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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.
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!
Yaesu has announced their latest compact 160-6 M transceiver: the FTDX10. Based on the specifications, it looks like it borrows heavily from the FTDX101 series, which is a very good thing.
At 5″, the color TFT display is larger than that of the IC-7300 & IC-705. The specifications appear to be benchmark with excellent dynamic range (3rd IMDR quoted at “109 dB or more”).
We’ll post more details as updates become available. Wimo has listed a pre-order price of €1,550.00 w/out shipping or VAT.
We are pleased to introduce the FTDX10, a new long-waiting compact HF/50MHz 100W SDR Transceiver!
– Hybrid SDR Configuration
Like the FTDX101 series, the new FTDX10 utilizes the Yaesu Hybrid SDR configuration – Narrow Band SDR and Direct Sampling SDR. The Narrow band SDR receiver emphasizes excellent receiver performance, while the Direct Sampling SDR provides a Digital Processing Real-Time Spectrum Scope.
– Narrow Band SDR with 3 types of Roofing Filters and Phenomenal Multi-signal receiving Characteristics
Like the FTDX101 series, the Down Conversion type receiver configuration with the first IF at 9MHz has been adopted. It makes it possible to incorporate excellent narrow bandwidth crystal roofing filters that have the desired sharp “cliff edge” shape factor. Thanks to the Narrow Band SDR with the latest circuit configuration including 500Hz, 3kHz and 12kHz roofing filters and lownoise oscillator, the RMDR (Reciprocal Mixing Dynamic Range) reaches 116dB or more, the close-in BDR (Blocking Dynamic Range) reaches 141dB or more, and 3rd IMDR (third-order Intermodulation Dynamic Range) reaches 109dB or more, in the
14MHz band at 2kHz separation.
– 250MHz HRDDS (High Resolution Direct Digital Synthesizer) affords Quiet and Clear Reception
The local circuit of the new FTDX10 uses 250MHz HRDDS method same as the FTDX101 series. Thanks to its characteristics that improve the C/N (carrier to noise) ratio and the careful selection of components in the design, the phase noise characteristic of the local signal achieves an excellent value of -145dB or less in 14MHz at 2kHz separation.
– 3DSS (3-Dimensional Spectrum Stream) on the 5-inch Full-Color TFT Display with Touch-Panel Functionality
The 5-inch Full-Color panel shows the 3DSS display. By touching the frequency display, the numeric keypad is displayed, and the active band and frequency adjustment can be set by direct input. Frequency setting and adjustment can also be performed by turning the MAIN dial or touching the scope display. Similar to the FTDX101 series, the MULTI display, RX operation status display, Center, FIX and Cursor modes are available at WiMo.
– Front Panel Designed for Superior Operating Efficiency
MPVD (Multi-Purpose VFO Outer Dial), is a large multi-purpose ring around the outside of the VFO dial that enables control of
Clarifier, C/S (custom selection function) and recall of memory channels.
– Remote Operation with optional LAN unit (SCU-LAN10, see WiMo Website)
Remote operation of the transceiver is possible with the optional SCU-LAN10 and SCU-LAN10 Network Remote Control Software. In addition to controlling the transceiver basic operations, the versatile scope displays enable sophisticated operation such as monitoring the band conditions on a large display at a location away from the ham shack by connection to a home LAN network.
The features of the new FTDX10 include:
– 15 separate band pass filters
– Effective QRM rejection with the IF DSP (IF SHIFT/WIDTH, IF NOTCH DNF, DNR, COUNTOUR)
– High-quality and super stable final amplifier utilizing the new push-pull MOSFET RD70HUP2
– Aluminum Heat Sink with 80mm low-noise axial flow cooling fan
– High Speed Automatic Antenna Tuner with a large capacity 100-channel memory – RF & AF Transmit Monitor
– Microphone Amplifier with Three-stage parametric Equalizer (SSB/ AM mode)
– QMB (Quick Memory Bank)
– Band Stack Function
– Optional speaker – SP-30 designed for the new FTDX10
– Optional roofing filter (300Hz) – XF-130CN available
The new FTDX10 will be available in early December 2020 at WiMo.
Radio Features:
– HF/50MHz band 100W Transceiver
– Hybrid SDR configuration utilizing a Narrow Bandwidth SDR, and a Direct Sampling SDR
– Narrow Band SDR enables Phenomenal Multi-signal Receiving characteristics (2kHz RMDR 116dB+, 2kHz BDR 141dB+, 2kHz 3rd IMDR 109dB+) – Down conversion,
9MHz IF Roofing Filters produce Excellent Shape Factor
– 250 MHz HRDDS (High Resolution Direct Digital Synthesizer) Ultra Low-Noise Local-Oscillator System
– 15 Separate Powerful Band Pass Filters (BPF)
– Effective QRM Rejection with IF DSP (IF SHIFT/WIDTH, IF NOTCH/DNF,CONTOUR,DNR, APF)
– High-quality and Super-Stable Final Amplifier utilizing the new push-pull MOSFET RD70HUP2
– 5-inch Full Color Touch Panel and 3DSS (3-Dimensional Spectrum Stream) Display
– MPVD (Multi-Purpose VFO Outer Dial) enables Outstanding Operating Performance
– Quick Memory Bank (QMB)
– Supports CW operation with multiple functions such as: CW zero-in, CW Auto zero-in, CW Reverse, CW decode, CW keying Signal form Shaping by FPGA and others
– RTTY (FSK)/ PSK Encode/Decode Function
– Other practical features such as Optional RF Gain Selection by IPO. Automatic Gain Control, Quick Split Function – SD Card Slot
– Remote Operation via Internet with optional LAN-Unit (SCU-LAN10 see WiMo website)
Supplied Accessories:
Microphone SSM-75E
DC Power Cable w/Fuse
Spare Fuse
6.3mm 3-contact Plug
Operating Manual
70MHz – 70.499999MHz (Specifed performance, UK Amateur bands version only)
TX
1.8 – 54MHz (Amateur bands only)
Modulation Type: A1A(CW), A3E(AM), J3E(LSB,USB), F3E(FM),F1B(RTTY),G1B(PSK)
Frequency Stability: ±0.5ppm (32°F to +122°F/0? to +50?, after 1min)
Supply Voltage: DC 13.8V ±15%
Circuit Type: Double-Conversion Superheterodyne
Intermediate Frequencies 1st IF 9.005MHz; 2nd IF 24kHz
RF Power Output: 5W – 100W (CW, LSB, USB, FM, RTTY, PKT); 5W -25W (AM)
Case Size(W x H x D): 10.47 x 3.58 x 10.35(inch) / 266 x 91 x 263 (mm) *Protruding parts not included at WIMo
Weight (Approx.): 13lbs/ 5.9kg
Many thanks to SWLing Post contributor, Dan Robinson, who shares the following photos and short videos of a prototype Tecsun PL-368 at the 2020 Shanghai International High-End Hi-Fi Expo.
The PL-368 appears to be the updated and upgraded model of the Tecsun PL-360/PL-365 series.
Something I note immediately is the most welcome addition of a numeric keypad for direct frequency entry:
In addition, there’s a “Sync” button indicating the PL-368 will sport synchronous detection, hopefully, with USB/LSB selectable sideband.
Photos
Note, all of the following photos and video were shared by Benny in the Tecsun PL-880 group:
Videos
Dan also shared the following short videos (click links to view):
Many thanks to a number of SWLing Post readers who’ve noted that Sangean Europe has removed the ATS-909X2 from their website and stopped taking pre-orders.
Dan Robinson received the following response from Sangean Europe after an inquiry:
“The ATS-909X2 is postponed, so we cannot send a product yet. I’m sorry for the inconveniences.”
Before I had even taken delivery of the new Icom IC-705 transceiver, a number of SWLing Post readers asked me to do a series of blind audio comparison tests like I’ve done in the past (click here for an example).
Last week, I published a series of five audio tests/surveys and asked for your vote and comments. The survey response far exceeded anything I would have anticipated.
We received a total of 931 survey entries/votes which only highlights how much you enjoy this sort of receiver test.
In this challenge, I didn’t even give you the luxury of knowing the other radios I used in each comparison, so let’s take a look…
The competition
Since the Icom IC-705 is essentially a tabletop SDR, I compared it with a couple dedicated PC-connected SDRs.
WinRadio Excalibur SDR
The WinRadio Excalibur
I consider the WinRadio Excalibur to be a benchmark sub $1000 HF, mediumwave, and longwave SDR.
It is still my staple receiver for making off-air audio and spectrum recordings, and is always hooked up to an antenna and ready to record.
In the tests where I employed the WinRadio Excalibur, I used its proprietary SDR application to directly make recordings. I used none of its advanced filters, AGC control, or synchronous detection.
I also consider the Airspy HF+ SDR to be one of the finest sub-$200 HF SDRs on the market.
The HF+ is a choice SDR for DXing. Mine has not been modified in any way to increase its performance or sensitivity.
In the test where I employed the HF+ I used Airspy’s own SDR application, SDR#, to directly make recordings. I used none of its advanced filters, AGC control, noise reduction, or synchronous detection.
I thought it might be fun to include it in a comparison although, in truth, it’s hardly fair to compare a $160 receiver with a $1300 SDR transceiver.
The Belka, to me, is like a Lowe HF-150 in a tiny, pocket package.
Elecraft KX3 QRP transceiver
The Elecraft KX3
The KX3 is one of the best transceivers I’ve ever owned. Mine has the CW roofing filter installed (only recently) and is, without a doubt, a benchmark performer.
If you check out Rob Sherwood’s receiver test data table which is sorted by third-order dynamic range narrow spaced, you’ll see that the KX3 is one of the top performers on the list even when compared with radios many times its price. Due to my recording limitations (see below) the KX3 was the only other transceiver used in this comparison.
Herein lies a HUGE caveat:
The WinRadio application
As I’ve stated in SDR reviews in the past, it is incredibly difficult comparing anything with PC-connected SDRs because they can be configured on such a granular level.
When making a blind audio test with a stand-alone SDR radio like the IC-705–which has less configurability–you’re forced to take one of at least two paths:
Tweak the PC-connected SDR until you believe you’ve found the best possible reception audio scenario and use that configuration as a point of comparison, or
Attempt to keep the configuration as basic as possible, setting filters widths, AGC to be comparable and turning off all other optional enhancements (like synchronous detection, noise reduction, and advanced audio filtering to name a few).
I chose the latter path in this comparison which essentially undermines our PC-connected SDRs. Although flawed, I chose this approach to keep the comparison as simple as possible.
While the IC-705 has way more filter and audio adjustments than legacy transceivers, it only has a tiny fraction of those available to PC-connected SDRs. Indeed, the HF+ SDR, for example, can actually be used by multiple SDR applications, all with their own DSP and feature sets.
In short: don’t be fooled into thinking this is an apples-to-apples comparison. It is, at best, a decent attempt at giving future IC-705 owners a chance to hear how it compares in real-word live signals.
Recordings
The Zoom H2N connected to my Elecraft KX2.
Another limiting factor is that I only have one stand-alone digital audio recorder: the Zoom H2N. [Although inspired by Matt’s multi-track comparison reviews, I plan to upgrade my gear soon.]
The IC-705 has built-in digital audio recording and this is what I used in each test.
The WinRadio Excalibur and Airspy HF+ also have native audio recording via their PC-based applications.
With only one stand-alone recorder, I wasn’t able to simultaneously compare the IC-705 with more than one other stand-alone receiver/transceiver at a time.
As I mentioned in each test, the audio levels were not consistent and required the listener to adjust their volume control. Since the IC-705, Excalibur, and HF+ all have native recording features, the audio levels were set by their software. I didn’t post-process them.
Blind Audio Survey Results
With all of those caveats and disclaimers out of the way, let’s take a look at the survey results.
Blind audio test #1: 40 meters SSB
In this first test we listened to the IC-705, WinRadio Excalibur, and Belka-DSP tuned to a weak 40 meter station in lower sideband (LSB) mode. Specifically, this was ham radio operator W3JPH activating Shikellamy State Park in Pennsylvania for the Parks On The Air program. I chose this test because it included a weak station calling CQ and both weak and strong stations replying. There are also adjacent signals which (in some recordings) bleed over into the audio.
Radio A: The Belka-DSP
Radio B: The WinRadio Excalibur
Radio C: The Icom IC-705
Survey Results
The Icom IC-705 was the clear choice here.
Based on your comments, those who chose the IC-705 felt that the weak signal audio was more intelligible and that signals “popped out” a bit more. Many noted, however, that the audio sounded “tinny.”
A number of you felt it was a toss-up between The IC-705 and the Belka-DSP. And those who chose the WinRadio Excalibur were adamant that is was the best choice.
The WinRadio audio was popping in the recording, but it was how the application recorded it natively, so I didn’t attempt to change it.
Test #2: 40 meters CW
In this second test we listened to the Icom IC-705 and the Elecraft KX3 tuned to a 40 meter CW station.
Radio A: Icom IC-705
Radio B: Elecraft KX3
Survey Results
The Elecraft KX3 was preferred by more than half of you.
Based on your comments, those who chose the KX3 felt the audio was clearer and signals had more “punch.” They felt the audio was easier on the ears as well, thus ideal for long contests.
Those who chose the IC-705, though, preferred the narrower sounding audio and felt the KX3 was too bass heavy.
Test #3: Shannon Volmet SSB
In this third test we listened to the Icom IC-705 and WinRadio Excalibur, tuned to Shannon Volmet on 8,957 kHz.
Radio A: WinRadio Excalibur
Radio B: Icom IC-705
Survey
The Icom-705 audio was preferred by a healthy margin. I believe, again, this was influenced by the audio pops heard in the WinRadio recording (based on your comments).
The IC-705 audio was very pleasant and smooth according to respondents and they felt the signal-to-noise ratio was better.
However, a number of comments noted that the female voice in the recording was actually stronger on the WinRadio Excalibur and more intelligible during moments of fading.
Test #4: Voice of Greece 9,420 kHz
In this fourth test we listen to the Icom IC-705, and the WinRadio Excalibur again, tuned to the Voice of Greece on 9,420 kHz.
Radio A: Icom IC-705
Radio B: WinRadio Excalibur
Survey
While the preference was for the IC-705’s audio (Radio A), this test was very interesting because those who chose the Excalibur had quite a strong preference for it, saying that it would be the best for DXing and had a more stable AGC response. In the end, 62.6% of 131 people felt the IC-705’s audio had slightly less background noise.
Test #5: Radio Exterior de España 9,690 kHz
In this fifth test we listened to the Icom IC-705, and AirSpy HF+, tuned to Radio Exterior de España on 9,690 kHz. I picked REE, in this case, because it is a blowtorch station and I could take advantage of the IC-705’s maximum AM filter width of 10 kHz.
Radio A: Icom IC-705
Radio B: Airspy HF+
Survey
The IC-705 was preferred by 79% of you in this test.
Again, very interesting comments, though. Those who preferred the IC-705 felt the audio simply sounded better and had “punch.” Those who preferred B felt it was more sensitive and could hear more nuances in the broadcaster voices.
So what’s the point of these blind audio tests?
Notice I never called any radio a “winner.”
The test here is flawed in that audio levels and EQ aren’t the same, the settings aren’t identical, and even the filters have slightly different shapes and characteristics.
In other words, these aren’t lab conditions.
I felt the most accurate comparison, in terms of performance, was the 40M CW test with the KX3 because both employed similar narrow filters and both, being QRP transceivers, are truly designed to perform well here.
I essentially crippled the WinRadio Excalibur and Airspy HF+ by turning off all all but the most basic filter and AGC settings. If I tweaked both of those SDRs for optimal performance and signal intelligibility, I’m positive they would have been the preferred choices (indeed, I might just do another blind audio test to prove my point here).
With that said, I think we can agree that the IC-705 has brilliant audio characteristics.
I’ve noticed this in the field as well. I’m incredibly pleased with the IC-705’s performance and versatility. I’ll be very interested to see how it soon rates among the other transceivers in Rob Sherwood’s test data.
The IC-705 can actually be tailored much further by adjusting filter shapes/skirts, employing twin passband tuning and even using its noise reduction feature.
If anything, my hope is that these blind audio tests give those who are considering the Icom IC-705 a good idea of how its audio and receiver performs in real-word listening conditions.
Many thanks to SWLing Post contributor, Dan Robinson, who shares two note-worthy links regarding the new Tecsun H-501.
The first link is to a set of internal shots of the H-501 found on Radioafiction.com. Click here to view.
Image Source: Radioaficion.com
The second link, Dan shares as a warning.
Evidently there’s an inventory of the H-501s on NewEgg.com where they’re being sold for $584.49 US each:As Dan points out, that’s insane pricing--! Not only that, but I’m willing to bet this isn’t the final export version that will be the most up-to-date and will certainly be less expensive. I’ll be waiting for Anon-Co to offer these.
I’ve purchased computer parts from Newegg before–they’re a good retailer, but I suspect this inventory is actually being offered by a third party. As a precaution, I’m not even linking to Newegg as I don’t want to inadvertently suggest purchasing one at this price.
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
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.
Many thanks to SWLing Post contributor, Steve Allen (KZ4TN), who shares the following guest post:
