Tag Archives: Software Defined Radio

Propagation-Triggered Spectrum Recording

Many thanks to Jon Hudon of SDRplay who shared the following on the SDRplay Facebook page:

One of the SDRplay user community, Jukka, has started an interesting discussion on what he has called ‘propagation-triggered recording’ – he outlines the concept, and what he is doing, on our forum – see http://www.sdrplay.com/community/viewtopic.php?f=9&t=1839

The idea is that you monitor signals to determine if conditions are particularly good and can thereby trigger an I/Q recording of a whole band during that particular propagation high point -Jukka welcomes more comments on this idea.

Many thanks, Jon. I would certainly be a fan of this as so many times I’ve missed fantastic band openings while travelling. It would be nothing short of brilliant to come home to automatic SDR spectrum recordings taken during prime propagation. At the moment, propagation is so dismal, rare openings are worth recording!

As Jon points out above, check out the SDRplay forum for more details.

Cloud-SDR: a remote access system for a number of popular SDRs

Many thanks to SWLing Post reader, Sylvain (F4GKR), who writes:

I am Sylvain, from Cloud-SDR, a new company selling software to get remote access to your existing SDR receivers through the Internet.


  • currently supports : SDRPlay, Perseus, BladeRF and AirSpy. LimeSDR to come when received and tested.
  • client software is free (can be used as standard SDR receiving software with locally connected devices),
  • server software starts at 110 Euros, VAT may be added depending on customer location,
    easy to use

From the Cloud-SDR website:

The Cloud-SDR Concept

You need a way to remotely access your existing SDR receiver? To stream your IQ samples to another remote computer over the network?

Cloud-SDR is a commercial software solution to enable real time RF data sharing or processing through the cloud.

Cloud-SDR can collect real-time IQ complex samples from an SDR hardware device connected on one machine, stream the samples to a second machine for demodulation or analysis, then send the resulting stream to third machine for storage.

In standalone mode, Cloud-SDR can execute signal processing tasks described with embedded JavaScript DSP engine.

Because network bandwidth is limited compared to SDR receiving bandwidth, the core concept of Cloud-SDR is to move the processing along the cloud to where it is required or possible : the DSP chain is divided in sub-tasks that are spread between computers interconnected through Internet.

Very cool, Sylvain!

I like the fact your system supports popular affordable SDRs like the SDRplay RSP & AirSpy and that you can stream your IQ samples.

Click here to read more on the Cloud-SDR website.

Build a Raspberry Pi-powered SDR

Many thanks to SWLing Post contributor, Jeremy Clark (VE3PKC), who writes:

I have developed an SDR receiver that may be of interest to your readers. It can be used directly with the Raspberry Pi2B/3B. It comes in several versions DIP/SMD.

Check out this MP4 movie:

I have two eBooks which are basically design manuals for the DIP and SMD version of my SDR receiver. Each eBook has an Internet linked parts list, so that the reader can get their own parts to keep costs down. The DIP eBook is $7.90 CAD and the SMD book is $14.90 CAD.

Click here to view Jeremy’s website.

Thank you, Jeremy–this looks like a fascinating construction project!

Readers: just to be clear, Jeremy is selling eBooks detailing construction–not kits. He did mention if you’re interested in obtaining the PCB, he can sell this as well.

Medium wave SDR spectrum with over 20 transatlantic signals: a quick tour


Tour of a medium wave spectrum with over 20 transatlantic signals

Hi there, I thought some of the readers of SWLing Post might be interested in a review of a MW spectrum with multiple transatlantic signals – all with audio. This is one of the recordings I took with the 200 metre Beverage antenna and although I haven’t properly counted, I believe it generated about 50 catches that were either personal firsts or best-ever receptions. You will note that this video is nearly 20 minutes long, whilst the recording is only just over 5 minutes, thus to capture the signals listed below and demonstrate audio to you, it was necessary to effectively ‘rewind’ a few times. I haven’t annotated the video, however, the stations I’ve paused on to demonstrate audio are listed below. There are actually more catches in this spectrum, but hopefully the video will give you a good idea of propagation on the morning of 10/10/16 and the effectiveness of the Beverage/Elad FDM DUO combination. Also note, I didn’t have time to fully optimise the demodulation settings, so for example, I haven’t used AM SYNC in this demonstration. Individual videos of all catches, with optimised settings appear on my YouTube channel Oxford Shortwave Log. I hope you enjoy it! Recorded in Oxford UK on 10/10/16 at 02:00 hrs UTC. Thanks for watching and I wish you all great DX!

590 kHz VOCM Saint John’s
600 kHz CBNA Saint Anthony
620 kHz CKCM Grand Falls-Windsor
660 kHz WFAN New York
710 kHz WOR New York
730 kHz CKAK Montreal
750 kHz CBC Radio 1 Bonavista Bay
790 kHz WAXY (presumed)
800 kHz VOWR
970 kHz WBGG
1010 kHz CFRB Toronto
1030 kHz WBZ Boston
1130 kHz WBBR New York
1190 kHz WLIB New York
1280 WADO New York
1390 WEGP Presque Isle
1400 kHz CBC Radio 1 Gander
1440 kHz WRED Westbrook
1510 kHz WMEX Boston
1520 kHz WWKB Buffalo
1570 kHz XERF La Poderosa, Mexico
1580 kHz HJQT Verdad Radio 1580 kHz, Bogotá, Colombia
1610 kHz Caribbean Beacon, Anguilla
1660 kHz WGIT Puerto Rico

Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

Chris tracks down sources of radio noise


Many thanks to SWLing Post contributor, Chris Smolinski, who shares this guest post from his blog, RadioHobbyist.org:

Yet Another !&*%$! Noise Source

by Chris Smolinski

The past few days, I have noticed higher than usual noise levels, generally on the lower frequencies, and particularly on the longwave band, including the 285-325 kHz DGPS band, where I run nightly SDR recordings, to later process the data and decode and detect DX DGPS stations using my Amalgamated DGPS app.

Thinking back to what new electronics devices have been added to the house, two came to mind, a new cable modem, and a new ethernet switch. The switch is up here in the shack, so it seemed to be a likely candidate. The switch is a D-Link DES-1008E 8-Port 10/100 Unmanaged Desktop Switch. It uses a mini USB port for power, using either the included AC adapter, or power from a USB port. When I installed it, I decided to not use the AC adapter, but rather a USB port on my UPS, figuring it was better to not add yet another potentially noisy switching power supply to the mix.

The test was easy, I just unplugged the power to the switch. Sure enough, the noise vanished. Great, the switch is a RFI generator. Or is it? As another test, I plugged it into a port on a USB hub. No noise. Hmm… so it seems that the noise is indeed from the USB port on the UPS. I did not notice any increase in the noise floor when I got the UPS a few months ago, but It’s something I should look into again, just to be sure. The UPS is a CyberPower CP1350PFCLCD.

Here’s a waterfall from the SDR, showing the DGPS band, 280-330 kHz. You can see where I changed the power to the switch from the UPS USB port to the USB hub, the bottom part of the waterfall is when the switch was still powered by the UPS (click to enlarge it):


I still have a noise source just above 305 kHz to hunt down.


I decided to see what I could do to improve things, and reduce the noise floor.

Here is the baseline, after no longer powering the switch from the UPS:

First, I relocated the AFE822 away from the computer and rats nest of assorted cables behind it, powered from an HTC USB charger:

The squiggly noise around 305 kHz vanished!

I then switched to an Apple USB charger / power supply, as their products tend to be a bit better made:

Another improvement, the overall noise floor is a bit less now.

But can we do better? I then switched to an older USB hub for power to the AFE822, that I thought might be better filtered:

I then changed to a linear supply plugged directly into the AFE822. I don’t notice any obvious improvement? Maybe it even looks like a little more noise? Difficult to tell. You can see a DGPS station popped up on 304 kHz while I was switching things around, between the last two tests, it was likely Mequon, WI.


Thank you for sharing this, Chris! I find a wideband spectrum/waterfall to be such a useful tool for tracking down sources of noise. Not only can you “see” the noise, but you can measure its bandwidth and identify what portions of the dial it affects.

Follow Chris at RadioHobbyist.org.