Shortwave listening and everything radio including reviews, broadcasting, ham radio, field operation, DXing, maker kits, travel, emergency gear, events, and more
It dawned on me recently, perhaps due to sloppy thinking or unintended distractions, that I never wrote about my modified Loop on Ground (LoG) receive antenna that I use at parks and such. For over a year now, I have been using 3-conductor rotor wire bought cheap at the local hardware store and have wired the conductors in series. Grayhat (Andrew) was the inspiration when he decided to create a folded dipole along the side of his house.
The usual construction of a LoG antenna for shortwave is a single wire of about 60 feet in circumference in order to not go above one wavelength for 20 meter band usage. If you recall, going above one wavelength will start creating weird lobes in the reception pattern. See – Loop-On-Ground Antenna Part 2.
However, I did not like this 19 foot diameter wire on the ground in public parks just waiting to be tripped over. Like, the time when a horse got loose from its owners and almost tripped over my 60 foot wire. I don’t think I would have liked the resulting lawsuit!
So out of fearful necessity I took some leftover RCA 3-conductor rotor wire, about 29 feet of it, and wired a loop with the conductors in series. This gives about 81 feet of total conductive length. But since it is folded onto itself, there is an undetermined loss of resonant length. Callum (M0MCX) of DXCommander fame has experimented and found folded dipoles need three times more length in the folded section to reach resonance, so my loop is probably around 69 feet (electrically). See – Fold the end of a Dipole Back – What’s Happening?.
In the picture below, the black wire with Ring Terminal at the bottom goes all the way around to the other side, soldered to the green wire, which goes around and is soldered to the red wire, which goes around to the Ring Terminal at the top, plus tie-wraps to hold the wires together.
The next picture is how the Wellbrook Medium Aperture preamplifier is connected to the loop with BNC cable that goes to the 12V power injector. I have had this Wellbrook unit for maybe 6+years with no signs of problems. WARNING – do NOT use the Wellbrook preamplifier in the presence of high powered RF energy like your Amateur Radio antenna pumped with 1000 watts from a linear amplifier; the Wellbrook premap might just overload and get damaged! I did use this loop and preamplifier at last year’s 2022 ARRL Field Day and was able to get away with it because we were only using 100 watts per station. Listening to the 9pm 3916-net trivia group was fun but I still needed to keep it away from the transmitting antennas. Continue reading →
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 →
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Earbuds for Shortwave Listening
by TomL
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, TomL, who shares the following guest post:
Summer DX – Sporadic E, FM band
“Sporadic E” DXing is a specialty of some DXers. I have never dabbled in it being content with mediumwave or shortwave listening. However, it was truly fun to spontaneously hear this happen while driving on the Interstate highway, Wednesday August 4 around 6pm Central Time.
To quote from an ARRL propagation article:
“As frequency increases still further, signals will eventually pass through the F1 layer to the F2 layer. Because this is the highest reflecting layer, the distance spanned by signals reflecting from it is the greatest. The maximum skip distance for the E layer is about 2000 km. For the F2 layer that increases to about 4000 km—a significant gain.”
I was listening to the local classical music station WNIU in DeKalb, IL which is a good 50 kW transmitter about 10 miles behind me near the Interstate highway. A different station was breaking through. Eventually, I heard a familiar Christian song “You Make Me Brave” swamp the classical music. I noticed it was a remake of a song made about 10+ years earlier. The two signals fought it out and then I heard the station ID “Spirit FM” and a short humorous segment called “Attitude Adjustment”, then more music. Finally the local classical music station won out and I thought I would look up the station ID of that contentious station later.
When I googled “90.5 Spirit FM”, it came up with a station in Tampa Bay, FL called WBVM. Cool! Just to be sure, I went to the station web site and looked up their playlist and this confirms what I heard:
Curious about the transmitter, Radio Locator said it was a 100kW station and gave the Long/Lat coordinates. I then went to Google Earth and mapped an approximate distance of 977 miles (1572km), give or take 10 miles:
I did not have time to get on the shortwave radio to see if the 10 meter band was busy since I had things to do. But it is a very nice surprise to hear in my old car radio an FM station almost 1000 miles away. For one thing, Analog radio is still fun. Secondly, things are busy this summer if you are at the right frequency and time!
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.
A quick reminder that the rebroadcast of Radio Gum Tree Episode 2 will take place tomorrow: June 18, 2021 at 9:45 EDT (or June 19, 2021 at 01:45 UTC) on on 5850 kHz. You can find the program notes for these Test broadcasts at this web site address: www.radiogumtree.com/?p=54
Many thanks for putting together this Comb Stereo series, TomL!
Many thanks to SWLing Post contributor, TomL, who notes:
Episode 2 of Radio Gum Tree will be rebroadcast this coming Friday night June 18, 2021 at 9:45 EDT on on 5850 kHz in case anyone missed it. Episode 3 should be on June 25.
You can find the program notes for these Test broadcasts at this web site address. I will not be archiving the broadcast on the internet due to music copyright concerns.
