N9EWO Review :
"Belka - DX" Direct Conversion DSP
  Micro HF Receiver



The stellar absolutely tiny sized Belka-DX all mode HF receiver.
Puts most Chinese made portables to shame for performance !
However general ergonomics is another story. No MWBC or FMBC coverage (see text).
DX model replaced with "Belka" 3rd generation which now covers LW and MW bands (not tested).
(N9EWO Photo)

N9EWO Review :  Belka-DX Direct Conversion DSP Micro HF Receiver (Generation 2)
2 Samples were tested for this report (one with and other without internal speaker option).

Model : Belka-DSP (no longer manufactured, replacement now has LW and MW coverage, see text)
Country Of Manufacture : Belarus

Approx. Serial Number of Test Samples : (none was found on either test sample case)
Firmware Versions Tested : Unknown

Test Antenna's :
- Included 25 inch telescopic whip
- Short 20 foot [6 meter] indoor wire antenna
- Comet DS150S Discone Antenna (30 foot [10 meter] height)
- RF Systems MLBA-MK2 long wire (55 foot length [16.7 meter] - 24 foot [7.3 meter] height at peak)
- Comet H-422 Dipole 31 feet [9.4 meters] in length  (24 foot [7.3 meter] height) - Straight Configuration)

PRO :
- A
bsolutely TINY size !
- All metal case including a metal knob.
- Outstanding Sensitivity (with included whip or external antenna).
- Excellent audio quality (headphones).
- Excellent Selectivity (with proper selections provided).
- Decent dynamic range even with long wire outdoor antennas.
- Rock solid stability with a 0.5 PPM TXCO.
- Useful
pseudosynchronous detection (see text).
- No chuffing, muting or other nasties when tining.
- Long and Medium Wave coverage with 3rd Generation Belka model (see con)
- Dead on frequency display through it's entire tuning range.
- Easy to read LCD display that is QUIET and has timed or continuous on white backlight.
- BNC antenna connector.
- Near excellent AGC that also gives zero clipping distortion with SSB and ECSS modes.
- 4 front panel tac buttons have excellent tactile response.
- Battery indicator that is accurate.
- IQ output jack (Belka-DX and Belka models only, not tested)
- 4 front end filters.
- Accurate signal strength meter (see con)
- Internal speaker option for Belka-DX and Belka models (see con).
- Memory / VFO selection with Belka (3rd generation) model.
- 32 or 36 memory channels that store frequency, mode, tuning step and sensitivity setting. (see con).
- Off timer function.

CON :
- Limited number 32 or 36 memory channels that are also too easy to overwrite.
- Memory entries lack alpha tags.
- Fidgety mechanical encoder tuning knob.
- Encoder has rotational play (see text)
- Sour ergonomics.
- Glued in lithium ion type battery makes replacement difficult, dangerous and near impossible.
- No band or memory channel scanning.
- No band presets.
- No squelch control.
- Damage will occur if 2 conductor phone plugs are used (see text)

- Antenna input is high impedance only (see text).
- S-meter has no standard S-Unit markings (see text).
- Internal speaker option has very limited output.
- Uses USB "Micro" power connector.
- No way for user to update firmware.
- No FMBC frequency coverage.
- No or decent MW frequency coverage (DSP and DX models)


Absolutely TINY size / Fair Ergonomics  / Metal Case and Knob  / Internal glued in Lithium Ion Type Battery.

Belka-DX size is at a super SMALL 3.5 x 2.0 x 0.8 inches (86 x 50 x 20 mm) not including knob and BNC antenna. Weight at 3.52 ounces (100 grams). Entirely made in a all metal case with screws. Even the lone knob has a metal shell (plastic base).

The most disconcerting con with the Belka is the use of a lithium ion type battery. It's a glued on pack to the inside of the rear cover. When it comes time for replacement one has to pry off this battery to replace it. Good luck with that as that is a extremely dangerous procedure (if it should be attempted at all) ! We would have preferred use of say 3 AAA Ni-Mh batteries in a holder even with a shorter run time between charges ! By the way it's battery meter LCD icon is most useful and accurate.

NOTE : There is an overpriced after market internal speaker option called the LSP3W that also increases the internal battery capacity even a bit more over the original headphone version (2200 vs 2500 mah). It also adds 2 swinging feet for tilting the receiver. This makes the cabinet less stealthy (not tested). Appears the availability of this product is difficult ?

USB micro jack is used for charging the internal lithium ion type battery (sorry it's not a USB C), Current consumption is slated at 80 ma (with headphones) which is a battery miser indeed. With the headphone only versions (which contain a higher capacity battery) operation time is like 24+ hours on a single charge. With the speaker option installed is at around 10+ hours (smaller battery plus the speaker use).

As can be expected with only FOUR pushbuttons on it's spartan front panel it's ergonomics are like a trip down a side of a extremely steep mountain in a coaster wagon. Would not say that it's totally hostile, but is not very good either. But being what it's sheer size is one should give time to adjust to it's operations including it's
fidgety tuning encoder. However even after some use we were still having a frustrating time overwriting wanted memory channels (it's so easy to do that).

Front Panel Buttons (selection is made with it's single mechanical encoder knob):
VOL : Volume and Sensitivity adjustments
MOD : Mode Select / Bandwidth (high cut) / Low Cut (bass)
MODES Available :  CWU, LSB , USB , AM1 (Standard AM), AM2 (Double Sideband pseudosynchronous Detection), NFM
MEM : Memory Channel Enter / Select (32 or 36 memories store frequency, sensitivity level, tuning step and mode)
PWR : Power On / Off (press and hold) /  Backlight Options
ENCODER KNOB (press in) : Tuning Step (10, 20, 50, 100 hz 1K 5K, 10K, 50k), (press and hold while rotating, fast  advance)


Frequency Coverage (Depends on Generation) / No FMBC / No Squelch / 32 (or 36) Memories / No Scanning

Frequency coverage varies a bit depending on what generation (version) you are talking about.. First and second generations (versions) did not cover the medium wave broadcast band (2nd stated at 1.5 MHz but that is short of not). Later 3rd model covers from .1 to 31 MHz (not tested, see chart below) and also gives for 4 more memory channels.

If you need FM broadcast on portable set, the Belka does not offer that period (look elsewhere). Narrow FM MODE is offered which is a nice touch. So one can properly  tune into CB FM, 10 meter amateur band FM stations and a crazy HF pirate that appears once in awhile using narrow band FM mode.

Speaking of  memory channels those 32 (or 36) store frequency, sensitivity (RF Gain ?), tuning step and mode. There is no scanning or searching of either up-down frequency or memory channels with the Belka. When you enter a memory channel it ALWAYS starts with number 1 and forced to rotate the knob to go where you want to be for the proper channel. He would have liked to seen say 50 or even 100 memory channels, but of course that would have added more stress in the ergonomic mess.

There are no preset band presets provided. So the user has to create those using the limited memory channels.

Generation (Version)
Frequency Coverage
MHz
Number of 
Memory Channels
 Belka - DSP (1)
[Note : Does not support internal speaker option]

3.5 to 30


32
Belka - DX (2)
1.5 to 31
32
Belka (3)
0.1 to 31
36

No Internal Speaker / Internal Speaker Option Works OK / Push In - Mechanical Encoder Has Rotational Slop

Original Belka-DSP (Generation 1) had no internal speaker period and is not possible to install the external speaker kit in it either as it is soldered in - hard wired. So the only way to listen to the receiver is to use a pair of headphones / earbuds, or some external speaker hook up.

WARNING : Be careful when plugging in any earphone / speaker (ditto for the IQ output). As covered in the manual, one should NEVER use a mono type 2-conductor plug as that will short out the amplifier and damage it.

We tested the internal speaker option which was in one of test samples and works adequately in most QUIET indoor situations (so be it a bit weak at maximum level). Outdoor use was limited not having not enough punch so headphones or a amplified STEREO speakers had to be used.

When the external speaker option is used the battery capacity / size size is reduced and gives for a much shorter operational time. So this is a trade off thing.

The lone mechanical rotary encoder has rotational play. That is when you go counter clockwise rotation to clockwise there is noticeable amount of rotational play-slop feeling. This is common with encoders that also have a push in function (and the Belka has that to select the tuning step).
Overall it works fine,but for the record.

Direct Sampling Scheme with DSP / ROCK Stable / No Way to Update Firmware

Belka receivers use a direct conversion quadrature scheme and DSP. With the Belka-DX model tested there are 4 front end bandpass filters. This makes for excellent out of band signal rejection. It can tune down to 10 hz steps (display shows 1 hz minimum, but this for show only).

Reference oscillator uses a quality 0.5 PPM TXCO. This is unheard of in price point of the Belka. Gives for outstanding stability and a DEAD on frequency display.

There is no way for the user to update the firmware like with many other SDR / DSP receivers these days. A bit of a disconcerting bug but being operation was stable with both test samples is not as important as it could have been.



Belka-DX "Generation 2" block diagram. The Belka was developed by Alex, EU1ME.
Direct conversion
quadrature design with decent front end filtering.
Later "Belka" model adds one extra front end bandpass filter for 0.1 to 1.5 MHz.

Superb Sensitivity / Selectivity / Stability / Audio Quality / BNC Antenna Connector /  High Impedance Antenna Input ? / AGC

Belka is excellent on all performance bases. Sensitivity is simply breath taking even with it's with included short included whip. However being the case is all metal, body hand capacitance can greatly affect whip reception (but not always). If you just set it on the table and no longer touch it sensitivity can take a take a big dive. One needs to add a counterpoise of some kind say adding a wire to the ground side of the BNC. Just using a long headphone cable does the trick nicely too (provided you are listening with headphones that is).

Ditto with selectivity, first rate. A number of well chosen bandwidths are provided. As with many DSP based receivers In AM mode they sound wider than listed. So the 4 kHz widest filter sounds like 8 kHz (which is preferable for our wider filter desires).

Bandwidths Available on Belka-DX Test Samples (see text):
USB, LSB, AM1, AM2, NFM : 2k, 2.4k, 2.7k, 3k, 4k hz
CW U : 200, 600, 700, 900 and 1k hz 


Yes, a desirable BNC antenna socket is used. This is much more robust over over any SMA type. However it's of a high impedance input only. So is suggested to add a resistor and capacitor as indicated in later owners manuals for proper matching when using say a low impedance dipole external antennas. This is not absolute as it will function without these parts and in practice we did not notice much difference here using 50~75 ohm outdoor antennas.


All Belka's have a high impedance antenna input. While perfect for whip and long wire antenna's,
this is not proper for use with dipoles and other low-Z types. Later owner manuals
indicate to add a resistor and capacitor for proper matching (see text above).


Audio quality is another home run. Absolutely with no bug-a-boos or hiss nasties and AGC clipping does not exist in SSB / ECSS modes (clean). AGC is near excellent even if lacking any decay rate adjustments and even a bit too fast (all modes). A low cut off adjustment is also provided in the bandwidth screen but most will just leave this at it's minimum low level. This will be dependent on headphones / external speaker used.


We need to give credit again to it's rock solid stability with a display that is dead on accurate across the entire tuning range. So no need for those unhandy "pain in the rump" calibration and non linear setting schemes found with Chinese sets to offset bad engineering. ECSS is excellent with the Belka with it's dead on frequency display and rock solid stability (oh yes the decent AGC performance in the mix too).

"pseudosynchronous detection" Improves Most Signals, But What Actually Is It ? / Accurate Signal Meter But No S-Unit Scale

AM2 mode on the Belka is marked as "pseudosynchronous detection" (what the #&!! is that). In our testing it appears to be another type of synchrophase detector type circuit (in double sideband). Mind you it helps a bit with fading distortion and pulling a signal out of the noise. But it is clearly NOT a true Synchronous Detector.

One AM2 grumble was with SOME WEAK signals that contained severe fading / flutter, in this case it was best to leave it in AM1 (standard AM detection) or use ECSS as these signals tended to get washed out. Anyway it is useful and desirable to leave on with most (but not all) AM mode signals in our testing.

Belka's have a most accurate signal strength bar type meter. However no standard S-Unit scale is provided. Photo below of a conversion handy chart as posted on SWLing.com developed by 13dka.


Belka's bar type signal strength is most accurate. However it lacks a S-Unit scale.
"13dka" provides a handy conversion scale (as posted on SWLing.com).

Dynamic Range Decent / Sensitivity Control / Spurious Signals

Dynamic range is decent. Overloading was not detected even when connected to decent outdoor antennas at peak listening time (say on 49 meter SWBC at night). Thankfully a sensitivity adjustment (volume control button on second press) is provided to fix that issue if swamped say by a local amateur radio operator or such.

We never detected excessive spurious signals in testing.


Availability ? / How does one purchase a Belka Receiver ?

The Belka receivers (now generation 3 only, not tested) can be purchased direct from the manufacture in Belarus here. Or an alternative dealer Mobimax via Bulgaria. However is more expensive here but perhaps a bit more stable with worldwide events as they are these days. In any event availability could be indifferent at times. These are the only 2 places to order a Belka at the time this report was complied.

Best Micro Portable Ever Tested - If not one of the Better Portables ever tested for Performance !

While most portables can also be used comfortability at home using external antenna's / AC adapters, the Belka sets are simply not well suited for that purpose for hour after hour listening sitting at a desk. It's just too tiny with it's struggling ergonomics. However if you need the ultimate portable with excellent performance for the backyard or camping, this is clearly the best MICRO-Small set we have ever tested. Yes even when compared to the bit larger Sony ICF-SW100 (also previously tested). However using a glued in lithium ion type battery is very disconcerting and wish that say 3 common AAA removable nickel-metal-hydride cells in a battery holder were used instead even if shorter operating time. WARNING (once again) : If one replaces that battery, it's an extremely dangerous and risky operation when "prying" the old one out.

We found overall performance of the Belka-DX greatly excels over ANY of the Chinese receivers we have tested to date (only exception is the Tecsun Grundig Satellit 800). A breath of fresh air indeed. It's like having a super tiny high performance communications receiver in your pocket / hand. Just be prepared to get accustomed to the fidgety tuning encoder and poor ergonomics. However the price is much more than say a Tecsun PL-330 or PL-365 and that has to be considered with any decision to purchase one (along with possible availability issues).


Dave N9EWO
N9EWO, all rights reserved
Ver 3.0

The Sony ICR-4800 Pocket Receiver
Year was 1981 and Sony released the tiny pocket analog ICR-4800. Sold for $ 100. USD street price when released (was closed out for around $ 70. in 1984). Looked very exciting, but that was short lived once out of the box. Had limited frequency coverage. No FMBC, missed the important 41 and 22 meters as well as the lower tropical bands altogether. Single conversion, superhet with a one IC design so whistles and other spurious signals were all over the place. Whip sensitivity was only so-so at best and don't even think of connecting a 30 foot long wire to it with it's dreadful dynamic range. Operated on 2 AA batteries or external voltage 3VDC jack (NEGATIVE TIP). The Sony ICF-SW100 came years later, but had a weird clam shell design and sour SSB and Sync Detection performance along with only having ONE IF bandwidth filter !

But how we wished for decent performing pocket SWBC receiver back then. We of course have tested the Chinese pocket sized PL-330 and PL-360/PL-365 sets which all work well enough (except for nasty SSB / Sync AGC distortion) but construction and buttons/knobs are fair at best. Sony released improved pocket models after the ICR-4800 that used dual conversion, improved SWBC band coverage and FMBC. One model being the ICF-4900 / ICF-4910 (not tested).


The tested analog Sony ICR-4800 (sold from 1981 to 1984). Frequency coverage was MWBC ,
SW bandspread in the 49, 31, 25, 19 and 17 Meter bands. No FMBC or extended MWBC.
While it looked exciting, used single conversion and gave extremely sour performance.
Of course no SSB or amateur band coverage. (N9EWO Photo Edit)


N9EWO's SWL set up in early 1980 that included a Yaesu FRG-7000.
Sitting on the left was the excessively drifty Panasonic RF-2800.
Pioneer Centrex KD-12 cassette recorder in the lower right.
 Even back in that day I ALWAYS had a recorder ready for instant use. (N9EWO Photo)

Belka - DX  Links (all subject to change without notice)

eham Reviews on the Belka-DX

Belka-DX Owners Manual
Belka DX Quick Reference Guide


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