Category Archives: Shortwave Radio

Shortwave Radio Recordings: RCI, BBC, VOA circa 1979 & 1981

National RF 75-NS-3 receiver kit

National RF, of California, has introduced a new “semi-kit” receiver: the RF 75-NS-3. Here’s an excerpt from the product description page of the National RF website:

National RF’s 75-NS-3 receiver is a complete super-hetrodyne mini high frequency receiver, designed specifically for the short-wave listener, electronics enthusiast or radio amateur, who wants to use their hands and build a radio. The receiver is offered as a semi-kit in which the electronic assembly is loaded and functionally tested at the National RF facility. The customer must then go to the grocery store (yes…the grocery store!), procure a can of [Spam] lunch meat, eat it or give it to the dog, and then proceed to drill and paint the can, in order for it to become the receiver’s enclosure! […] Detailed drilling instructions and final assembly instructions are provided as part of the kit. All other parts required for completion of the receiver are provided as well. Recognizing that the finished assembly looked somewhat like the fabled Collins receiver of the ‘60s, the 75S-3, (particularly when the can is painted a light gray) National RF engineers dubbed it (with tongue firmly planted in cheek, of course) the 75-NS-3! Although we have had fun packaging this receiver in a lunch meat can, it is nothing to turn your nose at! Its performance and portability will surprise you, and it is an ideal radio to bring with you on any trip!

The receiver architecture is that of a single conversion super-hetrodyne receiver, that is capable of receiving AM, SSB, or CW. The receiver incorporates a dual gate FET as an RF amplifier with manual peaking and gain controls. A ceramic filter is used in the IF section with a front panel switch that controls a broad or narrow IF response. Other front panel controls include audio drive, BFO setting, and a band switch for the HF bands. The 75-NS-3 has internal receive frequency coils that are switched at the front and rear panels. The frequency range of the receiver, over three band set positions, is 3.5 through 12 MHz. This allows reception of several international short-wave bands, the 80, 60, 40, and 30 meter amateur radio bands, and of course, WWV time and frequency standard stations at 5 and 10 MHz.

For those who simply want a lower cost receiver to monitor the shortwave frequencies, National RF offers two variants of the original receiver: the 75-NS-1 and the 75-NS-2. Both are based on the design and circuit of the 75-NS-3, but do not have the band switching and frequency range of the 75-NS-3 receiver. The 75-NS-1 covers between 3 and 6 MHz, including the 80 and 60 meter amateur band. The 75-NS-2 covers between 6 and 12 MHz, including the 40 and 30 meter amateur bands. Both units have the fixed ceramic resonator band width set for about 6 KHz. And, of course, they are both designed to fit in the tasty potted meat can!! All other specifications presented apply to both of these models as well.

Pricing of the 75-NS-x versions:

Type 75-NS-1 Mini HF Receiver Semi-kit (covers 3 to 6 MHz) $189.95
Type 75-NS-2 Mini HF Receiver Semi-kit (6 to 12 MHz) $189.95
Type 75-NS-3 Mini HF Receiver Semi-kit (band switched from 3.5 through 12 MHz in three switched positions) $269.95
Shipping and Handling to within the US $10.00 each

Click here to view on the National RF website.

The Avion AV-DR -1401 DRM receiver to ship in October

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Many thanks to several SWLing Post readers who shared this RadioWorld article about the new Avion AV-DR -1401 portable DRM receiver. According to RadioWorld, the AV-1401 will be sold through Amazon India as of October 2015 for approximately $175 US.

Click here to read the full article.

Could radio be a catalyst for revolution in North Korea?

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Many thanks to SWLing Post contributor, Richard Langley for sharing this article from The Guardian. The following is an excerpt:

Kim Cheol-su, who was born in Pyongsong City and defected from North Korea last year, says that up to 30-40% of DPRK citizens now listen to pirate radio, and that listening to the broadcasts made him realise the true nature of Kim Jong-un’s dictatorship.

Speaking at a roundtable discussion on the implications of the broadcasts in Seoul – and of the North’s thundering reaction – he said: “Children know that Kim Jong-un weighs more than 100kg. It’s because they are repeating what they hear from their parents, who listen to these foreign programmes.”

He added that the majority of North Korean citizens, desperate for news of the outside world, listen to the propaganda broadcasts which fan the flames of their doubt about the regime. The majority of those who flee to the South do so after hearing the broadcasts, he claimed.

“Before listening to the broadcasts, the citizens have no idea. But after they hear them, they realise the fact that the regime is deceiving people. They share what they have heard with their neighbours and friends.”

Kim also highlighted the fact that he heard about the Arab Spring movement through the broadcasts, and learned of the death of Libya’s former president, Muammar Gaddafi. “If the UN were to guarantee for us, as they did for Libya, help in opposing the regime, I believe that we would revolt as well,” he said.

Kim said lot of people listen to Radio Free Asia, as it comes in the clearest. “Personally, there were some programmes I liked on Open Radio for North Korea, so I used to tune in to those as well. However, short, one-hour programs were easy to miss. They were often finished by the time I found the frequency they were on.”

As for the contents of the broadcasts, Kim said having defectors talk freely about their lives was the best approach, and that programmes should include information on how to defect, offering examples of the kind of support and policies that exist for defectors in the South.

Read the full article at The Guardian online.

Guest Post: Joris’ home brew Si4835-based receiver

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Many thanks to Joris van Scheindelen (PE1KTH)–an SWLing Post contributor from the Netherlands–for the following guest post:

High Tech AM-FM DSP Receiver From

The old mode AM is still an interesting mode for amateur radio communication, also in amplitude CW.

Building your receiver is not difficult and quite fun. The semiconductor industry makes interesting integrated receiver chips today that will be useful for an AM receiver. Not only for broadcast reception but also for amateur AM reception or as part of an AM transceiver.

Silicon Labs also makes Si4734/35 receivers; these need a CPU to control the receiver, but are of interest for amateur use because the frequency can be tuned in 1 KHz steps and the audio channel bandwidth in 7 steps. There is no need for the transmitter to be on the receiving channel…

Si4835 AM-FM receiver

Looking for a small SW broadcast receiver design, and pocket size, I came to the excellent range of modern DSP receivers in a single chip from Slicon Labs.

I made a test bed set up has been made for the Si4835 AM-FM receiver.

The target specification was:

minimal components,
no micro-controller,
low power,
backlash free mechanical tuning,
good sensitivity,
earphone,
robust housing,
a short and small antenna system for outdoor use,
and minimal controls.

The Si4835 makes miniature design possible on a PCB (see photo Figure 1).

The red Dip (band) switch was replaced by a rotary switch in the final receiver design (Figure 4).

The receiver power is minimal 2 x 1.2 = 2.4 volts or a one cell LI-ION accu.
5 volts is the maximum for the Si4835 chip; current consumption is 30 mA.

Fig 1. Testbed setup for the Si4835.

The receiver has an RF pre-amplifier transistor and the LF amplifier is the TDA7050T.
All receiver functions are in the chip; the schematic is very simple and can be built with minimal components (see schematic appnote AN555 Fig 2. below).

Only an LF amplifier has to be added to complete the receiver.

Fig 2. Receiver schematic Si4835 in the AN555 application note.

The Si4835 receiver has the following frequency bands–they are divided in sub bands 800 or 900 KHz wide (See Figure 3). The frequency step tuning is 10 kHz on AM, following the international broadcast raster standard.

Fig 3. Si4835 receiver sub bands.

This means there are 80 or 90 receive channels in the sub bands and make finding the BC stations on the scale more easy. The 10 KHz scale steps are linear. The frequency stability is locked to the 32 kHz X-tal via the synthesizer so there is no frequency drift. The AM LF audio channel is 5 kHz wide set by the DSP filter. Volume control can be done width 2 up-down push switches or by a LF potentiometer..

Fig 4. The experimental pocket aluminium receiver housing on PCB2.

Receiving results

I have been testing many hours and I am surprised about this little receiver.

The receiving results are excellent on FM and AM and signals of 2 -3 uV are well received.

Also the audio quality is good–especially on FM. As can be seen in the frequency table the 40 and 20 meter band are in the range. Clear AM phone amateur transmission has been received when the transmitter was tuned on the 10 kHz raster in 40 meter band on AM.

Also AM modulated CW signals can be received bud not un-modulated carrier CW–they sound “plop…plop”.

The 5 kHz wide LF channel is a bid too wide so many CW signals pass through the audio at the time, but if AM modulated that should not be a serious problem.

The broadcast stations in the SW bands (when the daytime conditions are good) up to 20 MHz are good and strong.

Conclusions

The Si4835 receiver can be a fine broadcast receiver for outdoor work and if an AM transmitter is tuned in the 10 kHz raster this receiver can also used for amateur phone reception.

Addendum: The Si4734/35 is a better amateur AM Receiver

The Si4734 and Si4735 are a better receiver choice for amateur AM purpose because the frequency tuning can be done in 1 kHz steps. Also the BW of the LF channel can be adjusted to 1 kHz wide.

In Fig 5. from the programming APP note you see the code 0X3102 AM CHANNEL_FILTER it is possible to adjust the audio width by sending this code to the Si4734/35.

Fig 5. From the programming APP note

The LF bandwidth can be set on 1, 1.8, 2.5, 2, 3, 4 and 6 kHz wide.

This is excellent for modulated CW and AM phone discrimination in the audio channel.

The disadvantage is the need of an CPU and LCD display, “away from a minimalistic design”.

See also the note 1 and 2 improved 100 Hz rejection. See data sheet of the Si4734/35.

It look like that this receiver is a good receiver for building a modern AM-(AM)CW receiver or in a transceiver application. Tuning can be done digitally.

Think about this receiver [and the Si4835 chipset] when you intent to build a high tech AM – T/RX.

73 ‘ Joris van Scheindelen PE1KTH

What a fantastic home-brew receiver, Joris! I love the simple design of your receiver and the fact that it’s quite portable. Thanks so much for sharing your notes and documentation.

Shortwave Radio Recordings: Radio Spaceshuttle International

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SWLing Post and SRAA contributor, Jim Clary (ND9M/VQ9JC), recorded the following final broadcast of Radio Spaceshuttle International while on board a US Navy ship off the coast of Rota, Spain. Jim notes:

I was packing up to leave my ship and return to the USA this week when the latest SWLing Post e-mail showed up with info about SSR’s final broadcast literally seven minutes before he was to come on the air. I’d already broken down the receiving gear, but it came back together in record time, and I was able to get the recorder going with a minute before the transmission started.

Click here to download Jim’s recording as an MP3, or simply listen via the embedded player below. Note that Jim’s recording starts a few minutes before the broadcast begins:

Jim, thanks so much for putting all of your receiver and recording kit back together to make this recording!

Kim Elliott on shortwave radios & signal jamming in 2015

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(Source: USC Center on Public Diplomacy)

BBC Russian Wants to Expand, But It’s Not So Easy

The BBC, as part of its 2015 Charter Review document, announced proposals to “invest” in BBC World Service. This includes a desire for a “bigger digital presence in Russian through a new digital service on platforms such as YouTube and the Russian equivalent Rutube, together with TV bulletins for neighbouring states. We would also start a feasibility study for a satellite TV channel for Russia.”

[…]The feasibility of BBC satellite TV for Russia is problematic. Very few Russians have rotatable satellite dishes, surfing the Clarke Belt in search of outside news. About 25% of Russian homes have fixed Ku-band satellite dishes to receive proprietary domestic direct-to-home services such as TricolorTV and NTV+. Western Russian-language news channels are not included in these channel packages and are unlikely to be invited aboard. Content from Western Russian-language broadcasters, including Voice of America and Radio Liberty, is also legally not welcome on Russian domestic terrestrial television and radio stations.

[…]So far, Russia has not blocked the Internet content of Western international broadcasters, at least not on a continuous basis. The Kremlin’s repeated denials of any intent to block Internet content suggest that it has at least been thinking about it. And recent press accounts indicate that Russian authorities may even try to ban anonymizers and other methods used to work around online censorship. Circumvention tools would have to become even cleverer, and Russian users would have to be willing and able to use them. In an extreme scenario, Russia could physically cut off the landlines of Internet traffic into the country. Then no circumvention tool within the Internet Protocol would work.

This could bring BBC Russian full circle to the venerable but unfashionable medium of shortwave radio. To be sure, Russians are out of the habit of listening to shortwave. Shortwave is no longer used for domestic broadcasting in Russia. BBC Russian eliminated its shortwave broadcasts in 2011. But, if need be, Russians could dust off their Cold War era shortwave radios. Or they could purchase inexpensive Chinese-made portable radios with shortwave bands.

In addition to traditional voice broadcasts, text, images, and even formatted web pages can now be broadcast using existing shortwave transmitters, and received on any shortwave radio. The audio must be fed to a PC or mobile device equipped with appropriate (free) software. Such a method allows reception of content even in difficult reception conditions, and allows unattended reception. This new capability of existing shortwave broadcast technology has been demonstrated through the VOA Radiogram experiments.

If Russia blocks Internet content from abroad, it will also probably try to jam shortwave radio content from abroad. Most jamming transmitters of the Cold War era have been dismantled or have fallen into disrepair. Many of the jamming transmitters are outside of Russia, in former Soviet republics. Reviving a shortwave jamming apparatus would be a much more expensive proposition than blocking Internet content. Various Cold War anti-jamming tactics, using various tricks of ionospheric propagation, can be employed. Text via shortwave would be even more resistant to jamming than voice broadcasts.[…]

Read the full article by Kim Andrew Elliott at the USC Center on Public Diplomacy online.