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Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post:
Additional Thoughts on the Malahit DSP-2
Potential for Noise Reduction Using Non-Whip Antennas
Latest Firmware Changes
by Dan Robinson
After my last update on the Russia-made Malahit DSP-2, I thought it important to add something about the receiver, as it could well influence those who may be on the fence about purchasing one.
In a series of communications, Georgiy at Malahit team has stressed steps taken to attempt to deal with internal interference seen across the bands. And he has asserted
that noise spikes lessen if the receiver is connected to a non-whip antenna.
Most of my tests have used whip antennas of various lengths, in various locations indoors and outdoors, because it’s my view that portability is a major attraction of these small SDR receivers.
Many thanks to SWLing Post contributor, Grayhat, who shares the following modification he made to a Noise-Cancelling Passive Loop antenna last year. He’s kindly allowed me to share his notes here, but apologized that at the time, he didn’t take photos of the project along the way and recycled many of the components into yet another antenna experiment.
Cut the R1 (0 Ohm resistor – jumper) so that the center tap of the transformer won’t be connected to ground, then solder a short piece of wire to the tap.
The first pic (top) shows the balun seen from top side, the arrow indicates the small hole going to the transformer tap.
This pic shows the bottom of the board with the trace to cut and the spot for soldering the tap wire (needs cleaning with a bit of sandpaper to remove the cover paint). The solder is as easy as 1-2-3 once the trace is cut and the spot cleaned just insert a wire from the top of the board and solder it to the bottom and there you go!
Build the NCPL using “fat” coax (RG8 will do) with the top cross connection.
NCPL modification schematic
Side note: the top “cross connection” is the weak point, so it would be a good idea putting a short piece of (say) PVC pipe over that point, the piece will also help suspending the loop or sticking its top to the support pole, as for the feedpoint, a small electrical junction box will fit and protect the tiny balun from bad weather
Now the difference: connect the two center conductors of the NCPL to the balun input and the braid to the wire going to the center tap (as above).
Such a configuration will give some advantages over the “standard” NCPL one. The loop will now be galvanically isolated from the feedline/receiver so it will have much less “static noise.” Due to the tap, the typical 8 pattern of the loop will be preserved, this means that the loop will now have much deeper nulls.
By the way, the balun could just be wound w/o buying it. I suggested the nooelec since that way anyone with little soldering ability will be able to put it together. Oh and by the way it’s then possible adding a small preamp at the balun output if one really wants, any preamp accepting a coax input will work. 🙂
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Summer DX – Sporadic E, FM band
“Sporadic E” DXing is a specialty of some DXers. I have never dabbled in it being content with mediumwave or shortwave listening. However, it was truly fun to spontaneously hear this happen while driving on the Interstate highway, Wednesday August 4 around 6pm Central Time.
To quote from an ARRL propagation article:
“As frequency increases still further, signals will eventually pass through the F1 layer to the F2 layer. Because this is the highest reflecting layer, the distance spanned by signals reflecting from it is the greatest. The maximum skip distance for the E layer is about 2000 km. For the F2 layer that increases to about 4000 km—a significant gain.”
I was listening to the local classical music station WNIU in DeKalb, IL which is a good 50 kW transmitter about 10 miles behind me near the Interstate highway. A different station was breaking through. Eventually, I heard a familiar Christian song “You Make Me Brave” swamp the classical music. I noticed it was a remake of a song made about 10+ years earlier. The two signals fought it out and then I heard the station ID “Spirit FM” and a short humorous segment called “Attitude Adjustment”, then more music. Finally the local classical music station won out and I thought I would look up the station ID of that contentious station later.
When I googled “90.5 Spirit FM”, it came up with a station in Tampa Bay, FL called WBVM. Cool! Just to be sure, I went to the station web site and looked up their playlist and this confirms what I heard:
Curious about the transmitter, Radio Locator said it was a 100kW station and gave the Long/Lat coordinates. I then went to Google Earth and mapped an approximate distance of 977 miles (1572km), give or take 10 miles:
I did not have time to get on the shortwave radio to see if the 10 meter band was busy since I had things to do. But it is a very nice surprise to hear in my old car radio an FM station almost 1000 miles away. For one thing, Analog radio is still fun. Secondly, things are busy this summer if you are at the right frequency and time!
Many thanks to SWLing Post contributor, Jock Elliott (KB2GOM), who shares the following guest post:
Really cool trick the CCrane Skywave SSB will do — the “radio butler”?
To paraphrase Ratty from Wind in the Willows: ” “Believe me, my young friend, there is nothing–absolutely nothing–half so much worth doing as simply messing about with radios.”
That is precisely what I was doing . . . messing, simply messing about with the CCrane Skywave SSB.
Then I observed something. Just above the LIGHT button is some lettering: “ATS.” Not having taken notice of it before, I looked it up in the manual. It stands of Automatic Tuning System, and the manual says this about it:
“This feature programs all receivable stations in the AM, FM, Air and Shortwave bands to memory buttons. To use ATS, select your desired band: AM, FM, Air or Shortwave, and press and hold the ATS button for two seconds. The CCrane Skywave SSB will scan the entire band and automatically set all available stations in sequence 1-20. If more than stations are available, then the remaining stations will be preset to the next memory page, and so on.”
So I tried it; I punched in a shortwave frequency — 9250 — and pressed and held the ATS button for two seconds. The Skywave then muted itself and went to the bottom of the shortwave bands — 2300 — and started silently scanning through all of the international shortwave bands, hopping from one shortwave band to the next. Occasionally it would stop and silently store a frequency. After a while it stopped, unmuted, and began playing the very first memory that it stored. I checked the other memories that were stored and — sonofagun! — there were stations stored in each memory. Some of them were really faint, and I had to mess with single sideband and bandwidths to make them fully copyable, but they were there, automatically scanned and stored by the CCrane Skywave SSB. Obviously, you might want to repeat the ATS scan as shortwave propagation changes, say, from day to night.
Well, I thought, would it do it also for Air frequencies? Short answer: it certainly will. And it will do the same for AM, FM, and — get this — if you put the Skywave SSB in single sideband mode, it will scan the ham bands, automatically changing sidebands appropriately as it hops from ham band to ham band. Note: when you check the memories stored during an ATS ham band search, you may not find anything there, simply because ham transmissions come and go much more often than international broadcasters.
There is one downside to the ATS function. When the Skywave scans and stores stations, it does so starting at Page 1, Memory 1 of the memory system . . . always. So, if you scan the Shortwave frequencies and store frequencies they will be stored starting at Page 1, Memory 1, wiping out anything that you have already stored there. If you then use ATS on the Air band, it will then write over whatever you stored from the Shortwave frequencies. I wish there were a way for the user to designate at which page in the memory system ATS will begin storing frequencies so that the information stored starting at Page 1, Memory 1 is not constantly overwritten.
However, there is another trick the Skywave will do: if you have used ATS to scan and store Air frequencies in Page 1 of the memory system (which it does automatically), you can then press and hold the UP and DOWN buttons at the same time, the Skywave will then scan through the Air frequencies that are stored there. Further, there is a squelch function on the Skywave that works only on the Air frequencies. So, with a little persuasion (very little), the CCrane Skywave turns itself into a civilian air scanner.
The ATS function on the CCrane Skywave SSB is a bit like having a radio butler: “I say, Jeeves, find me what’s on the air this evening.” A short while later, Jeeves reports back: “Here you are, sir, I found 10 shortwave stations you might like to listen to.”
Frankly, I don’t know if other modern shortwave portable radios offer a similar function, but if you have a CCrane Skywave SSB, give the ATS function a try; it’s pretty slick.
Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post:
Test Driving The Russia-Made Malahit DSP-2
Poised on Edge of Greatness? (Some Challenges To Overcome)
by Dan Robinson
By now, the Malahit SDR is well known in listening hobby circles. We have the made-in-Russia original, and those manufactured in China with various firmware and some physical differences such as location of the tuning encoders.
At the same time, we saw the development and appearance of the Belarusian Belka SDR. I consider the latest Belka DX to be the ideal portable – a sensitive diminutive miracle that has become a must-have device for many of us.
As for the Afedri LAN-IQ, I held off on purchasing one until the “Standalone” version was available. It is made in Israel by a Russian developer who supports the receiver with fairly frequent firmware revisions (though upgrading remains a bit of a challenge involving some obscure boot-loading software).
I waited and observed reviews of the original versions of the Malahit. When its designer, Georgiy (RX9CIM), announced availability of the new DSP-2 version of the receiver, with expanded coverage to 2 GHz and a claim of improved performance, I finally purchased one.
As was observed in one of the early SWLing Post articles “It seem[ed] the project is open source, the schematic, PCB and software are available to download. . . we hope [these] receivers become popular and available world wide [and that] this new project “shakes” a bit the industry of shortwave receivers.”
Malahit project authors RX9CIM George, R6DAN Vladimir, and R6DCY Vadim, had the apparent objective of “designing a low-cost portable SDR radio, using only easily obtainable components and to become the natural successor of the popular Degen and Tecsun radios.”
At the time, the price for a finished Malahit, with an ARM chip at its center was about $195 US. Coverage was to 1 GHz – this has since been extended to 2 GHz. Synchronous AM mode was added, and the DSP-2 also comes with an internal battery tray for a single 18650 Li-on battery.
This is a change from the original flat Li-on cell, and in my opinion a welcome one since 18650s are easily obtainable. Being able to easily change out a battery is important, rather than messing around with soldering (the famous Reuter Pocket receiver made in Germany should take a hint).
In this age of the SDR, we’re all familiar with the SDRplay series and various AirSpy receivers, along with other SDRs such as the RX666/888. Before that, we had the famous Perseus, which still has a strong following, and numerous WinRadio receivers.
See the articles here on the SWLing Post assessing the performance of these, as well as reviews at eHam.net, and numerous SDR dongles all over eBay, coming from China. There is also an SDR group on Groups.io.
Of course, receivers and transceivers with panoramic displays began to appear some years ago – the ICOM IC-R8600 and IC-7300 are examples of how this technology was integrated into the listening and amateur radio markets.
What we had not seen was integration of this kind of technology into portables. Even in its latest iteration, the Belka DX has a small screen without any PAN display. So, the advent of the Malahit has made this kind of advanced display widely available.
The price, by the way, for my DSP-2 as of July 2021 was 19,500 Russian rubles, with an extra 2,000 rubles for express delivery via Russian Post (though due to COVID Georgiy stressed that no guarantees could be made as to timing). That’s $263 – not a small investment and rivaling the cost of a Tecsun ATS-909x and H-501x.
According to the description I received when ordering, the Malahit DSP-2 was improved over the previous version with the following differences:
Frequency range – from 50 kHz to 380 MHz, and 400 MHz to 2 GHz
Improved RF shielding and hardware improvements to reduce interference
Changes in software functions
Dimensions changed to 140x 88x 39mm
18650 battery
The DSP-2 is in a thin black metal cabinet with dimensions 5 x ½ by 3 x ½ by 1 x ½.
A power button and headphone jack are on the right along with a power LED. On the top, we find the SMA antenna input, and a small telescopic whip is included.
The speaker, capable of some decent audio, is located on the inside rear of the receiver – audio level exceeds that of the Belka DX with its very small speaker, but the Belka has a clarity that often exceeds the Malahit.
My first testing of the DSP-2 was indoors, in a far corner on the top floor of my home, using just the included whip antenna. For comparisons, I used a Tecsun PL-368 with its whip antenna and a Belka DX in the same location. I find that indoor testing tends to identify some issues that would not be apparent outdoors.
In this, the Tecsun PL-368 and other Tecsun portables consistently performed best, followed by the Belka DX and the Malahit. This may be surprising, but shows that radios specifically designed for shortwave reception, often provide better reception because they are matched better with their internal telescopic antennas.
Now, when I say “best” I mean best basic audio quality, using auto-memory and ETM functions on the PL-368 and 990x. But what those radios can do with the signal after that point is pretty limited – there is no NR (noise reduction), you’re limited to a handful of set bandwidth selections, and SYNC mode leaves much to be desired.
Which is where the Malahit comes in with its numerous levels of flexibility, accessed through MENU icons on the lower part of the screen: HARD, AUDIO, VISUAL, NR, MODE, and BAND. I refer the reader to the Malahitteam site links showing the user manual (this is still a bit in the rough, with translation from Russian) and another link with a Quick Start guide written by John Pitz (KD8CIV).
KEY HIGH POINTS ON MALAHIT
SUPERIOR COLOR DISPLAY
The color display, also seen on numerous China-made clones, is the best on any handheld SDR. Where the Belka LCD is a basic utilitarian tool that performs well for that receiver, the Malahit display is an invitation to the wonderland of what this receiver offers.
At the top are small icons for: SQ, NB, NR, AGC, ANT, PRE, MODE. Right of center, and controlled with pushes of the small volume encoder knob, are ATT, VOL, FILTER, and the battery icon. Below those are headphone and speaker icons and an excellent, if small, frequency window. Pushing the small encoder knob selects/controls volume, attenuation, and main filters. The large tuning knob, with a press, selects step increments.
EXCELLENT NOISE REDUCTION
Noise reduction on the Malahit is superb, as many users have observed. It’s activated directly with a front panel icon and Threshold is adjustable with an icon under AUDIO, with 0 to 30 increments. NR is so good that I compare it with the latest firmware version on the ICOM IC-R8600 – it’s actually probably better than the ICOM even near and at the highest 30 level.
EXCELLENT FILTERING
Whereas the Belka DX offers fixed audio filtering values accessible via its front panel, the Malahit DSP-2 offers continually variable LOW FREQUENCY adjustment from 0 Hz to 2350 Hz, and HIGH FREQUENCY adjustment from 100 Hz all the way up to 150,000 Hz. This is in addition to standard NARROW, NORMAL, and WIDE filter options selectable with the volume encoder knob. This is nothing short of extraordinary for a handheld portable receiver.
The latest (and possibly last) Tecsun receivers offer set value multiple bandwidths, which is excellent but is a throwback to radio design from years ago. So, the DSP-2 capabilities can be compared to the kind of filtering that a Watkins Johnson or Cubic receiver have, but in the palm of your hand.
As I often observe, what we would have given in gold to have this kind of capability in consumer receivers during the glory days of international broadcasting!
AGC / MGC FLEXIBILITY
The Malahit allows the listener to use AGC, with choices of SLOW, MEDIUM, and FAST. But it also allows, again through the AUDIO settings menu, control of AGC GAIN 0 to 60, and AGC LIMITER 40 to 90 db. Wow – priceless! So even if you prefer, as I do, to listen to shortwave using AGC, you still have amazing flexibility. You can still switch to MGC with 0 to 60 range.
NOISE BLANKER FLEXIBILITY
Just as the Malahit delivers on AGC, so does it deliver with its regular noise blanker function. With NB activated, there are 3 configurations with a separate THRESHOLD icon adjustable for each of these. Amazing.
RF GAIN FLEXIBILITY
RF GAIN is adjustable from 0 to 59, and there is a separate icon for adjusting gain for the PRE-AMPLIFIER. Where the PREAMP comes in very handy is when one has the Malahit indoors – it provides a more sensitivity in situations where one is using the telescopic whip antenna, though care must still be taken not to overload the receiver and distort signals.
FCORRECT FUNCTION MAKES FOR EASY RE-CALIBRATION
The Fcorrect function located under the HARD settings menu enables one to re-calibrate the receiver to correct for error. This is similar to the capability that Tecsun added to its 330, 909x and 501x receivers (there are indications Tecsun has or will enable this ability also in the PL-368) but seems, based on my testing of the Malahit to be more effective. After I corrected my DSP-2 to about +57, calibration was pretty much on the money up and down the HF bands.
SQUELCH FLEXIBLITY
The Malahit not only has SQUELCH, but SQUELCH THRESHOLD control, another example of the tremendous flexibility in this receiver’s firmware. Since I do not do much listening outside of the HF bands, or have the antenna for it, I have not extensively tested the Squelch above 30 MHz and up to the maximum range at 2 GHz.
There is yet another feature described as adaptive noise canceling that allows the user to significantly improve the intelligibility of the received station under conditions noise and interference.
[From the manual]: The squelch uses different algorithms [depending] on filter bandwidth. With a bandwidth of more than 1 kHz, a squelch of more than suitable for speech type signal. With bandwidth less than or equal to 1 kHz, the squelch is suitable for tone type signals. Choice of algorithm is carried out automatically, depending on bandwidth. Meanwhile, squelch for speech signals can be used with NR (see further details on this in the manual).
FM RECEPTION WITH RDS
What the Belka DX lacks, namely reception of the FM range, the Malahit delivers in droves. FM sounds excellent to me, on the same level perhaps of the Afedri LAN-IQ Standalone receiver.
RDS is enabled by touching the waterfall area of the display which brings up the RDS information. The speed with which station information appears varies depends on position of your antenna and signal level.
As one user (Harold Hermanns) on the Facebook Malahit group observed: “ I don’t think it works very well. I just checked mine, and went to about 25 stations. The RDS or station name came up on only 5 stations. Letters I get are PS, PT, and PTY. When you tune a strong station, give it a minute or so, that’s what I did, and the RDS feature does work, but again, it’s not 100%. Maybe will be improved with firmware?”
The RDS information could be better organized – currently the name of the station, and name of the program scrolls on different lines. Another touch of the screen brings up an old style FM scale – this is nice, but I prefer the PAN display. Yet another touch returns the screen to the PAN display and waterfall. Mode options include NFM and WFM, and another option provides FM-STEREO. Also in FM, there is an auto-search function and station labeling
MISCELLANEOUS FEATURES
There are some other features in the mind-boggling list of options in various menus:
In FM (WFM) there is an eight position EQUALIZER function with SOFT, LIVE, CLUB, ROCK, BASS, JAZZ, POP, and VOICE positions.
A voltage monitoring function allows the user to turn off the receiver when voltage drops lower than 3.3 volts. As explained in the manual this is intended to preserve battery life and avoid full discharge.
Antenna selection can be 50 ohms or Hi-Z (preferred for telescopic antenna use).
As the Malahit manual details, internal gain of the receiving chip can be adjusted. Accessed from the HARD menu, this is too much for me to go into here, but it’s another example of the detail that went into designing the Malahit.
Brightness of the display backlight is adjustable as well as time after which backlight level is reduced to minimum and turned off completely. Rate of change of the display spectrum is adjustable as is spectrum display range, color, ratio of waterfall and speed and brightness of waterfall. Spectrum scale and view are adjustable.
There is a 5 page memory system, with M1 to M10 in each, so a total of 50 storable memories.
LOW POINTS OF THE MALAHIT
NOISE FROM THE DISPLAY
Example of noise on 1,000 kHz
As I was testing my Malahit DSP-2 it quickly became clear that there is one major low point, and thus a challenge for Georgiy and other members of the design team.
There’s no other way to say this: internally-generated noise remains the major issue keeping the Malahit from achieving greatness.
The developers of the Russian version receiver have not attempted to hide this, and users noticed it from the beginning, with one writer identifying “internally generated noise, which peaks at various frequencies” as one of the key drawbacks of the Malahit.
I had hopes that the DSP-2 version of the Russian-originated Malahit might have less of this problem. There are numerous internally-generated noise/buzzing spikes, some stronger than others, by my estimation at intervals between 125 and 200 kHz throughout the HF bands.
Example of noise on 6,000 kHz (RHC)
In the case of one huge noise spike appearing at or around 6,000 kHz – right over Radio Havana – it ruins any chance of hearing clear signals at, below and above that point. As you can see in my video, the Belka DX does not have this problem (note: apologies for mis-spelling Malahit as Malachit).
Via Telegram, Georgiy asserted to me that when using an external antenna, noise is not as serious, and notes differences between the Malahit and Belka. The Belka, he says, is a simpler device that concentrates only on shortwave, while Malahit is a wide band receiver with more complex DSP and user functions.
“When Belka cannot receive something, Malahit can. And where Belka does not have noise, Malahit has it. These devices are in different classes.”
The result is that a major workaround is often necessary – to disable the VIEW PAN&WTF option, a key feature that is a major highlight of the radio.
Georgiy says that this problem is mainly linked to telescopic antenna antenna operation because of the antenna’s proximity to the display. But as you can see in my video, when testing the Malahit and Belka on 6,000 kHz it’s a night and day situation.
A quick push of the power button blanks out the display completely – and seems to completely resolve the noise issue. But you don’t buy a radio to see a dark display, and it’s depressing to think that turning off a major feature, namely panoramic display, has to be part of standard operating procedure.
When testing the Malahit from its bottom frequency of 50 kHz, even with the PAN & WTF off, huge buzzing noise spikes are heard. In mediumwave/AM, they are seen at 615 kHz, 790 kHz, 965 kHz, 1140 kHz and so on.
If a radio had emerged from a known large manufacturer with this issue, such as Tecsun or Sangean, it would have been roundly condemned by users and reviewers and sent back to the drawing board.
Georgiy does say that in the new firmware interference from the display was decreased, with a “step of about 2.5 MHz, from 1MHz (i.e. 1MHz, 3.5MHz, 6MHz). After correction it will be with a step [of] 4 MHz”. I’m not quite sure what he’s saying with this, due to language issues, but the overall indication is that he is aware of this issue and will continue trying to tackle it in future revisions.
CW DECODING
In the MODE section of the Malahit there is no confirmation that the receiver is actually in CW. Decoding is enabled with an icon, but again no confirming icon at the top of the display. This is a bit odd.
Going to the Telegram app discussion group for the Malahit, and re-reading the translated Russian manual, I discovered that confirmation of CW appears as a white bar under the SPEAKER/HEADPHONE icon on the right. There is also a MINIMUM SNR option in decoding, with a 0 to 70 range.
A You Tube video (the Gerry DX channel) shows the decoding process and notes that it’s important to keep the filter setting at NARROW when attempting to use the decoding feature on the Malahit and also important to set the SNR at the right level.
One would think that this could be easily rectified, but adding a CW indicator to the top row of small icons on the front display might not be as easy as one thinks, unless the display can be modified to also display “CW” in the icon spaces for AM, LSB, or USB.
It turns out that CW decoding on the Malahit works quite well, at least in my attempts. I was able to decode fairly strong CW signals in 40 meters.
LCD/TOUCH SENSITIVITY
When I first got the Malahit, I was puzzled by what seemed to be a serious lack of sensitivity on the display when trying to use the touch icons to change configurations and modes.
This was so bothersome that I raised it with Georgiy who responded that this is by design. The present capacitive touch method, he says, is preferable and more comfortable for users. “If [we were to] change the touch [enable faster response] then [some] people will demand to decrease it.”
With benefit of some time, I have concluded that a slightly firmer and longer press of about half a second to a second almost always brings up the menu selected. But this is definitely a characteristic of the DSP-2, so potential owners should be aware of it.
ISSUE WITH CLOCK
Another issue that prospective purchasers should be aware of involves instances where the internal clock of the receiver does not retain the time, and the solution for this directly from Georgiy is not necessarily satisfactory.
“Yes, they need to be removed from the PCB” he says, a reference to two capacitors on the main PCB, C29 and C30 which are next to each other below a larger M7 device on the PCB.
These are SMDs so anyone without good soldering skills will be hard pressed to want to mess around with that PCB. This is not a confidence-builder, nor a solution – clearly these receivers should come from the supplier without such an issue.
This was upsetting enough for some users that the Malahit team faced some sharp criticisms. One user said the clock on his DSP-2 was working perfectly. Another said: “Unless I power off the unit the date stays good but the time is always 2 hrs and 10 minutes behind. As soon as I power off the unit the date defaults back to 15:08:2062.”
One user said: “Problem is voltage is very inaccurate causing the clock settings to be lost. I have tried several 18650 batteries (good Panasonics) and fully charged they are 4.2v, but the DSP-2 indicates 4.6v. When the battery runs down to 4.0v the clock settings are lost. Also, the battery indicator continues to show FULL. I think there is an internal problem with the DSP2. Perhaps the new design, or new internal parts are causing this. This is very disconcerting.”
In exchanges on Telegram, Georgiy said he personally checks each outgoing Malahit for sensitivity on each band, and clock operation, among other things. In a later comment just before this article went to press, Georgiy said that C29/C30 should be replaced only if there is a problem with the clock.
There is no mention by the Malahit team of any official return policy – which of course would be quite challenging and costly involving an additional round trip for a receiver back to Russia and then back again to the user.
On my DSP-2, which I have used with an Anker 26800 USB battery, so far my clock/date settings have maintained accuracy with no reset, even after the USB cable is unplugged from the receiver. I have not yet tested longer times to see if the clock/date is reset when voltage drops below a certain point.
[UPDATE: 22 July 2021]
In a message sent after publication, Georgiy says that the C29 and C30 capacitors will be deleted from the next series of the Malahit, and for now they are being removed from receivers that have not been sold yet.
[UPDATE 23 July 2021]
Further testing revealed that the observations of Malahit users are accurate. When voltage of a 18650B battery in my Malahit dropped below 3.7 v the receiver did indeed shut down — this is with the battery icon still showing 50%. So this is definitely an issue that needs to be addressed in future updates. That said, I got hours of operating time before the full 18650 dropped to the cutoff level — but obviously an inaccurate battery icon is something that the Malahit team will have to correct.
THE BATTERY GAME
Example of 18650 rechargeable batteries
The Malahit DSP-2 uses a 18650 Li-on battery. Unfamiliar to many people, these are actually well known among professional-grade flashlight collectors/users (flashlight collecting is another of my vices).
One of the first things I realized when my Malahit arrived was that my existing button top 18650 cells were too long to comfortably fit in the battery tray. A bit of research on the Facebook Malahit group page revealed that some users have modified the receiver to take two 18650 cells, with a double tray replacing the single tray.
The original Malahit tray requires shorter “unprotected” flat top 18650 cells. At the time I write this, there is a shortage of these cells at the major battery / flashlight suppliers (Battery Junction is one). DO NOT try to force a slightly larger 18650 in the stock Malahit battery tray!
So, one recommendation I would make to the Malahit Team in Russia would be to make it possible for the receiver to use regular protected button top 18650s, of the type one would easily use in a Tecsun receiver such as the 909x and H-501x.
However, in a message to me just before this article went to press, Georgiy said that the Malahit team has used “typical holders” available to them and that they had been unable to obtain a sufficient number of alternative trays for protected 18650 button top batteries. So, for now at least the Malahit will require unprotected flat tops.
My 18650B flat top batteries arrived just as I was completing this review – easily charged up in my Littokala charger, each then fit easily in the single battery tray and power the Malahit perfectly.
ENCODER KNOBS
Higher quality replacement knobs
The original encoder knobs on the Malahit can be replaced by higher quality, metal construction ones for the small and larger knobs. I got mine from Nikolay, a member in Russia of the Malahit Facebook group (he says he sources them from Switzerland, but I have not confirmed this).
I am, however, not sure that the new knobs can simply be installed on the Malahit – there are no set screws on the original plastic Malahit knobs and I chose not to mess around to see whether the metal knobs can easily be installed, at least for now. Price for the higher quality metal knobs: $17
[UPDATE 23 July 2021]
Nikolay Vedeneev in Russia produces high quality encoder knobs for the Malahit, Afedri, and Belka SDR receivers. He can be reached at: [email protected] and received a very positive review from Fernando Duarte who is known for his reviews of numerous receivers. Both of his knobs fit perfectly on the shafts of my Malahit DSP-2 and have a much better feel than the originals (NOTE: I used a 1.5 mm hex key to tighten the set screws) https://fenuradio.blogspot.com/2020/07/custom-tuning-knopfe-fur-jedes-gerat.html
The subtitle of this article asks whether the Malahit is poised on the edge of greatness. I believe it is, but anyone’s choice to join the Malahit user/fan club comes with some headaches.
We can only hope that the Malahit team can work on the problem of noise spikes that permeate the lower frequency ranges from mediumwave on up. There’s no way to minimize this: at $263 (the price of a DSP-2 as of July 2021) buyers should not have to be shutting off the display to eliminate noise.
As for the question of the clock on the DSP-2 not maintaining time/date, etc it’s clear that Georgiy and the Malahit team are aware of this issue and one hopes this could be checked off the list of concerns that users have raised.
Whether one needs all the bells and whistles that a Malahit offers is the major question, especially when the Belka DX offers excellent stepped (not continuously adjustable) audio filtering and a form of synchronous AM detection in what has to be the smallest high performance receiver ever available to the listener.
More than a few Malahit owners have observed that between 1.5 MHz and 30 MHz the Belka DX seems to be the better shortwave receiver, with no display noise issues, superb battery life and an amazing small size that makes it the ultimate ultra-portable.
In short, if you choose to step aboard the Malahit train you enter a world where there will be constant improvements in software and hardware, and bugs along the way, of which noise spikes issue is a perfect example. But if you’re someone who gets enjoyment from being on the leading edge of technology in radio development, the Malahit may be for you.
It’s impressive that the Malahit originated in Russia, not generally been known for innovations at this level. In recent years, Asia was the main source of advances from the likes of ICOM, Yaesu, AOR etc in the amateur radio area, and from Tecsun, Sangean, and Eton in the area of portable receivers for HF listeners.
Finally, one has to wonder about the potential that the Malahit design holds for integration into the kind of portables seen over the past two years. Some observers have asked why the LCD display and other features on the Malahit could not be part of a future receiver that looks like a Tecsun 990x or Sangean 909×2 with additional advances such as off-air microSD recording, and DRM.
FINAL ASSESSMENT: I boarded the Malahit bus fairly late, but I am definitely a fan. Owning one of these receivers is indeed a roller coaster – anyone climbing on should become a member of the Facebook and other discussion groups where users exchange views, suggestions, and their own experiences.
For ultimate portability in 2021, the Belka DX wins the race. But the Malahit wins on the sheer number of advanced signal processing and other features it contains, though it is hobbled to an extent by the problem of display interference.
If Georgiy and the Malahit team can continue to make steady progress in confronting the noise issue and fine tune the already amazing array of features, the Russia-made Malahit has a bright future ahead.
[UPDATE 24 July 2021]
In the latest firmware update to the Malahit DSP-2, Georgiy provides this
changelog. Note that this is still described as “TEST” firmware, so it’s still unclear
whether he intends to put out a non-TEST version of this particular upgrade:
Firmware 2.10 TEST:
fixed battery voltage indication
fixed behavior of encoder buttons at low supply voltage
protection against false switching has been made – for switching on by three, set switch 2 to the On position.
added test function – increased display frequency. This reduces noise and increases the number of frames per second; To enable this function, set switch 3 to On. The function may not work correctly, if so, please let me know
the level of interference from the display is slightly reduced
changed the distribution of frequencies to which the input high-pass filters are turned on
when HiZ is turned on, the power supply of the external active antenna is automatically turned off;
added indication of external antenna power on – now the ANT indicator is highlighted in red if this function is enabled
the algorithm for displaying the picture on the display, slightly reduces the level of interference
changed the panorama display mode from “Pan & WTF Disabled / Enabled” to “Pan & WTF Single / Always”, while the panorama image is now always present, but it is updated once (when the settings are changed) or always.
fixed attenuators bugs
[UPDATE 2, 24 July 2021 ]
Please read this updated post explaining why I believe you should hold off on making the DSP-2 purchase until software and hardware issues have been resolved.
I entitled this review an “Everyman” review because, while I am far from “normal” (just ask any of my friends!), I am not a hard-core SWL. I am a hard-core amateur radio operator perhaps, but only for the last decade(+). I have been casually listening to shortwave radio for about 50 yrs. So, my perspective on this radio comes from someone who cut his teeth on a Realistic DX-160 (still love those radios!), progressing through various desktop and portable radios, to three of my current favorites, the FRG-7, the Sangean 909X2, and the Sony 7600GR. Of course, this doesn’t count some vintage WWII-era radios and earlier, but they are favorites for other reasons.
Now, the purpose of this little reflection on equipment is to say all radios have their place in the pantheon of shortwave radios, and no one radio “does it all.” The Tecsun radio, I believe, fills a very specific niche in the radio world, and it is excellent for those purposes. It does not, however, rival other radios whose goals are different, such as ones designed around sound fidelity, digital signal processing, SDR capability etc.
What this radio does do is present a very capable radio in an ultra-small package, designed to fit easily for travel and for survival/emergency situations, or for armchair operation. That middle one may surprise you, so allow me to explain.
I have a previous model of this radio (GP-5/SSB still available) sold by CountyComm, which was modified from Tecsun’s stock production PL-365, to have features suitable for government use. This has become a rather popular radio for preppers because of those modifications. The idea behind this radio as a compact piece of kit for government embassy people was to have something which could be easily concealable, operated with one hand, and have a wide range of reception capabilities. Of course, good reception of shortwave, AM, and FM bands was considered a must. You can look at the CountryComm website to find out specific features of the modified units if interested, as that radio, or the PL-365, are not the subject of this review.
While not a real “prepper” myself, I was intrigued by the AM broadcast reception capabilities due to the plug-in ferrite antenna, and also liked the idea of the small footprint. In actual use I found the radio to be quite versatile, a good performer, but rather awkward to use as there was no quick way to get to specific frequencies, unless already programmed into a memory location. With no direct keyboard entry on the GP-5, going to random locations to channel surf was, for me, frankly a bit annoying.
Enter the PL-368 which boasts a direct keyboard entry! Yes!! This one feature has taken the radio to a new level of performance which makes it a joy to use in this reviewer’s humble opinion. (Full disclosure, the unit I received for this review was provided by ANON-CO, and is the latest model after the recent firmware update incorporated by Tecsun. However, I have no other connection to ANON-CO or Tecsun, and my willingness to do the review is purely based on my previous purchase and experience with the CountyComm model.)
Despite having an unusual number of stormy days and nights here in the Midwestern U.S. recently, I have managed to enjoy some very productive listening opportunities with this little radio. For example, being an amateur radio operator, I appreciate the ability to listen in on the amateur frequencies now an again, and the recent ARRL Field Day afforded me the opportunity to really test out the radio’s USB/LSB reception capabilities, and its ability to dig out signals on a really crowded band. I was quite impressed both with its DSP and bandwidth capabilities and the reasonable clarity of the audio when tuning in various signals. Does it have the richness of audio that my Sangean 909X2 has? No, of course not. The speaker is much smaller in the PL-368, but it was quite listenable. Likewise, listening to various nets on 80 meters was quite acceptable with the built-in antenna, where noise and local interference are common gremlins on any radio.
For shortwave stations I found the radio to be quite sensitive just using the built-in antenna, which is key to portable listening. If I have to attach an external antenna, my mobility becomes limited, and I might as well just listen to one of my desktop radios. Some reception examples include: NHK World Radio 9560, Helliniki Radiophonia Voice of Greece 9420, WRMI relay of KSKO 89.5’s Paul Walker from McGrath Alaska on 7780 (beamed to east coast U.S., as well as on 7730 beamed to west coast, Hawaii, and South Pacific).
Of course, reception of CRI, Radio Havana Cuba, and numerous religious broadcasts were heard on all the usual places. I also listened to WWV signals at various locations, my go-to initial band reception check, as well as listening to HF aircraft broadcasts, military planes training on 11175 (USB), and maritime weather broadcasts. While I did not try digital mode reception such as FT8 with WSJT-X from the headphone jack, I have no doubt I would have been able to monitor these stations on various bands easily as the signals were immediately recognizable. The same holds true for CW reception.
Operational Notes
For a thoughtful, in-depth review of many technical aspects of this radio Dan Robinson has written an excellent piece on the PL-368, along with an updated review of the latest firmware’s effect on the radio. One aspect worth mentioning in my experience with this radio is that, unlike Dan, I did not find an issue with changing sensitivity when touching/holding the radio versus the radio standing on its own. Your mileage may vary, of course, so this goes in the “for what it’s worth” category. Maybe this issue has been resolved in later production runs? Or maybe my capacitance is running low and I need more electrolytes<grin>!
Like Dan, I found the SYNC detection of USB/LSB to be marginal at best, mostly making the signals harder to hear. On the upside, standard reception was quite good, and I did not experience significant fading most of the time.
Below are some of the hidden keyboard functions as listed, provided by Anna of ANON-CO, but I wanted to mention a feature I have either forgotten when using my GP5 CountyComm model, or which has been added (sorry, I don’t have access to the GP5 right now as it is packed away due to a recent move in progress). When “speed tuning” as I call it (turning the tuning dial quickly) with the “step” selected to the smallest increment on SW, what starts as increments of 10Hz will jump to 50Hz at a time after a few moments. This helps in trying to quickly latch on to a signal when increments of 10 are not necessary. The tuning will revert to 10Hz units when stopped for a few seconds.
Now for some undocumented features:
Switch between internal ferrite rod and whip on AM (MW & LW)
Select the MW or LW band.
Press and hold key ‘3’ for about 2 seconds.
When the display briefly shows “CH-5” this means that the device is set to MW/LW reception using the telescopic antenna. The display shows MW (or LW) and SW on the left side of the screen.
When the display briefly shows “CH-A” this means that the device is set to MW/LW reception using the internal ferrite antenna. The display shows only MW (or LW) on the left side of the screen.
Adjusting the maximum volume level
Select the frequency band, then press and hold key ‘7’ for 2 seconds until a number is displayed. At this moment, rotate the [ TUNING ] knob to adjust and press the key ‘7’ again to save and exit.
Firmware Version
In power-off mode, press and hold [ VF/VM ] for 0.5 seconds until all characters on the display are shown, then wait a few seconds until the firmware version is briefly displayed in the middle of the display.
Extend SW-range for European setting (1621-29999 kHz)
In power-off mode, press and hold the [ 3 ] key to set the MW tuning steps to 9kHz.
Select the SW band, and then press and hold the [ 5 ] key for 10 seconds to enable/disable the SW frequency extension. The starting point of the SW frequency range will become 1621 or 1711 kHz.
Some Nitpicks (There had to be some, right?!)
I wish the batteries were still standard AA units instead of the flat rechargeable unit. This is merely a personal preference, but as a radio designed for carry-anywhere usage, I like a radio to use batteries I can pick up anywhere if needed. I tend to use rechargeable AA and AAA batteries anyway, but I like knowing I can use ubiquitous alkaline batteries available at almost any store in a pinch.
I suspect the change was made to allow for more space for the direct keypad entry, and that is definitely a tradeoff I am willing to make!
On a related note, the recharging port uses the USB micro-b connector which I have found in cell phones, tablets, etc. to be a weak point as cables often seem to go bad, or the connector itself gets damaged. The larger mini-b would be my preference, but hey, again, that’s a nitpick.
Finally, the case does appear to be a little thin which makes me wonder how it might survive if dropped or knocked off a table. This is not a deal-breaker by any means, but something to consider when carrying it around or when packing it for a trip. It may survive quite well, but that’s a test I don’t want to try out just to see what happens.
Final Thoughts
For me, as a casual shortwave listener, I look for several things in a portable radio. I want true portability – if a so-called portable radio must be tethered to an external antenna to work decently, chances are I am not going to use it often – my various desktop models attached to outdoor antennas will always out-perform a portable. I also want a simplified layout of controls. I do not want to dig through menus, have be a contortionist to work the buttons/controls, or carry a manual with me to find out how to use the radio each time because the controls are confusing. I also want reasonable audio and clarity, or the ability to fine-tune a signal to minimize adjacent signals.
I find the PL-368 does for me what I want a portable to do and does it reasonably well. Is it the best portable out there? No. Is it a benchmark radio? No. But it is extremely portable, easily handled with just one hand, and its reception capabilities put it far above some other portables I have used. If you are looking for something which can easily fit into a pocket, bag, or purse, this radio is great. If you want a radio which performs well over a wide range of signals using the built-in antenna, this radio fills the bill. And if you want true USB/LSB, along with good bandwidth options in your portable, this is a great choice. Cheers!
(edit, July 23, 2021: an additional “hidden” feature to be included in the shipping version not included in this reviewed unit is an SSB calibration capability – definitely a plus! — Robert)
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Recording Music on Shortwave Part 2 – Weak signal recovery
by TomL
The QRM noise cloud surrounding my condominium motivated my first foray into noise reduction software to find a little relief (Please refer to Part 1 posted here) using SDR recordings. I was able to use the freeware software Audacity to reduce some of that type of noise to tolerable levels on strong broadcasts. But what about non-condo noise, like out in the field??
NHK Japan
I took my trusty Loop On Ground antenna to the usual county park Forest Preserve which is relatively low in RF noise. I did some usual recording on 25 meters and poked around for something being captured by SDR Console. On 11910 kHz is NHK broadcasting daily from Koga, Japan. It is hearable at this location but is always an S7 or weaker signal despite its 300 KW of power no doubt due to being beamed away from the Midwest USA.
I recorded it using the SDR Console 10kHz bandwidth filter and created a separate noise recording from a nearby empty frequency. Here is the 2 minute portion of a Japanese music teacher. No noise reduction was applied:
I opened the noise and broadcast recordings in Audacity to see what I could do. Part 1 of my previously mentioned post details how I apply the Noise file. A big downside of using any kind of noise reduction software is that it is ridiculously easy to destroy the desirable characteristics of the original recording. Applying too much noise reduction, especially in the presence of constant, spiky lightning noises, will create both digital artifacts as well as very dull sounding results. So I used the Effect – Noise Reduction (NR) feature very carefully.
In this example, I used the Effect – Amplify feature on the one minute noise file. I applied just +1dB of Amplify to the whole file. Then I highlighted a 10 second section I thought was representative of the general background noise and chose Edit – Copy. Then, I opened the broadcast file, Pasted the 10 seconds of noise to the END of the file and highlighted just the 10 seconds of noise. Then I chose Effect – Noise Reduction – Get Noise Profile button. Amplifying the noise file by +1db does not sound like much but it seems to help according to my tests. Anymore than this and the Noise Profile would not recognize the noise without destroying the music.
I used the NR feature three times in succession using the following (NoiseReduction/Sensitivity/FrequencySmoothing) settings: Pass1 (3dB/0.79/1), Pass2 (2dB/1.28/1), Pass3 (1dB/2.05/0). Part of what I listened for was choosing the Residue circle and Preview button for any music or dialog that was being filtered out. If I heard something that came from the desired part of the recording in Residue, I knew that I hit the limit concerning the combination of Noise reduction and Sensitivity settings to engage. I used those Residue & Preview buttons over and over again with different settings to make sure I wasn’t getting rid of anything wanted. I also used the higher Noise reduction with lower Sensitivity to try to get rid of any momentary spiky type noise that is often associated with SWLing.
I messed around with a lot of test outputs of differing dB and Sensitivities and a lot seemed to depend on the strength of the broadcast signal compared to the noise. If the broadcast was weak, I could push the dB and Sensitivities a little harder. I also noted that with strong signal broadcasts, I could NOT use more than 1 dB of Noise reduction beyond a Sensitivity of about 0.85 without causing damage to the musical fidelity. This was a pretty low level of nuanced manipulation. Because of these minor level Audacity software settings, it dawned on me that it is very helpful to already be using a low-noise antenna design.
If the Sensitivity numbers look familiar, that is because I tried basing the series of Sensitivity on Fibonacci numbers 0.618 and 0.786. Don’t ask me why these type of numbers, they just ended up sounding better to me. I also needed a structured approach compared to just using random numbers! Probably any other similarly spaced Sensitivity numbers would work just fine, too.
Now if you really want to go crazy with this, add Pseudo Stereo to your favorite version of this file (also detailed in Part 1) and playback the file using VLC Media Player. That software has a couple of interesting features such as an Equalizer and a Stereo Widener. You may or may not like using these features but sometimes it helps with intelligibility of the voice and/or music [VLC will also let you right-click a folder of music and choose to play all it finds there without having to import each MP3 file into a special “Library” of music tracks where they bombard you with advertisements].
You can also turn on Windows Sonic for Headphones if you are using the Windows operating system. However, this can sometimes be too much audio manipulation for my tastes!
Here is the resulting NHK noise-reduced file with 9ms of delay with High & Low Filters:
Radio Thailand
Five days later I was out in the field again. This time I found Radio Thailand on 11920 kHz finishing up a Thai broadcast. It was a weaker S5 signal than the NHK example, so it would be a good test.
When I got home, I recorded the broadcast file at a Bandwidth filter of 8 kHz and using Slow AGC and the extra Noise file at 12kHz using Fast AGC. In a previous test I had noticed a very slight improvement in sound quality in the way noise seems to get out of the way quicker compared to Slow AGC (which is usually how I listen to shortwave broadcasters). I now try to remember to record the Noise file with Fast AGC.
Here is the original without any noise reduction:
This time the Noise file using Amplify +1dB did not help and I used it as-is for the 10 second Noise Profile. I then tried multiple passes of NR at higher and higher Sensitivities and ended up with these settings the best: Pass1 (1dB/0.79/0), Pass2 (1dB/1.27/0), Pass3 (1dB/2.05/0), Pass4 (1dB/3.33/0).
As a comparison, I tried recording only with SDR Console’s noise reduction NR1 set to 3dB and got this. I hear more noise and less of the music coming through:
Now for more crazy Pseudo Stereo to finish up the Audacity 4Pass version (nice Interval Signal of Buddhist bells ringing and station ID at the very end):
Summary
I do not understand why applying 3 or 4 separate 1dB Sensitivities of noise reduction is superior to just one Pass at 3dB Sensitivity (in Audacity) or the one 3dB noise reduction (in SDR Console). My guess is that doing 1 dB at different Sensitivities shaves off some spiky noise a little at a time, somehow allowing for more of the musical notes to poke through the noise cloud. Who knows but I can hear a difference in subtle musical notes and sharpness of voice and instruments. Probably the Fast AGC helps too.
Music is a Universal Language that we can share even when we don’t understand a word they are saying. And there is more music on the air than I thought. Some of these recordings sound surprisingly pleasing after noise reduction. The fake stereo is pumped through a CCrane FM Transmitter to a few radios in the home, or I can use the Beyerdynamic DT990 Pro headphones.
Enjoying the Music!
TomL
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Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post:
