www.arrl.org QST March 2023 45
Table 2
Signal Generators Manufacturers’ Specifications (not tested in the ARRL Lab)
Models JDS2900 and SDG 1032X Rigol DG1062Z
JDS6600-60M
Display 2.4-inch TFT color LCD 4.3-inch TFT color LCD 3.5-inch TFT color LCD
Max frequency of sine wave 60 MHz 60 MHz 60 MHz
Max frequency of square wave 25 MHz Two channels 30 MHz Two channels 60 MHz
Max frequency of triangular wave 25 MHz Not speci ed Not speci ed — ramp 1 MHz
Max frequency of pulse waveform 6 MHz 12.5 MHz 25 MHz
Max frequency of TTL waveform 6 MHz For custom waveforms 30 MSa/S 25 MHz, custom 25 MHz
Pulse width range 25 nS to 4000 seconds 32.6 nS to 1000 ks 16 nS to >1000 seconds
Square wave rise time ≤10 nS <4.2 nS <10 nS
Square wave jitter Not speci ed 300 ps+ 0.05 ppm of period 2 ppm +20 pS at <5 MHz
Frequency stability ±1 ppm/3 hours Not speci ed ±1 ppm
Each waveform length 2048 points 16 kpts 16 Mpts per channel
Waveform sampling rate* 266 MSa/S 150 MSa/S 200 MSa/S
Waveform vertical resolution 14 bits 14 bits 14 bits
Operating temperature 0 – 40 °C 0 – 40 °C 0 – 50 °C
Waveform types See text See text See text — 160 + arbitrary design
*Mega samples per second
The older-generation generators were capable of
CW-only output. Drifting due to heat (vacuum tubes
were very good at making heat) and drift in calibration
were major problems, as was the aging of components
with time. These problems drove the size and mechani-
cal design, as well as the type of oscillator used in the
unit. In turn, these considerations resulted in limits to
the frequency range available with multiple range switch
positions.
Nearly all such units had only one output channel and
had to be recalibrated periodically. For high-accuracy
frequency generation, many lab applications required a
stand-alone frequency counter, which had its own sta-
bility problems.
Finally, some models became available at a low or
moderate cost by sacri cing performance in the areas
just listed as problems. Homebrewed models requiring
selected parts often appeared as an exercise in art
rather than electronic design!
In this review, I look at ve different signal generators.
There are major differences in the design and resulting
capabilities between today’s models and those of sev-
eral years ago, before the availability of digital integrated
circuits and microprocessors.
Digital Synthesis
Rather than being concerned with inductance-to-capac-
itance ratio and the temperature coefficient of capaci-
tors, most generator manufacturers today look at a
repetitive waveform as a set of points. Each point has
an amplitude, and the more points read and convert to
an analog voltage (or digital waveform) per second, the
smoother the output waveform. Selecting a waveform to
generate is really selecting a point-generating program.
Picking the frequency selects how fast the points read
out. Usually, a microprocessor controls the operation,
and a digital readout (or a counter on the front panel)
provides the frequency value being generated.
Each manufacturer has its own techniques in the design
of the unit. For example, interpolation, smoothing, or
encoding may be used to ll in between generated
points. The digital number display may be offered as a
freestanding counter, as an extra feature. When looking
for a generator to use in your station, you may nd that
several units available online, especially imported units,
have similar front panels and speci cations. These
similarities may lead you to wonder if they are not the
same unit with a different name plaque! I selected a
cross section of available generators for this review. At
the low end are several similar units, and at the higher
end are those with more availability or better capabili-
ties. Table 2 summarizes the manufacturers’ main
speci cations of the tested units.
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