My, how time flies. This is a post I have been meaning to write for nearly 3 years now. Back in late 2018, after a search for a small portable SW receiver, I purchased a C Crane Skywave SSB. It had a lot of the things I wanted in a portable radio and, at the time, I felt that it offered a lot for a receiver of it’s diminutive size.

Then I became aware of an even smaller receiver called the Belka-DX. Designed and manufactured by Alex EU1ME in Belarus, this positively tiny radio used SDR technology and, judging by the reviews I was reading and videos I was watching on YouTube, there was no other receiver it’s size that felt and performed like a much larger communications receiver in the way that this one apparently did. It all seemed very encouraging, so I went ahead and ordered one directly from Alex in Belarus. The first time I tried to order direct from his site, my bank denied the payment. I got on the phone to advise them that it was a legitimate charge, and they gave me a one hour window in which to put the transaction through again. I returned to the site, ordered the Belka-DX, and the order was accepted.

There are 3 ways I know of to purchase Belka receivers –

1. Directly from Alex EU1ME, in Belarus. Alex supplies 2 versions, with and without a built-in speaker. In order to accommodate the built-in speaker, that particular version has a slightly smaller battery. The version with the built-in speaker currently costs 475BYN, which at the exchange rate at the time of writing, is about US$145. As of Aug 9th 2024, Alex’s site carries the message that international shipping is currently unavailable. I notice that in the Q&A, Alex noted in July that he hopes to resume shipping to the US in about a month. This was the message he posted, on July 18th 2024 – “We do ship to the USA but at the moment we need to to undergo technical expert appraisal so that our Belarusian customs could allow export abroad. We hope to restart shipping in a month. Shipping cost to the USA is 13 USD.”
   
   
2. From Mobimax in Bulgaria. This is the same receiver, but with a larger speaker back that also has two small fold-out legs. This increases the depth of the Belka, but allows you to have a speaker as well as the larger 2500mAH battery. The markings for the input and output connections on the sides are etched into the metal. In addition, the LCD display is fitted with a screen protector into which are etched the words “HAM tactical RCVR”. Mobimax sell two different packages containing this receiver. The only difference is that the very slightly more expensive package includes a 3.5mm stereo to 3.5mm stereo cable, for plugging the IQ output of the Belka to your computer for use with SDR software. The version of the Belka that Mobimax supply is currently 227 Euros, which is about US$247. The package with the IQ cable is just a few Euros more.
   
   
3. There is an eBay seller in Bulgaria who sells the same version that Mobimax does, but for the (in my opinion) rather high price of US$350. The main reason I can see that buyers might go for this seller is the convenience and comfort factor of being able to pay with Paypal on a site they are familiar with.

A few weeks after ordering, a small box arrived from Belarus. In it was the Belka-DX wrapped in bubble wrap, and a small telescopic whip antenna of about 28.5″ in length. No documentation was included in the box, though it is available online. I didn’t take any pictures of it then, so here are some of it now, 3 years later.

In the above image, the backlight is on. In the next one, it is off. The backlight can be customized to be on all the time, off all the time, or to stay on for 12 seconds after any button is pushed or the tuning knob is turned. In the next photo, to the left of the BNC is a micro-USB connector that is used for charging the receiver. Underneath it is a red LED that lights when charging. To the right of the BNC antenna connector is the 3.5mm earphone jack. It is important that a stereo TRS jack is used here. A mono jack will short out one of the channels and can damage the audio IC –

At 82mm x 50mm x 20mm, this receiver is small!

I’m not sure if this is still true of the version that comes with the internal speaker direct from Alex, but the speaker holes in mine were slightly imperfect. It was evident that they had been drilled by hand. Not a big deal, but I thought it worth noting –

On the right side is the tuning encoder. It rotates smoothly with no click stops, for that “big receiver” smooth tuning feel. Also on the right side is a 3.5mm jack for the IQ output –

This was the second iteration of this receiver. The first one, named the Belka-DSP, covered 3.5-31 MHz. The Belka-DX covers 1.5-31 MHz. There is now a newer version, known simply as “Belka”, that has impressively continuous coverage from 0.1 MHz – 31MHz. Yes – 100KHz to 31MHz!

There are, by now, a number of quite detailed reviews of this series of receivers online. One such review, which gives a good overview of the capabilities of this pint-sized communications receiver, was written by Dave N9EWO. Since purchasing my Belka-DX almost 3 years ago, I have used it regularly. There are several features that I find very compelling, which distinguish it from many other shortwave portables –

1. There is no chuffing or soft-muting in between frequency steps. As a result, when on the smallest frequency step of 10Hz, the effect is of smooth, continuous tuning.
   
   
2. Unlike the CC Skywave SSB and, I believe, many other portables of it’s type, it is absolutely solid on SSB and CW receive. The carrier injection on my C Crane receiver was unsteady on strong signals, leading to chirping on CW, and similar frequency instability on SSB. For a short while, I owned a CountyComm GP-5 SSB, which was even more unsteady. The Belka-DX handles like a proper communications receiver in this regard, being rock steady on strong and weak signals alike.
   
   
3. The frequency display is accurate. As far as I can tell, it is accurate to better than 10-20Hz across the frequency range. Because of this, I can easily tune it to a frequency, and know that it is there. The Belka-DX employs a 0.5ppm TXCO and as a result, has a high level of frequency stability. My Skywave SSB only tunes in 1 KHz steps. To interpolate between those steps, you have to push a button to engage the fine tuning, but are not able to read the frequency accurately in between those 1 KHz points. For many users, this might not be an issue, but for those who listen out for weak beacons and other signals that are not on 1 KHz “channels”, the continuous tuning and accurate frequency readout on the Belka makes such monitoring much easier. A couple of years ago, I went on a 4 /12 month long campervan trip around 6 Western states. At the time, one of my interests was listening out for low-powered unlicensed HF beacons. Standing in the vast expanses of the desert with the little Belka-DX in my hand, hearing a weak low-powered CW beacon from hundreds of miles away was magical. These beacons are home-made affairs, and usually running somewhere between 30mW and a watt. Being able to dial in the precise frequency on a handheld receiver that is even sensitive with the set-top whip is a boon with such pursuits.
   
   
4. You can tailor the passband for each mode. With my C Crane Skywave, and I believe many other similar receivers, the adjustable filtering (if available) is audio filtering, and doesn’t occur in the RF stages. The Belka is an SDR, and the custom adjustable filtering is the equivalent of filtering in the RF or IF stages of a conventional superhet.

Two things that I wasn’t too keen on, and which have been amended in the 0.1-31MHz version –

1. In CW mode, the frequency display doesn’t indicate the operating frequency. For example, with a 700Hz sidetone pitch selected, if you want to receive a CW signal on 7030 KHz, you have to tune the receiver 700 Hz below that frequency i.e. to 7029.3 KHz. You do get used to it, but it would be nice to have it display the actual operating frequency in CW mode. In the newest version, the 0.1-31MHz version, I have read that the receiver displays the actual operating frequency in CW. If you’re concerned with being able to read out the exact frequency (if searching for weak beacons on non-standard frequencies, for example) you’ll still need to ensure that you tune to the correct sidetone frequency in order for the frequency readout to be accurate. Personally, I’d love a sidetone feature for this, but I doubt that too many others would consider it to be an essential feature in a receiver (as opposed to a transceiver).
   
   
2. When stepping through the memory channels, you cannot hear those channels as you cycle through them. In order to hear the selected channel, you have to press the appropriate button to select and load it. Thus, you cannot easily scan through a number of preset memory channels to listen for activity. As with 1 above, I this has been remedied in the newest version of the Belka.

The audio quality from the Belka-DX is excellent when used with earbuds. The internal speaker doesn’t do it justice, though it is very useful when taking the receiver on outings. Power from the audio amplifier is adequate for most applications, though when plugging an external speaker in, it helps to use one that is sensitive. Some people use powered speakers. I have two external speakers on the bench, both unpowered, that I use with it. The main one is an MFJ-281 ClearTone speaker. It is sensitive, and produces good volume. The audio response from the mylar cone is restricted, and what I would characterize as communications quality. Audio is clear and intelligible. The speaker appears to have a natural resonance at around 650-700Hz, which is useful for CW. For those times when I need a little more fidelity, such as when listening to strong SWBC stations, or hams on AM, I use an old and compact hi-fi speaker manufactured by Cambridge Soundworks. It was discarded by one of my neighbors, and appears to be a mid-range unit. It is not as sensitive as the MFJ ClearTone speaker, but the Belka will still provide enough drive in a small, quiet room, which perfectly describes the conditions in my shack.

The small size and slim dimensions of the Belka-DX make it ideal for traveling. When using it at home with an external antenna connected, the ergonomics and ease of use are much improved when mounted on some kind of stand. There are a number of stands available, as well as files for those who wish to 3D-print their own. I remembered a clamp I once bought, that was designed to hold a cellphone for attaching it to a tripod, for making videos. The Belka is not quite as wide as a cellphone, so I used a couple of pieces of dense foam to pad it out, and screwed it to a small tabletop tripod. It works quite well, and improves the ease of use drastically when listening at home. When mounted like this, it feels like a serious and very usable SWL set-up. In the various SWL groups on FB that I frequent, I often see questions from folk asking about receivers that are good for SWL’ing. Portables such as the Tecsun PL-880, along with other similar receivers are often recommended. I think that this Belka makes an excellent receiver for all-round shortwave listening. It is not available in as many outlets as the more traditional shortwave portables, which is why I think that it isn’t as popular in the SWL community as it should be. If you are listening mainly to AM broadcasts on shortwave, then many of the portables will most likely work well. If you do a lot of SSB and CW listening though, the Belka is a solid and, to my mind, preferable option.

In the following picture, my Belka is mounted on a mini tripod (an Ultrapod) and connected to the MFJ ClearTone speaker. Behind and underneath the Belka, you can just see an Altoids tin which contains a high pass filter with a cut-off at about 2700 KHz. It was designed to prevent overload from strong local AM broadcast stations. More on that later in this post.

The Belka-DX is surprisingly sensitive when listening outdoors with the included telescopic whip. It does need a counterpoise, or the received signal strength suffers greatly. If you are holding the receiver, then your body acts as the counterpoise. If you are listening on earbuds or headphones, then the headphone cord acts as a counterpoise. If the receiver is sitting on a surface and using the internal speaker, then you’ll need to connect a counterpoise wire somehow. At home, it works really well when connected to my outdoor antena, which is a doublet at 47 feet, cut roughly for 40M, fed with 300 ohm twinlead, and matched to coax at the entrance to the shack, with a balun and Elecraft T1 tuner. I tune the T1 by squirting RF into it on the nearest amateur band. If you are using your outdoor antenna for listening only, then a simpler arrangement would suffice. This just happens to be the one antenna I also use for my ham exploits.

I live in a densely populated urban area, within a few miles of several medium power (5KW) AM broadcast stations. They often break through when I am using the external antenna with receivers that don’t have narrow filtering on the antenna input. My Belka-DX experiences strong AM breakthrough when used on the external antenna at all frequencies up to 4530 KHz. The moment I tune above 4530 – even by a single 10Hz step, the breakthrough stops instantly, suggesting that a different bandpass filter is switched in at the point. According to the manufacturer-supplied block diagram of the first version of Belka, known as the Belka-DSP, the input bandpass filters are from 3.5-7.5MHz, 7.5-15MHz, and 15-30MHz. The block diagram can be seen on this page by Fernando Duarte. I assume that for the Belka-DX, with it’s extended coverage down to 1.5 MHz, one of the bandpass filter crossover points is at 4530 KHz, the point above which all AM BC band breakthrough stops.

To solve this problem of breakthrough, I resorted to a little high pass filter that I have used successfully with other receiver projects. It’s a high pass filter that was designed by David WA7JHZ, details of which were given in K4SWL’s very wonderful and informative SWLing Post blog. You can see it here. David built his with molded chokes. I built versions with both molded chokes and toroids, and compared the response curves.

Trusty Altoids tins to the rescue. Here’s the version built with molded chokes, purchased from Tayda Electronics. The chokes are mounted vertically, and are a little hard to see in this image –

The small holes in the base of the tin were left over from a previous project that didn’t work out.

Then I built another high pass filter with toroids instead of molded chokes. I figured the toroids should have slightly higher Q and would present a better response curve. All 4 inductors were wound on T37-6 toroid cores with 26 AWG wire. The 2.7µH inductors had 30 turns and the 1µH ones 18 turns. The wires supported them about 4 or 5mm above the ground plane of the Altoid tin –

Dang, after all these years, Altoids tins still make very serviceable and cheap enclosures for small projects!

These filters were designed for input and output impedances of 50Ω. My one external HF antenna is a 40M doublet fed with 300Ω twinlead, and matched to 50Ω coax with a 1:1 balun and Elecraft T1 tuner. As mentioned previously, I briefly transmit a small amount of power on the nearest ham band to where I want to listen, to tune the T1. A manual tuner could be used here instead, and tuned for maximum noise. For listening, this is not too critical a procedure, and a single tune will cover the receiver for listening on a wide range of frequencies. The antenna input of the Belka is matched for the high impedance of the supplied short telescopic whip, and not for a 50Ω antenna. Nevertheless, I went ahead and plugged both versions of this HPF in between the antenna and the receiver, and they both served to completely eradicate every single trace of AM BC band breakthrough.

Using a NanoVNA, I measured the response curve of both filters from 1.5 MHz to 30MHz. Here’s the curve for the filter built with molded chokes –

FREQUENCY (MHz)	INSERTION LOSS (dB)
30	0
20	0.1
15	0.25
10	0.5
3.7	1
3	3
1.7 (1700 KHz)	41
1.5 (1500 KHz)	49

The 3dB cutoff point of this filter was actually 3 MHz, and the insertion loss small, with a virtually flat response from the 80M band up to the top of the 10M band. Here’s a close-up of the response between 1.5 MHz and 4 MHz –

The insertion loss of the toroid filter in the passband was a little lower, For all practical purposes though, there would be no discernible difference between the two filters. If you hate winding toroids, then by all means, build this filter with molded chokes, and it will kill your AM BC band breakthrough just as effectively as if you’d built it with toroids. Here’s the response curve of the toroid version from 1500 KHz to 30 MHz –

And from 1500 KHz to 4 MHz, giving a closer look at the area around the the 3dB cutoff point –

FREQUENCY (MHz)	INSERTION LOSS (dB)
30	0
20	0.04
15	0.12
10	0.25
3.7	0.82
2.8	3
1.7 (1700 KHz)	40
1.5 (1500 KHz)	48

There are quite a few internally generated birdies throughout the whole coverage range. However, the majority of them are only audible with no antenna connected, and are masked by band noise. The others, although audible over the band noise, are not troublesome. For a receiver this compact, and with this overall level of performance, it’s a small price to pay. I rarely noticed them during normal use. It would be nice for the end-user to have a way to update the firmware, though the extended coverage down to 100KHz that the new (V3) Belka enjoys required a hardware upgrade in the form of an extra bandpass filter.

For a more complete description of the improvements made with the newest Belka version, see 13dka’s guest post on Thomas K4SWl’s excellent SWLing Post blog. In short, the Belka is a fantastic general coverage shortwave receiver. It performs and handles like much larger tabletop communications receivers. It is so small that it can be carried anywhere with great ease, making the decision to do a little SWL’ing while on a hike, a walk, or any trip, a no-brainer. You can do a lot of serious shortwave listening with this receiver. Ordering direct from Alex in Belarus offers by far the lowest price and is, in my opinion, the way to go. When I think of my first communications receiver, an old, huge and very heavy British military R107 boat anchor, it is amazing to think that this light and svelte pocketable Belka-DX handily runs circles around it. An SWL can positively rule the shortwaves with this tiny and light miracle of wireless!

There are many other, far more comprehensive reviews on this receiver, but I have been wanting to sing the praises of the Belka (which is Russian for squirrel) for a long time now. I needed to get this out.

My, how time flies. This is a post I have been meaning to write for nearly 3 years now. Back in late 2018, after a search for a small portable SW receiver, I purchased a C Crane Skywave SSB. It had a lot of the things I wanted in a portable radio and, at the time, I felt that it offered a lot for a receiver of it’s diminutive size.

Then I became aware of an even smaller receiver called the Belka-DX. Designed and manufactured by Alex EU1ME in Belarus, this positively tiny radio used SDR technology and, judging by the reviews I was reading and videos I was watching on YouTube, there was no other receiver it’s size that felt and performed like a much larger communications receiver in the way that this one apparently did. It all seemed very encouraging, so I went ahead and ordered one directly from Alex in Belarus. The first time I tried to order direct from his site, my bank denied the payment. I got on the phone to advise them that it was a legitimate charge, and they gave me a one hour window in which to put the transaction through again. I returned to the site, ordered the Belka-DX, and the order was accepted.

There are 3 ways I know of to purchase Belka receivers –

1. Directly from Alex EU1ME, in Belarus. Alex supplies 2 versions, with and without a built-in speaker. In order to accommodate the built-in speaker, that particular version has a slightly smaller battery. The version with the built-in speaker currently costs 475BYN, which at the exchange rate at the time of writing, is about US$145. As of Aug 9th 2024, Alex’s site carries the message that international shipping is currently unavailable. I notice that in the Q&A, Alex noted in July that he hopes to resume shipping to the US in about a month. This was the message he posted, on July 18th 2024 – “We do ship to the USA but at the moment we need to to undergo technical expert appraisal so that our Belarusian customs could allow export abroad. We hope to restart shipping in a month. Shipping cost to the USA is 13 USD.”
   
   
2. From Mobimax in Bulgaria. This is the same receiver, but with a larger speaker back that also has two small fold-out legs. This increases the depth of the Belka, but allows you to have a speaker as well as the larger 2500mAH battery. The markings for the input and output connections on the sides are etched into the metal. In addition, the LCD display is fitted with a screen protector into which are etched the words “HAM tactical RCVR”. Mobimax sell two different packages containing this receiver. The only difference is that the very slightly more expensive package includes a 3.5mm stereo to 3.5mm stereo cable, for plugging the IQ output of the Belka to your computer for use with SDR software. The version of the Belka that Mobimax supply is currently 227 Euros, which is about US$247. The package with the IQ cable is just a few Euros more.
   
   
3. There is an eBay seller in Bulgaria who sells the same version that Mobimax does, but for the (in my opinion) rather high price of US$350. The main reason I can see that buyers might go for this seller is the convenience and comfort factor of being able to pay with Paypal on a site they are familiar with.

A few weeks after ordering, a small box arrived from Belarus. In it was the Belka-DX wrapped in bubble wrap, and a small telescopic whip antenna of about 28.5″ in length. No documentation was included in the box, though it is available online. I didn’t take any pictures of it then, so here are some of it now, 3 years later.

In the above image, the backlight is on. In the next one, it is off. The backlight can be customized to be on all the time, off all the time, or to stay on for 12 seconds after any button is pushed or the tuning knob is turned. In the next photo, to the left of the BNC is a micro-USB connector that is used for charging the receiver. Underneath it is a red LED that lights when charging. To the right of the BNC antenna connector is the 3.5mm earphone jack. It is important that a stereo TRS jack is used here. A mono jack will short out one of the channels and can damage the audio IC –

At 82mm x 50mm x 20mm, this receiver is small!

I’m not sure if this is still true of the version that comes with the internal speaker direct from Alex, but the speaker holes in mine were slightly imperfect. It was evident that they had been drilled by hand. Not a big deal, but I thought it worth noting –

On the right side is the tuning encoder. It rotates smoothly with no click stops, for that “big receiver” smooth tuning feel. Also on the right side is a 3.5mm jack for the IQ output –

This was the second iteration of this receiver. The first one, named the Belka-DSP, covered 3.5-31 MHz. The Belka-DX covers 1.5-31 MHz. There is now a newer version, known simply as “Belka”, that has impressively continuous coverage from 0.1 MHz – 31MHz. Yes – 100KHz to 31MHz!

There are, by now, a number of quite detailed reviews of this series of receivers online. One such review, which gives a good overview of the capabilities of this pint-sized communications receiver, was written by Dave N9EWO. Since purchasing my Belka-DX almost 3 years ago, I have used it regularly. There are several features that I find very compelling, which distinguish it from many other shortwave portables –

1. There is no chuffing or soft-muting in between frequency steps. As a result, when on the smallest frequency step of 10Hz, the effect is of smooth, continuous tuning.
   
   
2. Unlike the CC Skywave SSB and, I believe, many other portables of it’s type, it is absolutely solid on SSB and CW receive. The carrier injection on my C Crane receiver was unsteady on strong signals, leading to chirping on CW, and similar frequency instability on SSB. For a short while, I owned a CountyComm GP-5 SSB, which was even more unsteady. The Belka-DX handles like a proper communications receiver in this regard, being rock steady on strong and weak signals alike.
   
   
3. The frequency display is accurate. As far as I can tell, it is accurate to better than 10-20Hz across the frequency range. Because of this, I can easily tune it to a frequency, and know that it is there. The Belka-DX employs a 0.5ppm TXCO and as a result, has a high level of frequency stability. My Skywave SSB only tunes in 1 KHz steps. To interpolate between those steps, you have to push a button to engage the fine tuning, but are not able to read the frequency accurately in between those 1 KHz points. For many users, this might not be an issue, but for those who listen out for weak beacons and other signals that are not on 1 KHz “channels”, the continuous tuning and accurate frequency readout on the Belka makes such monitoring much easier. A couple of years ago, I went on a 4 /12 month long campervan trip around 6 Western states. At the time, one of my interests was listening out for low-powered unlicensed HF beacons. Standing in the vast expanses of the desert with the little Belka-DX in my hand, hearing a weak low-powered CW beacon from hundreds of miles away was magical. These beacons are home-made affairs, and usually running somewhere between 30mW and a watt. Being able to dial in the precise frequency on a handheld receiver that is even sensitive with the set-top whip is a boon with such pursuits.
   
   
4. You can tailor the passband for each mode. With my C Crane Skywave, and I believe many other similar receivers, the adjustable filtering (if available) is audio filtering, and doesn’t occur in the RF stages. The Belka is an SDR, and the custom adjustable filtering is the equivalent of filtering in the RF or IF stages of a conventional superhet.

Two things that I wasn’t too keen on, and which have been amended in the 0.1-31MHz version –

1. In CW mode, the frequency display doesn’t indicate the operating frequency. For example, with a 700Hz sidetone pitch selected, if you want to receive a CW signal on 7030 KHz, you have to tune the receiver 700 Hz below that frequency i.e. to 7029.3 KHz. You do get used to it, but it would be nice to have it display the actual operating frequency in CW mode. In the newest version, the 0.1-31MHz version, I have read that the receiver displays the actual operating frequency in CW. If you’re concerned with being able to read out the exact frequency (if searching for weak beacons on non-standard frequencies, for example) you’ll still need to ensure that you tune to the correct sidetone frequency in order for the frequency readout to be accurate. Personally, I’d love a sidetone feature for this, but I doubt that too many others would consider it to be an essential feature in a receiver (as opposed to a transceiver).
   
   
2. When stepping through the memory channels, you cannot hear those channels as you cycle through them. In order to hear the selected channel, you have to press the appropriate button to select and load it. Thus, you cannot easily scan through a number of preset memory channels to listen for activity. As with 1 above, I this has been remedied in the newest version of the Belka.

The audio quality from the Belka-DX is excellent when used with earbuds. The internal speaker doesn’t do it justice, though it is very useful when taking the receiver on outings. Power from the audio amplifier is adequate for most applications, though when plugging an external speaker in, it helps to use one that is sensitive. Some people use powered speakers. I have two external speakers on the bench, both unpowered, that I use with it. The main one is an MFJ-281 ClearTone speaker. It is sensitive, and produces good volume. The audio response from the mylar cone is restricted, and what I would characterize as communications quality. Audio is clear and intelligible. The speaker appears to have a natural resonance at around 650-700Hz, which is useful for CW. For those times when I need a little more fidelity, such as when listening to strong SWBC stations, or hams on AM, I use an old and compact hi-fi speaker manufactured by Cambridge Soundworks. It was discarded by one of my neighbors, and appears to be a mid-range unit. It is not as sensitive as the MFJ ClearTone speaker, but the Belka will still provide enough drive in a small, quiet room, which perfectly describes the conditions in my shack.

The small size and slim dimensions of the Belka-DX make it ideal for traveling. When using it at home with an external antenna connected, the ergonomics and ease of use are much improved when mounted on some kind of stand. There are a number of stands available, as well as files for those who wish to 3D-print their own. I remembered a clamp I once bought, that was designed to hold a cellphone for attaching it to a tripod, for making videos. The Belka is not quite as wide as a cellphone, so I used a couple of pieces of dense foam to pad it out, and screwed it to a small tabletop tripod. It works quite well, and improves the ease of use drastically when listening at home. When mounted like this, it feels like a serious and very usable SWL set-up. In the various SWL groups on FB that I frequent, I often see questions from folk asking about receivers that are good for SWL’ing. Portables such as the Tecsun PL-880, along with other similar receivers are often recommended. I think that this Belka makes an excellent receiver for all-round shortwave listening. It is not available in as many outlets as the more traditional shortwave portables, which is why I think that it isn’t as popular in the SWL community as it should be. If you are listening mainly to AM broadcasts on shortwave, then many of the portables will most likely work well. If you do a lot of SSB and CW listening though, the Belka is a solid and, to my mind, preferable option.

In the following picture, my Belka is mounted on a mini tripod (an Ultrapod) and connected to the MFJ ClearTone speaker. Behind and underneath the Belka, you can just see an Altoids tin which contains a high pass filter with a cut-off at about 2700 KHz. It was designed to prevent overload from strong local AM broadcast stations. More on that later in this post.

The Belka-DX is surprisingly sensitive when listening outdoors with the included telescopic whip. It does need a counterpoise, or the received signal strength suffers greatly. If you are holding the receiver, then your body acts as the counterpoise. If you are listening on earbuds or headphones, then the headphone cord acts as a counterpoise. If the receiver is sitting on a surface and using the internal speaker, then you’ll need to connect a counterpoise wire somehow. At home, it works really well when connected to my outdoor antena, which is a doublet at 47 feet, cut roughly for 40M, fed with 300 ohm twinlead, and matched to coax at the entrance to the shack, with a balun and Elecraft T1 tuner. I tune the T1 by squirting RF into it on the nearest amateur band. If you are using your outdoor antenna for listening only, then a simpler arrangement would suffice. This just happens to be the one antenna I also use for my ham exploits.

I live in a densely populated urban area, within a few miles of several medium power (5KW) AM broadcast stations. They often break through when I am using the external antenna with receivers that don’t have narrow filtering on the antenna input. My Belka-DX experiences strong AM breakthrough when used on the external antenna at all frequencies up to 4530 KHz. The moment I tune above 4530 – even by a single 10Hz step, the breakthrough stops instantly, suggesting that a different bandpass filter is switched in at the point. According to the manufacturer-supplied block diagram of the first version of Belka, known as the Belka-DSP, the input bandpass filters are from 3.5-7.5MHz, 7.5-15MHz, and 15-30MHz. The block diagram can be seen on this page by Fernando Duarte. I assume that for the Belka-DX, with it’s extended coverage down to 1.5 MHz, one of the bandpass filter crossover points is at 4530 KHz, the point above which all AM BC band breakthrough stops.

To solve this problem of breakthrough, I resorted to a little high pass filter that I have used successfully with other receiver projects. It’s a high pass filter that was designed by David WA7JHZ, details of which were given in K4SWL’s very wonderful and informative SWLing Post blog. You can see it here. David built his with molded chokes. I built versions with both molded chokes and toroids, and compared the response curves.

Trusty Altoids tins to the rescue. Here’s the version built with molded chokes, purchased from Tayda Electronics. The chokes are mounted vertically, and are a little hard to see in this image –

The small holes in the base of the tin were left over from a previous project that didn’t work out.

Then I built another high pass filter with toroids instead of molded chokes. I figured the toroids should have slightly higher Q and would present a better response curve. All 4 inductors were wound on T37-6 toroid cores with 26 AWG wire. The 2.7µH inductors had 30 turns and the 1µH ones 18 turns. The wires supported them about 4 or 5mm above the ground plane of the Altoid tin –

Dang, after all these years, Altoids tins still make very serviceable and cheap enclosures for small projects!

These filters were designed for input and output impedances of 50Ω. My one external HF antenna is a 40M doublet fed with 300Ω twinlead, and matched to 50Ω coax with a 1:1 balun and Elecraft T1 tuner. As mentioned previously, I briefly transmit a small amount of power on the nearest ham band to where I want to listen, to tune the T1. A manual tuner could be used here instead, and tuned for maximum noise. For listening, this is not too critical a procedure, and a single tune will cover the receiver for listening on a wide range of frequencies. The antenna input of the Belka is matched for the high impedance of the supplied short telescopic whip, and not for a 50Ω antenna. Nevertheless, I went ahead and plugged both versions of this HPF in between the antenna and the receiver, and they both served to completely eradicate every single trace of AM BC band breakthrough.

Using a NanoVNA, I measured the response curve of both filters from 1.5 MHz to 30MHz. Here’s the curve for the filter built with molded chokes –

FREQUENCY (MHz)	INSERTION LOSS (dB)
30	0
20	0.1
15	0.25
10	0.5
3.7	1
3	3
1.7 (1700 KHz)	41
1.5 (1500 KHz)	49

The 3dB cutoff point of this filter was actually 3 MHz, and the insertion loss small, with a virtually flat response from the 80M band up to the top of the 10M band. Here’s a close-up of the response between 1.5 MHz and 4 MHz –

The insertion loss of the toroid filter in the passband was a little lower, For all practical purposes though, there would be no discernible difference between the two filters. If you hate winding toroids, then by all means, build this filter with molded chokes, and it will kill your AM BC band breakthrough just as effectively as if you’d built it with toroids. Here’s the response curve of the toroid version from 1500 KHz to 30 MHz –

And from 1500 KHz to 4 MHz, giving a closer look at the area around the the 3dB cutoff point –

FREQUENCY (MHz)	INSERTION LOSS (dB)
30	0
20	0.04
15	0.12
10	0.25
3.7	0.82
2.8	3
1.7 (1700 KHz)	40
1.5 (1500 KHz)	48

There are quite a few internally generated birdies throughout the whole coverage range. However, the majority of them are only audible with no antenna connected, and are masked by band noise. The others, although audible over the band noise, are not troublesome. For a receiver this compact, and with this overall level of performance, it’s a small price to pay. I rarely noticed them during normal use. It would be nice for the end-user to have a way to update the firmware, though the extended coverage down to 100KHz that the new (V3) Belka enjoys required a hardware upgrade in the form of an extra bandpass filter.

For a more complete description of the improvements made with the newest Belka version, see 13dka’s guest post on Thomas K4SWl’s excellent SWLing Post blog. In short, the Belka is a fantastic general coverage shortwave receiver. It performs and handles like much larger tabletop communications receivers. It is so small that it can be carried anywhere with great ease, making the decision to do a little SWL’ing while on a hike, a walk, or any trip, a no-brainer. You can do a lot of serious shortwave listening with this receiver. Ordering direct from Alex in Belarus offers by far the lowest price and is, in my opinion, the way to go. When I think of my first communications receiver, an old, huge and very heavy British military R107 boat anchor, it is amazing to think that this light and svelte pocketable Belka-DX handily runs circles around it. An SWL can positively rule the shortwaves with this tiny and light miracle of wireless!

There are many other, far more comprehensive reviews on this receiver, but I have been wanting to sing the praises of the Belka (which is Russian for squirrel) for a long time now. I needed to get this out.