The db or decibels scale. This may depend somewhat on your hardware. The RTL2832 dongles have 2 different AGC settings. I wouldn't calibrate anything from this.

This is where peaks appear for the stronger signals. The red vertical line is the frequency I'm tuned to. You can tune to a peak by clicking on it. When you zoom this display in more the filter bandwidth will show up. You can't click within the filter bandwidth to change frequency, but you can click directly below in the waterfall.

The frequency cursor can be dragged from side to side and it will change the frequency. Hover over it and wait until you see a white rectangle attached to the cursor. Left click and drag.

This is the baseline and where small signals end up. The vertical height here can be adjusted with the RF Minimum slider below. With the AGC turned on the entire baseline will move up and down when there's a strong signal.

This little red arrow pointing left will move you down in frequency by whatever you've got the RF Sample Rate set to. When the RF scale is zoomed out it's a screen width, when it's zoomed in it's still the same frequency amount, so there'll be frequencies you can't get to that way. This and the right pointing arrow are good ways to look over big chunks of spectrum quickly. Ctrl-PageDown does the same thing.

The Frequency Scale, marked in KHz. If you hover your mouse over this you'll see a 4-pointed arrow, which is partly deceptive. Right-dragging left and right will change the Local Oscillator frequency and the frequency you're tuned to. Left dragging up and down will move the split between the spectrum and waterfall areas. You can't go 4 directions with 1 mouse button.

Notice that the tick marks are to the left side of the frequencies, not centered under them.

When you're zoomed in, dragging this just moves everything across the screen.

Timestamps: the time at which a signal change happened can be seen in the waterfall at this vertical level. A new time appears every few seconds. They're mostly 2 seconds apart, but sometimes 3. You can turn them off.

RF Waterfall. This shows a history of the peaks above in the spectrum area, scrolled vertically over time. In many frequency areas there are constant signals like from the computer or birdies that you'll want to ignore. Those appear as solid lines here. If somebody keys a transmitter and talks for a few seconds that will be a vertical dash here, so you might want to click on one. Repeaters are the exception since they're almost always keyed if a QSO is going on, so by looking you can't tell them from junk.

You can click here to set the frequency, even if the frequency you want is within the filter passband showing in the spectrum window. I've been looking for ways to fine tune, maybe this is it. Click on a signal in the spectrum window, that sets the center. Then zoom in with the RF display zoom slider, then after a few seconds click in the waterfall. It's hard to click accurately with a touchpad on a laptop. Ctrl-up/down arrow or the mouse wheel will fine tune also.

Right-pointing little red arrow: Moves you up in frequency roughly one screen width depending on the zoom factor. Ctrl-PageUp does the same thing.

This is the S meter. Click on the arc of the scale to set the squelch level to that level. You should see a little red line appear.

The AM button, selects amplitude (de)modulation. When you click this, or any mode besides FM, an AGC Threshold slider appears below.

The active button changes to yellow in the label and the green LED comes on.

ECSS: Exalted Carrier Selectable Sideband. I've seen the term before but I haven't figured out what it is really. A little like synchronous detection, I guess, had Wikipedia stumped. See these pages at Sherwood, Hard-core-dx.com, listenersguide.org.uk

I find it's nowhere near as nice as what I remember synchronous detection being like after trying it. It tunes up and down the band past the signal, refining its estimate of the exact frequency as it tunes, narrowing the error. Then it settles down to small deviations and gives you the option of listening to either or both sidebands It could be called AFC for AM.

It can be useful when there's a station crowding the one you want to listen to. Just select the ooposite sideband. If you narrow up the RF bandwidth you'll lose fidelity, but this lets you use the carrier and one sideband.

FM Button, which also enables the FM Bandwidth slider. Narrow band communications, medium bandwidth for 137 MHz weather satellites, broadband for FM broadcast, it's all on this button and the slider. No FM stereo though.

LSB (Lower Sideband). On the ham bands this is the norm for frequencies 40 meters and lower. Trying to use USB in a band with stations that are mostly LSB is like sitting at a crowded table if you're left-handed. Besides that, nobody will talk to you because they can't understand you.

It's really easy to understand the concept of SSB if you watch the spectra in an SDR program. A carrier shows as a single vertcal line. SSB transmssions will have one straight side (where carrier would be) and one one rough side due to modulation. USB and LSB differ in which side the rough edge is on. AM has 2 rough sides with a carrier in the middle. FM is a strange squirmy line in the waterfall. DRM is 4.5 - 10 KHz wide with a flat level top.

USB (Upper Sideband). Used in the 20 meter ham bands and higher, also for maritime WEFAX. Upper sideband is mostly the default sideband mode for non-hams.

CW button. Everybody knows what CW is right? Anyone who struggled for months to get their morse code speed up to 5 WPM isn't likely to forget. CW is carrier wave or continuous wave depending who you ask. Morse Code.

DRM Button. Digital Radio Mondiale. When you tune across some awful racket on the HF bands, it's possibly DRM. Some shortwave broadcasters are starting to use it. It's digitally encoded audio that has almost CD quality when it's decoded. Hams also use DRM to send digital voice and pictures.

After trying it, I find HDSDR doesn't actually have a DRM decoder built into it, which is a bit of a dissapointment considering the source code is freely available. Must be that was just one too many things to cram in, which most people might not be interested in. I got a copy of Dream for Windows and I was able to get Radio New Zealand once so far.

Local Oscillator A. SDRs work like a conventional superhetrodyne radio in that there's an oscillator running at some frequency near the frequency you want to tune. Think of that as the center of the range, and with some SDR software under some conditions there's always a signal right in the center of the range. Ignore it, that's the local oscillator. Actually they're more like Direct Conversion, but the local oscillator concept is the same.

The RF sampling rate determines how much frequency spectrum you see either side of the local oscillator. A 2 MHz sampling rate will let you see 1 MHz on either side of the local oscillator. If you want to look at a narrow range, like most ham bands are, you can zoom in, which is sampling the whole range and throwing most of it away. Or you can lower the sampling rate using the Bandwidth button and probably reduce the cpu load and memory usage. In most cases cpu load affects power consumption, so a laptop on batteries will run longer on a charge.

If you click on the A at the right of the "LO" it changes to B and jumps to an independent pair of frequencies. Click again to come back. A can be using a different demodulation method than B. This is done in software, because even my $20 dongle does it, and I'm pretty sure there's only 1 oscillator in there.

The digits in the frequencies can be clicked too. A normal left click moves +1 in that position, right click moves -1. Carrying and borrowing works, so 19 +1 becomes 20.

Another way to change frequency is just type any numerical digit which brings up a dialog box. Or use Ctrl-up/down arrow.

Tune frequency. This is the frequency you're actually listening to, which has to be within the range set by the RF sampling rate and local oscillator, otherwise nothing happens when you click on a digit. Changing frequency by clicking in the top 2 windows or typing in a frequency will show the result here. Changing a digit or clicking won't move the local oscillator, typing in a frequency will if needed.

The Volume slider does what you'd expect, nothing tricky here, except it seems to affect the sound level fed out to other applications. If you're running Fldigi, EasyPal, Dream, etc. from HDSDR's output this will have an effect. It will possibly need to run higher than you might like, but if you poke around in your Windows settings you'll probably find "Speaker Volume" where you can make it not so lound in the room. You'll need to turn it back up for normal listening.

An AGC Threshold slider shows up here in every mode except FM. There are several things that change depending on the context, this is one of them. "Higher gain for weaker signals" is what the tooltip says.

Soundcard Settings. This is covered below, and if you've only got one soundcard like on a laptop there isn't much you can change in it anyway. If you install Virtual Audio Cable that does show up here.

Bandwidth Settings. This is covered below, but it lets you choose input and output sampling rates. There are some strange linkages between things that seem at a lower level, like setting the RF sampling rate, RF gain, turning AGC on and off and a higher level like outside the ExtIo dialog.

General options. There's a lot of stuff in here, which I try to cover below. Many features are only accessible through this button. I got curious and looked: this is storing settings in the Windows registry. Nothing really wrong with that but I would prefer an easily editable unix style rc/ini file.

Full Screen button. This is even more full screen than simply maximizing the window. Sometimes it covers the task bar, sometimes not. Click it again to go back to normal. The screenshot above is full screen mode. Windows hint: Alt-print screen grabs an image of the current window into the clipboard, then bring up something like IrfanView, paste, and save. You can even paste into Word.

Stop button. This stops signal acquisition (CPU usage drops to 0) but leaves everything else alone. A few things will still work, like rearranging windows, moving sliders. When you click the Stop button it changes to a Start button.

Minimize will minimize the window, even from full screen mode. It leaves everything running. If you want to feed audio from HDSDR to another program like Fldigi or Wx2img, this lets you work with the other program. Of course you can also minimize and listen while you play Solitare or something.

The normal Windows minimize (-) does the same thing, but if you have HDSDR in full screen mode you won't see that.

Exit closes the program completely. Most settings are saved in the Windows Registry, and it should open up where you left it.

Record - records RF, the full input signal, by default. This makes huge files but you can tune around in the recordings later as if they were live. Most people will probably want to set this to "AF (demodulated audio)" in Options -> Recording Settings/Scheduler. The default place it saves to is "C:\Documents and Settings\username\My Documents\HDSDR" which you can change in the same dialog box. Recordings can be scheduled too, see below.

I don't see this as one of the options, but I found that rtl_fm makes time-lapse recordings by default. It only records when a signal's above the squelch level. This is useful because it leaves out silent periods, making it possible to log all activity on a frequency in a condensed form. I didn't experiment with this, HDSDR may do this too.

Play will prompt you for a wave or riff file to play. I didn't experiment with the types of wave files (sample rate, # of channels, integer/float, # of bits, endianess) in either record or play. I just assume it does "the right thing". If your recordings need to be in a certain format to suit another program you should practice first.

Pause pauses recording or playback of wave files, it deosn't affect RF. These buttons really just emulate a cassette recorder.

Stop record/playback, no effect on the RF side

Rewind, again comes under the category of cassette emulation. Jumps back to the beginning of a wav file that's playing.

Loop playback If you recorded something mysterious off the air and you want to listen to it over and over until you figure it out, or play it for a group of people over and over, this will do it. Or you can just loop your new favorite song over and over.

Reusable Slider. There's a slider here that is sometimes hidden, but it can be used for different purposes. The label on top changes according to what function is assigned to it at the moment. Among other things it can be FM Bandwidth, RF Gain, Noise Reduction adjust, RF Noise Blanker adjust, IF Noise Blanker adjust.

Several of the buttons to the left use this slider. When the button is active (lit up), right-click on it to bring up the slider if it isn't already. The slider-up state is remembered: if you have the slider up and de-activate the button the slider will disappear but re-appear when you activate the button again. Conversely, it doesn't always appear when the button is activated unless it was up before.

In FM mode, the slider is often used to set the FM bandwidth, which doesn't have a button. FM bandwidth was a bit of an afterthought, but you can also change it with the buttons in the output column after you click the Bandwidth button. A sampling rate of 96000 will set wideband (FM broadcast) FM for music. Set it back down to about 24000 for narrow communications FM or you'll find the volume level really low. Weather satellites in the 137 MHz range need a bandwidth somewhere in the middle.

To set the slider back to FM Bandwidth in FM mode after doing something else, click the FM button again.

NR (Noise Reduction) button, right-click to adjust.

All these buttons have a "lit up" effect when they're active. They can only be adjusted while they're active.

NB RF button, RF noise blanker, right-click to adjust.

NB IF button, IF noise blanker, right-click to adjust

RF Gain Adjust, uses the slider to the right of it. With the RTL2832, if Tuner AGC is turned on this can't do anythng. If the slider's showing FM Bandwidth, right-click on this button.

Mute Button. Mutes the audio, independent of the volume and squelch settings. Use this if you don't want to be bothered, period. This also kills the audio feed to other programs.

AGC OFF, Left-click to choose the next slower setting, right-click to speed up. AGC is always off in FM Mode.

Notch Filter "Click within the AF spectrum or waterfall display to set or remove notches.   Turn the mouse wheel to adjust notch bandwidth.   Right-click to clear all notches" Quoting the original tooltip.

Right-click on the button to clear notches.

CW Zap: Pitch Frequency Correction (CW Mode Only)

Automatic Frequency Control (CW Mode Only)

CW Peak Filter right-click to adjust (CW mode only)

Despread (CW Only)

Show lower audio display at full bandwidth (CW only)

Date and time (from system clock). Left-click toggles between UTC and local time.

CPU HDSDR: The percentage of the time that the CPU is busy running HDSDR.

CPU Total: The percentage of time that the CPU is busy with everything.

The right lower corner:

Set RF Waterfall Brightness. This does slightly more than that, it changes the mapping of signal intensities to positions in the color palette.

Set RF Spectrum Scaling. This will make the peaks in the spectrum window bigger, without making the window bigger.

59: Set RF Waterfall Contrast. Another way to mess with the color palette.

Set RF Waterfall Minimum Level. Moves the baseline up and down, useful if your noise level changes. I see this happen sometimes when changing antennas or if the AGC is reacting to a big nearby signal.

Set RF Display Zoom. This, in my opinion, is the most useful slider of all. Too bad it's kind of buried way over here. If you click on a signal that you see on the screen and you're not exactly where you intended to be (with a laptop touchpad that happens a lot), this will zoom in around the current frequency. Then next time the frequency is active click in the waterfall directly under it. If you need to you can do those steps over again. If the frequency turns out to be interesting, put it in Frequency Manager so it gets saved. If you save it you'll probably want to fine tune first so you save exactly the right frequency.

Set RF Display Resolution Bandwidth. This effectively sets the number of samples that are shown on the screen. Make this smalller to see finer detail, bigger to see less. The averaging to the right, the RF sample rate, and the zoom slider below are all related somehow.

Set the number of averaged FFT lines in the RF display. Under noisy conditions this might be useful. It blurs toegether (horizontally) the samples in the RF spectrum display window. Normal is about 2.

Set RF display speed. Turning this up makes the peaks update faster, but it also cuts down the amount of time a signal stays in the waterfall. Everything goes faster.

The db (decibels) scale for the audio spectrum window.

The audio spectrum window, similar to the RF one. This seems superfluous, and I'd like to be able to turn it and the audio waterfall off without turning off a lot else too. My CPU doesn't need to be updating these windows I don't use.

Drag this line to adjust the horizontal width of the AF spectrum and waterfall. This looks like it's probably a moving average line, but you can drag it to adjust the bandwidth. Drag it too far right and getting it back can be a challenge. I went to CW mode, clicked the CWFullBW button, back to FM, and I was just able to grab it. Almost made me reset everything. Some things do reset if you close the program and reopen it. At the bottom of Options -> Misc Options is the reset.

Dragging this line changes the RF bandwidth, at least in some modes. Thank you to ka2rrz for pointing this out.

There is a reset: F7 (Options) -> Misc Options -> Reset to factory Settings

Audio Frequency Scale. Hovering over this will give you the same 4-ended arrow as above. If you're zoomed in it works the way it does for the RF, otherwise it only adjusts the split between the windows on a right-drag.

To notch something out, turn on the notch filter, then click on the offending signal here.

Audio Frequency Waterfall. Works about the same as the RF one. Probably most useful if you're doing something related to audio frequency decoding like PSK31. You can spot whether somebody's using PL in here too.

Set AF Waterfall Brightness. Like above, it changes the way intensities map to the color palette.

Set AF Spectrum Scaling As with the RF one, it changes the spectrum window scaling, doesn't affect the waterfall.

Set AF Waterfall Contrast

Set AF Spectrum Minimum Level

Set AF Display Resolution Bandwidth

Set AF Display Zoom

Set AF Display # of Averaged Lines

Set AF Display Speed

Frequency Manager
Freq Manager

This is the Frequency Manager. Each of the 4 top buttons brings up a similar list. There's only one User list, but you can add (and delete) things in the other lists just the same way. I didn't experiment with populating the lists with lots of frequencies, but I assume there's no way to arrange the lists, like putting favorite frequencies into bands, which is OK really.

The EiBi button brings up a list of shortwave stations. You can go to the website http://www.eibispace.de and download 500k of listings, recently updated, in csv form. Close HDSDR, go to My Documents\HDSDR\CSV, and rename or delete the dummy eibi.csv. Rename the new one to eibi.csv and put it in place. Now open HDSDR, bring up Frequency Manager, and click on the EiBi button. You want BBC frequencies? (They don't target the US anymore) Type BBC in the filter box. Want to try DRM? Filter on digital. There are 10000 lines in the copy I grabbed. Don't expect them all to work though.

Notice that the pre-entered frequencies in both lists have the tune frequency set to the LO frequency, I'm not sure why. You won't hear much that way.

I was playing with 70ish MHz frequencies because here in the US we don't have a 4 meter ham band, but we do have a radio astronomy allocation of 73.0 - 74.6 MHz. I put the add-test-delete 70.250 into the ham bands list and I could delete it again with no problem, so I assume you can add to any of the lists. The Radio Bands list has shortwave broadcast band markings like 49, 41, 31 meters, while the Ham Bands list has 60, 40, 30 meters, etc.

The Filter box works like a Firefox filter box: if you type something in there only entries that match that string will show up. The descriptions, like my add-test-delete are what gets searched. Being right now a VHF/UHF user it's a little hard to imagine what using these on HF would be like. If you put in keywords like "police", "fire", etc, you could filter on those. I suppose you could put in SSTV or PSK31 frequencies, or nets you frequent. Only the first field gets filtered though.

When you bring up the frequency manager, the tune and LO frequencies and mode are all filled in on the bottom line from the main screen. You can edit those before saving, like if you know the frequency should really be on a 15 KHz boundary but you missed a little when you clicked. Fill in the description at the left side and save it by clicking "Add", it's easy to delete it again if you need to.

Double-clicking on a frequency in the list will set the frequency, LO frequency and mode to match quickly. If only it would scan...

Frequency Manager stores its data in csv (Comma Separated Value) files in a directory like:
    c:\Documents and Settings\username\My Documents\HDSDR\CSV\
replace "username" with your Windows logon username.

Oops, they're called csv files, but the actual separator is a semicolon (;). Other than that they look fairly standard. It should be trivial to import them into Access or maybe Excel. eibi.csv has a few commas, but not as field delimiters. If you've got a list of frequencies from something else and you're familiar with especially Access you should be able to put your data into this format. Take a look at the existing files first. The first line is the field names, the frequencies are in Hz.

The field positions and purposes within each line seem to be somewhat flexible. The EiBi file I got has fields different from the Ham Bands, Radio Bands, User files. They seem to be sorted by frequency from 16.4 KHz to 29.5 MHz. The EiBi file is a schedule, with a UTC column. But on second thought I wonder about that: there are "spy numbers" entries in there.

If you had one of the Fun Cube Pro+ dongles that did HF this would turn a modest laptop into an interesting shortwave radio.

You can't minimize the Frequency Manager, but it isn't modal: you can click beside it or drag it out of the way.

ExtIo Button

This is what the ExtIo dialog box looks like for my $20 NooElec dongle. Not a lot in there. The top 2 entries are grayed out, but they aren't if you click the Stop button first.

Here you have access to the 2 different AGCs in these dongles. If Tuner AGC is on, no manual RF gain setting is possible. Mine overloads a lot, but for the price I can't complain.

The frequency correction ppm is a value I had worked out before and also use with rtl_fm and SDR#. Too bad it's only integers. The Sample Rate is the RF sample rate which sets the width of the tuning range. Buffer Size I've never changed.

If you're on HF you can set this ppm value live. Tune in a WWV or other frequency standard station. Bring up the ExtIO and tweak the ppm until the peak lines up where it should. My dongle that's off by 102 ppm is off by 108 when I use my upconverter. Once it's set it's perfect the next day and stays there: no drift. Sometimes the exact frequency correction is between integer ppm values so I have to add a small offset if it's critical. According to ECSS on 15 MHz WWV I'm off 128 Hz.

Notice there's a (1) at the left of RTL2838UHID in the device list at the top. I think the list is populated by HDSDR looking through the ExtIo.dll files available, then using each one to probe for devices. If you have more than one type of SDR hardware, either of similar or different types, it should find it. I've got 2 of the same dongle and if I plug both in I can choose between them here.

If you've got 2 ExtIo files in your HDSDR directory you'll have to choose between them when the program starts up. If you want to try running 2 dongles at once you have to open 2 instances of HDSDR.

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