A FRESH LOOK AT ONLINE SDRs - PART 1

A FRESH LOOK AT ONLINE SDRs

Part 1 (inc. Asia and Europe)

(This post is an edited version of an article I wrote for "The World of Shortwave Listening" column of The Spectrum Monitor magazine - April 2023 issue. Further details on this excellent publication are available at www.thespectrummonitor.com)

In this blog a few years ago (January 2020), we highlighted the advantages and joys of operating physical and software-defined radios (SDR) remotely via the Internet. Sitting in front of a computer and accessing a receiver located on the other side of the globe remains a fascinating and magical part of the hobby.

We looked at the numerous features these receivers offered, including broad-spectrum access from VLF through to HF and VHF, their waterfalls, variable bandwidth filters, variable noise filters, variable AGC, all the standard modes (AM, synchronous AM, SSB, FM, CW, DRM), plus a range of extensions that include FAX, FSK, NAVTEX, SSTV, and WSPR. Having all these tools at our fingertips is a dream come true. 

We also discussed how these receivers could be utilized, such as monitoring broadcasts not beamed to your listening location, comparing reception between listening locations, and hearing low-powered stations close to remote SDRs. Plus, if you hold an amateur radio licence, you can monitor your own transmissions for signal and audio quality and judge how far your signal is reaching.

Since then, a few changes have affected how we access online remote receivers. The website known as SDR.HU folded several years ago. Another once-popular website that began in 2007, GlobalTuners (GT), still exists. However, some receivers don’t seem fully operational, regularly maintained or connected to decent antennas. The number of online receivers has dwindled, users are complaining, and the site’s administrators don’t appear responsive. By today’s standards, the GT interface is quite dated, with no waterfall display and a significant latency when tuning frequencies. In addition, it allows only one user to tune the receiver at a time. Nevertheless, a few aero and utility DX enthusiasts still use the GT website.

Then there is the WebSDR software developed and maintained by PA3FWM. A great range of global receivers can be found at http://websdr.org/. Most are operated by amateur radio operators and focus only on the HF, VHF and UHF ham bands. The advantage of WebSDR is that many users can tune the receivers simultaneously. And over the years, various antennas have been incorporated into these receivers. For example, the Northern Utah WebSDRs are hooked up to an impressive antenna farm for their six servers! However, you will find some variation in the onscreen layout and interface between receivers using the WebSDR software, which can be confusing when operating radios you don’t usually use. 

KiwiSDR

Last August, the developers of the popular wide-band KiwiSDR hardware announced that no more kits would be supplied. Ongoing global semiconductor shortages and a lack of any sustainable profit from the venture were cited as two of many reasons for the closure of the business. As a result, the developers decided it was time to move on. While this is sad to hear, it appears to be an understandable business decision.

Happily, however, the KiwiSDR website remains with lots of helpful information. And you can access the global range of SDRs through the list of online receivers at http://kiwisdr.com/public/ or through the world map of online receivers (my preferred method) at http://rx.linkfanel.net. Here you will find nearly 700 receivers spread across all continents except Antarctica. 

Indeed, the list of receivers has expanded significantly since my 2020 blog on SDRs. Most owners limit the number of users to between two and eight at any time, although a few owners have multiple SDRs at the same location. The main attraction to the KiwiSDR platform is the ease of use and flexibility each receiver offers.

Here are some of my favourite receivers from the KiwiSDR website.  They have been chosen for their quiet locations with little manmade (electrical) noise, their strategic locations when listening to global SWBC stations, or because effective antennas allow plenty of signals to be heard. I have purposely not included web links to these stations as their URLs are occasionally subject to change. But you can search for them by name on the Kiwi website or pick them out on the Kiwi map display.

Remember, sometimes receivers will be taken offline for software updates, testing or when the owner is using the antenna for his own amateur radio transmitting activities. So a particular receiver may not always be available when you want it. Also, consider that reception conditions in other parts of the world will exhibit different reception characteristics across the 24 hours compared to your own location, i.e. daytime versus nighttime reception across the shortwave spectrum.

Asia

GRMS IXB, Siliguri, India: Located in West Bengal at the foot of the Himalayas. This is a recent entry to the KiwiSDR list. It boasts very low noise compared to most of the other Indian SDRs and is wonderful for monitoring Asian and Middle Eastern broadcasts on its W6LVP loop.

Chongqing, China: Located in southwestern China, this SDR is useful if you monitor and check frequencies for the many CRI, CNR and PBS Xizang stations on SW and MW. It is also in an excellent location for spotting other Asian stations, such as the North Korean domestic KCBS outlets on 120, 90 and 75 mb. There is a low noise floor most times of the day, allowing Asian signals to be heard well. The Japanese ApexRadio 303WA-2 broadband vertical antenna does a competent job.

VN/SWL, Hanoi, Vietnam: This Hanoi SDR can sometimes be subject to high noise levels. Yet, it is well placed to monitor stations in most parts of Asia, especially South East Asian broadcasters and Chinese transmitter sites. I have often used it to assist me in identifying Asian signals that were too weak to pick up here in southern Australia.

FlyDog SDR, Oita, Japan: On the island of Kyushu in Southern Japan, the FlyDog hardware is a derivative of and compatible with the KiwiSDR, with 16-bit ADC sampling. The antenna is the ApexRadio 303WA-2 vertical. This is one of the better Japanese receivers. Excellent for studying Korean, Chinese and other Asian broadcasters on both shortwave and mediumwave.  

Europe

HB9CWK Hans-Ulrich, Heimiswil, Switzerland: Located in central Switzerland (near Bern), this is an excellent receiver for monitoring broadcasts throughout Europe, especially those low-powered “hobby” stations and Euro pirates. It can also be helpful in checking broadcasts from parts of North and Central Africa (e.g. Radio TV du Mali, Bamako on 5995 kHz between 0600 and 0800). The long wire antenna is set up in a low-noise semi-rural environment.

The Swiss KiwiSDR operated by HB9CWK

EA7HPM, near Seville, Spain: Good general coverage of Europe, parts of Africa and much of the Middle East. Uses a loop antenna. At times it can suffer from some low-level noise.

DK1MAX Feilenmoos, Bravia, Germany: Another low-noise receiver in a semi-rural environment (about 55 km north of Munich), offering the listener a chance to hear nearly all of Europe on shortwave. A simple 7m high, high-impedance antenna (probably some variation of a long wire) does very well. However, performance drops off considerably from 20 MHz up.

Click here for PART 2 

(inc. Middle East, North America, Oceania and South America)

73 and good DX to you all,

Rob Wagner VK3BVW

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