected by two range switches). The wave analyzer concept was developed at HP to test voice telecommunications circuits. It may also be used as a low frequency scalar network analyzer (it has a built in tracking source). Dr. Barney Oliver (Chief Engineer @ HP) designed a linear, air variable tuning capacitor for the 310 (and it's predecessor the 302). This allowed for the mechanical tuning counter seen (since the tuned frequency was a linear function of the capacitors rotation) . HP also produced a motor driven "tuner" that could be attached to the main tuning knob on the front of the analyzer. Then, by using the recorder output connected to an XY plotter (which HP also produced), a linear input versus frequency plot could be produced. This was truly a automatic network analyzer, produced in 1963! Another application cited by HP was the analysis of low frequency harmonic distortion products.

The meter on the front reads out absolute dB or volts of the tuned signal. A relative mode may also be selected allowing the receiver to be set to a fundamental signal and relative measurements made on harmonics.

A January, 1963 HP Journal article introduced the instrument.

The design is current by todays standards. The narrow IF bandwidths were produced by quadrature converting the signal to IQ channels at baseband where narrow frequency active filters could be built giving bandwidths of 200, 1000 and 3000 Hz. The IF was then translated back to 3 MHz and added together to remove the quadrature component. This method dates back to the late 50's (Weaver, Proc. of the IRE, 1958) for SSB generation. The method is still in use today in the DSP world by Harris Semiconductor. Their digital HSP50016 Digital Downconverter uses exactly the same principal to get very narrow digital IF bandwidths!

The instrument used HP's second generation "Glow FET" chassis. The inside of the 310 looks empty since it was built with transistors. All of the circuits are built on plug in cards and in separate shielded compartments.

All told, the transistor count in the instrument is just 60 devices. Using OPAMP's today the transistor count would be in the thousands! That's progress? The 310 is designed with the usual 60's selection of Germanium and Silicon transistors. If any of the Germanium devices fail, I'll have to rebias the circuitry for Silicon replacements.

I have found the instrument to be just great at receiving WWVB with my 4 foot loop. It has very good intermodulation performance for a "wide band" front end, as it rejects all of the much stronger LORAN signals less than an octave away in frequency. It is also very tolerant of the fluorescent lighting in my workshop (It's better than my Sony 2010).

The 310 has provision for AM, USB and LSB reception by the twist of a knob. A front panel BNC easily drives headphones for listening. I have received AM broadcast stations in Canada, Texas, and a low power AM station in Boise Idaho (from my northern California location). The 310 easily tunes around hetrodynes on crowded AM channels. The only deficiency it has as a receiver is relatively flat audio quality. I intend to improve that, with the inclusion of a 20 transistor audio amplifier IC (well, that is progress, I guess).

HP's first wave analyzer was the 302 designed in 1959, also a transistorized design. Then came the 310. The 312 came along next and featured a maximum frequency of 18 MHz. The 312 also sported a digital frequency display. The 312 looks very much like an upgraded 310 (same chassis). Next came the digital 3581 family. This analyzer dropped back to 50 kHz maximum frequency, but was much smaller. The last in the line was the 3586 produced in 1980. The 3586 is fully synthesized and covered 50 Hz to 32 MHz. Digital techniques applied to Spectrum Analyzers ended the need for Wave Analyzers and now cover the market that was once held by these instruments.

HP310 SPECIFICATIONS:

Frequency range.................................... 1 - 1500 kHz

Tuning Accuracy.................................... 1% +/- 300 Hz

Frequency Calibrator............................. 100 kHz (even and odd harmonics, up the band)*

Selectivity............................................... 200, 1000 and 3000 Hz BW, 3dB

Shape Factor.......................................... 2:1 (to -25 dB down)**

IF Ringing Immunity.................................. Very good (Butterworth response)**

Voltage Range........................................ 10 uV to 100 V full scale (140 dB)

Voltage Accuracy................................... 6% (on the meter)

Dynamic Range...................................... >70 dB

Input Resistance..................................... 10, 30 and 100 K ohms (Depends on full scale input range)

Power................................................... 110/230 VAC at 16 Watts

Weight.................................................. 44 pounds (it's that darn chassis!)

Front Panel Controls:

Max Voltage Range, Relative or Absolute, Range (in dB), Bandwidth, Mode (AFC, Normal, BFO, USB, LSB and AM). Frequency (Fine and Coarse), Zero Set, and Tracking (also AM Output) Amplitude.

The unit also incorporated a "sweeping" AFC circuit to keep the signal locked in on narrow bandwidths.

* The calibrator was supposed to be a 60/40% duty cycle square wave, my unit is closer to 50% duty cycle, so I only get odd harmonics of the calibrator (I need to fix this).

** HP did not originally specify these things, these are my "Supplemental Specifications".