On this page you can listen to and control a short-wave receiver located at the amateur radio club
ETGD at the
University of Twente.
In contrast to other web-controlled receivers, this receiver can be tuned by multiple
users simultaneously, thanks to the use of Software-Defined Radio.
The system is currently composed of a "Mini-Whip" antenna,
a homebuilt SDR board (pictured above; see here for background)
which samples the entire shortwave spectrum and sends all of this via
a gigabit ethernet link to a PC, where a special version of the
WebSDR server software processes it.
The Mini-Whip is based on a design from PA0RDT (google finds it); see
The active receiving element is about 5 by 10 cm large.
Such an antenna only works well with a good grounding;
ours is on top of a 20m high building, the upper part of which is all metal.
May 27, 2014:
Since a week or so, the system occasionally fails and then only gives periodic
brief bursts of audio. This is caused by a problem on the ethernet connection
between the SDR board and the server computer, and persists until I manually
reset that connection. Sorry for the inconvenience; I will of course try to
permanently fix it, but that may take some time.
More details for those interested: the link between the SDR and the server is
a gigabit ethernet link. On such a link, both sides "negotiate"
what speed to use, and the problem occurs when they have accidentally negotiated
to use 100 Mbit/s. That is not nearly fast enough to transport all data from the SDR
to the server, hence the interruptions.
I think the problem is on the SDR board, since improving the cooling of the
board recently helped a bit to improve the stability of the ethernet link.
But finding the real cause is not easy; it may be a bad contact or so.
Since one chatbox user apparently thinks he/she knows better and tells people
the problem is not in the ethernet connection, here
is an extract from the kernel log showing the relevant ethernet messages.
Update June 3, 2014:
Last Wednesday, I moved the fan on the SDR a bit so there's a bit more
airflow over the ethernet chip. I didn't expect much of it, but
we haven't had a single ethernet interruption in the 6 days since then!
(However, the chip shouldn't need so much cooling, so there must still
be something wrong in that part of the circuit.)
Update June 19, 2014:
Since yesterday, most of the time there has been a strong noise,
making the lower frequencies up to about 3.3 MHz unusable.
So far, we only know that it seems to originate outside our radio room,
since it disappears if we disconnect the antenna cable.
We'll try to hunt it down further soon.
Update June 21, 2014:
Yesterday around lunch time, I went out with a portable mediumwave radio
to try to find the source of the noise. However, while doing this,
the noise disappeared spontaneously, and it hasn't come back, yet.
The cause is still unknown. If it returns, we'll search further...
Questions and remarks about this WebSDR can be sent to the developer
and maintainer: firstname.lastname@example.org
(but please check the FAQ first).
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Bandwidth: ? kHz @ -6dB;
? kHz @ -60dB.
Or drag the passband edges on the frequency scale.
Or use scroll wheel and dragging on waterfall.
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This chatbox is intended to discuss the operation of the WebSDR.
Please keep the discussion civil and polite; that also means no swearing ("four-letter words").
The operators of this site disclaim any responsibility for text appearing in this chatbox.
Please keep in mind this chatbox is shared with up to over 200 users;
don't use it for chatter, nor for messages that are not about the operation
and use of this WebSDR, or about the signals received with it.