filter order of 40 works well and will
have little effect on program speed.
Tuning in an SSB station can be a
challenge as there is no carrier peak.
Tune to the left or right of the signal
depending if USB or LSB is used, and
adjust the frequency dial slowly until
voice is intelligible.
You may want to calibrate the
frequency dial more accurately. This is
a two-step procedure as there are two
crystal oscillators used here: one in the
RTL and one in the RF converter. To
calibrate the RTL, uncheck Shift and
connect a short wire of three or four
feet directly to an RTL antenna
terminal. This should allow you to pick
up a NOAA weather station in your
area — usually around 162.400 MHz.
Look up exact frequencies on the
Internet. Note that NOAA uses NFM.
Click Configure and adjust the
Frequency Correction (PPM) until the
dial reading corresponds to the NOAA
To calibrate your HF SDR receiver,
check Shift and tune to station WWV using USB — not
AM. WWV at 10 MHz is useful for calibrating. Use a high
value of FFT resolution — around 131,073 — so you can
see WWV peak clearly in the spectrum. Adjust the Shift
value until the dial reads the peak frequency accurately to
within 50 Hz. It will drift periodically, but that is the nature
of uncompensated crystal oscillators.
As noted above, if you bypass the HF converter and
use an antenna directly connected to the RTL, you can
take advantage of the very large frequency range of this
device — up to 1,766 MHz. Thus, you may be able to
directly pick up FM stations (and other stations like
NOAA) and two-meter ham repeaters if they are close
Hopefully, by now you should be having fun with your
SDR SW receiver. If you are having difficulties, go to
http://sdrsharp.com or the Yahoo SDR group and they
may be able to help.
Shortwave radio is more exciting now than ever
before. Many new AM broadcasters from China, Cuba,
Europe, and other places will keep you informed and
entertained. Religious broadcasters also abound.
Unfortunately, many of the interesting stations only appear
at night due to propagation conditions. Fortunately, the
powerful ones come booming in even in the daytime.
Listening to ham radio operators using SSB and Morse
code is also fun — especially during contests. Other
stations are using SSB too, such as Maritime WX on 8.763
MHz and Aviation WX on 10.051 MHz. These generally
use synthetic voices. If you are lucky — as I was — you
may hear one of the mysterious ‘numbers’ stations using
USB around 13.199 MHz. However, they are seldom in
the same spot twice. Also interesting are utility stations
such as WLO, which transmits on many frequencies and
provides high seas communication and weather
One of the exciting things you can do with this radio
is receive data transmissions such as WX FAX, SITOR,
RTTY, BPSK, WSPR, and EasyPal SSTV. These modes can
easily be decoded with available software, but to discuss
this further would require another magazine article!
If you like playing around with this radio and find the
subject fascinating, you may want to consider becoming a
radio amateur. Hams are involved with building and
studying receivers, transmitters, antennas, satellites, EME,
microwaves, and experimenting with new radio modes
such as WSPR, BPSK, Packet Radio, and more. If you are
considering joining the fraternity of radio amateurs, the
ARRL website may be the place to start. Be sure to check
out the new column here in Nuts & Volts, as well.
In the meantime, have fun with your new SW radio.
July 2015 45
FIGURE 7. SDR# opening screen — radio tuned to 10 MHz WWV.