Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Earbuds for Shortwave Listening
A few years ago I had bought the discontinued Sennheiser MM 50 earbuds for a cheap price on Amazon to use in my various radios. The portable radios in particular can use more fidelity because of their small, raspy speakers. I also like to listen without bothering others around me who might not want to listen. And earbuds are a LOT more comfortable for my ear lobes than any over-the-ear headphones I have ever used. Furthermore, the old Apple iPhone 4 earbuds were very harsh to listen to. However, a trade-off is that, generally, earbuds are somewhat fragile; one of the two pairs of MM50’s died through mishandling.
I was generally happy with them while listening to Shortwave broadcasters with a mix of news/talk and music. I especially liked them on Mediumwave listening; stations can sound surprisingly good when playing music. Then I tried using these earbuds on my Amateur Radio transceiver, a Kenwood TS-590S. I was impressed how clear they sounded with a lack of distortion, although there was too much bass. Fortunately, Kenwood supplies USB connected software with an TX & RX 18 band EQ (300 Hz spacing, not octaves).
Here is a frequency response chart I found from Reviewed.com for this model:
One of the notable things about these earbuds is the total lack of distortion. Most likely one of the reasons they sound so clear on Shortwave, which has many LOUD audio spikes.
I had not wanted to get Bluetooth earbuds. However, I had recently upgraded my cell phone and NO headphone jacks anymore! So, while I do not use Bluetooth yet for radios, I can see a time in the future to get a Bluetooth transmitter to plug into a radio with a headphone jack. I am reluctant since I do not like having to recharge my earbuds and I put in a lot of radio listening time. Am I supposed to buy two Bluetooth earbuds and swap while charging? Maybe in the future. And also, am I supposed to buy a Bluetooth transmitter for every non-Bluetooth radio I own? Not likely gonna happen.
In the meantime, I ordered cheap wired earbuds from Amazon. I had a $5 credit for trying Prime, so when I saw these Panasonic ErgoFit wired earbuds (RP-HJE120-K) for slightly over $10, I said to myself, “why not?”. Supposedly wildly popular, they are one of the most rated products on all of Amazon with 133,821 ratings/opinions (perhaps Russian bots?!?!?).
Here is a frequency response chart from ThePhonograph.com for these Panasonic earbuds:
You can see comparatively that the bass response in the very good Sennheiser MM50’s is much stronger, being good music earbuds. But for voice articulation, not as much, even though they have no distortion. The Panasonic ErgoFit’s have more modest bass, less of a dip in the lower midrange audio frequencies, and more importantly, has a peak near 2500 Hz and its harmonic 5000 Hz. The highest highs are also modest compared to the Sennheiser model. This general frequency response to “recess” the bass and treble frequencies and peak the 2500 Hz is very useful for voice intelligibility.
As described by the famous speaker-microphone-sound-system maker, Bob Heil relates what he learned from the scientists at Bell Labs many years ago. Speech intelligibility is enhanced when audio is compensated for our natural human hearing. Equalizing below 160 Hz, reducing the 600-900 Hz region, and peaking the 2000-3000 region centered at 2500 Hz will increase intelligibility dramatically. The story goes that Bell Labs was tasked by parent AT&T with finding out why the earliest phones in the 1920’s sounded so muffled and hard to understand. After many experiments, the scientists found the most important frequencies for our ears + brain to comprehend speech. In other words, our ears are not “EQ-flat” like a scientific instrument is. Continue reading →
Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. The second article will focus on construction notes. The third and final article will essentially be a Q&A about the SULA antenna. All articles will eventually link to each other once published.
This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!
Please enjoy and share SULA Part 1:
Introducing the Small Unidirectional Loop Antenna (SULA) 1-30MHz
A small and simple, unidirectional and DX-capable loop “beam” for SWLs!
In early June, Andrew (grayhat), SWLing Post‘s resident antenna wizard suggested a variation of the “cardioid loop” on the SWLing Post message board: The original “cardioid loop” is a small loop receiving antenna deriving its name from a cardioid shaped (unidirectional) radiation footprint. The design is strikingly simple but it has a few downsides: It relies on a custom preamp, it needs a ground rod to work and it is unidirectional only up to 8 MHz.
Andrew’s version had the components all shuffled around and it did not only lose the ground rod, it also promised a nice cardioid pattern over the entire shortwave, from a small, diamond shaped loop. Wait…what? It can be made using parts available on Amazon and your DIY store:
You need some 3m wire and PVC tubes to create a support structure to hold the wire, a 530 Ohm resistor and a 9:1 balun like the popular “NooElec One Nine”. Since it’s a “lossy” design, adding a generic LNA like the NooElec “LANA HF” would help getting most out of it. When you put that all together you have what sounds like an old shortwave listener’s dream: a small, portable, tangible, and completely practical allband shortwave reception beam antenna with some more convenient properties on top, for example, it is a bit afraid of heights.
That sounded both interesting and plain crazy, but the .nec files Andrew posted were clearly saying that this antenna is a thing now. Unfortunately Andrew suffered a little injury that kept him from making one of those right away, I on the other hand had almost all the needed parts in a drawer so I ended up making a prototype and putting it through some of its paces, with Andrew changing the design and me changing the actual antenna accordingly, then mounting it upside down. Let me show you around:
Small, diamond shaped wire loop (with 76cm/29.92″ sides), needing as little space as most other small loops.
Unidirectional with a ~160° wide “beam” and one pronounced minimum with a front/back-ratio of typically 20dB over the entire reception range 1-30MHz.
Moderate height requirements: It works best up to 3m/10′ above ground, where it gives you…
…a main lobe with a convenient flat takeoff angle for DX
Antenna is comparatively insensitive to ground quality/conductivity.
Wideband design, works best on shortwave and is pretty good up to 70cm.
A functional small beam antenna for shortwave reception that’s just as small and possibly even more lightweight (prototype:~250g/9oz) than your regular SML, that can be easily made out of easy to obtain parts and easily carried around for mobile/portable DXing and due to its cardioid shaped directional pattern also for direction finding, a “tactical” antenna that’s also doing DX? Unlike conventional, Yagi-Uda or wire beams it can achieve a low takeoff angle at only 3m/10ft height or less, the front/back ratio is typically better than that of a 3-element Yagi, with a particularly useful horizontal pattern shape. That it’s rather indifferent to soil quality could mean that more people get to reproduce the good results and being a real wideband antenna is making the SULA an interesting companion for multiband radios and SDRs. Really? A miracle antenna? Is it that time of year again? If I had a dollar for every….
For me, DXing has always been about the challenge of receiving difficult-to-hear radio stations, regardless of the type of station or frequency range. In my five decades in the radio hobby I’ve logged a lot of different kinds of stations – shortwave broadcast, medium wave, shortwave utility, longwave beacons, etc. But some of my favorite catches have been in the upper end of the medium frequency range.
Technically speaking, medium frequency (MF) is the range from 300 to 3000 kHz and includes the standard medium wave (AM) broadcast band. The upper end of the MF band, from 1600 to 3000 kHz (except for a small portion reserved for amateur radio), has always been assigned to various types of utility uses including broadcasts and other voice communications from regional maritime stations. And while digital modes and satellites have done a lot to change the nature of communication with ships at sea, there is still a lot of good human-voice DX to be heard.
Several dozen stations, mostly in Europe and North America, broadcast regularly scheduled marine information broadcasts in the MF range. These broadcasts are usually between five to ten minutes in length and include weather forecasts, navigational warnings, and other notices to keep ships at sea safe. On occasion it’s possible to hear two-way voice communication here between ships and shore stations, although that’s much less common today.
Nothing special is needed to DX the marine MF band other than a receiver that covers the frequency range and can receive USB mode (which all these broadcasts are in). However, for reasons explained below, I highly recommend using an SDR to make spectrum recordings of the entire band to go through later. Continue reading →
Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:
In search of benchmark signals: The International Beacon Project
If you – like yours truly – like to tinker with antennas and radios to get the most out of them, you likely have your own set of reference stations. If this is a new concept for you – reference stations are whatever stations you deem apt to check propagation, the general function of your radio, when trying to improve reception or comparing radios… They are ideally always on when you need them and come in various strengths and distances on several bands from all over the world. Traditional sources for that are of course time signals and VOLMET stations on HF, even though the latter are giving you only two 5-minute slots per hour for testing reception from a specific region and the former have their own specialities here in Europe:
A typical scene on 10 MHz, captured at home 30 minutes after the full hour: BPM voice ID from China mixed with something else, then Italcable Italy kicks in on top of some faint murmur possibly from Ft. Collins, in winter some South American time stations may stack up on that together with splatter from RWM 4 kHz lower…
A reliable source of grassroots weak signals is particularly desirable for me because I enjoy proving and comparing the practical performance of radios at “the dike”, a QRM-free place on the German North Sea coast. In the absence of manmade noise and the presence of an ocean adding 10dB of antenna gain, finding benchmark stations with “grassroots” signal levels turned out to be a different challenge than it used to be: With somewhat sizeable antennas the stations tend to be (too) loud there, even with the baseline ionospheric conditions under a spotless sun in its activity minimum. In short, my old benchmark stations didn’t work so well anymore and I had to find something new. Continue reading →
Many thanks to SWLing Post contributor, Bill Hemphill, who shares the following guest post:
Radio Schedules in a Simple Android Database
by Bill Hemphill
I am a program listener. I really enjoy listening to various radio stations direct and by internet streaming. Over time, I have come up with a couple of spread sheets that lists the program, station, time, date, etc. For example, following is the spreadsheet for the shortwave radio programs/stations that I enjoy:
As the program schedules change, I update the spreadsheet. This has worked quite well for me. I usually sort on the weekday and then print out the spreadsheet as a list by time and frequency for each day.
While this method works, it does mean that I have these multiple page printouts that I have to refer to. This got me thinking that it would be great to have this on my Android phone/tablet. Then I could refer to it no matter where I was located.
At first, I tried to use Google Sheets, but found that using a spreadsheet on the phone or even a tablet to be a pain. I then tried entering it into a calendar program, but also found that very cumbersome. Continue reading →
Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:
Revisiting the Belka’s “pseudo-sync detector”: A sync detector crash course!
“It’s usually hard to assess whether or not a sync detector helped with a particular dip in the signal or not, unless you have 2 samples of the same radio to record their output simultaneously and compare.”*
Since I was recently upgrading to the Belka DX in order to pass on the Belka DSP to a friend, I had briefly two examples of almost the same radio on the table at the dike. I tuned them to the same stations and recorded some audio clips with one radio on sync detector, the other in regular AM mode, to answer the question whether or not sync has “helped with a particular dip in the signal”. Then I thought that demonstration would be an opportunity to try an explanation on what exactly (I think) sync detectors are all about anyway, hoping to find a middle ground between “technical” and “dumbed down beyond recognition”.
The trouble with sync detectors
Perhaps no component of a shortwave receiver is surrounded by so much misconception and confusion as sync detectors. Full disclosure: Until quite recently, I had an, at best, vague concept on what they do myself. It seems it’s not so much that people don’t know how they work, what they actually do when they work is where the ideas often diverge. Continue reading →
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Recording Music on Shortwave Part 2 – Weak signal recovery
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??
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:
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):
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!
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