Last month we covered Part One of our three-part primer on software-defined radios (SDRs). While last month’s Part One focused on the nomenclature and components of a functioning SDR system, Part Two will take a look at some affordable SDR station options that will propel you into the world of SDRs for less than $200 US. We’ll cover Part Three in November, and we’ll dive a little deeper into the rabbit hole and cover higher-end SDRs and ham radio transceivers with embedded SDRs.
SDRs are affordable
If there’s one thing I’d like you to take away from this part of our primer, it’s that SDRs are truly affordable. For less than the price of a typical full-featured shortwave portable, you can own an SDR that covers almost all of the listening spectrum, and that does so with excellent performance characteristics.
We’re lucky to live in a time of phenomenal radio innovation. When I first jumped into the world of SDRs, the least expensive SDR that covered any of the bands below 20 MHz was about $500. That was only a few years ago, in 2010 or so.
Yet in the past three years, affordable SDRs have become the dominant radio product on the market. And these modestly-priced products have made the barrier of entry into the SDR world crumble overnight.
Today, even a $100 SDR has more features, more frequency range, and more functionality than a $1000 SDR from just a decade ago. Times have changed dramatically; indeed, the pace of innovation in this craft is simply amazing.
Before we begin looking at some choice sub-$200 SDRs, I’d just like to direct your attention to the first part of our SDR Primer (click here to read). Specifically, I’d like you to note one element I discussed in that article: the vital importance identifying your goals as an SDR owner. In other words, how do you plan to use your SDR? If you’re only seeking an SDR to listen to local ham radio repeaters, track cubesat satellites, or gather ADS-B information from aircraft, a $25 SDR will more than suffice. If you wish to use the SDR as a transceiver panadapter, or you wish to chase weak signal DX on the HF bands, then I’d suggest you invest a bit more.
I’d also like to remind you, as I noted in the previous article, that this primer will be limited in the SDRs I highlight. The reason for this is simple: there now exists a vast ocean of SDRs on the market (just search eBay for “SDR” and you’ll quickly see what I mean) so all models simply can’t be included in this introductory foray. I’ll be focusing here on several SDRs that cover the HF spectrum and above. I’ll also focus on SDRs with which I have personal experience, and which I consider to be “enthusiast” grade among a healthy community of users. Of course, this part of the primer will only include HF-capable receivers that cost a total of $200 or less.
Let’s take a look at what’s on the market in order of price, starting with the most affordable.
$10-$25: The RTL-SDR dongle
No doubt, many of you reading this primer have purchased an RTL-SDR dongle. Over the years, I’ve owned three or four of them and have even purchased them for friends. These dongles originally appeared on the market many years ago as mass-produced DVB-T TV tuner dongles based on the RTL2832U chipset. Very soon, users discovered that with just a little hacking, the dongle was capable of much, much more than its original intended purpose.
The dongle resembles a USB memory stick. On one end, you’ll find a standard USB connector. On the other, you’ll find an antenna port, typically SMA, to which one connects an antenna. Although it goes without saying, here’s a friendly reminder: make sure you’re choosing an antenna to match the frequency range you’re exploring!
I’ve seen this older model of RTL-SDR being sold for $9 at Hamvention.
Early RTL-SDR dongles couldn’t cover the HF bands or lower, but many models can now cover a gapless 500 kHz all the way to 1.75 GHz.
So, what can you do with an RTL-SDR dongle? In short, quite a lot! Here are a few of this simple device’s many applications and uses in our hobby. It can:
become a police radio scanner
monitor aircraft and ATC communications
track aircraft with ADS-B decoding and read ACARS short messages
scan trunking radio conversations.
decode unencrypted digital voice transmissions such as P25/DMR/D-STAR.
track maritime boat positions like a radar with AIS decoding.
And, of course, you can listen to any signals between 500 kHz up to 1.75 GHz––essentially, most of the radio listening landscape.
Is $25 still a little high for your budget? RTL-SDR dongles can be found for as low as $10 US, shipped, on eBay. While the cheapest of these dongles may suffice for some radio applications, I’m partial to the dongle produced by RTL-SDR.com, since they’re built in a tough metal enclosure, have thermal pad cooling, as well as extra ESD protection. Amazon has an RTL-SDR.com dongle starter package with antenna options for about $26. That’s, what, the price of three hamburgers? Two orders of fish and chips? And worth it.
Many third-party SDR applications support the RTL-SDR dongle, but my favorite is SDR# (click here to download).
So, the major pros of this little SDR are 1) obviously, the price; 2) many, many uses; and 3) the fact that it’s the most popular SDR on the market, with a massive online user base.
What about negatives? Well, to be frank––aside from the dongle’s budget-busting versatility––the fact is that “you pay for what you get.” You’re investing just $10-$27 in this receiver, so don’t expect exceptional performance especially on anything lower than 50 MHz. On HF, for example, the RTL-SDR could easily overload unless you employ external filtering.
Indeed, I’ve never used the RTL-SDR for HF DXing, but I currently have three dongles in service 24/7: two as ADS-B receivers, and one as a receiver for the LiveATC network. And these work hard. Indeed, It’s a workhorse of a device!
I suggest you grab an RTL-SDR and use it as an accessible step into the world of SDRs, and as an affordable single-purpose tool to unlock the RF spectrum!
When you invest a modest $99 US (or $120 shipped), and purchase the RSP1A, you take a major step forward in the SDR world.
UK-based SDRplay is an SDR designer and manufacturer that focuses on enthusiast-grade, budget wideband SDRs. SDRplay designs and manufactures all of their SDRs in the United Kingdom, and over the past few years, they’ve developed a robust user community, extensive documentation, and, in my humble opinion, some of the best tutorial videos on the market.
SDRuno windows can be arranged a number of ways on your monitor.
Although the RSP series SDRs are supported by most third-party SDR applications, SDRplay has their own app: SDRuno. Moreover, SDRuno is a full-featured, customizable application that takes advantages of all of this SDR’s performance potential and features. I should mention that installing the RSP1A and SDRuno is a pure plug-and-play experience: just download and install the application, plug in the RSP1A to your computer, wait for the USB driver to automatically install, then start SDRuno. Simplicity itself.
While the RSP1A is SDRplay’s entry-level wideband SDR, it nonetheless plays like a pro receiver and truly pushes the envelope of performance-for-price, and for other SDR manufacturers, sets the bar quite high. The RSP1A is a wideband receiver that covers from 1 kHz all the way to 2 GHz; equally pleasing the longwave DXer, HF hound, tropo-scatter hunter, and even radio astronomer. This affordable SDR really covers the spectrum, quite literally. Not only does the RSP1A cover a vast frequency range, but its working bandwidth can be an impressive 10 MHz wide and via SDRuno, the RSP1A will support up to 16 individual receivers in any 10 MHz slice of spectrum. All this for $99? Seriously? I assure you, yes.
Think of the RSP1A as the sporty-but-affordable compact car of the SDR world. It delivers performance well above its comparatively modest price, and is fun to operate. In terms of DX, it gets you from point A to point B very comfortably, and is a capable receiver which will help you work even weak signals––and very reasonably!
If you’re looking to explore the world of SDRs, would like a capable receiver with great LW/MW/HF reception to do it with, but also want to keep your budget in check, you simply can’t go wrong with the RSP1A.
Many years ago when I ventured into the world of SDRs, one of the only affordable SDRs which covered the HF bands was the FUNcube Dongle Pro+.
The Funcube Dongle Pro+, which resembles the RTL-SDR “stick” type dongle, was originally designed as a ground receiver for the FUNcube Satellite (cubesat) project initially made possible by AMSAT-UK and the Radio Communications Foundation (RCF). The original Funcube dongle did not cover any frequencies below 64 MHz, but the Funcube Dongle Pro+ added coverage from 150 kHz to 1.9 GHz with a gap between 240 MHz and 420 MHz.
In full disclosure, I’ve never owned a FUNcube Dongle Pro+, but I have used them on several occasions. I believe you would find that it is prone to overloading if you use a longwire antenna that’s not isolated from the dongle. In other words, during such use it seems to be subject to internally-generated noise. In my experience, the Pro+ worked best when hooked up to an external antenna fed by a proper coaxial cable.
To be clear, with the advent of SDRplay and AirSpy SDRs, the FUNcube Dongle Pro+ is no longer the budget SDR I would most readily recommend.
Still, the Pro+ is a very compact dongle that has a great history, and around 2012 really pushed the performance-for-price envelope. It still has many dedicated fans. No doubt, this product has had a huge influence on all of the sub $200 SDRs currently on the market, thus we owe it a debt of gratitude.
In 2016, after the remarkable success of the original RSP, SDRplay introduced the RSP2 and RSP2 Pro SDRs. The RSP2 is housed in an RF-shielded robust plastic case and the RSP2 Pro is enclosed in a rugged black painted steel case. In terms of receivers and features, the RSP2 and RSP2 Pro are otherwise identical
The RSP2 and RSP2 Pro provide excellent performance, three software-selectable antenna inputs, and clocking features, all of which lend it to amateur radio, industrial, scientific, and educational applications; it is a sweet SDR for $169 or $199 (Pro version). I know of no other SDRs with this set of features at this price point.
The RSP2 series has the same frequency coverage as the RSP1A. Of course, to most of us, the big upgrade from the SDRplay RSP1A is the RSP2’s multiple antenna ports: 2 x 50-Ohms and one High-Z port for lower frequencies.
The SDRplay RSP2 with plastic enclosure.
As with all of SDRplay’s SDRs, their own application, SDRuno, will support up to 16 individual receivers in any 10 MHz slice of spectrum.
Bottom line? Since the RSP2 has multiple antenna ports––and two antenna options for HF frequencies and below–the RSP2 is my choice sub-$200 SDR to use as a transceiver panadapter. (Spoiler alert: you’ll also want to check out our summary of the recently released $279 RSPduo from SDRplay in this review or in Part 3 of our primer before pulling the trigger on the purchase of an RSP2 or, especially, an RSP2 Pro!)
Sometimes big surprises come in small packages. That pretty much sums up the imminently pocketable AirSpy HF+ SDR.
The HF+ has the footprint of a typical business card, and is about as thick as a smartphone. Despite this, it’s a heavy little receiver––no doubt due to its metal alloy case/enclosure.
AirSpy’s HF+ was introduced late 2017. Don’t be surprised by its footprint which is similar to a standard business card to its left, this SDR is performance-packed!
Not to dwell on its size, but other than my RTL-SDR dongle, it’s by far the smallest SDR I’ve ever tested. Yet it sports two SMA antenna inputs: one for HF, one for VHF.
The HF port is labeled as “H” and the VHF port as “V”
When I first put it on the air, my expectations were low. But I quickly discovered that the HF+ belies its size, and is truly one of the hottest sub $500 receivers on the market! Its HF performance is nothing short of phenomenal.
The HF+ is not a wideband receiver like the FunCube Dongle Pro+ or RSP series by SDRplay. Rather, the HF+ covers between 9 kHz to 31 MHz and from 60 to 260 MHz only; while this is a relatively small portion of the spectrum when compared with its competitors, this was a strategic choice by AirSpy. As AirSpy’s president, Youssef Touil, told me,“The main purpose of the HF+ is [to have] the best possible performance on HF at an affordable price.”
Mission accomplished. Like other SDRs, the HF+ uses high dynamic range ADCs and front-ends but enhances the receiver’s frequency agility by using high-performance passive mixers with a robust polyphase harmonic rejection structure. The HF+ was designed for a high dynamic range, thus it is the best sub-$200 I’ve tested for strong signal handling capability on the HF bands.
You can very easily experiment and customize the HF+ as well; easy access to the R3 position on the circuit board allows you to make one of several published modifications. “During the early phases of the design,” Yousef explains, “R3 was a placeholder for a 0 ohms resistor that allows experimenters to customize the input impedance.” He goes on to provide in-depth clarification about these mods:
A 300 pF capacitor will naturally filter the LW/MW bands for better performance in the HAM bands
A 10µH inductor would allow the use of electrically short antennas (E-Field probes) for MW and LW
A short (or high value capacitor) would get you the nominal 50 ohms impedance over the entire band, but then it’s the responsibility of the user to make sure his antenna has the right gain at the right band
A custom filter can also be inserted between the SMA and the tuner block if so desired.”
Since the introduction of the HF+, it has been my recommended sub-$200 receiver for HF enthusiasts. If you want to explore frequencies higher than 260 MHz, you’ll have to look elsewhere. Also, note that longwave reception is not the HF+’s strong suit––although modifications to R3 and future firmware upgrades might help with this! Additionally, the HF+’s working bandwidth is 660 kHz; quite narrow, when compared with the RSP series, which can be widened to 10 MHz.
AirSpy also designed the free application SDR# to take full advantage of their receivers’ features and performance.
If you haven’t gathered this already, it’s simply a brilliant time to be a budget-minded radio enthusiast. Only a few years ago, there were few, if any, enthusiast-grade sub-$200 SDR options on the market. Now there are quite a number, and their performance characteristics are likely to impress even the hardest-core weak-signal DXer.
Still, some hams and SW listeners reading this article will no doubt live in a tougher RF environment where built-in hardware filters are requisite to prevent your receiver from overloading. Or perhaps you desire truly uncompromising benchmark performance from your SDR. If either is the case, you may need to invest a little more of your radio funds in an SDR to get exactly what you want…and that’s exactly where I’ll take you November in the final Part Three of this SDR primer series. Stay tuned!
Stay tuned for more in Part Three (November).I’ll add links here after publication.
Many thanks to SWLing Post contributor, London Shortwave, who recently shared his latest SDR project: a field-portable, ultra-compact, SDR spectrum recording system based on the PocketCHIP computer.
London Shortwave has built this system from the ground up and notes that it works well but is currently limited to the FunCube Dongle Pro+ at 192 kHz bandwidth. There is no real-time monitoring of what’s being recorded, but it works efficiently and effectively–making spectrum captures from the field effortless. The following is a video London Shortwave shared via Twitter:
I think this field portable SDR system is absolutely brilliant!
London Shortwave has done all of the coding to make the FunCube Dongle Pro + work with the PocketChip computer. Even though live spectrum can’t be monitored in the field, the fact that it’s making such a clean spectrum recording is all that really matters.
All London Shortwave has to do is head to a park with his kit, deploy it, sit on a bench, read a good book, eat a sandwich, then pack it all up. Once home, he transfers the recording and enjoys tuning through relatively RFI-free radio.
A very clever way to escape the noise.
The kit is so incredibly portable, it would make DXing from any location a breeze. You could easily pack this in a carry-on item, backpack or briefcase, then take it to a park, a national forest, a lake, a remote beach–anywhere.
What I really love about this? He didn’t wait for something to be designed for him, he simply made it himself.
Thanks again, London Shortwave. We look forward to reading about your radio adventures with this cool field SDR!
Mario and I were both tempted at one point to snag the Pro + at this price, but neither one of us needs another SDR. Please, someone buy it before I change my mind and buy it in a moment of weakness! 🙂
Sean Gilbert, WRTH’s International Editor, recently shared this audio he originally recorded on June 19, 2014. Sean writes:
With all the interest in space and the ISS at the moment, I thought I would share a recording I made on 19 June 2014 @ 1715 UTC. This is from the Russian part of the ISS and the audio (which is in Russian) is of the cosmonauts talking during a spacewalk (EVA as they are known). The person speaking is actually in space, outside of the ISS. The audio begins about 2 mins into the recording and lasts for about 5 mins.
[…]This was received on 143.625MHz NFM (+/- a few kHz due to doppler shift). Receiver here was a Funcube Dongle Pro + into a 2 element circular polarised turnstile in the attic. Signal was lost at a distance of 2000km (to the East of my location in IO92ma) at 3 degree elevation. Altitude of ISS was 418km above earth.
The image [above] shows a grab of the signal, exhibiting doppler shift due to the ISS orbit in relation to the earth.
[…]I would be interested to know what they are saying. […]To me this was far more exciting than receiving SSTV pictures from the ISS. I may never hear another EVA – I am just thankful that I found this as it was an announced/schedules EVA.
That is very cool, indeed, Sean! At some point, I must make an effort to venture up to the VHF neighborhood and attempt to hear the ISS.
I hope there’s a Russophone reader out there who can help Sean interpret the EVA dialog! Please comment!
I’m very grateful: one of the most common questions I’m asked by readers is how to cope with the radio interference so many listeners and amateur radio operators experience in high-density, urban areas. If this is you, you’re in for a treat–just keep reading:
Dealing with Urban Radio Interference on Shortwave
Shortwave radio listening is an exciting hobby, but for many of us city dwellers who either got back into it recently or tried it out for the first time not long ago, the first experience was a disappointing one: we could barely hear anything! Station signals, even the supposedly stronger ones, were buried in many different types of static and humming sounds. Why does this happen? The levels of urban radio frequency interference, or RFI, have increased dramatically in the last two decades and the proliferation of poorly engineered electronic gadgets is largely to blame. Plasma televisions, WiFi routers, badly designed switching power adapters and Ethernet Over Powerlines (also known as powerline network technology, or PLT) all severely pollute the shortwave part of the radio spectrum.
Does this mean we should give up trying to enjoy this fascinating medium and revert to using the TuneIn app on our smartphones? Certainly not! There are many angles from which we can attack this problem, and I shall outline a few of them below.
Get a good radio
The old adage “you get what you pay for” certainly holds true even when it comes to such “vintage” technologies as shortwave radio. Believe it or not, a poorly designed receiver can itself be the biggest source of noise on the bands. That is because many modern radios use embedded microprocessors and microcontrollers, which, if poorly installed, can generate interference. If the receiver comes with a badly designed power supply, that too can generate a lot of noise.
So how does one go about choosing a good radio? SWLing.com and eHam.net have fantastic radio review sections, which will help you choose a robust receiver that has withstood the test of time. My personal favourites in the portable category are Tecsun PL310-ET and Tecsun PL680. If you want a desktop radio, investigate the type of power supply it needs and find out whether you can get one that generates a minimal amount of noise.
It is also worth noting that indoor shortwave reception is usually best near windows with at least a partial view of the sky.
Tecsun PL310-ET and Tecsun PL680, my two favourite portable shortwave radios.
Identify and switch off noisy appliances
Many indoor electrical appliances generate significant RFI on the shortwave bands. Examples include:
Laptop, and other switching-type power supplies
Mobile phone chargers
Washing machines / dishwashers
Amplified television antennas
Badly constructed electrical heaters
Mains extension leads with LED lights
Identify as many of these as you can and switch them all off. Then turn them back on one by one and monitor the noise situation with your shortwave radio. You will most likely find at least a few offending devices within your home.
Install an outdoor antenna
If you have searched your home for everything you can possibly turn off to make reception less noisy but aren’t satisfied with the results, you might want to look into installing and outdoor antenna. That will be particularly effective if you live in a detached or a semi-detached property and have a garden of some sort. Of course, you will need a radio that has an external antenna input, but as for the antenna itself, a simple copper wire of several metres will do. An important trick is making sure that the noise from inside your home doesn’t travel along your antenna, thus negating the advantage of having the latter installed outside. There are many ways of achieving this, but I will suggest a configuration that has worked well for me in the past.
Fig.1 Schematic for an outdoor dipole antenna.
I have used a three-terminal balun (positioned outdoors), and connected two 6 metre copper wires to its antenna terminals to create a dipole. I then connected the balun to the radio indoors through the feed line terminal using a 50? coaxial cable. In the most general terms, the current that is generated in the antenna wires by the radio waves flows from one end of the dipole into the other, and a portion of this current flows down the feed line into your radio. The balun I have used (Wellbrook UMB130) is engineered in a way that prevents the radio noise current from inside your house flowing into the receiving part of the antenna.
Wellbrook UMB130 balun with the feed line terminal disconnected
There is a catch with using an outdoor antenna described above — the signals coming into your radio will be a lot stronger than what would be picked up by the radio’s built-in “whip” antenna. This can overload the receiver and you will then hear many signals from different parts of the shortwave spectrum “mixing in” with the station you are trying to listen to. An antenna preselector solves this problem by allowing signals from a small yet adjustable part of the spectrum to reach your radio, while blocking the others. You can think of it as an additional tuner that helps your radio reject unwanted frequencies.
Fig.2 Schematic of a preselector inserted between the outdoor antenna and the receiver
There are many antenna preselectors available on the market but I can particularly recommend Global AT-2000. Although no longer manufactured, many used units can be found on eBay.
Global AT-2000 antenna coupler and preselector
Risk of lightning
Any outdoor antenna presents the risk of a lightning strike reaching inside your home with devastating and potentially lethal consequences. Always disconnect the antenna from the receiver and leave the feed line cable outside when not listening to the radio or when there is a chance of a thunderstorm in your area.
Get a magnetic loop antenna
A broadband loop antenna (image courtesy of wellbrook.uk.com)
The outdoor long wire antenna worked well for me when I stayed at a suburban property with access to the garden, but when I moved into an apartment well above the ground floor and without a balcony, I realised that I needed a different solution. Having googled around I found several amateur radio websites talking about the indoor use of magnetic loop receive-only active antennas (in this case, “active” means that the antenna requires an input voltage to work). The claim was that such antennas respond “primarily to the magnetic field and reject locally radiated electric field noise”[*] resulting in lower noise reception than other compact antenna designs suitable for indoor use.
Interlude: signal to noise ratio
In radio reception, the important thing is not the signal strength by itself but the signal to noise ratio, or SNR. A larger antenna (such as a longer copper wire) will pick up more of the desired signal but, if close to RFI sources, will also pick up disproportionately more of the local noise. This will reduce the SNR and make the overall signal reading poorer, which is why it is not advisable to use large antennas indoors.
The other advantage of a loop antenna is that it is directional. By rotating the loop about its vertical axis one can maximise the reception strength of one particular signal over the others, once the antenna is aligned with the direction from which the signal is coming (this is termed “peaking” the signal). Similarly, it is possible to reduce the strength of a particular local noise source, since the loop is minimally sensitive to a given signal once it is perpendicular the latter’s direction (also known as “nulling” the signal).
It is further possible to lower the effect of local noise sources by moving the antenna around. Because of the antenna’s design, the effect of radio signals is mostly confined to the loop itself as opposed to its feed line. Most local noise sources have irregular radiation patterns indoors, meaning that it is possible find a spot inside your property where their effects are minimised.
Many compact shortwave loop antennas require an additional tuning unit to be attached to the loop base (much like the preselector described above) but broadband loops do not. Wellbrook ALA1530S+ is one such antenna that is only 1m in diameter, and it was the one I chose for my current apartment. I was rather impressed with its performance, although I found that I need to use a preselector with it as the loop occasionally overloads some of my receivers when used on its own. Below is a demo video comparing using my Tecsun PL680’s built-in antenna to using the radio with the Wellbrook loop.
As you can hear, there is a significant improvement in the signal’s readability when the loop is used.
Experiment with a phaser
Although the loop antenna dramatically reduces the levels of ambient RFI getting into the radio, I also have one particular local noise source which is way too strong for the loop’s nulling capability. Ethernet Over Powerlines (PLT) transmits data across domestic electrical circuits using wall socket adapters, as an alternative to wireless networking. It uses the same frequencies as shortwave, which turns the circuits into powerful transmitting antennas, causing massive interference. One of my neighbours has PLT adapters installed at his property, which intermittently become active and transmit data. When this happens, it is not merely noise that is generated, but a very intense data signal that spreads across the entire shortwave spectrum, obliterating everything but the strongest stations underneath. Fortunately, a mature piece of radio technology called antenna phasing is available to deal with this problem.
Fig.3 The principle of antenna phaser operation (adapted from an original illustration in Timewave ANC-4’s manual)
Signal cancellation using phase difference
A phaser unit has two separate antenna inputs and provides one output to be connected to the radio’s external antenna input. The theory of phase-based signal cancellation goes roughly as follows:
The same radio signal will arrive at two different, locally separated antennas at essentially the same time.
The phase of the signal received at the first antenna will be different to the phase of the same signal received at the second antenna.
This phase difference depends on the direction from which the signal is coming, relative to the two antennas.
The phaser unit can shift the phases of all signals received at one antenna by the same variable amount.
To get rid of a particular (noise) signal using the phaser unit:
the signal’s phase at the first antenna has to be shifted by 180° relative to the signal’s phase at the second antenna (thus producing a “mirror image” of the signal received at the second antenna)
its amplitude at the first antenna has to be adjusted so that it is the same as the signal’s amplitude at the second antenna
the currents from the two antennas are then combined by the unit, and the signal and its mirror image cancel each other out at the unit’s output, while the other signals are preserved.
Noise sampling antenna considerations
To prevent the possibility of the desired signal being cancelled out together with the noise signal — which can happen if they both come from the same direction relative to the antennas — one can use the set-up illustrated in Figure 3, where one antenna is dedicated to picking up the specific noise signal, while the other is geared towards receiving the desired broadcast. That way, even if the phases of both the noise and the desired signals are offset by the same amount, their relative amplitude differences will not be the same, and thus removing the noise signal will not completely cancel out the desired signal (though it will reduce the latter’s strength to some extent).
It is possible to use any antenna combination for phase-based noise signal cancellation. However, one has to be careful that, in the pursuit of removing a specific noise source, one does not introduce more ambient RFI into the radio system by using a poorly designed noise-sampling antenna. After all, the phaser can only cancel out one signal at a time and will pass through everything else picked up by both antennas. This is particularly relevant in urban settings.
For this reason, I chose my noise sampling antenna to also be a Wellbrook ALA1530S+. The additional advantages of this set-up are:
It is possible to move both loops around to minimise the amount of ambient RFI.
By utilising the loops’ directionality property, one can rotate the noise sampling loop to maximise the strength of the noise signal relative to the desired signal picked up by the main antenna loop.
Two Wellbrook ALA1530S+ antennas combined through a phaser
And now onto the phaser units themselves.
DX Engineering NCC-1 (image courtesy of dxengineering.com)
I have experimented at length with two phaser units: the MFJ 1026 (manual) and DX Engineering NCC-1 (manual). Both solve the problem of the PLT noise very well, but the NCC-1 offers amplitude and phase tuning controls that are much more precise, making it a lot easier to identify the right parameter settings. Unfortunately this comes at a price, as the NCC-1 is a lot more expensive than the MFJ unit. As before, a preselector is needed between the phaser and the radio to prevent overloading.
Below is a demo of DX Engineering NCC-1 at work on my neighbour’s PLT noise. I have chosen to use my SDR’s waterfall display to illustrate the nefarious effect of this type of radio interference and to show how well the NCC-1 copes with the challenge.
Fig.4 Final urban noise mitigation schematic
It would be fair to say that my final urban noise mitigation set-up, shown in Figure 4, is quite expensive: the total cost of two Wellbrook antennas ($288.38 each), a DX Engineering phaser ($599.95) and a Global AT2000 preselector ($80) comes to $1257. That seems like an astronomical price to pay for enjoying shortwave radio in the inner city! However, at this point another old saying comes to mind, “your radio is only as good as your antenna”. There are many high-end shortwave receivers that cost at least this much (e.g. AOR AR7030), but on their own they won’t be of any use in such a noisy environment. Meanwhile, technological progress has brought about many much cheaper radios that rival the older benchmark rigs in terms of performance, with Software Defined Radios (SDRs) being a particularly good example. It seems fair, then, to invest these cost savings into what makes shortwave listening possible. You may also find that your RFI situation is not as dire as mine and you only need some of the above equipment to solve your noise problems.
Filter audio with DSP
If you have implemented the above noise reduction steps but would still like a less noisy listening experience, consider using a Digital Signal Processing (DSP) solution. There are a number of different approaches and products available on the market, and I shall be reviewing some of them in my next post. Meanwhile, below are two demo videos of using DSP while listening to shortwave. The first clip shows the BHI Compact In-Line Noise Elimination Module at work together with a vintage shortwave receiver (Lowe HF-150). The second video compares using a Tecsun PL-660 portable radio indoors on its own and using the entire RFI mitigation set-up shown in Figure 4 together with a DSP noise reduction feature available in the SDR# software package, while using it with a FunCube Dongle Pro+ SDR. As a side note, it is worth remembering that while DSP approaches can make your listening experience more pleasant, they can’t recover what has been lost due to interfering signals or inadequate antenna design.
Set up a wireless audio relay from your radio shack
The above RFI mitigation techniques can result in a rather clunky set-up that is not particularly portable, confining the listener to a specific location within their home. One way to get around this is by creating a wireless audio relay from your radio shack to the other parts of your house. I did this by combining the Nikkai AV sender/receiver pair and the TaoTronics BA01 portable Bluetooth transmitter:
Head for the outdoors!
So you have tried all of the above and none of it helps? As a last resort (for some, but personally I prefer it!), you can go outside to your nearest park with your portable radio. After all, if shortwave listening is causing you more frustration than joy it’s hardly worth it. On the other hand, you might be surprised by what you’ll be able to hear with a good receiver in a noise-free zone.
What I love about my buddy, London Shortwave, is that he didn’t give up SWLing just because his home is inundated with radio interference–rather, he saw it as a challenge. As you can see, over the years, he has designed a system that effectively defeats radio interference.
I also love the fact that he uses an even more simple approach to defeating RFI: he takes his radio outdoors. A kindred spirit, indeed.
You were tasked to track down a radio kit that would keep you in touch with the world, and potentially afford you some very unique DX. [If you haven’t read the full virtual radio challenge, including all of the limitations you might face, I encourage you to check out this post before continuing.]
Your Reader Responses
And, wow, what excellent responses–! First, I want to thank all who participated in this challenge. Much like the results from our first Reader Challenge, no two responses were identical. I sincerely hope you enjoyed this exercise as much as I enjoyed reading what you’ve sent to the SWLing Post!
Below you will find responses from readers, representing remarkable diversity in radio set-ups. Note that my comments follow; they are italicized and in bold.
Now, with no further ado…I welcome you to radio DX in Laya, Bhutan!
I would set up all this gear either on a panel or in a small box for the sake of tidiness. This, involving crimping kit, crimps and wire, could be done before departure. Say $20 for the bits.
Job just about done but not quite…. solar panels only provide power when the sun is out… need a biggish battery to accept the solar charge during the day and give it back at night.
A nice wet cell 12 volt battery will do the job but that won’t be allowed on the ‘plane..what to do??
After flying into Bhutan at Paro and busing to Thimphu I would take time out to buy a 12V automotive battery. At first I considered a couple of 6V motorbike batteries but have been advised that motorbikes are uncommon in Bhutan but cars and trucks aren’t. No probs on-carrying that by truck, horse and porter so thats the 12V storage sorted.
Connect solar panel to charge regulator to my battery to my computer power supply and radio charging cables . Throw my wire antennas over the handy tree, pour single malt, put feet up……
Total cost excluded the 12 volt battery … about $600… Oh and must not forget to replace the supplied AA’s in the PL-660 with Sanyo Eneloops and also a few extra sets as spare…. and a copy of WRTH.
I must admit a bit of an advantage with this…. my boat is an off-grid installation and my wife was in Bhutan a few years ago.
Frank, I love how simple you’ve kept this set up. You are very wise to acquire a 12V auto battery locally, when you arrive in Thimpu. While Bhutan isn’t as commercially “developed” as many other countries, you can find basics like batteries, connectors, fuses and accessories in the capital city of Thimpu. Your experience off-grid on the open sea and with Bhutan, in general, have served you well. Thanks for your entry!
from Tim Rahto
[Note: Tim was so enthusiastic about this challenge that he proposed three different kits: one with a transceiver and two receive-only.]
Your radio challenge inspired me to ignore everything else I have to do today and write you up a response. [You’re welcome, Tim!]
I know your contest refers to shortwave listening and not ham radio, but we are talking about Bhutan here. According to QRZ, there’s only 9 callsigns in the entire country, with three of those belonging to radio clubs, special event stations, or DXpeditions. With that in mind, I put my station together with transmitting as well as receiving in mind.
Option 1: Yaesu FT-857D
For a radio, I chose the Yaesu FT-857D. I have one in my truck, and it’s survived four years of mobile operation without a hiccup. About the only knock I have on this radio is that the AM bandwidth is pretty wide for shortwave listening, but you can always put it into sideband if needed. It’s small, portable, and puts out 100 watts. Perfect!
Some would say I cut corners on the antenna, but I don’t think so. Considering the remote nature of the location and the need to keep things light and mobile, I went with a simple dipole. Easy to build, simple to repair, and works pretty well. I went the ‘roll your own’ approach and bought an Alpha-Delta dipole kit and wire for the antenna, and 100′ of coax to feed it all.
Tim, no doubt you had a lot of fun piecing together your radio kits! In each case you chose quality components–a smart decision since you want longevity and reliability in the field. I think there would actually be enough financial flexibility in each case to include a small back-up portable like the Tecsun PL-380 or similar. As you must know, the Lowe HF-150 is a surprisingly small tabletop radio with excellent performance; it would be easy to slip in a backpack or suitcase. Thanks for your entries!
For power storage, I’d go with sufficient numbers of AA size LSD NiMH batteries to be wired up into several 12V battery packs for solar charging… heavier than Li-Ion, but considerably cheaper, more durable, and should easily last through 2-years, where li-ion wouldn’t.
Probably throw a $100 Kaito KA1102 radio in there. The 1103 is infuriating. A long, long spool of wire for use as antenna once setup. And other bits and pieces.
Amazon says I’m $600, or $800 including the netbook, without really trying to find good deals. Lots and lots of accessories still needed, like 12V cell phone chargers, diodes and/or solar charge controller. I’d also throw-in other comforts, like plenty of different LED flashlights and lanterns, good external speakers and headphones. Plus lots of USB thumb drives just loaded up with movies and TV.
Rex, I like the idea of the KTOR pedal power when solar conditions are not favorable. in truth, using solar requires a little pre-meditation whereas pedal power could work anytime. Thanks for your entry!
from Timothy Johnson
Hi! This is a great challenge. I would take my Tecsun PL 660 and buy a solar AA charger. (And maybe $400 worth of AA duracells!) And for my backup……My Grundig FR200!
What? No gazillion dollar receiver with a four mile wire strung up?
Correct! It’s a fun challenge in a great location. I want to use the radio I use now to see what I can pick up. It’s a good location to pick up stations from the otherside of the world that I normally can’t get, but dream about what it would be like. The PL 660 isn’t a slouch when it comes to receiving, and it has SSB and the Airband! This is a fun challenge and it’s a great time to enjoy listening to the shows, not just seeing what I can get. Up in the mountians, I would need to rely on my shortwave for news around the world. I mean, what day is complete without Radio Havana Cuba’s slant on the news? I would hope over there I could get Iran’s Voice of Justice!
The FR-200 would be my back up to use if the solar charger breaks, or it’s cloudy for awhile. It’s a great portable with a built in dynamo. Plus its fun to use. Scanning the dial on an analog dial makes for relaxed listening. Kick back, pour whatever the locals drink, and see what comes in!
As an english/science teacher, I could introduce the students to the world and improve their english skills, while they teach me some of their language.
Anyway, great challenge!
I have had a lot of experience with the Grundig FR200. Unfortunately, it’s no longer available new from Grundig, but the same model is available from sellers on eBay as the Tecsun Green 88. Not only does it work well from the hand crank (2 minutes of cranking yeilds 40+ minutes of listening), but it also runs for 80+ hours on a set of AA batteries. It’s a durable radio as well. Thanks for your entry!
a) Install Linux (Fedora), GNU Radio, and other software for RTL SDR.
b) additionally install fldigi, multimode, HFfax software, NOAA weather decoder
c) make a QFH (Quadri Fillar Helix Antenna) for 137MHz NOAA satellite reception also usefull for VHF 2m reception, upon arrival at the destination. The wooden stick and batten used for it can be available free at the destination.
Total expences = 100+52+109+5+1.3 = 267.3 $
Still one have 1200 – 267.3 = $932.70
That’s an innovative SDR kit and certainly well within budget. In fact, you would have over $900 to purchase a backup radio, batteries, power generation and antenna accessories! Thanks for your entry!
from Cap Tux
Cap’s Virtual Radio Challenge Submission
As the challenges main objective is to listen to international broadcasters and DXing you only need a small portable receiver with very little power consumption. There are a lot of very capable receivers on the market now to fit the bill.
Remember, lugging a big receiver to the other side of the world is not going to be fun (and risk it being damaged en-route).
As the village is completely off the power grid I propose to use a small portable receiver & power source with a fairly good storage capacity i.e. at least 5 good charges from a fully charged source should give you a good few weeks of heavy usage.
Receiver: Tecsun PL-660 Receiver – A very capable shortwave receiver with MW/LW/FM with SSB and runs from 4 x AA rechargeable 1.2v Ni-Mh batteries.
This receiver is also capable of running/charging from a sustainable USB power source.
The PL-660 also has an auto scan and store that will sweep shortwave and store any stations it finds into memory, saves you tuning about.
You can charge this using a USB Charger for the Tecsun PL-660.
You may be lucky and have FM reception within range (unlikely, but possible), a general coverage receiver in most cases is not equipped with VHF BCB FM reception i.e. NRD-525, IC-R75 are not equipped with VHF FM.
In order to know what frequencies you need to tune into, realistically you will only have the first season i.e. A15 shortwave schedules for your target shortwave broadcasters.
You will not know the next seasons frequencies, you will need to listen into your favourite broadcaster nearer the time to get next seasons frequencies. Load the current seasons frequencies onto your laptop, or print them off.
The PL-660 has an external antenna socket by way of a 3.5mm socket, a long wire can be used. Personally, I would take my home-brew passive Mag Loop antenna which can fold up easily, why? in case of thunderstorms that could send static down an external long wire to the receiver, rendering it unusable.
You could always hang the long wire around your room to minimise static from thunderstorms. You get a long wire bundled with the PL-660, no need to buy another,
Sustainable charging power source for the receiver:
23000mAh Li-Po battery pack with solar panel (USB port & various outlets for laptop charging).
Technically you could ditch the 3 x AA internal batteries and power the Tecsun direct from the battery pack via the mini USB cable, however, assume you would want to run it autonomously from the charger or go out and about for a spot of Dxing. I propose purchasing 12 x 2400mAh rechargeable Ni-Mh batteries.
A phone or tablet is going to be a liability if dropped, a small netbook is going to be more robust for travelling and will have a longer running time from each charge.
I would also charge the laptop from my solar charger as it has a 19.5v option for charging. The MSI Wind U180 gives around 7.5 hours on a full charge (Loads of options for a netbook though).
The stock battery is about 7200mAh which the solar charger is more than capable of fully charging.
Tecsun PL-660: £64.64 incl shipping (all other shopping items include shipping)
Total: £318.28 ($517.06)
As this is well within budget you could buy two of everything for redundancy.
If AM BCB is your only concern a Tecsun PL-310ET will fit the bill, very small/light and cheap at around £32. There is also less chance of a small £32 radio being stolen.
In the end, I would probably take both my PL-660 & PL-310 as the PL-310 will give me the flexibility when out hiking or travelling within Bhutan and also acts as a backup radio.
Cap, I’m impressed with how frugal and portable you’ve kept your radio kit. Adding the Tecsun PL-310ET is a great idea. I imagine there would be superb opportunities to do mediumwave DXing with the ‘310. As a bonus, when traveling within the country, the PL-310ET would be easy to carry and use en route. Thanks for your entry!
FunCube Dongle Pro+ and Toshiba Encore 8″ running SDR# in a London park
To recap, the tablet-based SDR set-up costs $643. My experiments with FunCube Dongle Pro+ and SDR# software have convinced me that this combination makes for one of the best shortwave listening experiences in its price range. Here are a few reasons why:
– FunCube Dongle Pro+ is a sensitive SDR.
– SDR# has an excellent noise reduction algorithm that often turns laborious DXing into comfortable listening. It also has a robust synchronous detector, which, combined with its passband tuning and noise reduction algorithms can unbury almost any station from the surrounding co-channel interference.
However, given the remoteness of the location and the fact that there is no reliable electricity grid to speak of, we need a few extras:
You may recall that in my portable SDR solution there are two sets of batteries that need to be recharged:
– Toshiba’s built in Lithium Ion battery (via its USB port)
– 4xAA batteries for the Gomadic 5V Power Pack (used for supplying extra power to the SDR)
First, let’s get a compact, foldable solar panel:
1. Powerfilm F16-1200 20W foldable solar panel
I would go with Powerfilm F16-1200 20W foldable solar panel (buy it here for $210.99). Disclaimer: although I’ve never used any of the PowerFilm products or accessories, I have read good reviews of them from other radio enthusiasts. When folded, this solar panel measures merely 27.9cm x 16.5 cm – slightly smaller than an A4 notepad. Once fully opened, however, it can deliver 20W of power (15.4V, 1.2A), enough to charge the Toshiba tablet and 4xAA rechargeable batteries simultaneously.
The spares can be used in the following ways:
– To power the backup portable shortwave radio
– To have another batch ready when the batteries insde the Gomadic USB Power Pack run out.
– Using Gomadic, to charge the tablet outside daylight hours, for more daytime listening.
Now onto charging the tablet itself. For this I would use the Powertraveller Spidermonkey 4-Port USB Charger Hub at $38.76. Again, I haven’t used this product, but according to the specifications it can charge up to 4 USB devices and accepts input power between 5V and 30V. The reviews are largely positive, so it seems like a safe choice.
5. Powertraveller Spidermonkey 4-Port USB Charger Hub
Living off the grid has the advantage of there being minimal man-made radio interference. For this reason we can use a larger antenna than in my original proposal. I suggest buying 40m of POLYS18 Copper-Clad Steel Antenna Wire from Universal Radio (the total comes to $31.44), cutting it halfway, and attaching each half to one of the two antenna terminals on the Wellbrook HF Balun, mentioned in my previous article, thus creating a dipole.
12. BNC Socket to Composite 3.5mm Male Jack Plug Adapter
The subtotal for all of the above comes to $556.71. Adding on $643 for the tablet-based SDR solution brings the total to $1199.71, just 29 cents below the budget limit!
London Shortwave: since you frequently take this same portable SDR kit to the field, I have no doubt that it would perform well in rural Bhutan. Using a PL-310ET as a backup and even thinking to bring a couple antenna accessories shows how thoroughly you thought through this exercise. Knowing the copious amounts of radio noise (QRM) you deal with in London, you might decide to stay in RF quiet Laya after your assignment is over! Thanks for your entry! Readers: check out London Shortwave’s blog for more portable SDR fun.
from “Broad Wing”
Primary Radio – Comm Radio CR 1A ($614.95)
(Radio is light weight and very durable. It also picks up SSB etc. Even though it used up half the budget I figured it would be the best to have. It has an internal rechargeable battery. I can be charged with Goal Ten Battery Pack or Solar Panels)
Secondary Radio-Kaito KA-600 Voyager ($60.00)
(This radio is my back up as it has several ways to charge the batteries, solar crank, and electric when I can get to a city that has electricity. it should also be dependable. It also has a built in flashlight. This antenna uses AA rechargeable batteries.)
(I have used this antenna and find it to be very durable and a very good DX antenna for shortwave. It is made by a gentleman called Low Bander on e-bay.)
Secondary Antenna – Tinatena All Band Active ($32.90)
(I thought that if in the dead of winter, my primary antenna broke, and there were a couple feet of snow outside, I could use this one for a backup and not have to go out in the snow or storm. This antenna uses 9 Volt batteries.)
Antenna wire 12 gauge 50 feet ($27.94)
(Wire would be used to build a long wire antenna if needed or for repairs of the Super Sloper Antenna. Wire will also be used to hook up 2- 12 Volt sealed batteries to primary radio.)
40 foot solar panel extension cable MC4 converter ($22.99)
(This kit and the extra solar panel should charge up my batteries if the weather permits. The solar panel can be hooked up in tandem to provide quicker charging times or used on separate equipment. The Goal 10 charger will charge my Comm Radio when the power is low, and I can connect the radio to the kit when the sun is out just to recharge. When the sun is not out, or I have a long time without sun, I can use the Secondary Radio to conserve batteries.)
Set of batteries sold with 24 AA 2000 mAh, NiMH Batteries low discharge ($42.34)
9 Volt batteries, 4 pack ($15.96)
2- 12Volt 7ah sealed lead acid rechargeable batteries ($32.00)
Total Cost: $1198.73 -$ I200.00= $1.27 under budget. Good for a pack of crackers to take on the plane to munch on.
I am not buying any connectors as the primary antenna comes with coax and connector. All prices include shipping and handling charges and can be received in 7-10 days. In two years I will report back to you and tell you how the trip went.
I think choosing the CommRadio CR-1a as the centerpiece of your set up is wise. The CR-1a is very rugged and engineered to last. Most importantly, you can power and charge it on a wide range of voltages (6-18 VDC). That’s power flexibility! Thanks for your entry!
from Eric McFadden (WD8RIF)
What a fun thought-experiment!
For the shortwave listening station radio, I’d buy a Sony ICF-SW7600GR portable shortwave receiver. It’s stable, sensitive, selective, provides SSB and synchronous-detector, and runs on common AA cells. It’s available for about $132 on Amazon but I’d probably buy from Universal Radio.
I’d buy an Emtech ZM-2 “z-match” tuner ($65 in kit form, $90 built, direct from Emtech) to use between the Sony and the random-length wire antenna; I’d adjust the tuner’s two knobs for maximum noise in the receiver. A 3′ RG-8X coax BNC-to-BNC jumper ($6 at Universal Radio) plus a BNC-female to 3.5mm-male adapter (#4546, $3 at Universal Radio) would be used to connect the Sony to the tuner; the wire antenna would connect directly to the tuner’s binding post. A short length of wire could be used as a ground-connection or counterpoise, if desired. I’d also take a pair of solder-less alligator clips (less than $1 each, many sources) and a solder-less 3.5mm plug (I have one of these but haven’t yet found a source for a new one; I might have to make one) in case I would want to (or need to) use the random-wire antenna without the z-match tuner.
The receiver uses for four cells; one of the panels could (probably) charge a set of four cells each day and the Eneloop chemistry would allow the charged batteries to remain charged while not in use. The second 8-pack of Eneloops and the second Powerfilm solar-charger provide redundancy. It’s unlikely that one evening’s listening on the Sony would discharge a set of cells so it wouldn’t be a problem if the solar panel needs more than one day to fully charge a set of four cells.
If I choose the kit version of the z-match tuner and don’t buy an MFJ-1910 mast, the total comes to $449.
I am an amateur radio operator and would want to take along some sort of transceiver. Given my druthers, I’d take my Elecraft KX3 and forget about the ICF-SW-17600GB but that’s against the rules of this Challenge.
Since I can’t take my existing KX3, I’d buy a YouKits HB1B Four Band CW QRP Transceiver (80/40/30/20m, $300 from YouKits), a Whiterock MK-33 single-lever CW paddle ($30 from Electronics USA), two pairs of inexpensive over-the-head stereo earphones (~$10/ea), a ten-cell AA holder (#10AAT, $7 at Batteries America), and another set of 2000mAh AA Eneloop cells. I’d use the same random-wire antenna I deployed for the listening post, and the same Emtech ZM-2 z-match tuner to match the transceiver to the random-wire. The 8-pack of Eneloops plus two cells “borrowed” from the extra set purchased for the listening post would be used to make a 10-cell battery-pack for the transceiver. Using both Powerfilm chargers would probably allow me to fully-charge ten cells in a two-day period. I’d have to balance the charging needs of the listening post and the ham station but I think it wouldbe workable.
The cost of the ham station comes to $382.
The rules of the Challenge were unclear about whether the cost of a tablet/smartphone/PC was to come from the $1200. Either way, I’d probably limit myself to a 7″ tablet such as the Nexus 7 I bought myself last year for $150. A Powefilm USB + AA Foldable Solar Panel ($80 from Amazon) could be used to charge such a 7″ tablet. (And the same panel could be used to charge cells 9 and 10 of my 10-cell ham radio battery pack, allowing me to charge the ten-pack in a single day instead of needing two days.)
The grand-total of all of this stuff comes to $1,061, leaving enough to purchase a second ICF-SW7600GR to take as a spare.
I know this is just a mind-experiment but I’d love to hear what the HF bands sound like so many miles from any RFI sources!
Eric, I like how you’ve balanced your ham radio and shortwave listening needs in this kit. While there was no restrictions to keep you from using a KX3 (both a superb transceiver and general coverage receiver), your set up allowed for more extras and back-up supplies. Since a basic kit version of the KX3 costs about $930 (shipped) it would have eaten up much of your budget. Since I own a KX3, my first inclination was to design a kit around the KX3 as well (if the budget would have even been $100 more, I probably would have). With your kit, you have a little money to spare, plenty of antenna-making supplies, a fantastic antenna tuner for both SWLing and QRP, a benchmark portable receiver and a capable four band QRP CW transceiver as well. Great job! (Readers, Eric has an excellent website devoted to ham radio and QRP–his projects are beautifully documented.)
from RS Wood
By the sound of it, this is a Peace Corps assignment. May as well ask a former Peace Corps volunteer!
I’d personally recommend you keep a low profile: traditional peoples like those you find in Bhutan will see your fancy antenna on the roof and assume you’re a spy or something. I’d go for a portable shortwave – something in the $150-$300 range from Sangean or Tecsun, as well as a $35 indoor, powered antenna (they run on AAA batteries). Buy a second radio as backup.
For internet use, assume you’re going to be offline for long periods of time. Get a netbook, not a tablet/smartphone, and one or two USB hard drives for storing your stuff. Ditch gmail/hotmail and get an account from which you can download email and store locally when you’re in town (fastmail.fm, toast.net) – look for POP3, not IMAP. Idea is: you go into town, plug in somewhere, download and store your stuff locally, and can use your machine at your house, with no connection to the internet, to write. You might be able to get a GSM modem if service extends to your post; that’s another reason to have a machine with USB slots into which you can stick a USB modem (yes, dialup) or GSM (cellphone) modem. Used netbook on ebay should run you $200; add another $200 for external harddrives you bring stocked with stuff (ebooks, etc.).
Lastly, bring as many notebooks, pens, and books as you can. Speaking from experience, you’ll find yourself doing more reading and writing, and less internet. And I repeat: keep your radio low-profile. Whip out the huge radio and antenna and your neighbors will distrust you, seriously.
Good cultural points! This is true. In the past, I have given this same advice to aid workers traveling to impoverished urban areas. Not only does a conspicuous setup attract attention, but also (sadly) theft–not just of your radio, but anything else in your house. Fortunately, I have only heard positive reports from Bhutan–houses without locks, that sort of thing. Thanks for your entry!
from Ariel Jacala (NY4G)
For starters – I would either build from scratch or buy a new Elecraft K2. Since I would be on assignment for 2 years, I would need to be able to repair my gear. A K2 is built from through hole components so it is repairable. All I would need are some spare parts for the components that are known to be failure prone – mostly diodes. I would consult with W3FPR for his recommended list of spare components from his experience of repairing hundreds of K2s. If I can find a used one with a SSB module, so much the better. I would volunteer to build one for someone else just to get the build experience.
The next thing is toss up. Cabelas sells 500 watt generator for $350 dollars or do I get a small amp. Provided I can get gasoline from the villagers, the generator will make living here at least bearable – for lights, charging batteries and another power source other than the sun. The amp goes for $300 – a Hardrock50 which I have built. Is it worth the extra 6 or 7 dB from 10 watts? You bet. In an emergency I can use the extra 40 watts or for a long overdue ragchew in English.
There you go
Transceiver, batteries, solar panel with money to spare. – about $350 left.
Ariel: Very smart of you to consult Don Wilhelm (W3FPR) as he is the most knowledgeable source of info about the K2 and any weaknesses it may have. I have a K2 and completely agree–it’s probably the most capable transceiver that can be field serviced. The only weakness of the K2 (for this hypothetical trip) is the fact that it does not have a general coverage transceiver. For any broadcast listening, you’d want to use some of that $350 surplus for a portable receiver–easily accommodated in your budget! I know you Ariel, and am willing to bet that most of your radio time would be in the ham bands! Thanks for your entry!
from Anil Raj
Spend two years in Bhutan, off-grid and with no internet… Wow! That is probably the most extreme scenario one can think of! However, not completely alien to me as I work in the energy business setting up power plants in off-grid areas http://www.omcpower.com/
These are my thoughts:
Click to enlarge.
Clearly, the single largest limitation is going to be the availability of reliable power. A quick look at a solar insolation map for the region makes it clear that solar which would normally be the most convenient source of power cannot be relied upon in this case.
My choice for reliable power would be a combination of a solar charger with a set of Eneloops and the BioLite stove since all it needs to generate useful power are twigs and sticks. It generates about 3 – 4 Watts which can comfortably power a small radio. I’m pretty sure the stove would come in handy in the winter to keep warm as well! The daily ritual of lighting a small wood fire to listen to the radio might eventually become a meditative experience… Price $ 118.00 + $130.00 + $20.00
My choice here is the Sony 7600GR. It is time tested having been on the market for over a decade. In my opinion it has by far the most robust build quality in it’s price range. SSB is a must, and the Sony performs well in this department, and the AM sync is a bonus feature. The main reason for my choice however, is the frugal power consumption – about 50 mA. The Sony also happily runs off a 5 V supply like a USB charger which simplifies the power issue significantly. Price $ 130.00 on Ebay
Headphones are a must to keep power consumption low and my choice here are the “Sleep Phones” http://www.sleepphones.com/ The fantastic thing is that these also keep your ears warm (Himalayan winters) and of course you can use them in bed without the discomfort normal headphones or earbuds usually give. Price $ 40.00
Being a ham, it is obvious that a transceiver will have to be a part of the plan. Any of the traditional general coverage transceivers available today would immediately break the energy budget and not be viable for more than a couple of weeks. Here my choice is the Mizuho MX-14s handheld. This tiny rugged 20 M transceiver puts out 2 W on SSB and CW, fits in my pocket and hardly draws any power. My plan would be to keep it for emergency use only in case a license is not possible. I have used one of these for several years and know what is possible with 2 Watts and a good antenna. Power is from a set of Energizer AA lithium batteries which can hold a charge for up 20 years.
My choice would be the HyEndFed antennas EFHW and the most suitable would be the 20 M version which would work fine as a random wire for the Sony receiver as well as and End Fed Half Wave for the transceiver. These antennas are built to a very high spec with silver plated wire with teflon insulation etc. Price including feeder and adapters $ 120.00
So, all the bits and pieces together add up to about $ 1000.00 which is comfortably inside the budget. I would definitely spend the rest on woollen socks!
Anil, this is brilliant! What I like best is that your kit is based on your experience both with alternative energy and the equipment you’d plan to use. Having built a solar house myself, I also consulted a solar isolation map when first tackling this Bhutanese challenge. You’re right: unless you have a semi-permanent PV system to trickle charge a battery anytime you have solar gain, you could be disappointed if relying on portable solar alone. Though I had heard about the BioLite, I’ve never used one. I’m very tempted to buy one now. I see where it could provide two important resources at once: heat and power. I also love the idea of the Mizuho MX-14s HT transceiver; though it’s limited to 20 meters, that would be one of the best and most useful bands if you decided to get on the air. I’ve read that the Mizuho is nearly bullet-proof. Still, like Ariel with the K2, I would consult Mizuho MX-14s users in advance of the trip and perhaps stock up on components that commonly fail. Looks like they would be relatively easy to replace in the field (with an inexpensive battery-powered soldering iron). Thanks for your thoughtful entry!
What fun! Thank you all…
I know this sort of challenge may not appeal to everyone, but I really enjoy it. This sort of exercise forces you (though safely) outside the comfort-zone of a home radio set-up. Your responses are truly innovative.
Thanks, again, for your participation! If your response wasn’t included above, or I didn’t respond to you directly, please let me know: it’s possible I skipped over yours by mistake as there were quite a few responses to collate, and my email is managed by a rather discriminating SPAM filter.
Meanwhile, if you think of an alternative set-up–or would like to add your own to this post–please comment below!
I already have more than six future reader challenges waiting in the wings: all based on real inquiries from readers. I hope to post another in the near future.
Below, London Shortwave shares a guest post (also viewable on his blog) which describes in detail his design for his portable SDR around the FunCube Dongle Pro+ and an 8″ Windows tablet, and explains how effectively it works for him. This post includes recordings and a video; it’s an excellent tutorial:
At the outset, I thought that all that was necessary was a tablet (I chose Toshiba Encore 8″), the FunCube dongle itself and just some antenna wire. This turned out to be a naive assumption because the tablet’s USB interface injected enormous amounts of radio frequency interference (RFI) into the SDR, making listening on some shortwave frequencies essentially impossible. Just to be sure that I wasn’t being plagued by a defect of my chosen tablet model, I tried out the same set-up on a Dell Venue 8, with identical results.
To deal with the issue of tablet-generated RFI, I bought a galvanic USB isolator, which, in essence, is a box that breaks the electrical connection between the USB dongle and the tablet’s USB interface while allowing USB data to pass through in both directions.
Heros Technology galvanic USB isolator
Additional power for the SDR
The isolator resolved the RFI issue completely, but created another problem altogether: the device specifications state that the isolator’s power output is restricted to 100mA at 5V. This is sufficient for USB devices that are self-powered but not for the FunCube dongle that draws all of its power from the USB port to which it is connected.
USB Y cable
One way to supply extra power to a USB device is to use a “Y-cable”. Such cables have one extra USB plug that can be attached to a source of additional power (for example, a USB power bank). This solution is commonly used to connect power-hungry items, such as large hard disks, to low-power, portable computing devices (laptops and tablets). Having bought this cable, my next step was to find/improvise a battery that meets the USB power specifications (5V, 500mA).
Yet more interference
My first thought was to use the mobile USB power bank that I use to charge my iPhone while on the go. After all, it already has a USB port and supplies power with the right voltage. Once again, my expectations were confounded and RFI reared its ugly head! The power bank radiates significant interference into the circuit because it uses a switching regulator to maintain steady voltage. Luckily, I came across Gomadic’s portable AA battery pack with regulated 5V output that emits way less interference than any of the other USB batteries I tried (my intermediate solution used 4 rechargeable AA batteries and a makeshift USB connector, and although this resulted in zero additional interference I decided that it’s not safe to supply the SDR with unregulated voltage that doesn’t match the rest of the circuit). I used the handy passthrough USB voltmeter I bought in Maplin to check that Gomadic’s nice-looking gadget does indeed give out 5V as advertised.
So, what can one do with the remaining RFI from the additional power supply? It turns out that it can be mitigated quite effectively by inserting a balun (item 10 on Figure 2) between the SDR and the antenna wire (item 12). The balun is connected to the SDR with a coaxial cable (the “feed line”, item 11). Additionally, ferrite choke rings (item 9) attached to the feed line help reduce this RFI further: winding the feed line through the choke rings several times is sufficient. However, neither the balun nor the chokes are effective enough to replace the USB isolator! It appears they only help with the noise generated by the power supply, which is relatively minor anyway.
Cost vs Portability
When SWLing Post published the details of my intermediate solution, Dennis Walter – one of the engineers behind Bonito RadioJet – popped up in the comments section and suggested that my setup is too tedious, as it involves lots of cables, and that his SDR is superior in terms of portability and the supplied software. While I haven’t had the chance to evaluate RadioJet, I pointed out that the cost of his radio is significantly higher than that of all of my components put together. I also mentioned that the free SDR# software I use is superb: it sounds excellent and offers a number of features that many software packages and conventional radios don’t have. So, having finalised my design, I thought that it might be time to tally up the cost and listen to the results.
Adding up the prices of items 2 – 12 (and excluding the optional voltmeter) brings the total cost to $449 vs. Bonito RadioJet’s $689. For the price difference you can throw in the Toshiba tablet at $194 and still have some change, enough to buy a carrier bag and perhaps even a nice pair of headphones!
Figure 1. Radio components
Figure 2. Antenna components
In terms of portability, the entire setup fits nicely into an 11″ laptop carrier bag.
Figure 3. Packing the components into an 11″ carrier bag
Figure 4. Ready to go
Setting things up in the field is not particularly cumbersome, either:
Figure 5. Portable SDR setup in action in a local park
As for the results, listen to the below snippets and be the judge. The only thing I will say is that none of my other portable radios have ever given me this kind of performance, not even with the long wire antenna attached:
At one point I wanted to build an enclosure to house the FunCube dongle, the power supply and the USB isolator in a single tidy unit, but I no longer see the need. It’s easy to pack all of those items into the carrier bag and also they are all useful individually: the USB isolator can be paired with other SDRs, and I recently discovered a neat additional use for the Gomadic battery pack.
Well, that brings me to the end of this post. I hope my design will inspire you to come up with your own portable SDR system, and that you will share your results with me in the comments section. Happy listening!
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