Category Archives: AM

SDRplay announces the RSPduo: A 14-bit Dual Tuner SDR

(Source: SDRplay Press Release)

SDRplay announces the RSPduo – A 14-bit Dual Tuner SDR

Today at the Dayton Hamvention, SDRplay Limited is announcing the launch of a new Software Defined Radio product – the RSPduo.

The RSPduo is a radical new addition to the RSP line of SDR receivers from SDRplay. Architecturally, it is different from any previous RSP in that it features dual independent tuners, both piped through a single high-speed USB 2.0 interface.

The SDRplay RSPduo is a dual-tuner wideband full featured 14-bit SDR which covers the entire RF spectrum from 1kHz to 2GHz giving 10MHz of spectrum visibility. Initially using Windows based ‘SDRuno’ supplied by SDRplay, you can simultaneously monitor two completely separate 2MHz bands of spectrum anywhere between 1kHz and 2GHz.

Superficially the RSPduo looks identical to the highly popular RSP2pro and will be able to operate in a very similar way.

However, it also allows a completely new and exciting set of usage scenarios such as:

  1. Simultaneous monitoring of two widely spaced bands – e.g. 40m (HF) and 2m (VHF)
  2. Mixing and matching applications simultaneously – e.g. ADS-B and ATC scanning
  3. Phase and time coherent demodulation of two receivers

Scenario 3 is very difficult to achieve with two separate USB devices because of the uncertainty of USB latency. The RSPduo overcomes this limitation because all traffic goes through a single USB interface, thus enabling the possibility of the development of various types of diversity demodulation such as: spatial, frequency and polarisation which can bring
huge benefits in terms of improved performance.

Jon Hudson, Marketing Director at SDRplay commented:
“As well as adding a second independently controlled tuner, which in itself, offers a whole new set of exciting usage possibilities, the SDRduo features 14bit ADCs and a completely re-designed RF front end. These changes provide better RF selectivity and even more dynamic range, offering outstanding performance under extremely challenging reception conditions. The combination of performance and features makes the RSPduo our highest spec RSP yet and sets a new benchmark in the sub $300 SDR market”

Due to its exceptional combination of performance and price, the RSP family of receivers have become very popular and the RSPduo provides the next level of functionality for both amateur radio enthusiasts as well as the scientific, educational and industrial SDR community.

As well as being demonstrated at Hamvention, the RSPduo is available direct from SDRplay or via SDRplay’s network of channel partners and resellers

The RSPduo is expected to retail at approximately $279 USD (excluding taxes) or £199 GBP (excluding taxes).

For more information visit the SDRplay website on www.sdrplay.com

About SDRplay: SDRplay limited is a UK company and consists of a small group of engineers with strong connections to the UK Wireless semiconductor industry. SDRplay announced its first product, the RSP1 in August 2014

TWR’s Boniare MW station now most powerful in Western hemisphere

(Source: Radio World)

TWR’s Bonaire Facility Gets 440,000 Watt Makeover

In an era when most operators are reluctant to spend even very modest sums maintaining AM broadcast facilities, a southern Caribbean Island medium-wave broadcaster has “gone for the gold,” rebuilding its transmission facility and boosting power nearly five-fold from 100 kW to 440 kW.

The rebuild was more of a “second coming” for the 800 kHz facility, located in Bonaire, an island that is part of The Netherlands, situated about 100 miles off the Venezuelan coast. The station is owned and operated by Trans World Radio, one of the world’s largest evangelical media organizations.[…]

Click here to read at Radio World.

Sunset DX on Gary DeBock’s Cook Islands DXpedition

Many thanks to SWLing Post contributor, Gary DeBock, who shares the following notes from his Cook Islands Ultralight DXpedition:


Sunset on the Cook Islands

Aitutaki Sunset DX

Aitutaki in the Cook Islands had some dazzling sunsets, and [my wife] loved to take sunset pictures with her new phone. Of course, I participated as well. As a result, sunset DXing was pretty rare while on the trip, although 7 USA mainland stations crashed the Kiwi sunset skip DXing sessions later in the evening around 0700 UTC. None of the usual Vancouver-Seattle-Portland-San Francisco TP-DXing pest stations made it to the South Pacific, though– and I didn’t miss them a bit! 

610 KEAR San Francisco, California (5 kW at 4,610 miles/ 7,419 km) “Family Radio for the West Coast,” Christian religious format received at fair level at 0835 UTC on 4-12:

Audio Player

Click here to download audio.

640 KFI Los Angeles, California (50 kW at 4,570 miles/ 7,355 km) Strong (S9) level with commercial ads at 0633 UTC on 4-12:

Audio Player

Click here to download audio.

1070 KNX Los Angeles, California (50 kW at 4.570 miles/ 7,355 km) Powerful (S7) level with “1070 Newsradio” ID at 3 seconds, followed by national news at 0730 UTC on 4-10:

Audio Player

Click here to download audio.

1160 KSL Salt Lake City, Utah (50 kw at 5,144 miles/ 8,278 km) Powerful (S7) level with weather and station ID at 33 seconds, followed by public service ads at 0901 UTC on 4-12:

Audio Player

Click here to download audio.

1170 KFAQ Tulsa, Oklahoma (50 kW at 5,642 miles/ 9,080 km) Strong signal over apparent DU English co-channel with “Coast-to-Coast” ID at 44 seconds; thanks to Richard Allen for confirming the broadcast of the program on the station at 0845 UTC on 4-12:

Audio Player

Click here to download audio.

1430 KMRB San Gabriel, California (9.8 kW at 4,577 miles/ 7,366 km) Cantonese Chinese format at S7 level with commercial ads at 0830 UTC on 4-12:

Audio Player

Click here to download audio.

1640 KDIA Vallejo, California (10 kW at 4,633 miles/ 7,456 km) “1640-KDIA” ID at 6 seconds with Christian religious format at S5 level at 0807 UTC on 4-10:

Audio Player

Click here to download audio.


Thank you for sharing, Gary!  Your enthusiasm for MW DX is infectious!

Ivan performs two tests with the AirSpy HF+

Many thanks to SWLing Post contributor, Ivan Cholakov (NO2CW), who shares the following:

Thomas, there has been a lot of discussions regarding Airspy HF+ ever since it came out – heated exchanges regarding comparisons with peers, modifications and firmware updates.

I took my Airspy HF+ and conducted two tests with it:

Airspy HF+ vs. SDRPlay RSP-1A on HF and Medium Wave

Click here to view on YouTube.

Since I could not completely equalize the audio levels, I think it’s good to look at the peak to valley ratios on the display rather than the audio volume.

Airspy HF+ with the R3 mod on and off:

Click here to view on YouTube.

This comparison used SDR #. It may be helpful to run the same comparison on SDR Console V3. I may do that at a later time.

Both tests used W6LVP’s portable amplified receiving loop antenna in a noisy suburban backyard in Florida.

Many thanks, Ivan, for sharing these comparison tests! I agree with you that it’s most helpful to look closely at the peak to valley ratios on the spectrum display rather than using the audio levels as a measure.

Visit Radio Caroline’s MV Ross Revenge ship

(Source: Southgate ARC)

Radio Caroline Trip 2018

The Martello Tower group will once again be running a special event station GB5RC from the Radio Caroline ship the MV Ross Revenge over a long weekend 3rd to 5th August.

This weekend we have arranged 6 trips out to visit the ship for a tour of the ship including studios, transmitter room etc. There will be 3 trips on both the Saturday and same on the Sunday and each trip can carry up to 11 visitors.

Each trip is for the whole 11 people and cost is £275 so if you fill the boat it’s just £25 per person. Sailing times are 1.30pm 4pm and 6.30pm and each trip is around 2.5 hours round trip and will be from Mersey island in Essex.

Bookings will need to be paid in full. Please note we are not taking individual bookings for spaces on trips only bookings of £275 per trip. This is on a first come paid bookings only.

To book a trip call Paul G0HWC on 07810 607766

Bill scores a homebrew LW/MW magnetic loop antenna

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD) who shares the following:

I went to the Warminster Amateur Radio Club (WARC) hamfest [yesterday] in Bucks County, PA. For some time, I have been thinking about making a loop antenna for AM DXing. It was my lucky day. When I walked to the inside tables, on the very first table was this homemade loop antenna gentleman was selling from an estate.

I snatched it up for $40.

Attached are some photos of it. It’s 25” by 25”, with a swivel base. There are 23 turns of wire and I have no idea what size the capacitor is. I did some preliminary tests and it tunes from 280 kHz to 880 kHz. So it’s the covers the high half of the long wave band and the low half of the AM band.

It’s very well made and I fugue I can modify it to cover the entire AM band.

[…]I hooked the SDRplay RSP2 to it and was getting good signals of major stations all the way to 15 mHz.

That’s with it sitting on my dining room table. Of course the capacitor wouldn’t peak the signals.

So it was a great day at the hamfest!

Indeed that was a great find, Bill!  Someone spent a decent amount of time building that furniture-grade loop support. Indeed, it’s very reminiscent of 1920s-30s mediumwave loops!

What I love about your loop (and that of Thomas Cholakov) is that one can see how simple these antennas actually are to build. The only complicated bit is the support, but even that’s simple if you use the shield of a heavy coax or flexible copper tubing.

Thanks for sharing and enjoy logging DX with your new-to-you loop!

A full report from Gary DeBock’s Cook Islands (Aitutaki) Ultralight DXpedition

Many thanks to SWLing Post contributor, Gary DeBock, who shares the following notes from his Cook Islands Ultralight DXpedition:


“Frequent Flyer” FSL antenna – Lagoon beach DXing setup photo

Checking out transoceanic DX propagation at an exotic ocean beach site can provide the hobby thrill of a lifetime– if a DXer is lucky enough to choose the ideal time, place and gear to make the chase. All of these fell into place in an amazing way during a 5-day trip to Aitutaki Island (2600 miles due south of Hawaii) with Ultralight radio gear, resulting in the reception of MW stations in India, Bangladesh, Mongolia and Cambodia– all at over 6,800 miles.

Because of extensive QRM from Australia and New Zealand the total number of Asian stations received was limited, but it was definitely a case of quality over quantity. Phenomenal gray line propagation around sunrise shut down Japanese signals almost completely, but boosted up those from the exotic countries in east and south Asia. Korean station reception was limited to the big guns, which was also primarily true for Chinese signals. Except for the ANZ pest QRM, the conditions seemed custom-designed for a west coast DXer to go after the exotic stations which rarely– if ever– show up in BC, Washington or Oregon (even though the Cook Islands’ distance to them is greater).

7.5 inch loopstick C.Crane Skywave SSB Ultralight

Ocean beach propagation at sunrise was strong enough to bring in both 693-Bangladesh and 1431-Mongolia at S9 levels almost every morning on my Ultralight gear, and allow both 657-AIR and 918-Cambodia to break through ANZ QRM on April 12th. No doubt many more of these exotic stations could have been logged except for Australian QRM on 576, 594, 872, 883 and 1566, but this only added to the thrill of the chase. The overall results were exceptional for a DXer using only a 7.5 inch loopstick Ultralight radio and 5 inch “Frequent Flyer” FSL– all designed to fit within hand-carry luggage, and easily pass through airport security inspections. Thanks very much to Alokesh Gupta, Hiroyuki Okamura, Jari Lehtinen, Chuck Hutton and Bruce Portzer, who all assisted in the identification of these stations!

657 All India Radio Kolkata, India, 200 kW (8,075 miles/ 12,995 km) Recorded by accident during a sunrise check of the Korean big guns at 1641 on April 12, reception of this longest-distance station went unnoticed until file review after return to the States. The female speaker (in the Bengali language) is the third station in the recording, after the female vocal music from Pyongyang BS and the Irish-accented male preacher from NZ’s Star network. Her speech peaks around 40 to 50 seconds into the recording. The isolation of the Star network at the 55 second point was done by the Ultralight’s loopstick, not by the propagation. Thanks to Alokesh Gupta for the language and station identification:

Audio Player

Click here to download an MP3 of this recording.

657 Pyongyang BS Pyongyang, N. Korea, 1500 kW Like most east Asian signals the N.K. big gun sounded pretty anemic in the Cook Islands. Its female vocal music at 1641 on April 12th shared the frequency with NZ’s Star network (Irish-accented preacher) and AIR’s female Bengali speaker:

Audio Player

Click here to download an MP3 of this recording.

693 Bangladesh Betar Dhaka, Bangladesh, 1000 kW (7,960 miles/ 12,810 km) Probably the biggest surprise of the DXpedition, with S9 signal peaks on 4 out of 5 sunrise sessions. Frequently snarling with the Oz pest 3AW, it usually managed a few minutes on top of the frequency each morning from 1630-1700 UTC. Exotic South Asian music was the usual format, and was very easy to distinguish from the talk-oriented format of 3AW (and other Oz co-channels). This first appearance at 1652 on 4-10 featured a “Bangladesh Betar” ID by a male speaker at 8 seconds into the recording (thanks to Chuck Hutton for listening):

Audio Player

Click here to download an MP3 of this recording.

This was followed by a lot of exotic music until 3AW claimed the frequency just before the 1700 TOH:

Audio Player

Click here to download an MP3 of this recording.

The next day (4-11) the exotic station was back with S9 peaks, including this typical music and female speaker at 1625:

Audio Player

Click here to download an MP3 of this recording.

The exotic music from Bangladesh was in an S9 snarl with 3AW (and another Oz pest) from 1659 throughout the 1700 TOH on April 11th:

Audio Player

Click here to download an MP3 of this recording.

774 JOUB Akita, Japan, 500 kW Oddly enough, this was the only Japanese signal making it to the island during the entire trip. Mixing with a goofy-sounding 3LO announcer at 1613 on 4-11, the Japanese female speech concerns a “doobutsuen” (a “zoo” in Japanese, similar to what the frequency sounded like with the 3LO announcer):

Audio Player

Click here to download an MP3 of this recording.

819 KCBS Pyongyang, N. Korea, 500 kW The N.K. big gun managed a potent signal for its 3+1 pips across its “TOH” at 1630 on 4-12 but never could shake off RNZ’s Tauranga transmitter:

Audio Player

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909 CNR6 Quanzhou, China, 300 kW Strong signal with CNR ID (1:08) and Mandarin speech by male and female announcers. NZ’s Star network was apparently off the air at the time, since it was a real blaster when transmitting:

Audio Player

Click here to download an MP3 of this recording.

918 RNK Phnom Penh, Cambodia, 600 kW (6823 miles/ 10,981 km) Breaking through the Shandong and Oz QRM at an ideal time to dominate the frequency, its sign off transmission with the National Anthem peaked just before the 1700 TOH on April 12. Female speech in the Khmer language and exotic music are featured just before the anthem (thanks to Hiroyuki Okamura and Jari Lehtinen for listening, and identifying the National Anthem):

Audio Player

Click here to download an MP3 of this recording.

Chuck Hutton’s improved audio file of the same reception (thanks):

Audio Player

Click here to download an MP3 of this recording.

918 Shandong RGD Synchros (Multiple) The dominant Asian signal on the frequency, it rarely allowed Cambodia to sneak through. Here it is with female Mandarin speech at 1647 on 4-11:

Audio Player

Click here to download an MP3 of this recording.

Shandong RGD’s transmitters were poorly synchronized, resulting in the two-tone time pips at the 1700 TOH on 4-12 (during Cambodia’s National Anthem at 1:40, in the MP3 linked below). Although actually from two different transmitters, the sound effect sounds similar to that of a “cuckoo clock,” resulting in some initial confusion about their source:

Audio Player

Click here to download an MP3 of this recording.

972 HLCA Dangjin, S. Korea, 1500 kW The South Korean big gun played the part on most mornings, including this S9+ Korean female speech at 1631 on 4-12:

Audio Player

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981 CNR1 Synchros Changchun/ Nanchang, China, 200 kW/ 200 kW The first of three CNR1 frequencies which usually produced strong signals, this music // 1377 was received at 1624 on 4-12:

Audio Player

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1377 CNR1 Synchros (Various) Overall this was not only the strongest Chinese frequency on the band, but was the strongest Asian station on the band as well. Awesome S9+ signals were typical each morning, as with this male speech and music at 1622 on 4-12:

Audio Player

Click here to download an MP3 of this recording.

Another potent signal from this Chinese blaster at 1640 on 4-12:

Audio Player

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1431 Mongolia (Relay Station) Choibalsan, Mongolia, 500 kW This station was easy to receive on the first attempt, with very little competition on the frequency. It typically managed an S9 signal after 1630 daily with the BBC’s Korean service, which seemed to be broadcast during the peak sunrise enhancement time in Aitutaki’s ocean-boosted propagation. Here is BBC’s Korean male announcer at an S9 level at 1632 on 4-11, with the BBC interval signal at 47 seconds into the recording:

Audio Player

Click here to download an MP3 of this recording.

The Mongolian relay program prior to 1630 was also in Korean, with this female Korean speech at 1627 on 4-11:

Audio Player

Click here to download an MP3 of this recording.

1566 HLAZ Jeju, S. Korea, 250 kW A very poor signal was typical during this trip, with the Chinese service barely showing up under 3NE and two other DU English stations (probably 4GM and Norfolk Island). Whenever 3NE was in a fade it had a chance, since other two co-channels were running very low power. Here is the latter situation, with the weak Chinese barely audible under the DU English snarl at 1641 on 4-12:

Audio Player

Click here to download an MP3 of this recording.

1593 CNR1 Changzhou, China, 600 kW This was another Chinese blaster, with S9 signals typical every morning. Here it was at 1641 on 4-12 with male Chinese speech and music at 1377:

Audio Player

Click here to download an MP3 of this recording.

73 and Good DX,

Gary DeBock (DXing in Aitutaki, Cook Islands)


Amazing, Gary! Thank you for taking us along on your excellent Ultralight DXpedition. With a modest portable radio and a little antenna ingenuity, you’re enjoying some outstanding DX! You’re living proof of the point I was trying to make in a post yesterday!

Thanks again, Gary, and good DX!