Here are a few questions that have/may come up, and some answers. They may not be good
answers, but they are answers nonetheless. If you have a question
about the WebSDR, check out the Q&A below to see if it's already
been answered. Below are main topic headings - click on one to jump to it - or just peruse the entire page.
Supporting the Northern Utah WebSDR:
- "I've found this WebSDR 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.
Weird noises and other things on the bands:
What the 40 meter waterfall on the WebSDR can look like when
there are severe thunderstorms about, taken on 22 August, 2018 at about
1500M. The light, horizontal streaks are loud static crashes -
and since they are broadband, they occupy the entire band at the same
Right: A real-time lightning map (blitzortung.org) taken
at the same time of the western U.S. showing the very high lightning
activity within normal "skip" range of the daytime 40 meter band.
The left-hand picture shows only one obvious signal and two other
weaker ones. Why was the band so devoid of activity? Would you want to be on the air with weather (and the band) behaving like this? (Do you really have to ask?)
Click on either picture for a larger version.
- "I'm hearing a lot of static crashes on the lower bands (160/80/75/40) that make it hard to hear things. What's the deal?"
- When it is spring/summer/fall in the northern hemisphere, there
is a greater likelihood of thunderstorms - and lightning can cause very
loud static crashes. During the daytime, these bands are
generally "shorter" - that is, useful to only a few hundred miles - so
more distant thunderstorms may not be audible. At night, the
scene is different: Not only are these bands propagating over
greater distances, but in many locations heavy thunderstorms tend to
occur in the evening, not only allowing static crashes to be propagated
over a wider geographical area, but there are more of them!
- If you are interested in current thunderstorm activity across North America, I would suggest that you visit the Blitzortung web page (snapshot in Figure 1) showing "live" thunderstorm activity. This page represents data from (typically) volunteer
weather observers. There are many map options on this page
allowing you to check on thunderstorm activity across most of the world.
- "What are those light, horizontal bands that appear across whole waterfall?" (related to the question above - also see Figure 1.)
- Those are most likely static crashes - and that's what distant
lightning, propagated on HF like other signals - looks like and because
it is a burst of white noise it covers a wide range of frequencies at
once. The "brightness" of the crash on the waterfall is indicative if its relative
signal strength where "white" means that it is pretty strong!
Because it can be a strong,
broadband signal not even fancy DSP can do a lot about it, but this
WebSDR has a noise blanker that helps to clip the level of this noise
and allow a faster AGC recovery than would otherwise occur.
Propagated lightning static tends to be worse on the lower bands
(160, 80/75, 40) and is notably weaker on the higher bands.
- During the winter there are fewer thunderstorms across North
America and this is less common, but in the summer there are times where the bands are
constantly barraged with this type of noise.
- "What is that "buz-buz-buz-buz" that I keep hearing every few minutes?"
- We have no idea - it may be some sort of ocean wave
or ionospheric profiler. It seems to be audible on some band
nearly everywhere in the world.
- "Speaking of "buz-buz", what's the deal with the beehive in the logo?"
- Utah is known as the "Beehive State", the idea being that the
beehive is a symbol of industry as used in the "highly productive and
busy" sense. A suspiciously similar-looking beehive - complete
with bees flying about - may be seen on the great seal of the state of
- Somewhat amusingly, it is illegal in the state of Utah to
use a skep - that traditional-looking dome-shaped beehive. The
reason for this seems to be because these structures originally did not have
"movable frames to all the hive’s parts so that access to the
hive can be had without difficulty" and that harvesting honey from them
often required destruction of the hive and/or the need to kill many bees.
- The antenna? Bees have not passed any HOA restrictions on antennas as they are naturally equipped
with their own antennae and doing so would not be in their own
interest! Maybe they are causing the "buz-buz-buz-buz"!
- "What are those "sweeping things" that I see between 4.5 and 6.5 MHz (and maybe other places) - especially at night?"
- We think that those are coastal wave profile radars used to
analyze the ocean swells. A Wikipedia article on these types of
systems - and links to more information - may be found here: https://en.wikipedia.org/wiki/Wave_radar
sitting here listening and I hear a "twit" sound across the frequency as if
someone just tuned their transmitter's dial up the band quickly while keyed down. Who's doing that?"
- These are ionosondes - a sort of chirp radar that
is used to analyze the composition of the ionosphere. These
sweeping transmitters - along with synchronized receivers - function as
radars that can determine the height and density of the ionosphere, and
with similar devices at other frequencies (you can find them all over the HF spectrum) the quality of the refractive properties and the MUF (Maximum Usable Frequency)
can be dynamically tracked. By sweeping the frequency, the delay
in the time that it takes the signal to go up and back down from the ionosphere means that the return
signal will be at a slightly different frequency than that of the transmitter
which will have moved frequency in that time, so the difference in
frequency between the transmitted frequency and the return is
indicative of the total path length.
- Here are a few web sites that have information about/from those systems:
This is an example of IMD showing up on a "clean" 40 meter
signal. The signal is peaking about 10dB over S-9 with a little
bit of QSB. The noise floor is about S-4 meaning that the peaks
of this signal are about 40dB above the noise. Just to the right
of the signal (between 7250 and 7251)
one can see some energy that is related to voice peaks. Because
the waterfall can represent a wide range of signal amplitudes it is
quite typical for a transmitter with good IMD specs to appear to have
some splatter - but careful comparison of the waterfall's color and
brightness will reveal that in this particular case, that IMD is really
There are two other signals in the waterfall above: A weak LSB
signal at approximately 7253.5 kHz and a carrier with modulation on
either side at 7245 that is likely China Radio International.
Several weak horizontal streaks from distant lightning storms can also be seen.
Click on the picture for a larger version.
- "I notice on the waterfall that
a lot of stations seem to be 'wide', so I get on and tell them that -
but they say that they aren't overdriving and/or using an amp.
What's the deal?"
- First of all, are you a member of the "waterfall police"? If so, don't you have something better to do?
- Anyway, while it's sometimes the case that someone will overdrive their rig (quite hard to do these days) or overdrive their amplifier (not as difficult to do)
it's actually quite rare that one sees a signal that is indicative
gross overdriving of something in their RF transmit chain. With
the waterfall, what you can
see is something that has been going on for decades, but was either
misdiagnosed or went unnoticed and that is the intermodulation
distortion (IMD) on the transmitted signal.
- Conventionally, the measured IMD of a typical amateur transmitter are in the range of -28 to -35dBc (roughly 0.1% of the total transmitted power)
- that is, it will "naturally" produce low-level splatter that is 5-6
S-units lower than the peak signal: The use of an amplifier will
naturally make the IMD higher because the contribution of the rig is
added to that of the amplifier itself. What this means is that if
there is a background noise of S-4, if the signal that you are
receiving is at least 10-20dB over S-9 that these IMD products will
become visible on the waterfall and can be heard as a bit of splatter.
- In short: Just because it can appear on the waterfall display, do not automatically assume that there is something wrong with the transmitting station.
Some newer radios have some means of reducing IMD, such as
digital processing and/or a type of power amplifier that is designed to
reduce IMD which can reduce the IMD to somewhere in the -40 to -50 range. Figure 2 shows a typical example of a "pretty clean" signal appearing to have splatter. In
truth, all transmitters have a degree of splatter, but in the example
shown its spectral purity is well within the accepted limits.
Features of the WebSDR:
- "What is that "= kHz" button in the tuning bar used for?"
- In the "old days" with analog VFOs hams just plopped down
anywhere on HF "close" to the intended frequency - which made sense
since few dials were accurate to much better than 1 kHz. These days, where
nearly everyone has a digitally-synthesized transceiver that is actually both
stable and accurate in terms of frequency, most hams - at least in the
U.S. - seem to have taken to setting their frequency dial to
"something.00" kHz (or, occasionally, "something.50").
Why? It could be OCD, or it could just be that it's easier
to remember a "whole kHz" frequency that ends with zeros. Because
of this tendency I added the "= kHz" button to "snap" the tuning to the
nearest even kHz ("something.50" will round UP) because most
stations will be there, anyway - and it prevents you from needing to
click your mouse a bunch of times to dial it in. If you are using
SSB and tuning in a station that is at "something.50" kHz you can still
use "= kHz" - just hit the "- -" or "+ +" key and you will be stepped
down or up 0.5 kHz, which is still fewer steps than clicking the
button a bunch of times or directly typing in the frequency.
- "Your stupid clock is wrong - why don't you do something about that‽‽‽"
- It's really your stupid clock that is wrong: The clock on the WebSDR displays the time to which your computer is set!
- If the clock that you see on the display is wrong, you need to
find out why your computer's clock isn't set properly - it may be set
to the wrong time zone and/or it may not be getting a time update from
the Internet. Remember: If your computer's clock is a ways
off, it will ignore the Internet time until you manually set the time and get it "close" to the correct time and date.
- "What about those labels under the frequency scale/spectrum display? Where do those come from?"
- There are two types of labels under the display:
- Orange-ish labels: These are added by the sysop to indicate things like band edges, frequencies for various modes, certain stations (e.g. W1AW, international beacon network)
and certain nets and the items that are included is entirely at the
discretion of the sysop. These orange labels change twice daily:
At 5 AM and again at 5 PM local (mountain) time to reduce the the clutter. In many cases, clicking on these labels will set the WebSDR's tuning to that frequency and the mode (LSB, USB, AM, FM) appropriate to operation on that frequency.
- Green-ish labels: These exist ONLY
if you have defined frequency "Memories", otherwise you will not be
able to see them. Like the orange labels, clicking on them will
tune the WebSDR to that frequency. Remember: These green labels are stored as cookies on YOUR computer: If you clear your cookies, use a different browser or use a different computer, they will disappear.
- Once in a while the orange labels won't appear when the page loads. There are several ways to fix this:
- Make sure that the "Hide Labels" box is not checked.
- If the "Hide Labels" box is not checked, toggle it on and off again.
- Change the width of the waterfall using.
- Go to a different band and then come back.
- "When I listen on SSB (USB/LSB)
the audio sounds "wider" on the WebSDR than on the rig that I have at home and I hear
more 'splatter' from nearby stations? Why does the WebSDR have
such sucky filters?"
- Based on feedback, many WebSDR users listen casually to nets
and roundtables rather than try to dig weak signals out of the noise.
Because of this, the "default" LSB and USB filters are wider than
those typically found on sideband rigs to give better lows and highs.
For more "DX" type use, there are the narrow filters (e.g. "LSB-nrw" and "USB-nrw") that can be selected.
- You can also set the bandwidth manually to suit your tastes or the current conditions - The next section (below) tells you how.
another station really close to the frequency on which I'm listening -
how do I filter it so that I can hear what's going on where I'm
- If you own a radio made within the past 30 years you probably
have a "Passband Tuning" or "IF Shift" control that allows you to move
your filter back and forth. If you own a modern receiver you can
adjust the high and low sides of your filter independently to narrow
your bandwidth at the top or bottom end of the voice channel on which
you are listening to reduce that edge of the passband to remove some of
the adjacent-channel interference. On this WebSDR, there are
several ways to do this:
- Select the "Narrow" version of the mode that you are using (e.g. LSB-nrw, USB-nrw).
- Click on the "narrower" button to reduce your overall receive bandwidth bandwidth (there are actually two different buttons that do this...)
- Under the "Passband Tuning" section use the "<<IF
Shift<<" or ">>IF Shift>>" buttons to "slide" your
passband up or down, away from the interfering signal.
- Use the "<<Low PBT", ">>Low PBT" to slide the
low-frequency end of your receive passband down or up, depending on
which sideband you are using.
- Use the "<<High PBT", ">>High PBT" to slide the high-frequency
end of your receive passband down or up, depending on which sideband
you are using.
- On the screen, grab the low or high end "skirts" the passband with the mouse (e.g. hover the cursor over it then press-and-hold the left-mouse button while dragging it) to change the passband. It is recommended that you zoom in before doing this!
If you click any of the "USB" or the "LSB" buttons after
setting a custom bandwidth that it will reset them to the default
- "There is a loud tone (carrier) on the frequency where I'm listening - What is that?"
- Some of our amateur bands - notably 40 meters above 7200 kHz
and large chunks of the 80/75 meter bands are used for international
shortwave broadcasting in other parts of the world and shortwave being,
well, shortwave, we can often hear those signals - particularly at
night or early morning in North America. To a degree, you can remove this tone by
clicking the "autonotch" button near the volume control - but this will
remove only the carrier, not the modulation (speech, music.) At
other times you will hear short-duration carriers while people tune up
or, unfortunately, due to the occasional jamming. It is recommended
that you NOT
use this "Autonotch" feature when receiving CW signals as this will dutifully remove them!
- Note that this "autonotch" seems to be able to notch only one
tone at a time and during modulation from a received station it will
sometimes drop in and out (the tone appearing briefly) as the autonotch "hunts" for the strongest spectral component and briefly mistaking the speech for a tone.
- "How do I engage a noise blanker, noise reduction or other whizz-bang feature like that on the WebSDR?"
- Common types of noise reduction work best on periodic
noise such as the "buzz" of a powerline but works less-well on the
"white" noise of a quiet band where signals are simply weak and really
doesn't work at all when signals overlap. In an ideal situation,
a WebSDR uses a quiet receive site so that the majority of the noise
that it receives is "white" noise - so a noise reduction system would arguably be less effective.
- Having said that, there is an "impulse" type noise blanker that is always active on this WebSDR (configurable by the sysops, but not the user) to deal with the occasional power line noise that pops up: We're working with the power company to mitigate this.
This noise blanker also helps to take some of the "edge" off
strong static crashes/pops so that the AGC recovery can be
somewhat quicker so that a user will lose fewer syllables.
about a noise reduction? At this time, there is no additional
noise reduction feature available on this WebSDR - mostly because
adding this would increase the processor loading and reduce the number
of simultaneous users/bands that could be supported. It is
possible to route the audio that you are receiving through a noise reduction program that is on your
computer: In short, one uses a program such as "Virtual Audio
Cable" to route the audio to a program like "MMDSP" and then to your
speaker - although a cable from the output of one sound card and into another sound card (on the same or different computer)
can work in a pinch. There are articles on the Internet on how to
do this - and it is admittedly awkward, but it does work.
- "Some WebSDRs have a 'chat' function, but not this WebSDR - why is that?"
- Past experience by other WebSDR operators have shown that while
the "chat" function can be well used, a small number of people
tend to use it as a platform for abuse: Such is the nature of the
- Seriously, have you actually met people!?! Are you surprised about this??? Really?!?
Computer and usability issues:
- "I've been using the Chrome browser for a while and there's suddenly no audio (or some gaw-dawful noise) on the WebSDR? What's the deal?"
- Is your computer's audio - or the tab in Chrome - muted? Go to another web site that you know has audio (such as YouTube) to make sure that it works there.
- Google made changes to Chrome in April, 2018 that may have
disabled audio playback, but we have a web page just for this situation
- read more by going to the "Fixing Chrome" page.
- If you wish to use Chrome with your mobile device (phone, tablet) I strongly suggest that you, too, read the "Fixing Chrome" page!
- In early September 2018 a new version of Chrome was released
that seems to have comptability issues with the way the audio is
handled by the WebSDR, causing very loud white noise - either when you
first go to the WebSDR page or after having been there a while.
- Toggling the "mute" button below the WebSDR's volume slider
often "fixes" this - but it may only be temporary, if it works at all.
- If you have this problem, it's strongly recommended that you use another browser: The Firefox browser has thusfar been very reliable and robust when used with the WebSDR and is recommended.
- "I'm using my
computer/phone/tablet/piece of slate and the web page seems to load,
but I never hear any audio and/or see the waterfall. What's the
- The first thing to check is to see if you have an seriously
out-of-date browser and/or computer. There are some functions in
the code embedded into the web page that require "new-ish" browsers (e.g. newer than about 2014-2015, maybe...)
- Your computer/browser may be blocking scripts: The audio
be able to run for either to work. This could be a browser
setting or something in your device - perhaps a security setting - that
blocks such things. This is most common when using a
company-owned (e.g. work) device.
- Your network may be blocking something. The Northern Utah
WebSDR can be accessed using either the standard HTTP port 80, or it
could use its "normal" port 8901 - so it would be worth trying both (e.g. http:///websdr1.utahsdr.org:8901 or just http:///websdr1.utahsdr.org).
Your network's security infrastructure could be "inspecting"
packets and not like the audio and/or waterfall data that is being sent
and/or the data sent from your device to control the WebSDR for things
like frequency, mode, waterfall settings, etc.
- There are some instances where, for no
obvious reason that can be fathomed, it just "ain't gonna work" - at
least not without getting a networking nerd involved.
waterfall/words on the page take up only a small portion of my giant
monitor and/or it's all too small for my eyes and I want to make
everything bigger - how do I do this?"
- Many browsers have a "magnify" feature that allows one to
"embiggen" a web page and everything on it. On most browsers this
is done by pressing and holding the "ctrl" and then hitting "+" (plus)
key. For this you can use the "+" key on your numerical keypad,
or you can use the "+" key that shares the "=" (equals)
key next to the backspace - but that one will require that you hit
"shift" as well to access the "+". To reduce the size, use the
"ctrl" and "-" (minus) keys in the same way, or, on many browsers, you can use "ctrl" and "0" (the number zero)
to reset back to normal.
- Most modern browsers will associate this
setting to a particular web site and its pages and leave the other
web pages as they were so "embiggening" the WebSDR page won't cause all other pages to be embiggened in the same way.
often use a WebSDR when on a round table or net - but it's a pain to
mute the WebSDR when I transmit to avoid being driven crazier by the echo. Is there another way?"
- The most obvious way to mute the receiver is with the "Mute"
button near the volume control on the WebSDR. If you click this,
it actually stops the audio at the WebSDR, reducing its processor load
and network bandwidth. While this is preferred as it saves
bandwidth, there are other ways to quickly mute the audio:
- Many "multimedia" keyboards have a button on them - usually
along the top row - that, when pressed, will toggle the speaker audio on
and off. These buttons/keys often have a symbol that looks like a speaker with a diagonal line through it.
- Some newer browsers (recent versions of Chrome and Firefox)
have, in their tab along the top of the screen, a very small speaker
icon when they are at a site that has embedded audio. You can
click on that speaker icon on the tab to mute the audio, at which point
the icon will switch to a speaker with a diagonal line through it - but remember that you muted it that way when you want to hear the audio again!
Muting using this tab may be more convenient since the speaker
icon can be visible even if you have hidden the window with the WebSDR.
- On your computer/operating system it may be possible set up a shortcut or "hot" key to mute/un-mute the audio.
- Turn down/off your computer speaker.
- Rig some sort of relay keyed by your rig's PTT output that mutes your computer speaker(s). For a brief article describing one way in which this may be done, click here.
- "People report that they hear an echo on my signal, even though I turn down my speaker. What's the deal?"
- Of course, if you are transmitting and your computer is on the WebSDR and you can hear your own signal, some of the audio from your computer will make its way into your microphone - and it will
be heard, even if the volume is quite low: You should either mute
your audio completely, or wear headphones - although audio can "leak"
out of many headphones and still be heard because the microphone will
probably be near your head!
- If you have connected your rig to your computer to run "sound
card" modes like FT-8, RTTY, SSTV, JT-9 or many others it may be that
your "speaker output" is always
getting to your radio. Some radios (possibly including the Elecraft K3) seem to pass some of this audio
through, even when one is not in a "digital" mode which means that if
you are listening to a WebSDR, your computer audio may be getting into your rig directly and then being transmitted.
- The best way to avoid this - and to avoid other issues (such as transmitting email notifications, system sounds - or music) over the air is to use a separate sound card that is dedicated ONLY to
digital mods: This "other" sound card could be another device
plugged into your computer's internal expansion bus, or it could be a
USB device such as an
external sound card or a rig interface such as a SignaLink.
- By not
having computer system audio being sent to that "other" sound card you
won't get that echo or be embarrassed when your computer's audio gets
blasted across the 20 meter FT-8 sub band. It happens all of the time to others - don't let it happen to you!
- "I've noticed that if I listen
for a while, it suddenly stops with some sort of screen that talks
about a time-out. What's with that?"
- If you tune in a frequency on the WebSDR and then leave everything alone, the system will time you out after a while -
see the notice near the top of the web page on each server to find out
what the time-out might be - but it will be 90 minutes or more.
- Why do this? Experience has shown that some users may
forget that their WebSDR window is open and an even smaller number
would simply run it all of the time if they could, taking up bandwidth
and a "user" slot all of the time. Making it time out after a
reasonable period prevents anyone from permanently "squatting" on the
- If you do anything that proves to the system that you are still alive (change frequency, mode, band, volume, etc.)
this timer will reset, so it only affects users that might "set it and
forget it". Any of these time-out timers are at least 90 minutes (if not more)
and this should be enough time to sit through a net. If you are
in an hours-long round-table you will probably want to get into the
habit of occasionally changing something on the WebSDR like the waterfall width or adjusting the volume.
"Why is it this way?":
- "If I zoom in tightly on the location of the Northern Utah WebSDR on the map on the bottom of the page at the WebSDR.org web site
I see that there are several different WebSDRs, each in a different
location on the map, very close to each other. What's the deal?"
- This map uses the "grid square" information to show the
locations of the WebSDRs, but since the servers at the Northern Utah
WebSDR are all in the same place, only one of those markers would
appear - and which server, exactly, showed up on the map seemed to be
entirely random. To spread them out, only the "Yellow" WebSDR's
location is correct, with the other WebSDR(s) being one "sub-grid" off
from that of the main server.
- While zoomed out, you will still see only
one WebSDR on the map, but you will see all of them if you zoom in far enough..
- "What's the deal with 'high performance receivers'? Are there 'low performance' receivers?"
- There are two classes of receivers on the Northern Utah WebSDR:
The "High Performance" receivers that are relatively
narrow-banded (96 or 192 kHz wide) that use high-performance sound cards and QSD (Quadrature Sampling Detector)
mixers that can handle both weak and strong signals at the same time as
they use the same sort of hardware found in high-performance HF rigs.
- Those that are not "high performance" receiver use inexpensive
"RTL-SDR" dongles. The dongles are attractive in that they are
very cheap ($4-$80, depending on features - the ones we use are $20 each)
and can cover up to about 2 MHz of spectrum at once - but this comes at
a cost in performance: They have only 8 bit A/D converters which
means that if you adjust them to receive weak signals, strong signals
will badly overload them while adjusting for strong signals means that
it's likely that they won't hear weak ones. With proper filtering
and precise level adjustment one can get closer to a happy medium, but
their use is inevitably a trade-off. It's because they are so
cheap and relatively broad banded that they are an attractive way to get
"some" coverage over large frequency ranges with generally-acceptable
performance. In several cases, even though we could cover 2 MHz of bandwidth, we only cover 1 or 1.5 MHz - as in the case of the
31M-30M and the 15M-13M bands. This was done because there wasn't
anything of particular interest immediately outside this
frequency range, the receivers work slightly better with reduced coverage - and running them at less than 2 MHz bandwidth reduces processor loading.
- "Why do I hear signals belonging to hams outside some of the ham bands? Are they actually transmitting there?"
- This is a spurious (image)
response due to the way sound cards work. For example, at a
sampling rate of 192 kHz the highest frequency that can be accurately
represented is half this - 96 kHz at the Nyquist limit.
Frequencies above this will "wrap around" and move down, away
from 96 kHz. The sound cards contain low-pass filters that help
prevent this, but they aren't perfect "brick wall" which means that
they will respond increasingly weakly at the input frequency goes above
the Nyquist limit - but they aren't completely gone. To work
around this adjacent bands have a bit of overlap so that one can get
away from this response.
- Examples of this spurious response are
on 20 meters where a strong signal on, say, 14190 may also appear
around 14000 - 192 kHz below. In radios that use sound cards as
their input devices (e.g. most modern Elecraft transceivers)
this is avoided by only "looking" at signals that are well away from
the "edges" of the input bandwidth response where the Nyquist filter's
attenuation is stronger.
- "Why is 160 meters covered on two separate receivers?"
- You may have noticed that there is not only
receiver marked as "160M", but another, "lower performance" receiver
marked "AM-160M-120M" that also
includes the 160 meter band. When the Northern Utah WebSDR was
originally put online there wasn't enough equipment on-hand to cover
more than the bottom 96 kHz or so of the 160 meter band and the
remainder of the band had to be covered by the lower-performance
- Since then, we've updated the system to include the bottom
192 kHz of the 160 meter band, so it's almost completely covered, but
we still cover it with the other receiver - which also includes the
120 meter "tropical" shortwave broadcasting band and 2.5 MHz WWV/H.
Anyway, Murphy's law says that if you really
need to listen to something on 160 meters, it will be in that top 8 kHz
or so that the "main" 160 meter band isn't covering. Originally
the 630 meter band was covered with a band marked "630M-AM-160M" but a
dedicated 630 meter receiver has been installed that offers superior
performance over the
incidental coverage that had been available on on the "630M-AM-160M"
- "What's the difference between '75' and '80' meters - isn't that the same band?"
- Both "75" and "80" meters refer to the 3.5-4.0 MHz amateur band - and
the reference is somewhat historical: Decades ago, only the upper
half (or so) of the band was available for phone operation (in the U.S.)
and if one does the math, the top end of the band - 4.0 MHz - comes out
at exactly 75 meters. The distinction was that "75 meters"
referred to the phone portion and "80 meters" referred to the CW
- More recently, phone operation for U.S. (Extra class) amateurs
has been extended to 3.6 MHz, well into territory that was once the
sole domain of CW and digital.
Although historical, the convention remains: "75" meters
usually refers to the phone portion and 80 meters to the CW and (now) digital portion.
- On this WebSDR the designation of "75 PH" ( for 75 meter phone)conveniently
takes advantage of this nomenclature referring to the top
portion and "80 CW"
being the bottom of the band - although this last segment also includes
the very bottom portion of the phone allocation while "80 PH" refers to
the middle of the band that once was mostly the domain of CW.
- "Why are there several servers rather than all bands being on the same server?"
WebSDR software is designed to allow only up to 8 bands at once, so
additional bands must be hosted on another server. Using affordable
acquisition hardware (e.g. plug-in sound cards, various USB devices)
there are also definite, practical limiters on the number of these
devices that may be connected to one computer at once. Having
multiple servers also allows lower-performance (and less-expensive)
computer hardware to be used. As it turns out, we have access to
a large number of PCs of modest computing power for free, so we are inclined to
"Why don't you support (put a mode or feature here)?":
- "The WebSDR's receivers/antenna would be awesome for a (Skimmer, WSPR receiver, other cool thing) - why don't you do that?"
- It took a lot of effort to get the current suite of receivers
up and running - and there's still a bit of work to do before we really
consider adding lots more bells and whistles. Having said that,
we are keeping an eye on ways to interface with other programs/devices
to allow future integration of things like CW skimmers, propagation
analysis tools and the like - and the system was designed from the
outset to allow this.
- One thing that we'd like to be able to leverage is the fact
that we already have, for many of the amateur bands, "raw audio" of 96
or 192 kHz bandwidth that could be sent over the local network to
another server for such processing, independent of the existing
receivers - but this will take a bit of research and work to set up.
Whatever we do, we don't want it to have an adverse impact on the
existing system. Having said this, there are many "hooks" in the
system that could allow separate receivers to be implemented.
- There is
a totally independent WSPR decoder/monitoring receive system on site.
Presently, it has been configured to monitor the 630 and 160
meter bands (plus a few others), reporting with the callsigns "KA7OEI-1" and "KA7OEI-2". It is
possible that this may include other bands sometime in the future, but
this will depend on the available resources.
- "Can I use the WebSDR to receive digital modes like FT-8 or WSPR?"
- Because of resource and complexity limitations, the WebSDR currently has no built-in decoder for these modes, but it is
possible for you to route the audio that you are getting from the
WebSDR into a program that does the decoding. As with the noise
reduction mentioned above, it would be necessary for you to somehow
"pipe" your receive audio into the decoding program - with with a
program like "Virtual Audio Cable" or with a hard cable.
issue is that because of the nature of the Internet and the way your
computer processes sound, there may be occasional drop-outs and/or
changes in the delay between when the signal hits the WebSDR's antenna
and it comes out of your computer: While this may be an annoyance
on modes like CW or PSK31 where characters can be occasionally missed, this change
in timing can completely mess up the reception of WSPR, JT-9 and FT-8
transmissions, either degrading them or completely wrecking their
- Finally, remember that any mode that requires
tight clock synchronization (like WSPR, FT-8, JT-9, etc.) can also be affected if the overall delay across the network and in your computer is too great.
- "Why don't you cover from 0-30 MHz all in one swath?"
- This is a bit of a technical challenge to accomplish, requiring what is still exotic hardware (very fast A/D converter, a very fast processor platform such as a multi-core graphics card or dedicated hardware like an FPGA) and
without a "front end" using a GPU or FPGA this task is arguably beyond
the capability of almost any multi-core, multi-GHz computer that is
currently available. Such
hardware, while commercially available, is still quite expensive - as
in the thousands of dollars. Because of this, the support by the
WebSDR program is largely for acquisition methods that use relatively
inexpensive, consumer-grade, off-the-shelf hardware like sound cards or RTL-SDR dongles.
are less-expensive devices - such as the KiwiSDR that can
cover 0-30 MHz that FPGAs for their "heavy lifting" but these can
only support a handful of users at once. There are two of these receivers on site - see the KiwiSDR portion of this FAQ for more information.
- Finally, any RF
acquisition system that "inhales" the entire band from 0-30 MHz all at
once - even if it uses a 16 bit A/D converter (most don't!) - can have significant
issues related to signal dynamics: If it is adjusted to "hear"
the weakest (sub-microvolt) signals,
it will likely overload on stronger signals elsewhere in the
RF spectrum. In the case of a "direct sampling" radio like the
Icom IC-7300 or IC-7610 they get around this by having filters
that lets only a
small "window" of spectrum through at once along with dynamic gain
control: Neither of these may be done if you have many users at
random frequencies scattered across the entire HF
- "How about more bands. I want more bands!"
- The first priority was to support the "lower" bands such
and 40 meters as they are the most popular and useful on a WebSDR
system. In these days of lower sunspot activity the higher
bands (20, 17, 15, 12, 10 meters)
are hit and miss - particularly toward the 10 meter end of the spectrum - and as such,
the "lower" of these higher-frequency bands are being added first,
based on time, resources, and, to a lesser degree, the likelihood of
being open. As noted below, this system is entirely supported by
volunteers so there is a limit on time and expense that may be borne.
System quirks and a few random things:
- "Why do I keep hearing WWV/H in several places on the "60-49M" receiver?"
- This receiver uses an inexpensive "RTL-SDR" dongle which, with only 8 bits of A/D has rather limited dynamic range (in the 40-50dB range) making it prone to overload on very strong signals. The "WWV" problem, interestingly is not due to overload, but because there is too little RF
getting to the receiver input. For example, with just 8 bits
of A/D, one can have signals of +/- 127 or so - but during the daytime
when the band is quiet the A/D converter is only "tickling" A/D
readings of +/-2 to +/-4, which is equivalent of having an A/D
converter with only 2-3 bits!
The result of this is distortion, which is why
WWV is appearing in several places. The only reason that it isn't
worse than it is is due to the fact that the post-A/D sample rate is
2048ksps so the effective A/D resolution is improved due to
oversampling and the presence of noise - but this can only go so far to
help the situation.
- The work-around (aside from getting a "better" receiver)
would be to increase the antenna RF into the receiver a bit - but this
is a delicate balance: Too much signal and the receiver overloads -
so the proper balance that will suit widely varying signal conditions is
difficult to find on a receiver with dynamic range issues.
- Interestingly, it takes quite a bit A/D clipping (e.g. hitting full scale)
to have a significant effect on overall performance so it's a bit
better to put a little bit of excess signal into a receiver like this than it
is to put too little. Finding the best balance between
"underload" and "overload" takes a bit of ongoing work,
experimentation and continuing vigilance.
- "Why do the 31-30M, 25M or 19M receivers work fine at times and not others?"
the "60-49M" receiver, these use RTL-SDR dongles - with limited dynamic
range. At the time of installation the RF input level was adjusted on
a "best guess" basis - but we figured that experience would soon show
us if this setting was too high or too low. Clearly, there are times, for example,
when the 31M shortwave broadcast band is filled with high-power
broadcast signals that the setting was "too high." In time we'll do
further analysis and tweaking - and if there is enough interest,
possibly implement a separate, high-performance receiver just for the
30 meter amateur band.
- "What are those (faint) lines that I see on 160 and 80/75 meters during the day?"
- During daylight hours the 160 and 80/75 meter bands can be
extremely quiet which means that very low-level signals can start to
appear. On these bands some lines - usually faint - often show up
and these are due to intermodulation products of AM broadcast stations.
This effect is likely due to nonlinear junctions that intercept
the energy, mix together and then re-radiate and this could be from
long runs of rusty and/or corroded metal such as runs of barbed-wire
fence (of which there is a lot near the antenna!) or imperfect connections on the antenna itself and/or its supporting structure.
- At night these signals tend to disappear, probably due to a
combination of many of the AM broadcast stations that run 50kW during
the day lowering their power at night, but more likely due to the fact
that these bands get much noisier at night owing the reduction of
ionospheric absorption, the greater number of signals and the fact that
noise from all over can be more easily propagated to the receive
- "Where is 'Yooo-Tah' anyway?"
'dunno - it's somewhere west of Denver and northeast of Los Angeles. I
think that there's a big lake, a lot of seagulls, and some strange people that live
there that make it hard to find good beer. Oh, there are mountains, too...
- "I read about this site in Utah - you are using the large, steerable antenna there, right?"
- There are two antennas on this site: A large log-periodic
beam antenna and a larger, omnidirectional wire antenna on a taller
tower that is not as easily seen, either from the highway or via Google
Earth - and we are using the wire antenna. The log-periodic beam
is not being used: It is pointed due East and it is not
steerable - and it never was. Owing to issues with this antenna
and its tower, there are no current plans to use this antenna with the
WebSDR - but who knows what will happen in the future?
- "Why are signals on the 2 meter receivers on the weak side?"
- If you have listened much on the 2 meter receivers you might
notice that signals "seem" a bit weak - and they are, and there are
several reasons for this:
- Most of the "busy" repeaters are in the Salt Lake City area,
70-80 miles away. That, alone, will cause the signals to be
weaker than you'd expect for "local" signals.
- The WebSDR site is only a few 10s of feet above the level of
the Great Salt Lake, a vast area of brine and mud. As such, the
signals from afar - even though many of them originate from mountains
that are about a mile (1.6km)
above the lake, propagate on a very shallow angle above the ground
which puts them squarely in a fairly strong "Fresnel Zone" where ground
reflections can strongly affect signals. The same signals, if
received from the top of nearby hills, will be 10-15dB (about 2 S-units) stronger.
- To combat this a 5 element Yagi, pointed in the general
direction of Salt Lake City, is used for reception. To further
help, the receivers (RTL-SDR dongles)
are preceded with a bandpass filter and preamplifier before splitting
which helps, but there's only so much that one can really do!
- "Is the 6 meter receiver deaf or something - and what are all of those lines?"
- Yes and no. The 6 meter antenna, a full-sized J-pole at
the building, receives a bit of noise from the computers within and the
nearby power lines without, but the receiver itself can pretty easily
"see" that noise floor, so additional receiver sensitivity wouldn't
- Remember that 6 meters isn't usually open. In order to
hear signals on that band one will have to hope for Sporadic-E
propagation or some other type of event that will "open" the band.
Sporadic-E is somewhat seasonal and generally unaffected by solar
activity or the lake of it. It is most likely to occur in
May-June and to a lesser extent, late December and early January.
During periods of low sunspot activity it often "seems" as though
there are fewer Sporadic-E openings, but with fewer people using the higher bands (10-15 meters) and the curtailment of analog TV in North America (which removed useful signals that could indicate propagation) the activity may be lower. To be sure, some 6 meter propagation is strongly correlated to sunspot activity and being at a low point in the 11 year cycle doesn't really help.
- If you want to use the WebSDR to check for signals on 6 meters
it's recommended that you listen/look at the CW beacon portion of the
band (50.06-50.08 MHz) and in the area where FT-8 and other digital modes are active (50.293 MHz USB for WSPR, 50.313 MHz USB for FT-8).
- Those lines? We think that these are from all of the
computers located in the building. At some point we may try to
relocate the 6 meter antenna which should reduce the power line noise
and the weak spurious signals from the computers.
KiwiSDRs at this site:
Important: Please use the WebSDR and not the Kiwis on frequencies/bands that are already covered by the WebSDR for casual use. Read on to find out why.
See also the KiwiSDR FAQ - link
- "I should be using those Kiwis instead of the 'old' WebSDR, right?"
- NO! Please continue using the WebSDR system (rather than the KiwiSDR) for the frequency ranges that it covers.
- If you are listening on the amateur bands using modes that are covered by the WebSDR, please use the WebSDR instead!
- The WebSDR takes less bandwidth on your Internet connection and lower
processing power on your computer - plus it is known to work on many
different operating systems such as Windows, MAC and Linux - plus it
will also work on most portable devices, Android or iPhone.
- The KiwiSDR will probably never
work properly on many mobile devices, owing both to the vagaries of
what is supported by those platforms and the typically-small screen that
makes the design of a useful user interface difficult.
- It will likely never support the Internet Explorer browser - sorry.
- "If KiwiSDRs are so wonderful, why not use those instead?"
- As it happens, the "high performance" receivers at the WebSDR are more capable (in terms of signal-handling capability, overall sensitivity, etc.)
than the Kiwis because they have 16 bit analog-digital conversion with
strong filtering over a rather narrow frequency range. In
contrast, the KiwiSDR units have only only 14 bits of A/D conversion and
it's being hit with the entire spectrum from 0-30 MHz, more or less.
The lower bit depth and wider frequency input if the Kiwis tends to reduce its
performance - often in subtle ways, particularly in the presence of
other strong signals (including noise) that can (often) subtly mask the desired signals.
- The KiwiSDRs can handle far fewer
users. Originally, they were able to handle just 4 users, each
user getting a waterfall display, but latter versions of the software
have introduced an "8 user" version, with the trade-off that only the
first two users get a full-spectrum waterfall. In comparison, the WebSDR systems can handle at least 60 users each - probably more!
- "Are there other KiwiSDRs out there?"
- Yes, there are - go to sdr.hu to find a list of publicly-accessible KiwiSDRs.
- "I hear tell about these other receiver things at this site - what are those?"
- You are probably talking about the "KiwiSDRs" that are
co-located at this site. These are WebSDR-type receivers that are
capable of tuning from 0 through 30 MHz and able to receive a wide
variety of modes, but one should continue to use the "old" WebSDRs for the bands/modes supported by them.
- "I noticed that something is always hogging two or three user slots - why is that?"
- The KiwiSDRs have the ability to do their own WSPR decoding and
reporting, and that is what takes up these slots. These decoders
start up automatically when the Kiwi boots up and their slots are not available for general use.
- The automated WSPR decoders do not utilize any of the waterfalls that are available, so you don't have to worry about that.
- "The waterfalls seem a bit slow - what causes that?"
- The waterfall is a bit slower on these Kiwis than some others because:
- The internal communications rate between the FPGA (the main number crunching chip) and the computer had to be dropped from 48 Mbps to 24 Mbps to avoid causing (terrible!) interference to the 2 meter receivers at the WebSDR.
- At times, processor resources are being used to decode the WSPR signals, which also slows down the waterfall.
- In addition to the above, the more people that are using the
Kiwi, the slower the waterfall will get owing to less available
- "The Kiwi kicked me off/won't allow me to log in - why?"
- At present, the Kiwis will limit the duration of any single
listening period to 30 minutes and 90 minutes during any 24 hour
period. Because these receivers are a scarcer resource than the
WebSDR, there are stricter time limits on their use.
- If there are too many receivers already in use, it will give you a message saying so.
- Having said that, there are two Kiwis on site and if the first one is "full", it should forward you to the next one automatically.
- "I tuned below the AM broadcast band and don't hear squat. I thought you said that it would go down to 0 Hz?"
- While the receiver can go down to nearly zero Hz (more like 5-10 kHz, actually)
there's no guarantee that the antenna will! On the Northern Utah
WebSDR the antenna being used is designed for the 3-30 MHz range and
while it works for receive below this, it pretty much runs "out of
steam" by the time one gets to 300 kHz or so. Very strong signals
(such as WWVB at 60 kHz) can be heard weakly, but it would be really strong with a proper antenna!
- At some point in the future a dedicated LF/VLF antenna may be incorporated into the system to allow the KiwiSDR to hear LF and VLF in addition to HF.
- "Why won't the stupid thing work with my browser?"
- As noted elsewhere, do not
expect these to work properly with any portable device like an Android
or an iPhone owing to the peculiar and changing needs of these devices:
It would take a lot of work for someone to constantly update
things to keep them working!
- It will not work with Internet Explorer - and probably never will for the same reasons as above.
- Modern, mainstream browsers should work such as Firefox, Chrome and (probably) Safari. If you have trouble, try one of those before you try something "different".
- If you have your security settings adjusted too high, certain parts of the browser may not work.
- "What other things will the KiwiSDR do?"
- Besides being able to tune all over the
place, the Kiwi can do things like decode RTTY, CW, FAX and WSPR - to
name but a few. The KiwiSDR FAQ has a bit more information on what the receiver can do.
The KiwiSDRs have many more features than can possibly be covered here - please read the KiwiSDR FAQ
at this web site as well as the KiwiSDR Quick start guide (link)
and follow some of the links within for more information than you probably want.
- 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