Tag Archives: SDR Spectrum Recordings

Shortwave Archives, Spectrum Archives and the Radio Preservation Task Force meeting

This week, I’m looking forward to participating in the three day Radio Preservation Task Force meeting in Washington, DC.

The Radio Preservation Task Force (RPTF), a project of the National Recording Preservation Board of the Library of Congress, will be held on November 2nd, 3rd, and 4th, 2017 at the Library of Congress, Woodrow Wilson International Center for Scholars, and the University of Maryland.

I’ve been invited to serve on the RPTF Material & Digital Curation panel where I’ll have an opportunity to talk about our work with the Shortwave Radio Audio Archive and a new project I’ve been working on: the Radio Spectrum Archive.

The Radio Spectrum Archive

For several years, I’ve been championing the concept of archiving radio spectrum recordings.

As many of you know, through the use of software defined radios (SDRs), we can record not just one individual broadcast from one radio station at a time, but we can record an entire broadcast band, all at once. Each recording can easily contain dozens of stations broadcasting simultaneously. Later, via an SDR app, recordings can be tuned and listened to as if they were live. We believe spectrum recordings will be valuable material for the future historian, anthropologist, enthusiast, etc.

Screen shot of the RSA homepage.

I’ve published a new website for the Radio Spectrum Archive and I encourage you to check it out as it outlines our mission, goals and challenges. I also include a video demonstration using a spectrum recording from 1986 (originally recorded on a HiFi VCR!).

Note that the website is a work in progress, there are still sections to add including bios of our spectrum archive team.

Click here to check out the Radio Spectrum Archive website.

Though I didn’t mention this in my Patreon campaign post earlier this week, the Radio Spectrum Archive is yet another important radio project you are supporting with your pledge. This week, for example, extra funds help me with travel expenses associated with the RPTF conference (many thanks to a kind friend who is hosting me at his home for four nights, saving me several hundred dollars!).

If you have the means and would like to support the SWLing Post, the Shortwave Radio Index, the Shortwave Radio Audio Archive, and the Radio Spectrum Archive please use the link/button below to become a Patron. If you’d like more details or support options, check out this recent post.

Become a Patron!

And to all of you who have supported us through Patreon and with one time gifts: thank you, thank you, thank you!

If you’re not in a position to become a patron or coffee fund supporter, no worries! Just enjoy our radio sites and resources!

One more note: Due to travels and a heavy workload over the next couple of weeks, please allow extra time for replies to correspondence and comments. Thank you so much!

SDR Spectrum to Radio: Can someone please make this device?

The venerable RF switch box from the 1970s/80s allowed game consoles and computers to use analog TVs as monitors.

As I’ve mentioned in the past, I actively record and index radio spectrum recordings via my various software defined receivers. Indeed, I have at least 50 TB of SDR spectrum recordings at the moment–and that number is growing!

I was just chatting with SWLing Post contributor, Mark Fahey, and a familiar topic came up: the idea of an RF switch box for radios.

The concept is a piece of hardware that re-modulates–converts digital spectrum data from a digital storage device back to analog RF– and injects a signal into a real tabletop radio.

As Mark described:

“This is just like early computers and Atari-like games consoles did to allow the “computer” to display on a lounge room TV. The games console tricked the TV into thinking it was tuned to a TV station on “Channel 1 (or whatever the console outputted the video to).”

Radio time travel machine!

How cool would it be to take a spectrum recording from 2008, play it through your Hallicrafters SX-100, Kenwood R-1000 or Alinco DX-R8T, and tune through the 31 meter band? You’d receive Radio Australia, Radio Bulgaria, Radio Netherlands Worldwide, Radio Canada International, Voice of Russia and many other broadcasters that are no longer on the air. Indeed, there’s a strong possibility you might uncover DX you didn’t catch when the recording was first made.

I’m enough of a radio geek to know that I would thoroughly enjoy travelling back in time once in a while with a classic radio.

Additionally, this device would make it much easier for museums to create kiosks where visitors could tune through recordings of, say, important events in history.

Can it be done?

I know the technology is out there.  In fact, if you’ve ever been to a large hamfest where Icom, Yaesu or Kenwood have a number of their transceivers “on the air”–so customers can try out transceiver features–they are using a device called a “radio time machine.”

Icom uses recorded IF instead of live antenna input so customers can experience “contest conditions” while evaluating a radio.

The Radio Time Machine injects recorded analog RF, from a HiFi VCR, into the antenna ports of a vendor’s various transceivers. The recordings are typically of a ham radio band during a contest–that way, the customer can get a sense of how well the rig would perform under crowded band conditions.

These devices have limitations: while their bandwidth is ample to tune through the CW or phone portion of a ham band, it’s much too narrow for most broadcast bands. They’re also fed the recording from an analog HiFi VCR.

The device Mark and I dream of would convert digital spectrum files–from a WinRadio, Perseus, Elad, SDRplay, Airspy or other SDR–into analog RF any radio with an external antenna port could tune.

SWLing Post readers: you’re a diverse and knowledgeable community–please comment if you know what it would take to develop such a device and how it could be done. Is this a dream or could it become reality?

Visualising shortwave band activity throughout the year

This article originally appeared on the London Shortwave blog.

24-hour shortwave spectrum image, showing activity for a single day in the first week of February 2017 (©PA3FWM, Twente WebSDR).

As many of my readers and followers will already know, these days I mostly enjoy listening to shortwave radio via the outdoor spectrum captures I make in my local park. Although I have built a system that helps me deal with urban radio interference at home, some of the weaker signals still can’t make it through the indoor noise. Since I have a limited amount of time for making outdoor trips, capturing entire portions of the spectrum allows me to record a lot of shortwave signals simultaneously, which I can then explore individually at a later time. However, these trips still need to be carefully planned because the time of the day and the time of the year both affect long-distance signal propagation, and do so differently depending on the frequency range. For example, signals on the 16 meter band are usually at their strongest during the daylight hours, whereas the 31 meter band is at its busiest around sunrise and sunset. Because my current portable recording set-up allows me to capture only 10% (3 MHz) of the shortwave spectrum at any one time, I decided to carry out a systematic exploration of activity on the shortwave bands to help me time my outings so as to capture as many signals as possible during each trip.

Capturing the shortwave spectrum out in the field with a portable SDR set-up.

Luckily, I didn’t need to make any of my own measurements for this. For over a year, the wide-band WebSDR at the University of Twente has allowed its users to see what the shortwave spectrum has looked like over the past 24 hours in a single image. More recently, however, the creator of the service, Pieter-Tjerk de Boer PA3FWM, has opened up his spectrum image archives, so it is now possible to see the past conditions of the bands on any single day in the last two years. Intrigued by how band activity changes depending on the time of the year, I created a timelapse animation of these images by taking two from each calendar week and lining them up in sequence. With Pieter-Tjerk’s kind permission, I share this animation below.

First, a really fast version to illustrate the broad effects the time of the year has on peak activity times across the bands:


 Click here to view on YouTube

The X axis represents the frequency and the Y axis is the time of day, starting at the top. Conventional wisdom about band behaviour can be easily confirmed by watching this video: the 60m, 49m and 41m bands are mostly active after dark, with the 60m and the 49m bands being generally busier during the winter months. The 31m band is most active around sunset, but carries on all night until a few hours after sunrise. The 25m band is active during sunrise and for a few hours afterwards, and around sunset during the winter months, but carries on all night during the summer. Peak activity on the 22m and 19m bands is also clustered bi-modally around the morning and the evening hours, though somewhat closer to the middle of the day than on the 31m and the 25m bands. The 16m band is mostly active during the daylight hours and the 13m band is quiet throughout the year except for the occasional ham contest.

It almost seems as though someone positioned in the middle of the image’s right edge (corresponding to noon UTC) is shining two flashlight beams on the bands in a V-shaped pattern, and is changing the angle of this pattern depending on the time of the year: wider in the summer and narrower in winter. Here’s a slower version of the animation that shows some finer week-on-week changes:


 Click here to view on YouTube

Thanks to this data being made freely available, visualising and understanding these dynamics will help me schedule my spectrum capture outings in the weeks and months ahead.

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.

Capturing spectrum and logging band openings last night

My 31 meter band spectrum display last night. Strong signals across the board.

Waterfall display of the 31 meter band last night.

Last night, band conditions were superb above 7 MHz. Both the 31 and 25 meter bands seemed crowded with stations; for a moment, it felt like a true solar peak.

This morning, solar flares have dampened down the excitement but I imagine conditions could favorably change at times this weekend, so stay tuned!

I recorded the entire 25M band for a couple of hours yesterday evening and a large portion of the 31 meter band throughout the night. Fortunately, I had just invested in another Western Digital Caviar Green 3 TB SATA drive, so there was ample space to make these (very) large recordings. I think this brings my overall spectrum storage up to 12 TB!?!

I love the fact that these SDR band captures will make for good listening sometime this winter when the sun isn’t being so cooperative. I liken it to radio time travel, but I believe David Goren (of shortwaveology.net) said it best in a comment he posted in “Confessions of an SDRaholic: when 4.5 terabytes is not enough“:

“My approach to recording SDR band captures is like assembling a collection of fine wines. I tend to record captures when there are unusual propagational openings…and while recording a whole swath of frequencies for an hour or so you can still tune around and make discoveries and even record them singly.. And then once the capture is done, you have it as long as you want to keep it.. So, on a static-y summers day I can go to the shelf and pull down “Ye Olde Auroral MW Opening 10/15/11? or “Hot Bolivian evening on 60 meters.” and I can make discoveries to my heart’s content. Since I can listen to an hour’s worth of each frequency it will take a long time to exhaust the potential of any particular capture, esp. with the ability to refilter and change. multiple parameters of reception.”

See? (I tell my wife) I’m simply building my collection of fine wines!

Below, you’ll find some of the stations I logged last night (actually, this morning in UTC).

Logs:

31 meter band beginning 00:00 UTC, 25 OCT 2014

  • 9410 BBC English Nakhon Sawan
  • 9420 ERT Open/VOG Greek
  • 9455 China National Radio 1 Chinese
  • 9470 AIR National Channel Hindi/English (vy wk)
  • 9475 WTWW English
  • 9510 China Radio International Russian
  • 9520 PBS Nei Menggu Chinese AND Radio Romania International Romanian
  • 9565 Radio Tupi/Super Radio Deus e Amor Portuguese (QRM from CRI 9570)
  • 9570 China Radio International English
  • 9586 Super Radio Deus e Amor Portuguese
  • 9590 China Radio International Spanish
  • 9630 Radio Aparecida Portuguese
  • 9645 Radio Bandeirantes Portuguese
  • 9660 Radio Taiwan International Chinese
  • 9665 China National Radio 5 Chinese or possibly KCBS Pyongyang Korean
  • 9690 All India Radio English
  • 9700 Radio Romania International English
  • 9705 All India Radio English
  • 9710 China Radio International Portuguese
  • 9730 Adventist World Radio Manumanaw Karen or possibly 9730 Myanmar Radio Burmese
  • 9740 BBC English (vy weak)
  • 9800 China Radio International Spanish
  • 9810 Radio Havana Cuba Spanish
  • 9820 Radio 9 de Julho Portuguese
  • 9855 Voice of America Tibetan
  • 9860 Voice of Islamic Rep. of Iran Spanish
  • 9870 AIR New Delhi Hindi
  • 9880 Voice of America Chinese (vy weak)
  • 9935 ERT Open, VOG Greek
  • 9965 Radio Cairo Arabic
  • 10000 WWV Ft. Collins

25 meter band beginning  0100 UTC, 25 OCT 2014

  • 11520 EWTN (WEWN) English
  • 11580 SOH Xi Wang Zhi Sheng Chinese/Cantonese
  • 11590 Radio Japan Hindi (vy weak)
  • 11620 China National Radio 5 Chinese
  • 11640 Radio Free Asia Uyghur
  • 11650 China Radio International Chinese
  • 11670 Radio Havana Cuba Spanish
  • 11695 Radio Free Asia Tibetan
  • 11710.7 Radio Cairo Spanish (transmitter noise)
  • 11760 Radio Havana Cuba Spanish
  • 11780 Radio Nacional da Brasilia Portuguese
  • 11825 Bro Stair
  • 11840 Radio Havana Cuba Spanish
  • 11855 Radio Aparecida Portuguese
  • 11870 EWTN (WEWN) Spanish
  • 11905 Sri Lanka BC English/Hindi
  • 11955 Radio Romania International French
  • 12020 VoA Deewa Radio Pashto
  • 12025 UNID
  • 12070 Radio Cairo Spanish (jammed or transmitter noise?)
  • 12105 WTWW Spanish