Tag Archives: Wellbrook

The Bonito Boni whip: proving to be excellent portable antenna for DXing

Hi there, if you’re a subscriber to the Oxford Shortwave Log YouTube channel, you will be aware that I have been using a Wellbrook ALA1530 H field antenna, for 15 months or so, with (at times) excellent results. A while back I was on the lookout for a second antenna, however at more than £250, I couldn’t justify purchasing a second Wellbrook. Ultimately I splashed out on the Bonito Boni whip E-field wideband active antenna (20 kHz to 300 MHz) and with a very compact form-factor suitable for DXpeditions/portable operation in general, the Boni whip definitely ticked all the boxes. Furthermore, with reasonable second and third order intercept points of +55 and +32.5 dBm respectively, the Boni whip, on paper at least, looked like a pretty good buy at around £100.

 

Initial testing at home confirmed, perhaps not surprisingly that the Boni whip could not match the SNR provided by the Wellbrook ALA1530 in a noisy, urban environment. However, less predictably, the Boni whip has proven to be a truly excellent antenna away from the ubiquitous blanket of ‘electrosmog’ at my QTH. Furthermore, it really is so compact, I simply leave it in the car in a small flight case, with a portable and connectors etc. for ad-hoc listening sessions. Since returning from my most recent trip to Brazil, I have had a chance to review my most recent catches with the Boni whip, some of which are realy pleasing and most definitely underline the excellent performance of this diminutive antenna. In particular, signals from Radio RB2  on 11935 kHz and Radio Aparecida on 11855 kHz, both low power Brazilian stations, are testament to how sensitive the Boni whip is in an electrically quiet environment. Check out also the quality of longwave signals from Poland and the  Czech Republic – simply amazing for such a physically short antenna. Finally, there’s a personal first from Lusaka, Zambia, Voice of Hope Africa on 13680 kHz. All the more rewarding that this was actually copied in my work office!

I hope you found this article interesting. There are embedded reception videos below and text links for all, which will take you directly to the relevant video on the Oxford Shortwave Log YouTube channel. Thank you for reading/watching/listening and I wish you all excellent DX!


 

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

Click here to watch on YouTube

 

Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

North American and European medium wave signals into Oxford, UK

Hi there, I’ve been rather preoccupied of late, initially with the brilliant Tecsun PL-310ET and latterly with the even more brilliant Eton Satellit. However, in the background (as always), I’ve been trying to catch transatlantic medium wave DX. My listening schedule is broadly based on shortwave DXing during daylight hours – when I’m not at work of course, typically a Friday afternoon or at weekends – and always with a portable. Evenings usually start off with a tune around the tropical bands, followed by setting up the Elad FDM DUO to run some medium wave spectrum recordings overnight. In the past few days though, my daylight DXing has been bolstered by my NooElec RTL-SDR and ‘Ham it up’ upconverter. I bought the device over a year ago and after some initial exceitement, it quickly became quite obvious that I needed a reciever with a bit more ‘oomph’! However, it’s actually proving very useful to view signals on a  spectrum, even when I’m conducting most or all of my listening on a different (i.e. higher performing) receiver. Ultimately, the RTL-SDR is always going to be a compromise, with relatively limited sensitivity, but because by it’s very nature it has excellent selectivity, overall it’s a reasonable performer. My particular RTL-SDR performs quite well if a decent antenna is employed with it, such as a longwire or the Wellbrook ALA1530 active loop.

Anyway, back to the medium wave DX. In the past month or two, I’ve copied a number of stations from North America, with really nice signals, including WRCR Rampano – New York, WFED Federal News Radio – Washington DC, WENE – Endicott and WUNR – Brookline from Newton, Mass. I’ve also recorded a lovely interval signal from RAI Radio 1, Milano and further European signals from Magyar Radio, Budapest and Radio Slovenija 1, from Ljubljana. During the past 18 months or so of DXing, I have been mostly ignoring signals coming into Oxford from the continent. However, that changed a little after I stumbled across the RAI Radio 1 interval signal, which complete with the rather rousing Italian National Anthem, inspired me to dig out some more European DX. I’m actually finding European DX quite rewarding, particularly because it feels new again – not surprising since I haven’t listened to Europeans on medium wave for any length of time since the 1980s. I hope you enjoy the reception videos – embedded video and text links follow below and I wish you all the very best DX. 


Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on youtube

 

Click here to watch on YouTube

Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

Medium Wave DX: CBC Radio 1 Gander, 1400 kHz, remarkably clear signal in Oxford UK

CBC Radio 1, Gander, heard in Oxford UK

A really great signal from CBC Radio 1 Gander – the best I’ve ever heard on this or any other medium wave frequency, complete with a clear station ID and very much out of season so-to-speak. I can’t remember recording any Medium Wave transatlantic signal with an audio bandwidth filter of 7 kHz, which says everything about the relative strength of this signal; 2.5 to perhaps 4 kHz would be more typical. As the subscribers to my youtube channel Oxford Shortwave log will know, I dabble in Medium Wave DXing, however, it requires a lot of patience because conditions of good propagation can occur quite infrequently. This is where the band recording features incorporated into the Elad FDM-SW2 software (and similar software for other SDR receivers) come into their own, allowing you to record the entire medium wave band, for example, for later analysis. As for the Wellbrook ALA1530 active loop antenna, I can’t praise it highly enough, both in terms of combating QRM and overall performance as a function of compactness.

Recorded in Oxford UK using an Elad FDM DUO and Wellbrook ALA1530 active loop antenna (indoors) on 29/06/16 at 03:00 hrs UTC.

Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

 

Guest Post: London Shortwave’s guide to mitigating urban radio interference

London-Urban-CityMany thanks to SWLing Post contributor, London Shortwave, who is kindly sharing this guest post–a brilliant article he recently posted on his own website.

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

by London 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.

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:

  • Plasma televisions
  • Laptop, and other switching-type power supplies
  • Mobile phone chargers
  • Dimmer switches
  • Washing machines / dishwashers
  • Amplified television antennas
  • Halogen lighting
  • LED lighting
  • 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.

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

Wellbrook UMB130 balun with the feed line terminal disconnected

Antenna preselectors

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

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

Global AT-2000 antenna coupler and preselector

Risk of lightning

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)

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)

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

Two Wellbrook ALA1530S+ antennas combined through a phaser

And now onto the phaser units themselves.

Phaser units

dxe-upload

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.

Cost considerations

Fig.4 Final urban noise mitigation schematic

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.

Acknowledgements

Many of the above tricks and techniques were taught to me by my Twitter contacts. I am particularly grateful to @marcabbiss@SWLingDotCom, @K7al_L3afta and@sdrsharp for their advice and assistance over the years.


Thank you–!

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.

I encourage all SWLing Post readers to bookmark and search London Shortwave’s website. It’s a treasure trove for the urban SWL. We thank him for allow us to post this article in its entirety.