44 March 2023 QST www.arrl.org
power output, and it is recommended to simply leave
the transmit power at the maximum setting. I reduced
the computer’s audio input drive to keep the receive
level indicator out of the red, but that was the only
adjustment needed in my con guration.
My portable operations have taken me very far a eld, at
least through a swath of the central United States. My
favorite portable operating position is from a picnic
table, although the small size of the QDX makes it easy
to set up nearly anywhere. I have a portable aluminum
table that also works well. It is rare that I operate exclu-
sively in digital modes, so I need enough room for a CW
transceiver. I may be something of a heretic, but I rarely
operate QRP when I am activating a park unless there
is a considerable hike involved. Then the station is as
light as possible. My “tailgate” and picnic table opera-
tions are usually accompanied by a Yaesu FT-991A for
CW. There is always plenty of room for the QDX. Keep
in mind that the QDX requires some sort of computer,
although there are many con gurations that can be
used for this purpose. A Raspberry Pi, which is about
the same size as the QDX, could be linked wirelessly to
a tablet or iPad, making for a compact and versatile
setup.
Hans Summers, G
Ø
UPL, founder of QRP Labs and the
designer of the QDX, provides a better technical
description of the operation of the radio, but here’s my
take. As a musician, I understand the term “transposi-
tion.” To transmit, the radio uses an analog-to-digital
conversion of the audio input signal, which is sampled.
The sample of each audio frequency is then “trans-
posed,” or transformed, directly to appropriate RF fre-
quencies. These are not sideband signals injected to
produce a suppressed carrier SSB transmission. The
transmitter produces pure frequency shift keying without
any spurious mixing products.
The receiver is an SDR that uses an intermediate fre-
quency for the nal extraction of the tones — rst in
digital form, then fed as audio to a built-in sound card,
and nally sent via USB to a computer. Anecdotally, the
receiver passband is nearly devoid of noise. In very
unscienti c terms, the radio doesn’t seem to “hear”
much of anything aside from the intended signals. This
may, in part, have to do with portable operations, but
even still I nd that, compared to other QRP FT4/FT8
setups I have used, the signal-to-noise ratio appears to
be much better with the QDX. Compared to other QRP
setups, my experience is that the QDX hears well
enough that there is bigger spread in SNR readings,
and because the QDX hears so well, a reply with the
other station being unable to hear it seems to be more
frequent than with other radios I have used.
The QDX does an excellent job of leveraging the modes
available in WSJT-X and several other popular modes.
Conclusion
Overall, the QDX is an excellent transceiver. It is com-
pact, easy to use, and nearly foolproof. I highly recom-
mend purchasing the case unless you are highly skilled
at fabricating your own enclosures, or if you have a 3D
printer, as some templates are available online. The
radio is a worthwhile addition to my go-box for portable
operations, but it would function equally well as a dedi-
cated radio in the shack.
Manufacturer: QRP Labs, www.qrp-labs.com. Avail-
able in two versions at the same price: 80, 60, 40, 30,
and 20 meters (the reviewed unit), and the new 20, 17,
15, 12, and 10 meters. Price: $69 for the kit version, and
$20 for the optional enclosure; an extra $45 for the
assembled version.
Signal Generators
Bottom Line
There are a ordable signal generators out
there that may be a good starting point for
someone new to this kind of tool. For the most
advanced users, or if you want to maximize
your investment right from the start, it may be
best to purchase a unit that also comes with a
calibration certifi cate with traceability.
Reviewed by Paul Danzer, N1II
n1ii@arrl.net
You can no longer buy a signal generator like you used
to. Although some manufacturers divide their products
into two classes — analog signal generators whose pri-
mary output is CW (sine wave), and vector or digital sig-
nal generators whose primary output is complex digital
waveforms — most analog signal generators can gener-
ate square, triangular, and various digital waveforms.
Most digital signal generators also can generate CW.
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