Category Archives: Mediumwave

Guest Post & Review: Test Driving the Russia-Made Malahit DSP-2

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.

News about the Malahit began to spread in 2019, with articles here on the SWLing Post, including two in February and April of 2020 (https://swling.com/blog/2020/02/the-malahit-dsp-a-potential-holy-grail-portable-sdr/ and one in which the Malahit was put up against an Afedri LAN-IQ SDR (https://swling.com/blog/2020/04/fenu-posts-a-malahit-dsp-afedri-lan-iq-head-to-head-comparison/ ).

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).

VIDEO: Malahit With Display Generated Noise

Click here to view on YouTube.

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: nickstrannik@gmail.com 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

VIDEO

Click here to view on YouTube.

POISED ON THE EDGE OF GREATNESS

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.

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Guest Post: Recording Music on Shortwave Part 2 – Weak signal recovery

An example of an AirSpy SDR# software screen.

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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The Icom IC-705: Is this really a new holy grail SWL/BCL receiver?

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


The Icom IC-705: Is this really a new holy grail SWL/BCL receiver?

by 13dka

When Thomas got wind of its development in 2019 he immediately asked “could the Icom IC-705 be a shortwave listeners holy grail receiver?”. I usually wince a little when I hear “holy grail” because it means very different things to different people, it’s also a moving target with many people aiming at the spot where it was decades ago. But Thomas certainly had a very level-headed assembly of technical performance, quality and practicality requirements in mind when he used that term, and I thought he might be onto something!

There are some excellent, trustworthy reviews of the IC-705 out there. The following is not one of them, I just want to share an opinionated breakdown on why I think this is an interesting radio for SWLs/BCLs indeed, also deliberately ignoring that it’s actually a transceiver.

Jumping shop

While the era of superhet/DSP-supported tabletop holy grails ended with the discontinuation and sell-off of the last survivors more than a decade ago, powerful PC-based SDR black boxes were taking over the mid-range segment and it became very slim pickings for standalone SWL receivers: Thomas just recently summed up the remaining options here.

Between the steady supply of inexpensive yet serviceable Chinese portables, upgraded with a least-cost version of DSP technology, and the remnants of the high end sector there’s very little left to put on the wish list for Santa – that doesn’t need to be paired with a computer that is.

No surprise that SWLs/BCLs in search of new quality toys with tangible controls are taking a squint over the fence to the ham transceiver market: Hams are still being served the best and the latest in radio technology in all shapes and sizes, and even entry-level rigs usually come with feature-rich general coverage receivers. But transceivers never had SWLs much in their focus in the past decades, and particularly not BCLs: Frontend adaptation, additional AM filters, switches and functions would’ve meant increasing costs and so transceivers were never perfected for that purpose. DSP and SDR technology allowed for improvements on that without actually adding (much) hardware and so some interesting alternatives surfaced in the past years, but most of them still come with little downers, at least for BCLs.

Continue reading

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Radio Waves: Shedding Light on the Hindenburg, Chip Shortages, NPR at 50, and July 4th SAQ Grimeton Transmission

Icom IC-756 Pro Transceiver Dial

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Ron, Rich Cuff, and the Southgate ARC  for the following tips:


Radio Amateur’s Vintage Home Movie Film Sheds Light on Hindenburg Disaster (ARRL News)

Vintage home movie film provided by New Jersey radio amateur Bob Schenck, N2OO, was the highlight of a PBS documentary about the Hindenburg disaster. The film, shot by his uncle Harold Schenck, may provide clues as to what initiated the disastrous 1937 fire that destroyed the airship Hindenburg and claimed 35 lives as the German zeppelin was landing at Lakehurst, New Jersey. Harold Schenck tried to interest government investigators in his film, shot from a different angle than newsreel footage that begins only after the fire was well under way, but it was largely overlooked. “Nobody ever asked for it,” Bob Schenck explains in the documentary.

The Schenck film is the highlight of a PBS “NOVA” documentary, Hindenburg: The New Evidence, that investigates the issue in considerable depth in an effort to unlock the secrets of the cold case. The program aired on May 19 and remains available for streaming.

“My dad had bought this nifty Kodak camera — a wind-up movie camera, 8 millimeters — and he couldn’t come [to the Hindenburg landing] because he worked,” Bob Schenck recounted during the documentary. “So, he asked my uncle and my mom if they would take some shots and see the Hindenburg land.”

Bob Schenck approached Dan Grossman, an expert on airships, including Hindenburg, in 2012 during a commemoration of the disaster that forever memorialized radio reporter Herbert Morrison’s plaintive on-air reaction, “Oh, the humanity!” The NOVA documentary not only shares Schenck’s footage, which provided new clues to re-examine the cause of the explosion. The documentary also reviews scientific experiments that helped investigators come to a fresh understanding of what set off the fire. [Continue reading…]

Will chip shortage hit ham radios ? (Southgate ARC)

Glenn O’Donnell K3PP of Forrester Research notes the chip shortage may have a more serious impact than first thought and gives Amateur Radio rigs as an example of what might be affected

Self-described as a “ham radio nut,” O’Donnell discussed one of his hobbies to explain how the sway of tech titans could impact smaller companies as industries compete for limited resources.

“In this hobby, the newer radio “toys” are advanced technology, but the hottest radio might sell 5,000 units per year. If Apple wants 100 million chips, but the little ham radio company wants 5,000, Apple wins!” O’Donnell said.

Read the article at
https://www.techrepublic.com/article/global-chip-shortage-the-logjam-is-holding-up-more-than-laptops-and-cars-and-could-spoil-the-holidays/

NPR at 50: A Highly Selective History (Washington Post)

The network’s half-century evolution from an audio experiment to a media powerhouse

Today NPR is one of Washington’s most familiar and influential media companies, operating out of a gleaming, ultramodern broadcast facility on North Capitol Street. Its radio programs, online content, and podcasts reach millions of people around the world. But when it launched 50 years ago, in April 1971, National Public Radio was a decidedly scrappy enterprise.

How did a modest radio project from a bunch of audio idealists evolve into the multimedia behemoth that we now spend countless hours listening to? To celebrate NPR’s anniversary, we’ve put together a look at its history and transformation. Please note: If you would like to imagine the whole thing being read to you in the voices of Nina Totenberg and Robert Siegel, we won’t object. Click here to read the full article…

SAQ Grimeton Transmission on July 4th (Southgate ARC)

The annual transmission event on the Alexanderson Day with the Alexanderson Alternator from 1924, on VLF 17.2 kHz CW with the call sign SAQ, is scheduled for Sunday, July 4th, 2021.

The Alexander Grimeton Association are planning to carry out two broadcasts to the world from the old Alexanderson alternator SAQ. Only required staff will be in place, due to the ongoing pandemic.

Transmission schedule:

  • Startup and tuning at 10:30 CET (08:30 UTC) with a transmission of a message at 11:00 CET (09:00 UTC)
  • Startup and tuning at 13:30 CET (11:30 UTC) with a transmission of a message at 14:00 CET (12:00 UTC)

Live Video from World Heritage Grimeton Radio Station
Both transmission events can be seen live on our YouTube Channel.
The live video starts 5 minutes before the startup and tuning.
https://mailchi.mp/aff85163e64f/alexanderson-day-2021?e=2c0cbe870f

 


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Medium Wave Circle website sports updates and upgrades

Many thanks to SWLing Post contributor, Steve Whitt, who writes:

Hello Thomas

Just a brief note to tell you about exciting developments here at the Medium Wave Circle.

We’ve just launched our new-look website at

https://mwcircle.org/

And we’d like to share the news far and wide.

Some of the features of the new website are:

    • easy to use membership with secure online payment
    • access to the full archive of Medium Wave News (all 500 issues)
    • access to the latest 2020 Editions of the All Time DX Heard in the British Isles
    • a new section for news and feature articles
    • a completely new and re-written library
    • For the first time we also host the archive of the European MW Guide which was the most
    • complete directory of radio stations in Europe.

All the content is either new or completely revised and updated. Most importantly we want our website to be unique and that is why the features, photos, QSLs and audio clips are not to be found elsewhere online.

The new website has been carefully designed to work on desktop PCs, laptops, ipads and even smartphones. It has also been updated to improve security – you will notice the https web address & the padlock next to the url in your browser.

Click here to check out the new site!

Introduction to Long Distance Medium Wave Listening

Thanking you in anticipation.

Kind regards

Steve Whitt

I like the new look and upgrades!  Thanks for sharing, Steve!

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Guest Post: Remembering the great “Radio Moving Day” of 1941

Many thanks to SWLing Post contributor, Bill Hemphill, who shares the following guest post and addendum to his most recent post on BBC Re-Tune messages:


Radio Moving Day

by Bill Hemphill (WD9EQD)

After listening to the BBC “Re-Tune” broadcasts, it reminded me of when the United States had its own “Re-Tune” day on March 29, 1941.  It was referred to as “Moving Day”.

At 3:00 am, 802 of the 890 radio stations moved frequency.  Following are a couple of articles about this day:

http://www.jimramsburg.com/the-march-of-change-audio.html

https://www.radioworld.com/columns-and-views/in-1941-stations-confronted-39moving-day39

And a previous SWLing Post article:

https://swling.com/blog/2021/04/am-radio-history-80th-anniversary-of-the-havana-treaty/

Like the BBC, there were also broadcasts helping listeners to get ready:

Audio Clip 1

Audio Clip 2

Audio Clip 3

Audio Clip 4

 

I love how it was used as an opportunity to get the radio listener to call on the radio technician to re-program the radio push buttons.  And of course while the technician is there, have him do a full alignment and maybe replace a tube.

The March 1941 issue of Radio and Television Retailing (Pages 16-17) had the article “Radio’s Opportunity for Contact”.

Link:  https://worldradiohistory.com/Archive-Radio-Retailing/40s/Radio-Retailing-1941-03.pdf

While the entire article is an interesting read, the first few paragraphs sums up the opportumities:

THE OPPORTUNITY for contact with consumers using pushbutton-tuned radios., afforded by dramatic March 29 broadcast station frequency shifts, represents an absolutely unique invitation to move more major merchandise, with the promotional expense at least partially covered by service and accessory sales.

Imagine what slick automobile salesmen could do if roads were suddenly altered in such a manner that 10,000,000 cars required some adjustment to operate properly, what refrigerator salesmen might accomplish if a change in current necessitated motor manipulation, how laundry equipment salesmen would positively gloat over the glut of prospects if that many people with old machines actually asked them to call.

Calls make sales, as the records of many home specialty retailers conclusively prove, and the beauty of this particular opportunity to make them lies in the three-fold fact that cold-canvassing is completely unnecessary, that the motivating power of any campaign built around it is obviously not just trumped-up by the trade and that only dealers selling or servicing radios can capitalize in all departments of their business.

So valuable from a major merchandising sales angle is the opportunity to call upon consumers afforded by the necessity for changing pushbutton settings that we suspect many radio retailers will hesitate to charge for this adjustment.

This may be particularly true where consumers so contacted are obviously prospects for new merchandise and will undoubtedly occur in some instances where customers are still being carried on time-payment accounts.

The Feb 1941 issue of Radio Service-Dealer (Page 8) also stressed the opportunities.

Link: https://worldradiohistory.com/Archive-Radio-Service-Dealer/40s/Radio-Service-Dealer-1941-02.pdf

From Page 8:

Reallocation of Broadcast Frequencies M arch 29th Opens Big Job For Service men Resetting Nation’s Push-Buttons

YOUR JOB

There are approximately 10 million push-button receivers in operation in this country. It will be your job to re-set the buttons for the new frequencies in the shortest possible time and with the least amount of confusion. It will also be your job and your opportunity to inspect these receivers for faulty operation. No such opportunity is likely to present itself again, so make the best of it.


And on page 7 of the Mar 1941 issue of Radio Service-Dealer has the article FREQUENCY REALLOCATION SERVICING PROBLEMS

Link: https://worldradiohistory.com/Archive-Radio-Service-Dealer/40s/Radio-Service-Dealer-1941-03.pdf

The first Problem discussed is the IF Frequency:

1A—If a station with a strong signal intensity happens to be operating on double the frequency of the intermediate frequency of a receiver, there is liable to be a heterodyne whistle. The frequency of 455 kc has been used as the standard intermediate frequency on receivers manufactured in the United States.  One main reason for selecting this frequency was that the broadcast frequency of 910 kc was assigned to Canada and, therefore, the possibility of a heterodyne note being produced on a receiver in the United States was at a minimum. Under the terms of the reallocation several American stations will be moved to 910 kc thus producing a problem in the cities where these stations are to be located. If a heterodyne note is heard due to this cause the remedy is to shift the intermediate frequency to one side or another.


Thank you, Bill, for shedding more light on Radio Moving Day and, especially, providing us with the broadcaster and technician’s point of view.

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BBC Radio Stations Broadcasting Re-Tune Instructions

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who writes:

Hi Thomas,

The BBC in their transition to digital radio has started closing some of their AM radio stations.

See following link:

https://www.bbc.co.uk/reception/work-warning/news/mw-closures-2021

The AM stations being closed are broadcasting “Re-Tune” instructions on their frequencies.

Not sure how long they will be doing this. The “Re-Tune” messages are interesting.

I have used the G4DYA KiwiSDR web receiver to listen and record some of the “Re-Tune” messages.

Most are just straight forward instructions, but Radio Hereford-Worcester on 738 has recorded individual

messages by several of their on-air personalities. The messages just loop continuously.

Attached are MP3 files for 738 Radio Hereford-Worcester, 1035 Radio Sheffield, 1341 Radio Ulster and 1503 Radio Stoke.

73

Bill Hemphill, WD9EQD

Recordings

738 Radio Hereford-Worcester

1035 Radio Sheffield

1341 Radio Ulster

1503 Radio Stoke

Thank you so much for taking the time to make these recordings and for sharing them with us here!

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