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A few years ago, during the Covid lockdowns, I rediscovered a box full of my old audio cassette tapes on the bottom shelf of a cupboard in the basement. These cassettes contained many vintage recordings I made between 1970 and 1999, including shortwave, AM, FM and even a bit of TV audio.
I suppose I was a bit lucky, but sometimes not so much.
The box was closed and had basically been in a dust free, climate controlled environment for the previous 22 years (1999-2021). Prior to that (1970-1999), the cassettes were subject to much use and reuse, often being left out (for convenience) unprotected, then being packed up and moved a few times to a new QTH, always within southern Ontario, Canada.
In the early 1970’s, and on a student’s budget, I even resorted to repurposing a couple of cheap demonstration music cassettes by placing a piece of scotch tape over the ends so I could record over the existing music. Inevitably, some “prize” recordings were accidently erased over the years when a cassette was needed urgently and one was thrown hastily into the recorder without a proper check.
Around 1983, I made a decent recording of Radio Mogadishu in Somalia on the out of band frequency of 6790 kHz, but it seems to have been corrupted from being left in the recorder and not discovered until it was too late. Unfortunately, the mistake occurred right over the moment of the actual station ID:
In spite of all of this, I need to feel fortunate that so many of my recordings actually survived for 30, 40 and even 50+ years in spite of my neglecting them for so long. A great deal of this material has since been sorted through and digitised, then saved on the Internet Archive in order to preserve this radio history. I have also regularly submitted some of these recordings to the Shortwave Radio Audio Archive.
Here is a link to my material on Archive.org, which I am constantly adding to. Most files have audio, however, some are “read only.”
Many thanks to SWLing Post contributor and noted political cartoonist, Carlos Latuff, who shares this special dive into the world of radio both in and targeting the Korean peninsula. His report includes off-air recordings along with his own original artwork.
Koreas’ Radio War
by Carlos Latuff, a special for the SWLing Post
The war that divided Korea in two began in 1950. A truce was signed by both sides in 1953, but a peace agreement never came to fruition. Therefore, North Korea and South Korea remain at war. And this war is not just happening on the ground, but also over the airwaves.
Every day, a battle for hearts and minds takes place on AM, FM and shortwave. Whether the DPRK broadcasts are directed to South Korea, or South Korean broadcasters (including clandestine ones) broadcast to the DPRK.
I bring here a small collection of radio listenings made between February 29th and March 17th, all of them happened in Porto Alegre, Brazil, using a XHDATA D-808 receiver, with long wire antenna (outdoor), except for Radio Free Asia, listened with a Toshiba TR 486 receiver, using a telescopic antenna (indoor). Translations from Korean to English were made using transcription and translation apps.
KBS World
KBS World Radio was created in 1953, the year the truce was signed between the two warring Koreas, under the name “The Voice of Free Korea”, and today, as a public radio station, it broadcasts to several countries in different languages. Its programming includes news, music, variety, and of course, opposition to the DPRK government.
As part of the effort to promote “regime change” in the DPRK, the Seoul government, through its intelligence service, maintains clandestine radio stations (“Echo of Hope” and “Voice of the People”) whose role is basically broadcast 24 hours a day anti-Communist propaganda to North Korea, along South Korean and American pop music.
Echo of Hope
Voice of the People
Radio Free Asia
Created by the CIA in 1951, at the height of the Cold War and the conflict in Korea, Radio Free Asia has undergone changes throughout its history, but continues to be operated by the United States government and aims, in its own words, to “provide independent, uncensored and accurate local news” for countries like China, Vietnam and, of course, North Korea. Content directed at the DPRK follows the same principle as South Korean clandestine broadcasters: basically anti-Communist orientation, in order to achieve a “regime change”. The articles broadcasted on the radio are the same as those published on the Radio Free Asia’s website.
KCBS Pyongyang
Korean Central Broadcasting Station (KCBS) Pyongyang is the DPRK’s domestic radio station, whose programming reaches North and South Korea, even being heard in Japan. News about the achievements of North Korean leader Kim Jong-un, music and attacks on Seoul government, seen by Pyongyang as a puppet regime.
Voice of Korea
On October 14, 1945, the year Japan was defeated in World War II, KCBS Pyongyang and Voice of Korea were founded (domestic and international radio stations respectively). Voice of Korea broadcasts programming in several languages ??to the world via shortwave. The content is not much different from KCBS Pyongyang: achievements of North Korean leader Kim Jong-un, attacks on Seoul government and the United States, and traditional/patriotic music.
February 9, 2023 – 04:12:00 p.m. UTC – Frequency: 12015kHz
The announcer describes in laudatory and emphatic terms the recent solemn military parade which took place on the night of February 9 to 10 in Kim il-Sung square in Pyongyang. I recorded for 5’40” in order to show the stability of the signal (no fading) but the recording is too long, at least I think so. It’s up to you to cut if this recording catches your attention
The receivers may have improved but I believe that North Korea now uses more modern and more powerful transmitters (200 kW according to the site www.short-wave.info).
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Old Fashioned Band-Scan after the Solar Storms
by TomL
This is just an old fashioned band scan to randomly see what I could hear after last week’s solar perturbations when the Solar Flux Index went well over 200. I considered what I could hear on the shortwave broadcast bands, even though the SFI had quieted down to around 135. Would the ionosphere still be holding on to the charge built up during the solar storms? The date and time was January 30, 2023 around 1400 through 1600 UTC. By the way, as of today (February 2), the bands are dead and cannot hear any of these even though the Solar Flux is about the same!
I will not have time to describe my antenna setup now at my noisy Condominium in detail. I have been experimenting with a DX Engineering NCC2 antenna phasing device for the past year with somewhat good results. I had to place dedicated receive antennas in many different ways in order to find an arrangement that works in conjunction with the two Ham Radio antenna wires out on the porch. Sometimes it helps by lowering the noise, sometimes the native antenna by itself, or peaking the signal, has better reception even though it might be slightly more noisy. By matching one of two receive-only antennas (the left Heathkit switch) with one of the Ham Radio antennas (the right Daiwa switch), I can usually eke out some extra decibels of signal-to-noise improvement. Continue reading →
I’m traveling at present and staying in a hotel where, let’s just say, QRM is heavy.
I decided to cruise the KiwiSDR network and found myself on the VK2GGC KiwiSDR in Hunter Valley NSW, Australia. As I was band-scanning, I stumbled upon Shortwave Australia on 4,835 kHz around 9:40 UTC.
It was great hearing this low power shortwave broadcaster on the air again! Check out the recording below with ID:
WebSDRs are such a wonderful resource when you truly need to escape QRM. It’s fun to travel the globe and tune through the bands like a local. Again, it’s great to hear Shortwave Australia again–I’m curious if anyone has logged them as DX from home.
Today marks the 20th anniversary of 9/11; a day where we honor all of those who were lost, their families/friends, and all of those who who served during and after the attacks.
This morning, I’ve been listening to a number of off-air shortwave radio recordings made on September 11 and 12, 2001. Many thanks to the amazing contributors at the SRAA who shared these with us over the years. For this radio enthusiast, these recordings brings back memories even more vividly than video coverage.
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Recording Music on Shortwave Part 2 – Weak signal recovery
by TomL
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??
NHK Japan
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:
Radio Thailand
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):
Summary
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!
TomL
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