[NLRS] FunCube

[Doug Reed]

The $20 DVB-T dongle certainly is NOT a contest grade receiver. With
less than 50dB dynamic range, it overloads easily. One of the main
issues with the dongle is how to prevent overload from happening or
how to recognize when it is happening.

The first thing people want to do is hook it up to a "real" antenna.
Then they either wonder how it can receive anything among all the
trash signals or they blew up the input with too much signal and
wonder how come it hears nothing at all. So far I haven't blown up any
of my dongles, but I haven't hooked them to an outside antenna either.

It may not be as bad as I'm painting it because many people are
connecting the dongles to roof antennas cut to 1000MHz for receiving
ADSB transmissions from airplanes, and they are working. Or perhaps
they were smart and added a shorted quarter-wave stub at the bottom of
the antenna to act as a bandpass filter?

But if I hooked a dongle up to a old TV antenna, I'd expect the dongle
to get blasted by every strong signal in the area, starting with the
FM and TV broadcasts from Shoreview, adding the pagers running at the
nearby hospital, the cellphone towers in every direction, and even
KSTP AM from their towers a mile away. The front end of a dongle makes
even a police scanner or a Baofeng HT look like a narrow-band device
because both of those have coils to filter by band.... .

Yes, compared to a "real" SDR, the DVB-T dongle is a toy. The Funcube
was designed to be a teaching toy for SDR. But there are many
high-performance SDR "tools" available and you can always tell them by
their price tag...

If somebody wants to ask questions about SDR "tools" I can't provide
the answers. If someone doesn't even know the questions to ask about
SDR, then the SDR "toys" like the DVB-T dongle, the Softrock kits, and
the Funcube dongle are a relatively painless place to start. Once you
know what you want, then you can buy an SDR "tool" and (hopefully) get
the right one the first time.

73, Doug Reed, N0NAS.