Copyright © 2013 American Radio Relay League, Inc. - All Rights Reserved
by Mark
J. Wilson,
A Look at Gasoline Powered
Inverter Generators
Portable power for your ARRL Field Day station
Reviewed by Bob Allison, WB1GCM
ARRL Test Engineer
The fall of 2011 was a difficult time for
New England residents who experienced the
effects of Tropical Storm Irene and a surprisingly heavy late October snowfall spaced a
month apart. Both storms caused widespread
power outages and those with backup generators maintained some comforts of normal life.
My generator is an inexpensive 1000 W ac
generator powered by a two stroke 63 cc
engine. It’s enough to start our oil burner for
heat and hot water, plus some lights and the
TV. It’s not enough to run the refrigerator
Generators I grew up with all ran at one speed
— 3600 rpm (to produce 60 Hz) — and were
noisy. Today there is a lot of interest in a type
of generator that is technically advanced,
more fuel efficient, lighter weight and quieter
— the inverter generator. Inverter generators
produce high voltage, multiphase ac that is
rectified to dc — similar to an automobile
alternator. This dc power is then converted
back to very clean and consistent ac power by
a solid state power inverter. A microprocessor
controls the process as well as the speed of
the engine. Unlike older constant speed
generators, inverter generators can run at idle,
providing power to small devices. If demand
for more power appears at the generator’s
outlet, engine speed increases. This feature is
intended to improve fuel economy and can be
switched on or off. (The various manufacturers have different names for this feature, but
the concept is the same and I’ll refer to it as
ECONOMY mode throughout the review.)
For this review we chose four widely available inverter generators in the 2000 W class
— the Champion 73536i, Generac iX2000,
Honda EU2000i and Yamaha EF2000iS.
All of the units were available locally from
power equipment dealers, outdoor stores,
industrial suppliers or box stores in the $600
to $1000 range. Prices shown in the tables
are what we paid but will vary depending on
dealer. Other inverter generator models are
available with lower or higher power ratings.
Generators in this class provide enough
power for a light duty, backup power source
at home or to run a power tool on the job.
But how well do they work in a radio environment? All four appear to be attractive
candidates for ARRL Field Day or emergency operation and so we conducted a
variety of tests to determine how “radio
friendly” each of these generators is.
The Tests
Load Test: Each generator was connected to
a load consisting of two strings of incandescent light bulbs adjustable from 0 to 2500 W
in 50 W steps. We measured the generator
output voltage, frequency and sound level as
the load increased up to the maximum rated
output. In each case, the sound level was
measured with a calibrated instrument at a
distance of 9 meters from the muffler side of
the generator. Sound levels will vary depending on location.
Power per Gallon Test: Each generator was
run out of fuel, refueled with precisely one
cup of gasoline, then restarted and placed on
a 1000 W load until it again ran dry. Running
time was noted and used to calculate kilowatt
hours per gallon of gas (kWh/G).
Waveform Test: The Lab’s Tektronix TDS3052B storage oscilloscope captured the
ac waveform during no-load and full-load
conditions. Waveforms for each generator
are available online.1
No-Load to Full-Load Test: Using the
oscilloscope at a slow sweep speed, measurements were made at the point at which a full
load was applied to the generator from a no
load condition. This tough test shows how
ARRL Lab test results are available
online at
Bottom Line
Inverter generators have advantages over normal ac generators, but
have some disadvantages as well.
With additional filtering, they can be
made “radio friendly.”
quickly a generator responds to a drastic load
change with ECONOMY mode on or off.
Oscilloscope plots from this test are available
online (see Note 1).
Conducted Emission Test: Conducted emission can have a major impact on Field Day or
emergency operation as wideband RF noise
is injected into the power wiring that then
acts as an antenna. For our tests, we used a
100 foot extension cord. Each generator
was swept for conducted emission using a
Rohde & Schwarz LISN (Line Impedance
Stabilization Network) and a Rohde &
Schwarz EFH3 handheld spectrum analyzer.2
Radiated Emission Test: Each generator was
placed on a cart and rolled around near a
40/20 meter dipole (15 feet high) to check for
radiated emission from the electronics or
ignition system. A nearby battery powered
transceiver attached to the dipole (our simulated Field Day setup) listened for changes in
noise level or ignition noise while I tuned up
and down each band. The transceiver was also
used for listening to conducted emissions with
an extension cord plugged into a generator.
Circular Saw Test: Chances are you will
need a generator to power a tool. I tried to
run a 15 A maximum circular saw with each
Before operating a power generator, carefully
read the operator’s manual and safety precautions. All four generator manuals recommend
grounding the generator and determining local
grounding codes. If you have any questions
about wiring or grounding a power generator,
ask a licensed electrician.
I recommend using an in-line ground fault
circuit interrupter (GFCI) outlet with each
generator. They are available online or in
most hardware stores or home centers. If you
plan to use a generator during power outages
at home, have an electrician install a transfer
switch to isolate the generator from the
power lines.
April 2009 QST, page 48 for an explanation
of conducted emission level limits.
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June 2012 49
Copyright © 2013 American Radio Relay League, Inc. - All Rights Reserved
Four Generators with a Lot in Common
All four generators weigh less than 50
pounds (dry) and have a durable, brightly
colored plastic shell that holds up well when
bumped or scraped. All are fairly close in
size, about as big as a 1980s boom box, with
comfortable handles to move them about.
You shouldn’t have much trouble loading
any of them into your vehicle and transporting them to a portable operating location.
higher speed, ready for a sudden increase in
demand for power.
All have single cylinder, four stroke engines
and require slightly less than 1⁄2 quart of oil in
the crank case. Each has a low oil level
shut-off feature, a good thing for those who
forget to add oil before starting for the first
time or who are lax on maintenance. Each
has a slightly recessed exhaust pipe, reducing
the risk of painful burn blisters.
Champion 73536i
Each generator produces a clean, stable
60 Hz ac waveform, suitable for running
radio gear, computers or other sensitive
electronics. Each has two 120 V, 20 A ac
outlets. All have a 12 V dc battery charging
outlet, though it is for the charging of a small
automotive or lawn tractor sized battery only.
The 12 V dc output waveform is full of
transients and is unregulated — don’t try
running any 12 V device from this outlet!
All but the Generac have the ability to run
two identical units in parallel with an
optional cable to essentially double the
power capability without sacrificing portability. There is no provision for using two
generators to create 240 V ac.
To improve fuel economy and reduce noise
when the generator is lightly loaded, each
has an ECONOMY switch. With ECONOMY
switched on, the generator runs at an idle
speed with up to 300 W or so output. With
ECONOMY off, the engine runs at a much
Although the generators are similar in specifications, features and appearance, we found
many differences in performance.
This bright yellow and black 1700 W (2000 W
surge) inverter generator reminds me of a road
hazard sign. In the box I was pleased to find
the manual, a container of motor oil, funnel,
spark plug wrench and battery charging cable.
Unlike the other three generators, round
pillars dominate each corner of the plastic
shell. They are designed to fit a matching
generator so the two units can be stacked
vertically and run in parallel. This is a smart
idea that takes up less surface area and
presents less of a trip hazard from the cabling.
The manual is well written and has a wiring
diagram, but what impressed me most was
the exploded parts diagram complete with a
parts list. The mechanically inclined can
repair this generator at home. The Champion
meets California clean air standards and gets
3 out of 10 on the green scale (0 is the
For description sake, let’s pretend this generator is an automobile, with the exhaust pipe
at the back. The Champion has the controls
clustered around the pull cord,
on two panels on the right side.
Three LEDs — a yellow OIL
Champion 73536i, s/n 11MAY1801016
Engine: four stroke, single cylinder, 80 cc.
light (lights at 1800 W threshFuel capacity: 1 gallon.
old) and the green OUTPUT light
AC output: 120 V at 60 Hz.
— are at the top left. To the
Power output: 1700 W, 2000 W surge.
right of the LEDs are the
DC output: 8 A at 12 V dc (battery charger).
ECONOMY and engine on/off
Weight: 49.2 pounds (dry).
Size (HWD): 16.3 × 19.3 × 13.3 inches.
switches. Below the LEDs are
Price: $599
the choke knob and fuel shutoff
valve. On the bottom panel, the
Lab Testing: Load Test, Eco On
top row has the ac outlets and a
Load Output Frequency Sound Level*
socket for the optional parallel
(V ac)
operation cable. The bottom
row features outlets used during
parallel operation, the battery
charging outlet, dc circuit
breaker and a ground terminal.
On top are a vented gas cap and
carrying handle. Large vents at
Eco off No load
Fuel efficiency: 4.333 kWh/G
*See text.
Annoyingly for me, a lefty, all of the generators are designed to be started by a righthanded person. Fortunately, the recoil starter
handle was very easy to pull on all but one of
the front and back ends provide cooling. The
left side engine access panel is secured with
four screws without retaining clips so be
careful if you remove them. The exhaust has
a spark arrestor.
Figure 1 — Conducted emissions from the inverter generators.
50 June 2012 ARRL – The national association for Amateur Radio 72.2
Copyright © 2013 American Radio Relay League, Inc. - All Rights Reserved
After the usual oiling, fueling and choking,
the Champion came to life on the first pull.
The pull was smooth and easy. I let this
generator and the others run about 15 minutes before testing.
Voltage varied a reasonable 4.7 V from
no-load to full-load. Response from no-load
to full-load was fast with the ECONOMY
switch off and took 1.5 seconds to come up
to full voltage with the ECONOMY switch on
(more on this type of response later). With a
2000 W load, the generator provided power
for one minute before the ac switched off.
The motor still runs in this condition and has
to be shut off to reset the circuit breaker.
As shown in Figure 1, conducted emission
was quite high with RF radiated from the
extension cord causing high noise levels
across most of the HF bands. Ignition noise
was eliminated by moving the generator
30 feet away from the antenna. The fuel
economy test produced 4.333 kWh/G, the
lowest of the four generators. Unfortunately,
the Champion 73536i failed to run a circular
saw, with the OVERLOAD light lighting and
the ac shutting down in both ECONOMY
Generac iX2000i, s/n 6463450C
Engine: four stroke, single cylinder, 127 cc.
Fuel capacity: 1 gallon.
AC output: 120 V at 60 Hz.
Power output: 2000 W, 2200 W surge.
DC output: 5 A at 12 V dc (battery charger).
Weight: 49.6 pounds (dry).
Size (HWD): 18 × 22 × 12 inches.
Price: $589
Lab Testing: Load Test, Eco On
Load Output Frequency Sound Level*
(V ac)
Eco off No load
Fuel efficiency: 4.390 kWh/G
*See text.
During the no-load to full-load
test the Generac responded
poorly with ECONOMY mode on
or off. There was a noticeable
delay before the generator got
up to full voltage output. With
ECONOMY mode switched on,
there was a total dropout of
power for a brief moment.
Manufacturer: Champion Power Equipment,
10006 Santa Fe Springs Rd, Santa Fe
Springs, CA 90670; tel 877-338-0999;
Some good news: the conducted
emission (Figure 1) was lower
than the Champion or Yamaha
but was still quite noticeable in
the receiver. Radiated emission
was stronger and the generator
had to be moved 50 feet away
from the test antenna for the
ignition noise to subside.
Generac iX2000
This orange 2000 W (2200 W surge) inverter generator has the largest displacement
engine at 127 cc and can provide more
power than the rest. It came with an orange
funnel for adding oil, a bottle of motor oil,
a two wrench set and a battery charging
The right side of the generator has the pull
cord, fuel valve and choke control. The front
end contains the control panel. At the top are
a yellow LOW OIL LEVEL light, a red OVERLOAD
light and a green READY light. Below the
LEDs is the dc battery charger socket with
circuit breaker. To the right are two ac
outlets and at the bottom, the engine on/off
switch and ground lug. The engine access
panel is released by loosening only one
screw, which has a retaining clip. At the top is
a vented fuel cap that also has a little priming
pump. The front and back are well vented.
There was no spark arrestor at the end of the
exhaust pipe.
The manual didn’t indicate that this model
Generac meets California emission standards. I checked the website and found this
model to be compliant in 49 states. The
manual is adequate but does not provide
mode, the engine speed was
slow to pick up as the load
gradually increased. Each time a
light bulb was turned on in the
string, the motor speed hunted
around a bit before settling
down. This was by far the
noisiest generator of the lot, with
or without a load. During testing,
it vibrated to the point where the
engine access panel screw
unscrewed itself. The Generac
ran at its specified peak load of
2200 W for 10 seconds before
shutting off both the ac and the
engine. I tried but could not get
the OVERLOAD LED to light
before shutdown. The Generac
had the lowest voltage variation
between no-load and full-load
conditions, only 1.1 V.
a wiring diagram as found in the other
Even with its larger displacement engine, fuel economy was
just a bit better than the smaller
80 cc Champion engine, providing 4.390 kWh/G. The Generac
iX2000 passed the circular saw
test, but the saw was slow to come up to
speed. You may get impatient with this
generator if you have a lot of wood to cut.
Before I could start this unit, I had to clip off
a needle-like projection on the choke control.
It appeared to be an injection molding flaw
with the plastic. Bandaged up and aggravated
by my injury, I failed to carefully read the
manual. After nearly pulling my arm off, I
discovered that the engine must be primed by
a pump built into the gas vent on the gas cap.
Once primed, it started on the third pull.
Each pull was not smooth and unlike the
other generators, I could feel some compression from the piston moving in the cylinder.
This red 1600 W (2000 W maximum)
inverter generator carries the highest list
price of the four, although we got ours from
longtime QST advertiser Mayberry Enterprises for $899 including shipping. The
Honda arrived with only a manual and no
other accessories.
The load test was interesting. In the ECONOMY
The right side of the generator has the pull
Manufacturer: Generac Power Systems,
S45 W29290 Hwy 59, Waukesha, WI 53187;
tel 888-436-3722;
Honda EU2000i
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June 2012 51
Copyright © 2013 American Radio Relay League, Inc. - All Rights Reserved
cord, fuel valve and choke lever. Engine
access is on this side as well, the cover
secured by one screw with a clip. Indicators
and outlets are at the front. Top row:
ECONOMY mode switch, parallel operation
outlets and ac outlets. Bottom row: a red OIL
ALERT light, a red OVERLOAD light (lights at
2200 W threshold) and a green OUTPUT light.
The OUTPUT LED also acts as a simplified
run-time hour meter. It blinks once after
100 hours of operation, twice for 200 hours
and so on. The front and back have large
vents for cooling and there is a spark arrestor
on the exhaust. This particular model does
not meet California emission standards,
though Honda offers a similar model available for sale in California. The manual is
very good and includes everything needed to
know to run and maintain the unit.
The Honda EU2000i started on the first pull.
I found the voltage to be a bit high, 127 V ac
output with a 100 W load. The voltage varied
4.6 V from no-load to full-load. With the
highest loads, the Honda was quiet with very
little visual vibration. The no-load to fullload response was the best of the four. I ran
the Honda with a 2000 W load for its rated
30 minutes with not one hint of overheating or
While the Honda has levels of conducted
emission as high as the other three on
160 meters, the levels drop off quickly, making this the least offending inverter generator in this department. See Figure 1. Though
some noise can be heard, a receiver is usable
with this generator attached to an extension
cord. Ignition noise was fairly low as well.
The 98.5 cc engine provided
4.480 kWh/G, number two in
the fuel economy department.
The Honda powered a circular
saw flawlessly in both ECONOMY
Honda EU2000i, s/n EAAJ-2263469
Engine: four stroke, single cylinder, 98.5 cc.
Fuel capacity: 0.95 gallons.
AC output: 120 V at 60 Hz.
Power output: 1600 W, 2000 W maximum.
DC output: 8 A at 12 V dc (battery charger).
Weight: 45.6 pounds (dry).
Size (HWD): 16.7 × 20.2 × 11.4 inches.
Price: $899
Lab Testing: Load Test, Eco On
Load Output Frequency Sound Level*
(V ac)
Eco off No load
Fuel efficiency: 4.480 kWh/G
*See text.
Manufacturer: American Honda
Power Equipment Division,
4900 Marconi Dr, Alpharetta,
GA 30005; tel 770-497-6400;
Yamaha EF2000iS
This royal blue 1600 W (2000 W
maximum) inverter generator
included a manual, spark plug
wrench and battery charging
On the right side is the control
panel, arcing around the pull
cord handle. At the top of the
panel are a red OIL WARNING
light, a green AC pilot light and a
red OVERLOAD indicator. While
testing, I found the OVERLOAD
indicator illuminated at the
1850 W threshold. Lower on
the control panel are a black
ECONOMY mode switch and a
red engine on/off switch. About
halfway down are the fuel
shutoff valve and a choke control
that must be pulled out when
starting the engine. Below the
choke are terminals for running
two generators in parallel and
two ac outlets. At the bottom of
the control panel are the dc
receptacle, dc circuit breaker and
ground terminal.
At the top are a carrying handle
and a vented fuel tank cap. The
Yamaha is the only generator of
the four with a fuel gauge, although I noticed
the generator ran a long time while the gauge
read E. The front and rear sides have large
vents for cooling. The exhaust pipe has a
spark arrestor. The left side of the unit has two
screws (no retaining clips) that secure the
engine access panel.
The manual is clearly written with ample
illustrations and instructions for servicing
the generator. A wiring diagram is included.
This generator meets California air pollution
standards and rates 3 out of 10 on the green
After filling the EF2000iS with oil and fuel,
I pulled out the choke rod and gave it one
easy, slow pull. It started! After a few seconds, I pushed the choke rod in and the
Yamaha settled down into a soft purr with
ECONOMY switched on.
The Yamaha overall was the quietest at low
rpm. No vibrations of the case were noticed,
even at full load. The output varied 5 V ac
from no-load to full-load — reasonable, but
the most output change of the four generators.
The no-load to full-load testing showed a very
slow but steady response with ECONOMY mode
on, but a very quick recovery with ECONOMY
mode off. I placed the Yamaha on a 2000 W
load. In 20 seconds, the overload circuitry
kicked in and shut off the ac and the engine.
Figure 1 shows the conducted emission of the
Yamaha is very high all the way up through
the 20 meter band. We placed the generator
100 feet away from the operating table with
the extension cord running perpendicular to
the test dipole antenna, which was an additional 30 feet away. On the battery powered
transceiver, an S9 level of noise peaks with
slightly lower levels of hash were heard across
40 meters and S8 across 20 meters — all with
the generator in the ECONOMY mode, at idle.
Increasing the demand increased the noise
level. Clearly, there is a need for filtering at the
ac outlet (more on that later).
With the extension cord unplugged and the
Yamaha running with the ECONOMY mode off,
the radiated emission was found to be mostly
from the ignition system. With the generator
parked directly under the antenna (15 feet up),
a few S units of ignition noise from the spark
plug was observed. Turning on the receiver’s
noise blanker removed all of it; moving the
generator 30 feet away (off the broad side) also
reduced the ignition noise to nothing.
The Yamaha EF2000iS won the fuel economy
test by a significant margin, creating 5.37
kWh/G. I suspect this is due to the generator’s
small 79 cc displacement. The engine ramps up
quickly in the no-load to full-load test, so for
power tools I would leave ECONOMY mode on.
52 June 2012 ARRL – The national association for Amateur Radio Copyright © 2013 American Radio Relay League, Inc. - All Rights Reserved
Yamaha EF2000iS, s/n 7DK 1516423
Engine: four stroke, single cylinder, 79 cc.
Fuel capacity: 1.11 gallons.
AC output: 120 V at 60 Hz.
Power output: 1600 W, 2000 W maximum.
DC output: 8 A at 12 V dc (battery charger).
Weight: 44 pounds (dry).
Size (HWD): 17.9 × 13.3 × 11.0 inches.
Price: $990
Lab Testing: Load Test, Eco On
Load Output Frequency Sound Level*
(V ac)
Eco off No load
Fuel efficiency: 5.347 kWh/G
*See text.
Conclusions and Observations
A radio amateur’s requirements for portable
power are different from those of the average
user. A homeowner’s generator, acting as a
backup power supply, usually works with
fairly static loads. Power demand usually
stays at one level for a while. On the other
hand, a generator used for powering an SSB,
AM or CW station is faced with a dynamic
load, one that changes rapidly with modulation or on/off keying. How do these generators respond to dynamic loads?
Figure 2 — Conducted emissions from the Yamaha EF2000iS inverter generator
with no filtering (blue line), a commercial Corcom filter (green line) and a filter built
in the ARRL Lab (purple line).
respond, the increased load
disappeared. Keying slowly, I
could make all but the Generac
make the sound of a grunt or
laugh. Also, the line voltage
would momentarily dip while
keying; the Generac responded
poorly to this test by speeding up
and slowing down in an erratic
manner. Though no chirp was
detected in my test receiver, I did
this test with only one transmitter. I suspect some transmitters
may wobble in frequency or
chirp with a momentary voltage
dip. I would recommend leaving
ECONOMY mode off so that the
engine runs at a higher speed,
ready for a momentary increase
in load while transmitting.
Manufacturer: Yamaha Motor Corp,
6555 Katella Ave, Cypress, CA 90630; tel
An option is to use the generator to operate
one or more battery chargers and run all
transceivers from battery power. That way it
is possible to take advantage of the ECONOMY
mode, provided that the generator output is
filtered, which leads me to the next topic.
Conducted Emissions
The biggest finding of this review is the high
conducted emission levels of these inverter
generators. My little 1000 W conventional ac
generator has very low conducted emission
levels, but the output waveform has a harmonic in it and is not nearly as clean as the
inverter output. As with inverters used to
generate ac from batteries, inverter generators are power generating devices and don’t
plug into a wall outlet, so they are not held to
FCC Part 15 conducted emission level limits.
There are two ways to attack this problem
— buy a commercially made filter or build
one. Figure 2 shows the Yamaha’s conducted
emission with no filter, with a commercially
made filter made from Corcom (www.cor.
com), and with a homemade filter whipped
up by the ARRL Lab’s RFI expert, Mike
Gruber, W1MG. Most of the conducted
emissions are common mode, though some
is also differential mode. The amount of each
mode may vary with different model inverter
generator. Mike believes with some experimentation, patience and some 2.4 inch
diameter type 31 toroids (www.fair-rite.
com), the owner of an inverter generator can
greatly reduce the conducted emission level.
More information is available online at www.
(click on AC Line Filters).
Click to see
an overview of
four ­portable
I set up a 200 W transmitter and 300 W of
incandescent lighting. With ECONOMY mode
on, 300 W is just below the threshold of
increased engine rpm. As I keyed the transmitter, each generator would try to respond to
the increased load by momentarily trying to
raise its rpm. Before the engine speed could
QST – Devoted Entirely to Amateur Radio
June 2012 53