Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:
The Chameleon CHA-RXL Pro: Improved Amp Board Raises the Game
by Dan Robinson
Back in 2021 I reviewed the CHA-RXL loop by Chameleon. This loop antenna is sold by major retailers such as DX Engineering, Gigaparts and Chameleon itself – the company is a well-known name in antennas and other equipment for the amateur radio world.
I compared the CHA-RXL to Wellbrook 1530 and W6LVP loops feeding into a four-position Delta antenna switcher, and then to a Raven 16 port multicoupler which maintains good steady gain.
My Wellbrook is mounted on a telescopic mast about 15 feet above ground level, with a rotor. The W6LVP (using LMR400 coax) is tripod-mounted with an overall height from ground of about 12 feet. It has special filters to prevent strong medium wave signals from bleeding into HF.
I have since added a UK-made loop (essentially a copy of a Wellbrook loop but smaller diameter and made of metal) combined with a W6LVP amp. This W6 amp does not have filtering to block strong mediumwave signals. In all, I have four loops into my Delta switcher, which feeds about two dozen receivers.
There is by the way quite robust discussion at https://groups.io/g/loopantennas about various loops, including the Chameleon. And this past July, Steve Ratzlaff posted news about the upgraded loop amp board which will ship with what is now the CHA RXL Pro, saying:
“Chameleon has completely redone their CHA RXL loop amp board from the previous poor-performing loop amp that I tested some time back, and sent me one of the new production boards to test. I’m happy to say it tests very well especially for LF sensitivity, and I can now give it my “seal of approval”. The new board is a version of the LZ1AQ loop amp.”
It turns out, according to an email from Don Sherman of Chameleon, that Steve is one of the engineers who helped design the new amp board for the CHA RXL Pro, and on the Loop Antenna group he provides a folder in which he placed previous test results with “new files of the new board (sweep of the new RXL Pro loop amp, and a picture of the new amp PCB).”
Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us Part Two of a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. The second article focuses on construction notes. This third and final article will essentially be a Q&A about the SULA antenna.
This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!
Please enjoy and share Part 3:
Part 3: SULA Q&A
Q: Where can I ask questions, discuss all aspects of the the SULA or collaborate in its further development?
A: There is a thread dedicated to the SULA in the new SWLing.com message board: https://swling.net/viewtopic.php?t=55
Q: Since the antenna is “lossy”, what’s the point of having a “beam”?
A: The answer is once again “SNR”: First off, remember that the LNA is there to make up for most of the losses. Secondly, this is all about the noise pickup, 20dB less gain/more losses outside the main lobe means also a reduction of atmospheric/cosmic/whatnot QRN and of course everything manmade from all these sides. The wide horizontal lobe is more or less one hemisphere horizontally, but the flat-ish vertical pattern makes that only a slice of it. In other words, there will be less QRN and QRM pickup from the back and the top. The idea is that the SNR will ideally increase more than the preamp’s noise figure will cost and it often sounds like this is what actually happens. Of course it’s also nice that you can turn an unwanted signal down using the more or less pronounced notch in the backside pattern up to 21 MHz – also very helpful for direction finding.
Q: Do I need a rotor?
A: It depends. If you are one of the lucky few still having a low-QRM-environment at home and you want to put it in the backyard, you really may want to be able to turn it remotely. If you’re using it portable you can simply rotate the mast manually. If you have local QRM or can’t mount it very far away from your or other houses, you may want to rotate the back of the antenna towards that source, leave it at that position forever and enjoy what’s coming in on the pretty wide main lobe of the antenna. The horizontal lobe covers more or less half of the horizon, depending on your stations of interest and location you could get away with never turning the antenna at all.
Q: Is it better than the XYZ loop?
A: Hey, that’s exactly what I wanted to ask you! 🙂 Even though the SULA is very similar in appearance and performance to a good SML working in ideal (ground conductivity) conditions, the SULA is a pretty different animal with a different behavior: Regular small loops, besides being bidirectional, can lose quite a bit of their low angle sensitivity over “poor” ground while the SULA is supposed to be retaining its properties better over any type of ground. Also, while many SMLs are tuned for VLF through the lower portion of the shortwave, the SULA complements those with quite uniform (good) properties up to 30 MHz and beyond.
Q: I have an end-fed random wire or dipole strung up from the house to a tree etc. – can the SULA beat that?
A: That’s quite possible. To get low takeoff angles from horizontal wire antennas you need to string them up at least 1/2 wavelength high, that’s 20m/66ft on 40/41m, 10m/33ft on 20m and so on. If you can’t do that, the SULA may be your ticket to listen farther beyond the horizon. Also, wire antennas are often strung up to match space restrictions or avoid QRM vectors and that way you may end up with some directionality in directions you don’t want, or no directionality at all when the wire is too low. Another noteworthy point is the ground: For most horizontal antennas, better ground means a considerable higher takeoff angle so the dipole needs even more height for low angles. The SULA’s takeoff angle benefits a little from the better ground and only gets a little worse over poor ground.
Q: Do I really need an LNA?
A: I hope so? Of course it depends… if you are going to try this antenna in a very noisy environment, the LNA may have little to no benefit. The noise is limiting your “radio horizon” to very loud signals anyway and for those you may not need an LNA, ever. On the other hand, the antenna is very lossy and in a quiet environment where noise is not an issue at all, weak signals may drop below the sensitivity threshold of your receiver without the LNA. The less noise you have, the more you’ll be able to benefit from an LNA. You will also need one when your radio isn’t all that sensitive, similar to the requirements to run a YouLoop. Andrew kept the loop impedance as constant as possible in order to allow any low impedance coax preamp to work behind the Balun. Any LNA with 20dB of gain should do, as per usual, better stuff may bring better results.
Among the sparse offers for decent shortwave LNAs, the NooElec LANA HF seems to be the only decent LNA sold via Amazon. It’s comparatively low-cost and unlike the other offers on Amazon, ready to be powered via Bias-T or even via Micro-USB and therefore happy with 5V. Since I also had the balun from the same company I could simply connect that all with a couple of these cute little SMA plumbing bits and it worked. The downside is its unknown but perceivably low resilience against intermodulation (low 3rd-order intercept point), this is usually not a problem with such a small loop but it can be in the presence of nearby transmitters.
If you do have nearby transmitters and don’t mind sourcing an LNA from Europe, Andrew recently pointed me to preamps from here. They offer a moderately priced preamp with a 2N5109 transistor (based on the W7IUV design) for a high IP3 value and low noise, which is also available in PCB-only and fully assembled versions including a compartment. They also offer Bias-T boxes.
Another alternative would be https://www.sv1afn.com/en/product-category-5/-6.html – the design (using a GALI-84 MMIC) is promising more headroom than the LANA HF (which seems to use the lower voltage GALI-39), but needs 12V power like the W7UV preamp above. This LNA is available in a ready-to-use box as well.
Q: What is special/different about this antenna? There are already very similar designs!
A: It’s supposed to be simpler and more compact/portable, and it seems to deliver more consistent results over the entire coverage range in different usage environments than similar designs. The SULA was designed to be made with things that are particularly easy to obtain, or which were already obtained — many of us SWLs have some of that Nooelec stuff in our drawer anyway, even when (or because) we’re not habitual antenna builders and balun winders. Now making a better balun and buying a better preamp is not hard and could even bring better results but the point is that you don’t have to. In summary, this is not meant to be a miracle antenna, just number of compromises re-arranged to create a particularly uncomplicated, small, unidirectional loop antenna that aims for DX, for apartment dwellers and DX nomads like me.
Many thanks to SWLing Post contributor, Matt Blaze, for the following guest post:
by Matt Blaze, WB2SRI
Followers of this blog may be familiar with my “shortwave radio shootouts” that I post from time to time. The idea is to compare how well different radios demodulate the exact same signal. Basically, I take a bunch of radios, hook them up to the same antenna via an RF distribution amplifier, tune the radios to some distant signal, and record the audio output from them simultaneously. Sometimes that kind of comparison can be more revealing of actual real-world performance than lab measurements or technical specifications.
The other day, I decided to do the same thing, but for antennas instead of radios. Essentially, I inverted the setup. Instead of hooking up different radios to the same antenna, I hooked up identical radios to different portable antennas and recorded them demodulating the same signals at the same time.
In this first of perhaps a series of these antenna shootouts, I wanted to compare three portable amplified magnetic loop antennas. When I say “portable” here, I mean broadband antennas that can pack reasonable compactly for travel and that can be set up and broken down easily for use “on location”, say on a picnic table or hotel balcony, or perhaps installed temporarily on a roof, without too much fuss.
The antennas are:
– The Wellbrook FLX1530LN with a 1 meter diameter loop of LMR400 coax. This is my “standard” portable antenna (I use a telescoping broom handle for the support; I wrote about it here as the “signal sweeper” last year). Excellent performance, but on the bulky side for travel. Performs well from LW through HF. Not cheap, at about USD 225 including shipping for the amplifier and power injector, but not including the loop, mounting hardware, or feedline.
– The Wellbrook FLX1530LN with a 0.5 meter diameter loop of RG142 (a stiff “aircraft grade” version of RG58 that holds it shape well at this size). I used some 1/2 inch PVC pipe as the vertical support. Because of the smaller diameter loop and thinner coax, it packs down to a much smaller and lighter package than the 1 meter LMR400 version.
– The K-180WLA, an inexpensive (about USD 60) 0.5 meter loop from China, sold on eBay and Amazon. The loop is steel wire (which can be wound down to a small diameter for transport), and the kit includes everything you need, including a rechargeable power injector. (However, the power injector uses a noisy voltage booster, so I substituted my own bias-T injector for these experiments). Ostensibly covers LW through VHF, but the low end coverage is, shall we say, somewhat aspirational, as you will see.
– I also recorded, for comparison, the built-in ferrite bar (for LW/MW) and whip antenna (for HF) of the receiver.
This is, of course, only a small sampling of portable loop antennas, both commercial and homebrew. But I wanted to start with what I had on hand and with what meets my own needs. (I omitted from consideration loops that require tuning, since I want to be able to install the antenna without needing access to it every time I change frequency).
For each signal captured, I oriented and positioned each antennas to maximize signal quality, taking care to move them away from each other and interfering metal objects. So you’re hearing (approximately) the best each antenna had to offer (on my roof under suboptimal band conditions).
The receivers I used were four Sangean ATS-909×2 portable LW/MW/SW/FM/Air radios. I believe this to be the best currently available (relatively inexpensive) portable shortwave receiver on the market. It has excellent performance (and is admirably resistant to overload and intermod when used with an active antenna). It lacks a sync mode, but that’s rarely implemented well on portable radios anyway. As a practical matter, it has a good line-level output jack, and I already happened to own four of them.
As in my other shootouts, for each signal, there are a total of five recordings: a monoaural recording of the audio from each of the four antennas, plus a narrated stereo recording comparing a reference (the 1M Wellbrook) on the Left channel with each of the other antennas in succession on the Right channel. The stereo recording is intended as a quick overview, but it will only make sense if you listen in stereo, preferably with good headphones. (You can switch the earcups to get a quick comparison as you listen.)
I bought [an Eton Elite Satellit] on Amazon and received it today. Here is a link to my YouTube review.
I have made several radio videos on YouTube recently and your audience may enjoy them.
Many thanks for sharing your initial review, Nick! I look forward to seeing any comparison videos you might produce as well!
By Jock Elliott, KB2GOM
When you live in an antenna-challenged situation as I do (stringing long wire antennas outside is problematic for me), the result is a never-ending search for an improved signal.
Along the way, I decided to test the MFJ 1020C active antenna/preselector, and I liked it pretty well. My conclusion was: Bearing in mind that it won’t improve every signal you want to hear, if you live in an antenna-challenged situation, the MFJ 1020C – particularly if you can get 20-50 feet of wire outdoors or run around the perimeter of a room – may be just what the doctor ordered.
After my test of the 1020C, I had an online conversation with Andrew (grayhat), and he suggested that I might want to have a look at the MFJ 956 passive selector. Its major claim to fame is: “Boost your favorite stations while rejecting images, intermod, and phantom signals! The MFJ-956 Pre-Selector/Antenna Tuner greatly improves reception from .15 to 30 MHz — especially below 2MHz. It has tuner bypass/ground receiver positions. The MFJ-956 measures a compact 2 x 3 x 4 inches.”
MFJ was kind enough to send a 956 to me, and while I did not test it below 2 MHz, I found that it proved very helpful in tuning in the BBC mid-winter broadcast to Antarctica. I started out with the MFJ 1020C. Lots of noise and fades. Reception was somewhat better using the 1020C (compared to bypass), but then I switched to MFJ 956. I found I could copy better with the 956, even though it provides no amplification. Tuning slightly off-peak offered the best copy, better than bypass. I was listening in USB. In all, it is a useful piece of gear.
While poking around the MFJ website I discovered the MFJ 1046 Receiver Preselector, 1.6-33 MHz. Among other claims, MFJ has this to say about the 1046: “MFJs new Passive Preselector has extremely high dynamic range! It improves the performance of nearly any HF or shortwave receiver/transceiver. It vastly improves the most expensive receivers. Especially helpful to those with broadband front-ends that are prone to overload.”
Sounds promising, I thought, so I emailed Thomas, SWLing’s Maximum Leader, to see if maybe MFJ would like me to have a look at one.
A happy accident
A few days later, package arrived.
I was unpacking it when the Brain Dudes interrupted.
Brain Dudes: Hey!!
Brain Dudes: That thing look a little weird to you?
Me: Whaddya mean?
Brain Dudes: Look at the front . . . what do you see?
Me: Well, on left, a knob labeled GAIN; next to that, and ON/OFF button; moving to the right, a BAND selector switch, and finally a TUNE knob.
Brain Dudes: And what is the MFJ 1046 supposed to have?
Me: A big tuning knob, an ON/OFF switch, and a BAND selector switch . . . maybe this is an improved model . . .
Brain Dudes: How ‘bout you look on the back panel . . . what do you see?
Me: The usual connections for antenna and receiver . . . and a plug-in socket for an external power supply.
Brain Dudes: Is a passive preselector supposed to have a power socket?
Me: No . . .
Brain Dudes: OK, final clue, Sherlock: suppose you read the label on the front panel.
Me: MFJ 1045C. Holy smokes! They sent me the wrong unit!
(I hear the Brain Dude yelling at someone in the background: “Finally, the light comes on! I told you switching to decaf was a bad idea!)
Brain dudes: So they sent you the wrong unit; suppose you test it anyway since it’s here.
So I did. And it turns out that MFJ sending the 1045C instead of the 1046 was a happy accident because the 1045C, which is an active preselector, delivers excellent performance across the board.
This is what MFJ says about the 1045C: “Lets you copy weak signals. Rejects out-of-band signals, images. 1.8 to 54 MHz. Up to 20 dB gain. Gain control. Dual gate MOSFET, bipolar transistors for low noise, high gain. Connect 2 antennas, 2 receivers. Coax and phone jacks. 9-18 VDC or MFJ-1312D.”
Once the antenna, receiver, and power supply are connected (I used the power supply that MFJ sent me with the 1020C), I operate the 1045C in much the same way as the 1020C:
- With the unit in BYPASS mode (the ON/OFF button out), tune the receiver to the frequency you want to hear.
- Set the GAIN knob to around 3 or 4.
- Set the BAND knob to the band with the MHz that you are tuned to.
- Press the ON/OFF/BYPASS button in. This turns on the active preselector and amplification circuits and a red light comes on to let you know the unit is activated.
- Slowly turn the TUNE knob back & forth. At some point in its tuning range, you will hear the signal and/or noise peak.
- Finally, adjust the GAIN knob for maximum intelligibility of the signal. Sometimes tuning slightly to the side of the peak works best.
I tested the MFJ 1045C with my end-fed indoor antenna (see link above) and with the short dipole (also, see link above). I also did head-to-head comparisons with the MFJ 1020C and those two antennas.
Here’s what I found:
- The indoor end-fed antenna (which is 45 long) out-performs the short dipole (which is 6 feet total length) in all cases. That’s no surprise, but bear in mind that not everyone has a situation in which they can deploy the longer antenna. The 6-foot dipole definitely out-performs the whip antenna on my Satellit 800.
- The 1045C has a broader range of amplification than the 1020C. It appears to reject adjacent channel interference as well or better than the 1020C, and, to my ear, the 1045C has a lower noise floor. If you turn the GAIN knob fully to the left, it gets to a position where it appears to actually attenuate the signal. And I never found a situation in which, if properly tuned, the signal delivered by the 1045C was at least equal to the bypass signal, and many times it was significantly better. In short, in the HF range the 1045C appears do to everything that the 1020C does (with the exception of the 1020C’s screw-in whip antenna) and do it better.
- When using the 1045C with a portable (my Tecsun 880), I found that I could hear the noise peaks better than with the 1020C, which is a great help in tuning for best performance.
So why would you chose the 1020C or the 956 over the 1045C? Short answer: if you are a MW or LW enthusiast. According to MFJ, the 1045C covers 1.8 to 54 MHz; the 1020C covers .3 to 40 MHz, and the 956 covers 150 kHz to 35 MHz.
However, if you are an HF weenie like I am who enjoys teasing out faint signals, and particularly if you are faced with a sub-optimal antenna situation, the MFJ 1045C, in my opinion, is definitely worth a try.
Shameless plug: check out the SWLing Post Message Board there are often interesting discussions going on there.
Many thanks to SWLing Post contributor, Jack Kratoville, for the following guest post:
My Perfect Radio Trifecta
by Jack Kratoville
Last Fall, I asked SWLing readers to assist me in my decision as to what portable radio I should take on a two-week trip to Germany. While I came up with an initial list of portables I already own, there were some excellent suggestions on what I might pack. (Sidenote to Thomas – yes, my wife and I packed everything we needed into two carry-on pieces, including my 3 radios. Your expertise continues to serve us well!) To all else, thank you again for your thoughts, suggestions and comments.
The Tecsun PL-310ET was a top choice of many, yet one I had previously never taken into the field. It seemed a logical choice for this trip. The second is the Sangean PL-210 and it just fits in any pocket. The third is a DAB receiver someone had given me, tossed in a drawer, and forgotten about until I realized Germany implemented DAB to replace the MW and LW bands. The only name I can find online is the DAB-8. Being quite small, it made the cut and I shoved it in between a couple of tee shirts.
At our destination, I quickly realized I could not have chosen a better trinity for myself. Here’s why.
If this had been the only radio I brought, I would have been more than satisfied. SW signals abound (the war just two countries away was certainly a factor.) A quick hit of the ETM feature at the top of the hour brought in 40-50 listenable signals, with only a scant few broadcasts religious in nature. Even during the day, I could capture 25 easily. With the bandwidth set at 3 kHz, sound was most impressive. While some were the same broadcast on different frequencies, my only real disappointment was the lack of English-speaking broadcasts – but that was to be expected. The PL-310ET scans relatively fast and holds on to strong signals quite nicely.
We stayed with relatives who lived high on a hill not far from Kiel, in the north of Germany. One push of the ETM feature on FM filled the dial with German voices playing mostly English pop music (the eighties apparently a favorite decade there too.) Simply put, the selectivity on this radio is phenomenal. Odd / even frequencies happily sharing adjacent homes on the dial. And with the pre-emphasis on European FM at 50, the sound from this portable was absolute perfection. As a matter of fact, my first complaint about this radio was a bit of harshness on our over-processed FM commercial stations. In Europe, the audio characteristics of classical, pop, rock and talk stations was simply sweet.
My first night on the AM band was a disappointment. One, maybe two signals that didn’t come in very well. Thankfully, I quickly remembered to flip it to 9kHz and – wow! The BBC, Spanish, Italian, and signals that sounded very much like eastern Europe came booming in. I did not expect all of this and can easily say this was the most fun I’ve had band scanning and DXing in a long, long time! Traveling domestically, I’m more apt to load a memory page, but in this situation, the ETM feature was incredibly useful.
For all DXing, I only used the whip and internal antennas. The battery indicator dropped one notch on the second to the last day we were there. The PL-310ET is an absolute true travel performer.
The Tecsun PL-310ET now sits proudly alongside my CCrane Skywave, Digitech AR1780, Eton Executive Satellit (Grundig edition) and the semi-retired Grundig G5. When we travel to London next year, there’s no question this gets packed again.
A radio that became my constant walking companion during Covid. Hand-sized with a really nice on-board speaker for its size. The sensitivity is impressive and considering its PLL circuitry, has excellent selectivity on FM. AM was also impressive for an antenna no more than a half-inch – if that. It went with me to Hamburg, Berlin, Frankfort and Denmark; always just a quick pull from the pocket for a quick scan. To say I like this radio, well, I own three.
My curiosity in DAB was basically zero. One reader actually PM’d me and offered their own DAB receiver, saying I should check it out. (Thank you, Mike, for that generous offer.) This radio sounds great, but has very poor FM reception. (No MW). It does have inputs for mp3 and Bluetooth, so I figured just in case there was nothing to listen to, I could stream something on it. Its small size was the biggest factor in making the trip. Once settled, a quick daytime scan grabbed nine signals easily on DAB and they sounded great. It was the only band that featured more traditional (even country!) music. It’s back in the drawer at home, but I am very glad it made the trip.
I truly had a blast listening to the various captures on these three radios, the Tecsun being the most impressive and fun. I’m sure many newer models would be excellent choices, but not once did I wish to have something bigger or better. That doesn’t happen on trips very often, so perfection indeed.
My apologies to those looking / hoping for recordings. I stopped recording from the radio back when I opted to purchase 45rpm records rather than record them, complete with DJ patter on my father’s Webcor reel-to-reel. Once I got into the biz, I recorded enough DJ patter to last a lifetime! Again, thanks to everyone for their input.