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After listening to the BBC “Re-Tune” broadcasts, it reminded me of when the United States had its own “Re-Tune” day on March 29, 1941. It was referred to as “Moving Day”.
At 3:00 am, 802 of the 890 radio stations moved frequency. Following are a couple of articles about this day:
I love how it was used as an opportunity to get the radio listener to call on the radio technician to re-program the radio push buttons. And of course while the technician is there, have him do a full alignment and maybe replace a tube.
The March 1941 issue of Radio and Television Retailing (Pages 16-17) had the article “Radio’s Opportunity for Contact”.
While the entire article is an interesting read, the first few paragraphs sums up the opportumities:
THE OPPORTUNITY for contact with consumers using pushbutton-tuned radios., afforded by dramatic March 29 broadcast station frequency shifts, represents an absolutely unique invitation to move more major merchandise, with the promotional expense at least partially covered by service and accessory sales.
Imagine what slick automobile salesmen could do if roads were suddenly altered in such a manner that 10,000,000 cars required some adjustment to operate properly, what refrigerator salesmen might accomplish if a change in current necessitated motor manipulation, how laundry equipment salesmen would positively gloat over the glut of prospects if that many people with old machines actually asked them to call.
Calls make sales, as the records of many home specialty retailers conclusively prove, and the beauty of this particular opportunity to make them lies in the three-fold fact that cold-canvassing is completely unnecessary, that the motivating power of any campaign built around it is obviously not just trumped-up by the trade and that only dealers selling or servicing radios can capitalize in all departments of their business.
So valuable from a major merchandising sales angle is the opportunity to call upon consumers afforded by the necessity for changing pushbutton settings that we suspect many radio retailers will hesitate to charge for this adjustment.
This may be particularly true where consumers so contacted are obviously prospects for new merchandise and will undoubtedly occur in some instances where customers are still being carried on time-payment accounts.
The Feb 1941 issue of Radio Service-Dealer (Page 8) also stressed the opportunities.
Reallocation of Broadcast Frequencies M arch 29th Opens Big Job For Service men Resetting Nation’s Push-Buttons
YOUR JOB
There are approximately 10 million push-button receivers in operation in this country. It will be your job to re-set the buttons for the new frequencies in the shortest possible time and with the least amount of confusion. It will also be your job and your opportunity to inspect these receivers for faulty operation. No such opportunity is likely to present itself again, so make the best of it.
And on page 7 of the Mar 1941 issue of Radio Service-Dealer has the article FREQUENCY REALLOCATION SERVICING PROBLEMS
1A—If a station with a strong signal intensity happens to be operating on double the frequency of the intermediate frequency of a receiver, there is liable to be a heterodyne whistle. The frequency of 455 kc has been used as the standard intermediate frequency on receivers manufactured in the United States. One main reason for selecting this frequency was that the broadcast frequency of 910 kc was assigned to Canada and, therefore, the possibility of a heterodyne note being produced on a receiver in the United States was at a minimum. Under the terms of the reallocation several American stations will be moved to 910 kc thus producing a problem in the cities where these stations are to be located. If a heterodyne note is heard due to this cause the remedy is to shift the intermediate frequency to one side or another.
Thank you, Bill, for shedding more light on Radio Moving Day and, especially, providing us with the broadcaster and technician’s point of view.
A few weeks ago, Chameleon Antenna sent me a pre-production model of their new wideband magnetic loop antenna called the Chameleon CHA RXL.
I’ve evaluated and reviewed a number of Chameleon’s ham radio antennas (primarily on QRPer.com). I find that the quality of their products are second to none. Price-wise, they tend to be at the top of the market, but keep in mind they machine and manufacture all of their antennas here in the US and they’re incredibly rugged; indeed, military-grade. And in the spirit of full disclosure, I’m proud Chameleon has been a sponsor the SWLing Post and QRPer.com since last year. My sponsors are by invite only and focus on companies I trust with our radio community’s business.
When Chameleon shipped the CHA RXL to me, it wasn’t from their factory, it was directly from the field: Fort Irwin, to be exact.
(Source: NTC Operations Group, Ft. Irwin)
This CHA RXL sample had been used by NTC Operations Group Fort Irwin (who, incidentally, won QRPX this year–click here to read the PDF report).
I was told that the condition of the antenna could be very rough after the QRPX because it had essentially been sandblasted in the desert winds. I was also told that someone accidently transmitted 5 watts into it at some point but it didn’t seem to harm it (for the record, like all amplified receive-only loops, it’s not designed to take RF).
Tony (W0NTC), who was one of the Ft. Irwin radio ops, sent me this note as he dropped off the shipment at Fort Irwin’s FedEx:
“Had a blast with [the CHA RXL], and it was absolutely critical while I was operating in the Army HF Low Power Competition (think tons of high powered MARS stations piling up and drowning out the 20W or less competitors). It absolutely crushed some localized RFI from a huge building I operated behind, and the receive on it I can only describe as “layered” in that I could hear stations somewhat clearer than usual if they transmitted simultaneously. Receiver I used was the IC-705 with default Auto Notch and Noise Reduction.”
Tony volunteered all of this info–I never asked him how it performed.
A few days later, I wasn’t sure what to expect when I opened the box although I knew that my operating locations were nowhere near as cool as its position next to a Humvee at Fort Irwin in the photo above!
I pulled the CHA RXL out of the box and it looked cosmetically flawless to me.
Frankly, there’s not a lot to get damaged. The 36 inch diameter loop is made of rigid aluminum and has a Navy gray powder coating. The preamplifier unit is completely sealed and made of a high-impact plastic/PVC type material. The steel loop is attached to the preamplifier loop flanges with wing nut connectors.
The only potentially vulnerable part of the antenna system is the Bias-T box which would normally be located in your shack close to your receiver.
If I mounted the CHA RXL permanently outdoors, I would use Coax Seal around the BNC connection point, of course.
Although the CHA RXL has a supplied mounting bracket for permanent installations, I love the fact that the preamp box has a 1/4” x 20 threaded camera socket on the bottom. This makes for a brilliant portable loop because it can so easily be mounted on a standard heavier-weight tripod! All antenna manufacturers should give us tripod mount options when possible.
On the air
One of the reasons amplified receive loop antennas have become so incredibly popular over the past couple of decades is because they do an amazing job mitigating radio frequency interference (RFI) a.k.a. “QRM.” If you live in a neighborhood with significant radio interference, you really should consider some form of loop in your antenna arsenal.
Ironically, at home, I live in pretty much an RFI-free zone. I’m surrounded by tens of thousands of acres of national forest, so I’ve only used amplified loop antennas in the past for mediumwave DXing–mainly, when I wanted to take advantage of their amazing ability to null out unwanted signals.
Many years ago, I purchased a Pixel Loop Pro antenna (now under a different name via DX Engineering), mounted it outside where it lasted almost a year before a bear decided to pull it down and chew through the coaxial feedline. He/she did so with enough energy that it ripped down the loop and damaged the connector end of the Pixel’s pre-amp. This all happened when our family was travelling for two months in Canada. Why bear, why?!? But I digress…
The CHA RXL version I was shipped has one single rigid loop–the “EU” version’s loop comes in two pieces (for easier shipping/transport)–but I had no problem fitting the entire assembled loop in the back seat of my Subaru or my truck (as long as no one was sitting back there at the time). If you plan to travel with your loop a lot, consider the “EU” version!
I’ve taken the CHA RXL to my parent’s home a couple of times and enjoyed doing a little mediumwave and shortwave listening. Inside the house, the loop would attenuate RFI nicely, but when outside it would all but eliminate many sources of RFI.
At their house, I primarily used my Icom IC-705 for cruising the bands (being careful, of course, to disengage the transmit function).
Listening time in my hometown, though, was very limited. Since the CHA RXL is so portable, I decided to set it up at home on our porch for a few days, giving me an opportunity to test both the Sangean ATS-909X2 and Tecsun H-501x with an external antenna.
I’ve especially appreciated using the CHA RXL on mediumwave. Even from our screened-in porch, I can rotate the loop and use its excellent nulling properties to pick out multiple station IDs on crowded frequencies.
I’ve spent time on shortwave, too, and found that it certainly gave these two portables a signal boost.
In fact, it was by using the CHA RXL that I discovered the audio level difference between AM and SSB on my ATS-909X2 is very minimal when an external antenna is connected.
I’m sure you’ll hear the CHA RXL in action when I post audio clips and recordings in upcoming reviews.
Summary
If I owned a CHA RXL loop, one of the first things I’d do is build a power cord for it with an in-line fuse and terminated with an Anderson Powerpole connector. Since the operating voltage of the Bias-T is 12-14 VDC, it would pair perfectly with one of my Bioenno LiFePo4 batteries, offering a power source with longevity in the field–ideal for a group LW/MW/SWL DXpedition.
It’s difficult for me to truly comment on the loop’s performance because I don’t have another loop at present for comparison. I can say that it’s amazing on mediumwave, where I’ve spent much of my listening time this past week. I believe shortwave reception has been at least on par with my former Pixel Loop, if not better. It’s hard to say, in truth, because propagation conditions have been so poor lately. The CHA RXL loop does effectively mitigate noise!
I’m not sure if the CHA RXL is currently on backorder or not, but I would suggest you check out the product page on Chameleon’s website and possibly contact them if you’re interested. They’ve a number of options and accessories to consider.
One thing for sure: this must be one of the most rugged and durable RX loop antennas on the market. In addition, that Navy gray powder coating helps this rigid aluminum loop disappear against the sky. I believe you could strategically mount this loop and the friendly neighborhood association may never notice–it’s pretty stealthy. Speaking of which…
Josh’s CHA RXL install and demo video
Josh over at Ham Radio Crash Course recently installed a CHA RXL on his house and tested it on several bands, comparing it with a number of his external antennas:
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Recording Music on Shortwave
by TomL
I recently became curious about the seasonal music updates posted by Alan Roe. It is a nicely detailed list of musical offerings to be heard. Kudos to Alan who has spent the time and effort to make it much easier to see at a glance what might be on the airwaves in an easy to read tabular format. I do not know of any other listing specifically for shortwave music in any publication or web site. I especially like the way it lists everything in UTC time since I might want to look for certain time slots to record. For some listings, I would need to go outdoors away from noise to listen to certain broadcasts. Current web page is here: https://swling.com/blog/resources/alan-roes-guide-to-music-on-shortwave/ .
As a side note, I have also found a lot of music embedded in the middle of broadcasts that are unannounced, unattributed, and not part of a regular feature program. That can be a treasure trove of local music you might not be able to find anywhere on the internet. It can be worth recording a spectrum of frequencies using the capabilities of the SDR and then quickly combing through the broadcasts at two-minute intervals (most songs are three minutes or longer). In maybe ten minutes, I will have at least identified all of the listenable music that may or may not be worth saving to a separate file.
Whether at home or outdoors, I have wanted to try to record shortwave broadcasts of music using my AirSpy HF+ but never getting around to it until now. There is a certain learning curve to dealing with music compared to just a news summary or editorial. I found myself wishing I could improve the fidelity of what I was hearing. From static crashes, bad power line noise, fading signals, and adjacent channel interference, it can be quite difficult to get the full appreciation from the musical impact.
I am starting to monitor the stronger shortwave stations like WRMI, Radio Romania International, Radio Nacional do Amazonia, etc. These type of stations can be received in a strong enough manner to get good quality recordings (at least according to shortwave listening experience). I am also finding that I appreciate much more than before the effort that these broadcasters put into creating content/commentary to go along with the music and little pieces of background info about the music or the artist. I have also noticed how exact some broadcasters are in timing the music into the limited time slots. For instance, Radio Romania International tries to offer one Contemporary piece of music exactly at 14 minutes, Traditional music exactly at 30 minutes, and a Folk tune exactly at 52 minutes into the program (whether in English, French, or Spanish), with nice fade-outs if the music goes too long.
One thing I ran into was to bother checking my hearing range. If someone has impaired hearing, it does not make much sense to create files that have a lot of sound out of one’s hearing range. I found this YouTube video (among a bunch of others) and listened to the frequency sweep using my Beyerdynamic DT-990 Pro headphones (audiophile/studio type headphones). My hearing is approximately from 29 Hz through 14400 Hz. Of course, the extremes fall off drastically, and as with most people, my hearing is most sensitive in the 2000 through 6000 Hz range.
Recording Workflow
Let’s assume that you already know how to record IQ files using your SDR software and can play them back (In the example below, I recorded the whole 49 meter band outputting a series of 1GB WAV files). Then, when playing back to record to individual files, I have to choose the filters and noise reduction I want. This gets subjective. If I do not want to keep huge numbers of Terabytes of WAV files over time, I will want to record to individual WAV files and then delete the much larger spectrum recording. You might tell me to just record to MP3 or WMA files because there is that option in the SDR software. We will get into that as we go along. For the time being, I do not want to keep buying Terabytes of hard drives to hold onto the original spectrum recordings.
After lots of trial and error, I came up with this workflow:
Record the meter band spectrum of interest using the SDR software.
Record individual snippets of each broadcast in that spectrum to new individual WAV files. This includes not lopping-off any announcer notes about the music I want to retain. I also have to choose the bandwidth filter and any noise reduction options in the software. Because I am not keeping Terabytes of info, this is a permanent decision.
Take an individual recording and apply more processing to it.
Convert the processed recording to any number of final output formats for further consumption and/or sharing.
Repeat steps 3 & 4 to take care of all the individual WAV files.
Step 4 allows me to create whatever file format I might need it to be: WAV, MP3, WMA, or even use it as background sound to a video if I so choose. There are also different ways to create some of these files with different quality settings depending on what is needed. I have chosen to listen to the individual WAV files for personal consumption but there may come a time to create high quality MP3 files and transfer those to a portable player I can take anywhere (or share with anyone).
The example below is a snippet from the latest Radio Northern Europe International broadcast on WRMI. WRMI has some decent equipment and I like how clean and wide is the bandwidth of many of the music programs. This is captured on the AirSpy HF+ using SDR Console V.3 with a user-defined 12kHz filter (11kHz also seemed somewhat similar sounding).
If you click on the ellipses, you can Copy an existing filter, type in a new title and change the bandwidth. I also played around with the different Windowing types and found that I like the Blackman-Harris (7) type best for music and the Hann type for smooth speech rendering (the Kaiser-Bessel types can also have more “punch” for voice recordings). Click OK TWICE to save the changes.
I also use Slow AGC and the SAM (Sync with both sidebands) to reduce the chance of distortion as the signal fades. I found that trying to use only one sideband while in Sync mode would make the reception open to loss of Sync with the musical notes warbling and varying all over the place!
Noise Reduction
The SDR Console software has a number of noise reduction choices. I tried NR1 through 4 and found the smoothest response to music to be NR1 with no more than 3 dB reduction. More than this seemed to muffle the musical notes, especially acoustic instruments and higher pitched voices. Part of the problem has to do with trying to preserve the crispness of the articulation of the sound and combating shortwave noise at the same time. At this time, I have chosen NOT to use any NR mode. More about noise reduction below.
Generic MP3 sounds really bland to my ears, so creating higher quality files will be important to me. I have been using Audacity which can apply processing and special effects to WAV files and export to any number of file formats. WAV files are a wonderful thing. It is a “lossless” file format which means that every single “bit” of computer input is captured and preserved in the file depending on the resolution of the recording device. This allows one to create any number of those “lossy” output formats or even another WAV file with special effects added. You can get it here:
One special effect is listed as “Noise Reduction”. I literally stumbled upon it while reading something else about Audacity (manual link). Here is how I use it for a shortwave broadcast. Open the original spectrum recording (in this example the 49m band). Tune about 25kHz away from the broadcast that was just recorded. Remember, my hearing extends at least to 14.4k plus there is still the pesky issue of sideband splatter of bandwidth filters. The old time ceramic and mechanical filters use to spec something called “skirt selectivity” -60db or more down from the center frequency. This is still an issue with DSP filters even though they SAY they are measured down to -140dB; I can still hear a raspy sideband splatter from strong stations!
Find the same time frame that you recorded the broadcast and make sure it is the same bandwidth filter, AGC, and any noise reduction used. Now record one minute of empty noise to a WAV file. Fortunately on 5850 kHz, WRMI has no adjacent interference.
Now in Audacity, open the noise sample and listen for a 5 to 10 second space to copy that is relatively uniform in noise. We don’t want much beyond that and we don’t really want noise spikes. The object is to reduce background noise. In this case, I chose Start 39 seconds and End 44 seconds. Choose Edit – Copy (or CTRL-C).
Choose File Open and find the broadcast WAV file in question. Now click on the end-of-file arrow or manually type in the Audio Position (in this example 1 minute 15 seconds). Now Paste (or CTRL-V) the 5 seconds of noise to the end of the broadcast file. Now, while the pasted noise is still highlighted, go immediately to Effect – Noise Reduction and choose the button Get Noise Profile. It will blink quickly to read the highlighted 5 seconds of noise and disappear.
Now select all with CTRL-A and the whole file is selected. Go immediately to Effect – Noise Reduction and choose the parameters in “Step 2”. Through some trial and error, I found 3db reduction has a noticeable effect without compromising the music. I have used up to 5 db for some music recorded with narrower bandwidths. Higher levels of noise reduction seemed to create an artificial flatness that was disturbing to me. I also use a Sensitivity of 0.50 and Frequency smoothing of 0. You can choose the Preview button while the Residue circle is checked to actually hear the noise being eliminated. Press OK in order to process the noise reduction. You should now see the waveform change slightly as the noise is filtered. In a nutshell, I find this to be a better noise reduction than using 3db of NR1 in the SDR Console software. Don’t forget to snip off those 5 seconds of noise before saving the file.
Pseudo Stereo
The SDR Console software has an Option for Pseudo Stereo (for playback only) and it can be useful for Amateur Radio receiving, especially in noisy band conditions when one is straining to hear the other person’s call sign and location. There is a way in Audacity to add a fake kind of stereo effect to mono audio files. I found a useful YouTube video that explained it very clearly.
I do everything listed there except for the Reverb effect. I find that too fake for my tastes.
I found the added 10ms of Delay on the right channel to be a little too much, so I use 9ms.
My High Pass filter settings are 80 Hz and 24dB/octave. This is based partly on my hearing preferences as well as established industry standards. There was a lot of science and audio engineering that went into creating the THX home theater crossover standard. There is also science that says that anything below 200 Hz is omnidirectional. The suggested 48dB/octave is too steep in my opinion.
My Low Pass filter settings are more squishy. The YouTube video suggests 8000 Hz and 6dB/octave. I feel that is too gentle a rolloff into the upper midrange. I use 9000 Hz at 12dB/octave for very strong, high quality shortwave broadcasters like WRMI. For more constrained quality broadcasts, like due to limited bandwidth (Cuban broadcasters) or adjacent channel interference, I will decrease down to 8000 or 7000 Hz but still use a 12dB/octave rolloff. This is subjective but it also means I am making a conscious decision to add that processing to the recording for future listening.
MP3 Quality
Typical MP3 files are a Constant Bit Rate of 128k. Some interviews and voice-only podcasts are only 64k. This is adequate but for recording detail in the music I prefer higher quality settings. Frankly, with these days of 4G cell phone service and Unlimited Data minutes on cell phone plans, there is NO good reason to limit MP3 files to just adequate quality levels. The typical MP3 file sounds limited in frequency range (muffled sounding) to me and very lacking in dynamic range (narrow amplitude). This would include limits on stereo files which are about twice the file size of mono files.
I have tried creating WMA files and I actually like the quality a little better than high quality MP3 files. The WMA files seem slightly more “airy” and defined to my ears. But it is a proprietary format from Microsoft and not all web sites or devices will easily play them. They are also a fixed standard and one cannot easily change the quality settings if forced to use a lower quality rendering.
There are many web sites talking about MP3 files, but I found this blog post helpful in summarizing in one paragraph the higher quality settings for a nice MP3 recording using VBR-ABR mode.
So finally for my examples. Since most web sites still prefer MP3 files, I have created these using that blog post’s suggestions. Typically this is Min bitrate=32, Max bitrate=224, VBR quality=9, and Quality=High (Q=2). Let’s see if you can hear the differences. It would be much easier to hear if we were listening to WAV files, but those are way too big to post on this web site! The software I used is Xmedia Recode and I find it easy to use.
Many thanks to SWLing Post contributor, Grant Porter, who notes that Ham Radio Outlet has the Eton/Grundig AN200 loop antenna on a closeout sale for $15.00.
As Grant notes, this is an especially great deal if you live near an HRO retails store.
Many thanks to SWLing Post contributor, Gary DeBock, who shares his extensive 2021 Ultralight Radio Shootout.
This is truly a deep dive featuring five popular ultralight portable radios and examining mediumwave, shortwave, FM, and AIR Band performance.
The review is an amazing 40 pages long! In order to display the entire review, click on the “Continue reading” link below.
2021 Ultralight Radio Shootout
Five Hot Little Portables Brighten Up the Pandemic
By Gary DeBock, Puyallup, WA, USA April 2021
Introduction The challenges and thrills of DXing with pocket radios have not only survived but thrived since the Ultralight Radio Boom in early 2008, resulting in a worldwide spread of the hobby niche group. Based upon the essential concepts of DXing skill, propagation knowledge and perseverance, the human factor is critical for success in pocket radio DXing, unlike with computer-controlled listening. The hobbyist either sinks or swims according to his own personal choices of DXing times, frequencies and recording decisions during limited propagation openings—all with the added challenge of depending on very basic equipment. DXing success or failure has never been more personal… but on the rare occasions when legendary DX is tracked down despite all of the multiple challenges, the thrill of success is truly exceptional—and based entirely upon one’s own DXing skill.
Ultralight Radio DXing has inspired spinoff fascination not only with portable antennas like the new Ferrite Sleeve Loops (FSL’s) but also with overseas travel DXing, enhanced transoceanic propagation at challenging sites like ocean side cliffs and Alaskan snowfields, as well as at isolated islands far out into the ocean. The extreme portability of advanced pocket radios and FSL antennas has truly allowed hobbyists to “go where no DXer has gone before,” experiencing breakthrough radio propagation, astonishing antenna performance and unforgettable hobby thrills. Among the radio hobby groups of 2021 it is continuing to be one of the most innovative and vibrant segments of the entire community.
The portable radio manufacturing industry has changed pretty dramatically over the past few years as much of the advanced technology used by foreign companies in their radio factories in China has been “appropriated” (to use a generous term) by new Chinese competitors. Without getting into the political ramifications of such behavior the obvious fact in the 2021 portable radio market is that all of the top competitors in this Shootout come from factories in China, and four of the five have Chinese name brands. For those who feel uneasy about this rampant copying of foreign technology the American-designed C. Crane Skywave is still available, although even it is still manufactured in Shenzhen, China—the nerve center of such copying.
Prior to purchasing any of these portables a DXer should assess his own hobby goals, especially whether transoceanic DXing will be part of the mission– in which case a full range of DSP filtering options is essential. Two of the China-brand models use only rechargeable 3.7v lithium type batteries with limited run time, which may not be a good choice for DXers who need long endurance out in the field. A hobbyist should also decide whether a strong manufacturer’s warranty is important. Quality control in some Chinese factories has been lacking, and some of the China-brand radio sellers offer only exchanges—after you pay to ship the defective model back to China. Purchasers should not assume that Western concepts of reliability and refunds apply in China, because in many cases they do not. When purchasing these radios a DXer should try to purchase through a reputable seller offering a meaningful warranty—preferably in their own home country.
One of the unique advantages of Ultralight Radio DXing is the opportunity to sample the latest in innovative technology at a very reasonable cost—and the five pocket radio models chosen for this review include some second-generation DSP chip models with astonishing capabilities. Whether your interest is in domestic or split-frequency AM-DXing, FM, Longwave or Shortwave, the pocket radio manufacturers have designed a breakthrough model for you—and you can try out any (or all) of them at a cost far less than that of a single table receiver. So get ready for some exciting introductions… and an even more exciting four band DXing competition!
Many thanks to SWLing Post contributor, Steve Whitt, who writes:
