Tag Archives: Spectrum recording

Pre-Detection Recordings: Any in existence, declassified and accessible–?

Many thanks to SWLing Post contributor, Chip, who writes:

I remember reading a number of years ago that the NRO/NSA was the largest consumer of magnetic tape, utilized for pre-detection recordings of various spans of spectrum, all over the world.

I’m wondering if those tapes become declassified at some point, and if they are available through FOIA requests. Were they just bulk erased, destroyed or sold at GSA auction along the way.

Do you know if anyone has ever queried into their existence, and if they have been electronically preserved to some other digital medium?

The idea that our government records huge chunks of spectrum, fuels thoughts in my mind of huge spans of non-classified spectrum from across the years. All the DX shortwave outlets captured for posterity.

Thank you for sharing this note, Chip.

Of course, I’ve always been interested in adding recordings like this to the Radio Spectrum Archive. If these recordings exist, I would love to see them added to the Internet Archive–who stores Radio Spectrum Archive recordings– so that they could be shared and enjoyed by all.

Post readers: If you have any information on this, please comment!

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Spectrum recordings with the new Belka-DX and a Zoom H1 digital recorder

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

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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?

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Dan shares solar eclipse spectrum files

Solar Eclipse 2017: In the path of totality

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A portion of the PARI campus

Tomorrow, we will be experiencing a total solar eclipse here in the mountains of western North Carolina.

Instead of enjoying the eclipse at home, I will be volunteering as a docent at the Pisgah Astronomical Research Institute in Rosman, North Carolina. Post readers might recall PARI as it was the location of our 2015 PARI DXpedition.

One of PARI’s 26 meter radio telescopes.

PARI is expecting at least 1,000 visitors tomorrow, from a number of countries. Many are scientists, astronomers, and guests who want to be in the path of totality.

On the PARI campus, we will be in totality for about 1 minutes, 47 seconds.

What makes the event truly special for PARI is that this is the first time in history a world-class radio astronomy observatory has been in the path of totality. To say the PARI astronomers are excited is simply an understatement. All four of PARI’s telescopes will be trained on our local star and gathering copious amounts of data.

If you don’t live in the path of the Eclipse, I invite you to check out PARI’s YouTube channel where they will host a live stream:

Click here to watch on YouTube.

Gathering spectrum

I will also be gathering data of my own during the event.

I will remotely record the entire mediumwave (AM broadcast) band several hours before, during and after the eclipse. I will also set up a separate SDR to record either the 31/30 meter bands and my buddy, Vlado (N3CZ) is kindly using his SDRplay RSP1 to record from 6 MHz – 8 MHz.

What do I expect to see/hear in the spectrum recordings? Certainly a drop in noise. If I’m lucky, I also hope to hear some DX anomalies–hopefully a signal or two that I wouldn’t normally here in the middle of a summer day.

I don’t expect any dramatic results (though I would love to be proven otherwise!) since the ionosphere takes time to change states. My buddy Mike (K8RAT) likens it to an oven: it takes time for it to heat up to the desired temperature, and it takes time for it to cool down as well. I’m not so sure the shadow of the moon, which moves at a good clip, will be persistent enough to change the state of the ionosphere in any meaningful way.

If it does, I’ll be there to record it!

There are many other radio related experiments happening during the solar eclipse. A notable one that you can even help with is the 2017 Ham Radio Eclipse Experiment.

SWLing Post contributor, Dan Srebnick also suggests a few stations you might try catching on the AM broadcast band. Dan notes:

Something to do during the solar eclipse on Monday. There are 13 clear channel AM stations along the path of totality. Give a listen for them:
[LIST OF AM CLEAR CHANNEL STATIONS]
kHz CALL Location Eclipse UTC
—— ——- —————- ————–
650 WSM Nashville, TN 18:28
670 KBOI Boise, ID 17:27
750 WSB Atlanta, GA 18:36
840 WHAS Louisville, KY 18:27
880 KRVN Lexington, NE 17:57
1030 KTWO Casper, WY 17:43
1040 WHO DesMoines, IA 18:08
1110 KFAB Omaha, NE 18:04
1110 WBT Charlotte, NC 18:41
1120 KPNW Eugene, OR 17:17
1120 KMOX St. Louis, MO 18:18
1190 KEX Portland, OR 17:19
1510 WLAC Nashville, TN 18:28

Kudos to Bob WB4APR (of APRS fame) for producing this list.

Post readers: Will you be in the path of totality or do you plan to enjoy a partial eclipse? Have you ever experienced a total solar eclipse? What are your plans if any? Please comment!

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Propagation-Triggered Spectrum Recording

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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.

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

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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.

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