The Chameleon CHA RXL amplified wideband loop antenna

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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.

Click here to check out the CHA RXL at Chameleon Antennas ($490 US).

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:

Click here to watch on YouTube.

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Tecsun H-501x pricing and availability via Anon-Co

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Anon-Co has started taking pre-orders for the Tecsun H-501x portable receiver. Click here to read Dan Robinson’s review of this radio.

Anon-Co will start shipping these on Monday, May 16, 2021.

Hard case version

The price will be $298.00 US for both the hard case and faux leather case versions.

Faux leather case version.

Shipping cost: Depends on the delivery country; slightly higher cost for the hard case version.
Faux leather pouch is not included with the hard case version. It can be included as a $15.25 add-on, but does not fit inside the hard case.
Hard case version: Limited stock available (more stock expected by the end of June).

Click here to check out the faux leather case version and/or the hard case version of the Tecsun H-501x at Anon-Co.

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KSOL via WRMI on Sunday, May 16, 2021

FTIOM & UBMP, May 16-22

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From the Isle of Music, May 16-22:
This week, we begin our coverage of Cubadisco 2020-2021 with music by the nominees of the Tradicional Variado (varied traditional) category of the awards.
The broadcasts take place:
1. For Eastern Europe but audible well beyond the target area in most of the Eastern Hemisphere (including parts of East Asia and Oceania) with 100Kw, Sunday 1500-1600 UTC on SpaceLine, 9400 KHz, from Sofia, Bulgaria (1800-1900 MSK)
2. For the Americas and parts of Europe, Tuesday 0000-0100 UTC on WBCQ, 7490 kHz from Monticello, ME, USA (Monday 8-9PM EDT in the US).
3 & 4. For Europe and sometimes beyond, Tuesday 1900-2000 UTC and Saturday 1200-1300 UTC on Channel 292, 6070 kHz from Rohrbach, Germany.
Our Facebook page is https://www.facebook.com/fromtheisleofmusic/
Our V-Kontakte page is https://vk.com/fromtheisleofmusic
Our Patreon page is https://www.patreon.com/tilford

Uncle Bill’s Melting Pot, May 16-22:
In episode 217, we listen to music from El Salvador.
The transmissions take place:
1.Sunday 2200-2300 (6:00PM -7:00PM EDT) on WBCQ The Planet 7490 kHz from the US to the Americas and parts of Europe
2. Tuesday 2000-2100 UTC on Channel 292, 6070 kHz from Rohrbach, Germany for Europe.
3. Saturday 0800-0900 UTC on Channel 292, 9670 kHz from Rohrbach, Germany for Europe with a directional booster aimed eastward.
Our Facebook page is https://www.facebook.com/UncleBillsMeltingPot/
Our V-Kontakte page is https://vk.com/fromtheisleofmusic
Our Patreon page is https://www.patreon.com/tilford

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2021 W9IMS Special Event Station Details!

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Now Underway: A More Typical W9IMS Special Event

By Brian D. Smith, W9IND

The fans are returning to the Indianapolis Motor Speedway this year, and with them comes a more traditional calendar for special event station W9IMS.

For hams and SWLs alike, that means a renewed opportunity to earn three newly designed QSL cards and the latest edition of the certificate known as the Checkered Flag Award.

The first W9IMS special event of 2021, saluting the upcoming IndyCar Grand Prix, is now underway and will continue through Saturday, May 15 (Race Day), ending at midnight Indianapolis time or 0400 UTC Sunday, May 16.

It’s the first of three W9IMS special events this year – two in May and the third in August – to commemorate the major auto races at the track. (Last year, because of Covid restrictions, two of the three races were held on the same weekend, and W9IMS followed suit by compressing its usual trio of special events into two.)

Here’s the remaining W9IMS slate for 2021:

May 24-30: Indianapolis 500

Aug. 9-15: NASCAR 400 at the Brickyard

Each of the three W9IMS events features its own unique QSL card, with the Checkered Flag certificate available to anyone who completes the clean sweep. However, you can still claim a single-event QSL or two even if you fail to bag the trio.

How to find W9IMS? The station will operate SSB daily on two bands, 20 or 40 meters, generally around 7.245 and 14.245 MHz, and could pop up at any time of day or night until local midnight Sunday. Keep a lookout, too, for digital activity – particularly FT8 and FT4 – on virtually any amateur radio band.

But the surest way to snare the station is this:

Go to the W9IMS web page (www.w9ims.org) and find the heading, “2021 Operating Schedule.” Beneath it are links to the operator schedules for this year’s three special events; time slots with a name and a callsign offer your best bet for a W9IMS contact.
Check DX Summit (www.dxsummit.fi) for spots that identify the current frequency or frequencies of W9IMS, if any. By typing “W9IMS” in the search box, you can customize it to show reports for only that station.

Remember, you can’t qualify for the 2021 certificate if you don’t catch the first event! So if you haven’t logged W9IMS by Saturday evening, keep in mind that the station traditionally conducts “happy hour” between 11 p.m. and midnight (0300 to 0400 UTC Sunday), with rapid contacts right up to the end. (But don’t stake your certificate on it: W9IMS special events may end early if the calls stop coming and/or band conditions deteriorate.)

For additional details, including QSL information, consult the W9IMS web page.

And in answer to the most-asked question: W9IMS operators transmit, usually remotely, from home stations in the Indianapolis area, but neither the ops nor the stations are physically located at the track.

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Should web-based SDR loggings be included and shared in regular logging columns?

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Operating a KiwiSDR in Iceland from my vacation spot in Québec (circa 2018).

Many thanks to SWLing Post contributor, Richard Cuff, who writes:

Radyo Pilipinas is one of those English language stations that are not very likely to make to my Pennsylvania location, even under excellent conditions, simply because propagation of their frequencies wouldn’t reach eastern North America when they’re on the air.

Web tunable SDRs change all that…I caught them today from 0315 to their 0330 signoff on 15640 and 17620, in English, with a chatty travelogue program.

I was listening via an Indonesian Kiwi SDR located in Jakarta.

I’m left wondering — is there interest in reporting logs like this? We wouldn’t normally include them in the regular Loggings column in the NASWA Journal, because I’m not tuning my radio, I’m in front of a computer screen tuning half a world away.

FWIW, Radyo PIlipinas broadcasts in English daily from 0200 to 0330 on 15640, 17700 (announced but not heard) and 17620 kHz.

73 – Richard Cuff / Allentown, PA (virtually in Jakarta, Indonesia…)

Wow–what a great question, Rich.

I suspect some DXers have very strong feelings about WebSDR loggings, both for and against.

In terms of loggings columns with various radio clubs and organizations, I suppose it’s up to the governing body to decide. As you say, I suspect it will come down to whether or not remote radio operation counts. With a KiwiSDR, for example, you’re controlling a remote receiver–one that is physically located in a known geographic spot–and the audio is being piped over the Internet. I know it wouldn’t be in the spirit of the thing if you submitted logs implying you’d logged Radyo Pilipinas from your home receiver and antenna. If, however, you disclose that you were using a remote RX station in Jakarta, the logging would be accurate. Whether or not it’s allowed is a separate issue.

Anyone care to share their constructive comments? What do you think about WebSDR loggings? Please comment.

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TomL’s guide to making and optimizing shortwave radio SDR music recordings

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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:

https://www.audacityteam.org

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.

https://technical-tips.com/blog/software/mp3-encoding-right–1334

One Minute Samples

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.

https://www.majorgeeks.com/files/details/xmedia_recode.html

Example 1: No noise reduction in SDR Console, no further processing