Tag Archives: Belka-DX DSP

Steve builds a simple SWL antenna tuner that pairs brilliantly with the Belka-DX

Many thanks to SWLing Post contributor, Steve Allen (KZ4TN), who shares the following guest post:


A Simple Antenna Tuner for SWL Radios

by Steve Allen, KZ4TN

After reading 13DKA’s excellent review of the Belka-DSP on SWLing.com a few weeks ago I knew I had to have one! The size, features, and performance of the Belka-DX (latest version of the Belka-DSP) is phenomenal. I won’t go into reviewing the radio as I couldn’t come close to 13DKA extensive review. If you are considering this SWL receiver his review is a must read.

I love bedtime SWLing and have been putting off setting up an outside antenna specifically to feed into the bedroom for too long. Given that the resonant frequency of the antenna would not be broad enough for the tuning range of the Belka-DX I decided to build a small antenna tuner just for SWLing.

After a couple of hours searching the internet for a simple tuner I found just what I was looking for on http://www.hard-core-dx.com/nordicdx/antenna/lab/tuner.html. It’s a simple L match using a single variable capacitor and coil.

For the coil I wound ~100 turns of 26 Ga wire on a one inch diameter wooden dowel. The wire size can be whatever you have on hand. I twisted a tap every 10 turns. I drilled a hole in each end and glued in a machine screw to mount the coil to the bottom of the enclosure. I’ve had this enclosure in my junk box for a long time and have been waiting for just the right project. The variable capacitor I used was one I found on EBay a few years ago that had two sections, 330 pF and 120 pF. I tied them together for 450 pF. For the rotary switch I had to scratch around on eBay for a while until I found a 12 position single pole.

The plans for the tuner suggested adding a fixed value capacitor with a toggle switch to increase the lower end of the tuning range. I found a 510 pF silver mica and wired it into the circuit.

The antenna I put up is a sloper about 30 feet long.The high end is up about 40 feet and the low end is at about 12 feet. I put the antenna and tuner to the test last evening and the reception on the Belka-DX was superb. With the tuner the strength of the signal would peak about 2-3 units when I found the sweet spot.

The tuner also does double duty as an attenuator for very strong signals.

One mod I made to the Belka-DX was the addition of some grip tape to the tuning knob. It makes fine tuning much easier.

I believe we will continue to see a number of innovative receivers coming to market in the near term utilizing SDR technology. The ratio of performance to size of the Belka-DX is truly amazing in my opinion.


Thank you, Steve, for sharing this brilliant weekend project! As always, brilliant craftsmanship!

Click here to read Steve’s other posts and projects.

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The new Belka-DX: Georges’ short review and tests

Many thanks to SWLing Post contributor, Georges Ringotte (F6DFZ), who writes:

I received the Belka-DX a few days ago, and it appears to be an outstanding receiver considering its price, its size, and quality of construction.

AGC and audio reproduction are way better than any Chinese SW receiver giving some superb receptions in CW, SSB and AM.

I shall not repeat that other have said, but I must add that the AM2 pseudo synchronous reception seems good to my ears and a bonus with weak signals.

I made some measures :

  • MDS is about -127 dBm in SSB mode, slightly better in CW mode
  • Sensitivity is constant from 1.5 to 30 MHz
  • Image rejection is over 70 dB, better than a KX3 that I tested a few years ago
  • I couldn’t measure selectivity because my HP generator is somewhat noisy, but the Belka-DX is very good, and also way better than Chinese receivers
  • “S meter” is calibrated as follows: -107 dBm = 10 and -37 dBm = 80, and on this range a 10 change equal a 10 dB change, very accurately. Over -37 dBm, S meter doesn’t move any more.
  • Even on my 2x18m center fed or my Hexbeam, I didn’t notice any signs of overload, but as you know the propagation is not outstanding, and BCL stations are not as bothersome as 40 years ago!
  • there are a few birdies, but if you move your frequency 100 Hz away, they disappear

In my opinion, considering the superb quality of reception, this receiver is outstanding.

Best regards.

Georges

Thank you for sharing this, Georges! Sounds like the Belka-DX is a performer!

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The new Belka-DX DSP now available via Mobimax

Many thanks to SWLing Post contributor, JMMHam, who comments:

The new DX version of BELKA -DSP is now available in the Mobimax Store. The new Belka-DX receiver is about 5 euros more expensive but great. I bought it here: https://www.mobimax.bg/en/BELKA-DX-shortwave-receiver

Very fast delivery !!!

Thank you for the tip! I’ve only had my Belka-DSP for a few weeks, and absolutely love it. 13dka’s review of it was spot-on.

It appears the main additions are:

We’ll have to see how it stacks up against the original Belka DSP which I consider to be one of the best portable HF receivers out there at the moment.

I purchased my Belka-DSP from Mobimax.

Click here to check out the Belka-DX DSP at Mobimax. 

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