||The KiwiSDRs at the Northern
If you plan to use the KiwiSDR - or other KiwiSDRs around the world - please review the KiwiSDR FAQ (link) for more general information.
Supporting the Northern Utah WebSDR:
- "I've found the entire Northern Utah SDR system to be very useful for my HF operating - how can I support it?"
- You can find out how to donate $$$ to help keep this WebSDR system online by going here
: Any amount is appreciated - large or small. While we have
some ads on the page, these provide enough to pay the power bill - but
not much more, so we need to come up with extra $$$ to fully cover
things like rent and maintaining the equipment or getting additional
gear for upgrades.
- "Hey dude - what's with the ads?"
- There are recurring expenses such as site rental and
electricity to name but two reasons for doing so. You can read
more about the rationale for doing this here.
- "Why are you doing this, and who is paying the bills?"
- The reasons for having WebSDR systems are stated on the "About" page. In short, to provide a service to the amateur radio community and
anyone else who is interested in the HF spectrum.
- At the present
time, the cost of the equipment and ongoing expense is being borne by a
small number of individuals who have donated time, money and materials
to get the system off the ground. Going forward, recurring expenses such as electrical power (we are the only users at this site!)
and additional needed for maintenance and upgrades will continue.
- We now have a way to donate $$$ to help keep this WebSDR system online by going here
: Any amount is appreciated - large or small.
- We also have what we hope are minimally-intrusive ads that we hope will cover at least some of recurring the expenses - For more info, please see the "Why Ads" article.
Why the KiwiSDR?
- "Why do you have KiwiSDRs in addition to the WebSDR?"
- Unlike the WebSDR, the KiwiSDR is capable of tuning continuously from (nearly) DC to 30 MHz, covering all HF amateur bands, shortwave broadcast bands and those in between.
- "If the KiwiSDR is 'better', I should be using it instead of the 'normal' WebSDRs, right?"
- Actually, even though they are using exactly the same antenna(s) as the normal WebSDR system, their performance is inferior
to most of the individual amateur band receivers on the WebSDR system.
This is because the "narrowband", "high performance" WebSDR
receivers use high-quality 16-bit A/D converters and narrow-band RF
filters on their front-end which improves their effective sensitivity
and makes them far more resistant to overload and noise degradation in
the face of other strong signals on the band and lightning crashes.
- The KiwiSDR uses "only" a 14 bit A/D converter - and that
"sees" the entire HF spectrum which means that strong signals in, say,
the 31 meter shortwave band can cause subtle degradation everywhere else. What's worse than that is lightning static that often appears from across the country on the lower bands (e.g. 160, 80, 40 meters)
that can simply overload the A/D converter, causing that same "crash"
to appear all across the HF spectrum - even though it really doesn't do
- "Which is better for ham radio usage - the KiwiSDR or the normal WebSDR?"
- For the reasons noted above, the KiwiSDR is better for things
like round-tables on most amateur bands: It can be slightly more
sensitive, more resistant to nearby signals, and more resistant to
out-of-band static crashes. In the opinion of many, the WebSDR
just sounds slightly "better".
- The KiwiSDR can, at most, handle 8 users - and some of those
user "slots" are permanently occupied by WSPR decoders tuned to various
bands as can be seen by clicking on the "Users" tab. In contrast,
the WebSDR systems can handle well north of 60 users at once.
- The audio delay on the normal WebSDR is only a fraction of a
second while the audio delay on the KiwiSDR is around 1 second, making
it harder to participate in round-tables!
- Note: If we see
too many people "sitting" on the KiwiSDR when they normal WebSDR would
be better, we will consider taking action to prevent this - so please don't do it!
- "Are there several KiwiSDRs?"
- Yes, there are two KiwiSDRs on site - the "main" one being found at kiwisdr1.utahsdr.org.
We are working on a configuration that will cause the first
KiwiSDR to automatically forward to the second when it is "full" of
users - but this isn't working (yet) at the time of writing.
- There are other public KiwiSDR system across the world: Go to the sdr.hu site for more information.
Operating the KiwiSDR and various issues:
- "The KiwiSDR just kicked me off - why?"
- To prevent "squatting" or other abuse, there is a maximum 30
minute time limit per session of the KiwiSDR and a maximum of 90
minutes per user during each 24 hour period.
- "How the hell do you tune this thing?"
- The easiest way to tune the receiver is to select the mode first (e.g. USB, LSB, AM) and then enter the frequency in kHz (including decimal places) in the bar in the upper-left corner of the pop-up on the right edge of the screen.
- You can also click on the waterfall display, the frequency bar,
or in the white (blank) area just above it - but note that the
frequency to which it will tune will be in the center of the receive passband as defined by the yellow brackets.
- On some frequencies above the frequency bar you will see
labels: Clicking on those will tune the receiver to the frequency
and mode defined by that label. (Users cannot change these labels.)
annoyingly, after you click to tune, your mouse cursor may drag
the frequency around. Click ONCE to change the cursor back
to normal to stop this.
- If you click and hold the left mouse button on the waterfall,
frequency bar or the area above with the labels, you can drag the
waterfall back and forth on the screen.
- "I somehow dragged the yellow
passband brackets around and now my (USB/LSB/AM) mode doesn't work
right. How do I 'fix' that?"
- If you have somehow changed the passband setting for a mode, it
will remain "changed" during your current session. Because this
is so easy to do by accident, there's a simple way to fix it:
- Hold the SHIFT key down while Right-Clicking
on the waterfall or frequency bar. In the options that show up
you will see "restore passband" and click on that to "fix" your mode
- On some browsers you'll get a dialog box from the browser
itself. I'm not quite sure how to dismiss this without also
making the dialog box go away other than selecting something like
- To make the box (from the KiwiSDR) go away (that is, if you don't want to pick anything) hit the ESCape key or left-click once somewhere on the waterfall display.
- "I used to see a waterfall for the whole HF spectrum, but I don't see it now. What's the deal?"
- It takes a lot
of powerful hardware to "inhale" all of the HF spectrum at once and
process it: Were it done only with a computer, the fastest PC
around may not even be able to do it unless it also used a fancy
graphics card's GPU cores as well! The "other" way to do this is
to use FPGAs (which are versatile programmable logic devices)
in which one can "program" specialized hardware that is very good at
this task - and the KiwiSDR has one of those. Because its
resources are limited, in addition to being able to receive signals,
this FPGA also has to function as a GPS receiver and it is what produces the data for the waterfall display.
Features of the KiwiSDR:
- "I hear that the KiwiSDR has some fancy features. What can you tell me about them?"
- The KiwiSDR has a number of additional features that are
available under the "Extension" drop-down tab. Very briefly,
- devl - A "development" tab that may or may not have any options. (They usually do not...)
- This can be used to receive and display HF FAX transmissions in the
browser. Within the tabs are lists of stations that may or may
not be transmitting and you may or may not even have propagation to
those stations. The map will slowly appear on the screen when properly tuned in.
- There will probably be a black bar somewhere in the picture
with the contents on either side. To manually synchronize the FAX
transmission place your mouse's cursor in the middle of that black bar
and while holding the SHIFT key, click the left mouse button.
- You will have to re-synchronize when you tune to another
station - and probably when the FAX transmissions from a given station
stop and resume.
- Read the KiwiFAQ for more information.
- fsk - This is the
same as RTTY, or RadioTeletype. The various settings allow both
Baudot and ASCII to be decoded but the precise configuration for these
modes is beyond the scope of this document. Read the KiwiFAQ for more information.
- ibp scan - On certain
frequencies in the upper HF bands are CW beacons located across the
world that transmit on a particular schedule, enabling one to quickly
determine if the band is open: This extension facilitates
monitoring of these beacons. Read the KiwiFAQ for more information.
- integrate - This sets
up a second audio-only waterfall that allows one to integrate over
time, potentially allowing persistent weak signals to be made more
visible. Read the KiwiFAQ for more information.
- iq display - Almost
every SDR uses "I" and "Q" signals to recover the signals and in this
mode, the amplitude of those signals are displayed on a phasor scope
with the "I" in one axis and "Q" in the other. If you tune in an
AM signal zero beat you can see this "spin" depending on the frequency
error. The box that pops up has various filtering and
phase-locking options. Read the KiwiFAQ for more information.
- lms filter - The
KiwiSDR has some noise reduction and notch filter capabilities that are
still a work in progress available under the "Audio" tab in the
right-hand window. This selection brings up some "knobs and
buttons" that directly affect how well these filters do/don't work.
Read the KiwiFAQ for more information.
- loran c - In some parts of the world (Russia, parts of Europe and Asia, east coast of the U.S.)
there are Loran C stations still in operation - or undergoing testing
with new technology that may result in the system being rebuilt as an
"un-jammable" augment to GPS. This extension allows analysis of
the signals from these stations. Read the KiwiFAQ for more information.
- navtex - This is an
information service used to pass along traffic to ships at sea.
Because of its naval use and the low frequencies involved, you
may not ever "hear" anything unless you have an antenna that works well
at these frequencies and you live near-ish a coastline. Read the KiwiFAQ for more information.
- S_Meter - This
provides a graphical analysis of the S-meter readings. This may
be used to track the fading of the station to which you are tuned or,
if they are "local", it may help facilitate that other station's
antenna testing. Read the KiwiFAQ for more information.
- TDoA - This allows
coordination with other KiwiSDRs to help determine the geographical
location of signals being received. At the present time, it takes
a 30 second snapshot of the signal in question and uses this, along
with a digital recording pulled from other selected stations (at least 3 are needed for an unambiguous fix) that can also hear this same station to calculate the likely location (to within a few 10s of miles/km at best): This means that if you have any hope of determining a station's location, it must be audible to all
other stations that you have selected, the transmission must be more or
less continuous over the 30 second period and that it must be the only station that was transmitting at this time. DO NOT
expect decent or consistent results from this system until you get
practice and have a better understanding of how it works. In
addition to the HELP button on this screen, please read the KiwiFAQ for more information.
- WSPR - This brings up
a window where one can select a band on which you can park a WSPR
decoder to decode any signals that might be there with the results
posted to wsprnet.org
using the source callsign of either KA7OEI-1 or KA7OEI-2. Note
that the KiwiSDRs at the Northern Utah WebSDR typically have
"permanent" WSPR decoders tuned to the LF (2200 meter), MF (630 meter),
160 and 80 meter bands - and often a few other bands as well. Read the KiwiFAQ for more information.
- "In the stats I see reference to a GPS receiver. What's that for?"
- Because the KiwiSDR uses a fairly powerful FPGA, it was easy to
add an inexpensive GPS "front end" chip and implement a "simulated" GPS
receiver on the FPGA. This allows the KiwiSDR to not only
determine its precise location, but it also allows it to precisely set
its "dial" frequency to within a fraction of a Hertz over time as well
as have a very accurate time-of day clock.
- It is this accurate clock that allows the KiwiSDR to participate with others in the TDoA ("direction finding")
function by precisely time-stamping the sound recordings that are
processed - along with those of other receivers - to determine the
signals' likely locations.
- The GPS clock is also used for WSPR reception which requires a precise clock along with frequency stability and accuracy.
- The results of the GPS receiver's operation (location, timing, etc) are not available to the casual user.
The KiwiSDRs have many more features than can possibly be covered here - please read the Quick start guide (link)
and follow some of the links within for more information than you probably want.
For more general questions about HF and the things you will hear, go to the WebSDR FAQ page
- For general information about this WebSDR system - including contact info - go to the
- For the latest news about this system and current issues, visit the latest news page.
- For technical information about this system, go to the technical info page .
Back to the Northern Utah WebSDR
- For more information about the WebSDR project in general -
including information about other WebSDR servers worldwide and
additional technical information - go to http://www.websdr.org