BELKA DX

[dxace1]

I echo the views of others on the Belka DX -- the addition of a speaker and battery back available
from Mobimax (https://swling.com/blog/2021/03/a-new-belka-dx-dsp-speaker-from-mobimax/)
makes all the difference.  Whereas before you had to have a mini to mini out to a speaker, plus
the antenna, now the Belka is the ultimate portable.  I recently was able to use the Belka DX on
the beach (see attached photo).  Its small size makes it perfect for setting on a carrying bag and
the apparent excellent sensitivity with a whip makes it the ideal beach radio.  There is a bit of signal
loss when not holding it in the hand, but nothing as serious as the Tecsun PL36xxxx series which suffer
from major signal loss if the receiver is not handheld.  Now, if as I expect, Alex modifies the Belka to
tune down to MW while not jeopardizing any of its current excellence, future models will be even better.
I think that if Alex were to come out with a slightly larger Belka that provides the superb features of
the Malachit series, then we're really talking about some fun.

[dxace1]

Belka has a SYNC mode?  News to me . . . .where and how is it activated?  Or do you mean ECSS with SSB?
UPDATE:  Ah, I see it now, AM2 is described as "pseudo-sync"  Not sure that can be compared to HF-150 and others...

I love this radio - it runs circles around my Tecsun's.  I've done a few experiments using both the whip vs my on-the-ground antennas (MMD dipole & longwire w/MLB) and although there is a difference in signal strength, as long as you're away from noise, the whip can easily hear what the other two can.  I was listening to WTF last night in bed rockin out to Queen's 'Fat Bottom Girls' - this past May was in Seattle and enjoyed arm chair copy of North Korea's English service on both 11710 & 9435 also with just the whip & earbuds.

The quality of the sync detector is the closest I've found to my HF-150 on a portable, but without  the selectable sidebands and low frequency rumble; paired up with a Bose Soundlink, it is killer!  The sideband audio is also excellent; very similar to my Ten Tec.

I should clarify that I ran the two external antennas through a MFJ 16010 tuner since it's input is designed for the high impedance whip.  Also, I'm getting around 10 -12hrs per charge which is fine for my use.

If I had any gripes, I would rather have a dedicated line out than the I/Q, but that's just me.

[Sealord]

UPDATE:  Ah, I see it now, AM2 is described as "pseudo-sync"  Not sure that can be compared to HF-150 and others...

I am talking about the recovered audio quality with moderate to strong signals using Belka's version.  Actually, the sensitivity of the DX makes for good copy of most AM signals using the AM2 mode.

13DKA's review of the DX has a good description of the “Pseudo”-Sync detector here and it's ability with weak signals here.

[~SIGINT~]

Ultimate test: I am currently listening to Drunken DJ Radio 6950 USB 0138 UTC 05 JULY 2021 with the BELKA-DX and telescopic antenna while sitting in the basement from a location 500 miles North of Toronto, Ontario Canada. The receiver is working like a charm on this pirate broadcast.

[Sealord]

Yes, there are actually some nice "hidden" options that you would never guess by pressing some "2 key" combinations.

Are these outside of what's mentioned in the manual & if so, would you mind sharing?

A simple trick I've used to improve reception if I don't have a conductive surface and want to listen using the internal speaker is to plug my earphones into the I/Q socket instead.

[~SIGINT~]

I am not aware of any undocumented "2 key" combinations. Only the ones mentioned in the manual.

For a counterpoise, technically, any piece of wire connected to the receiver ground (antenna, audio out or I/Q out) should work. Chances are that they are all common ground. My Sennheiser headphone has a 10 ft long cord so that in theory is a 10 ft long counterpoise.

A friend of mine just received his Belka today. I'll be looking forward to his feedback on the receiver.

[Ed H]

Jumping in a bit late here - I acquired a Belka DX a couple of months ago and have been extremely impressed with this little receiver. It has seen use with headphones and ear-buds and provides plenty of audio with either. For antennas, the whip is excellent if true portabity is needed, but the radio seems to work nicely with my external antennas.

I do a lot of monitoring for 22 m beacons, and put Belka to work, feeding the audio to a computer running Spectrum Lab. For this operation, it was a serious rival for any of the table-top receivers, and was excellent on this weak signal work.

For broadcast, the "pseudo-Sync" is very well implemented, and the recovered audio is very clear. It almost pains me to say it, but it's ability to "hang on" to a signal and maintain clarity perhaps exceeds the very good AMS of the Lowe HF-150 and HF-225

Before purchase, I had wondered if the minimalist controls could be difficult, but they are very easy to learn and use. It has a smooth and professional feel.

Count me very pleased to own this radio.

[~SIGINT~]

Ed H -> Question, do you use the audio output or I/Q output of the Belka to Spectrum Lab? I have read that the bandwidth of the I/Q output can be up to 192 kHz. Obviously this would also require a sound card in the PC capable of a 192 kHz sample rate. The I/Q output does open options to interface to external SDR software or decoders such as CW Skimmer plus the ability to create a digital recording of the spectrum for later processing. You can see an example of the later at the London Shortwave blog page: https://blog.londonshortwave.com/

[Ed H]

Thanks for the insight here SIGINT

So far, a quick test using just the headphone output - mimicking the same methods used with the conventional receivers. However, additional bandwidth would be a great benefit, particularly for monitoring 22m beacons. Since the whole band is only 14 kHz wide it could be monitored at once even with the basic audio facilities in the PC on my radio desk. I have yet to play with I/Q techniques, but plan to explore eventually.

[~SIGINT~]

Ed, you are all set. Most modern PCs do 44.1 kHz and 48 kHz and if you are lucky, 96 kHz. Anything above that generally requires a higher end sound card. If you are running Windows, you will find those settings in the "playback devices" and "recording devices". Make sure you use a uniform setting across both recording and playback devices to avoid re-sampling. I use both Spectrum Lab and Spectran. Spectrum Lab has a steep learning curve (and in my opinion is one of the "gold standards") but you have given me an excuse to try it with the Belka.

[Ed H]

Great - thank you.

I may have to borrow the other laptop for this - the cheap laptop at the radio desk is running from a plug-in USB sound I/O that I now realise only has mono input.

Further, I'd like to explore going really mobile with Belka and a spectrum analyser to check out HiFERs from other locations. A brief test with the laptop and the Belka receiving with the whip resulted in 5&9 reports to the computer, traced to the screen. Second test was to try a small tuned loop. Care with the feed decoupled most of the QRM from the PC. I think this had promise, but for the test, conditions were just awful.

Ed

[syfr]

Update from the Central Coast of Calif where I'm currently /6 for a few more days.

I'm near Santa Barbara, and just got in from listening to the Windy beacon on 4102 on the Belka....with the antenna fully collapsed to it's 6" length.  Just blows me away.

I'm really impressed by this little guy!

[syfr]

Great - thank you.

I may have to borrow the other laptop for this - the cheap laptop at the radio desk is running from a plug-in USB sound I/O that I now realise only has mono input.

Further, I'd like to explore going really mobile with Belka and a spectrum analyser to check out HiFERs from other locations. A brief test with the laptop and the Belka receiving with the whip resulted in 5&9 reports to the computer, traced to the screen. Second test was to try a small tuned loop. Care with the feed decoupled most of the QRM from the PC. I think this had promise, but for the test, conditions were just awful.

Ed

Hi Ed

Any further updates on these experiments?  I'd enjoy some mobile hifer experiments.   I'm going to see how the little rig works hooked to a hustler mobile in the car, but I'd like to try for some mobile Hifer QRSS receptions too.

Also...about those "hidden" two button options.........................................?

[~SIGINT~]

I have had my Belka mobile driving around in the Jeep and plugged into the sound system. It definitely requires an external antenna. I do not believe that it would need anything special for an antenna. Any unloaded (no coils etc ...) mag mount should work well. I have also used my Belka with a rubber ducky without issue.

[~SIGINT~]

BELKA-DX I/Q Output

I had the opportunity this past weekend to experiment with the I/Q output of the Belka. My quick tests revealed that is does work as expected.

Test #1 and screen shot #1 bellow is the Belka I/Q output connected to the PC's line input which is set to a 48 kHz sampling rate. As can be seen, Spectrum Lab can visualize a portion of the 40 metre CW band. Test #2 and screen shot #2 is CW Skimmer. Skimmer is decoding the Morse Code.