Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:

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Chameleon CHA-RXL:  Is This Pro-level Loop A Worthy Competitor To Wellbrook and W6LVP?

by Dan Robinson

At the end of summer 2021, I took up an offer from Chameleon to test and review their CHA – RXL loop antenna.  The company describes this as a “new design high-performance” LF, MF, and HF receive-only loop perfect for mobile RV and apartment situations and with low noise characteristics.

This is not a cheap antenna, like the Chinese-made MLA-30, but a heavy duty professionally-built unit designed to, as the old TIMEX watch commercial said, “take a licking and keep on ticking”.

Price for the CHA RXL is around $500, though the company dropped the price at to $382 – but only for the two section loop rather than the single piece antenna advertised on its site.

You can see the Chameleon on the company’s website here, but it’s also sold by Gigaparts, DX Engineering and other radio suppliers.  Chameleon lists features as:

Highly directional, balanced input preamplifier to eliminate environmental noise and ground loops, receives on new 2200m and 630m ham bands, flexible mounting and power options, and a stealthy [36 inch] Navy gray loop [that] fades into the background sky.

The built-in preamplifier, says Chameleon, “will enable clearer reception than many large horizontal wire or vertical antennas.”  Weight of the amplifier is given as 7 lbs.  The large pre-amp box is made of heavy metal, with a rubber gasket seal.

CHA RXL Amplifier Specifications

• Frequency: 135.7 kHz – 30.0 MHz continuous
• Power: 12V DC (120V AC wall adapter included USA ONLY)
• Mount: Mast or Camera Tripod
• Operating voltage: 12-14 VDC – Polarity Protected, Over-Voltage protection 15.5V – 20V (sustained voltage above 18V may damage the preamp)
• Gain: 25 dB @ 2.5 MHz, 12.5 dB @ 30 MHz (see graph)
• Noise Figure: < 5 dB
• P1dB: >0 dBm relative to the output
• OIP3: > +20 dBm
• Input (no damage): +20 dBm

Like Wellbrook, the W6LVP loop, the Pixel RF Pro-1B sold by DX Engineering, and other antennas, there is a Bias-T, on the Chameleon with 12 to 14 volt DC range, polarity and over-voltage protection of 15.5V – 20V and maximum current: 300 mA max with insertion loss of < 0.25 dB @ 30 MHz.

The CHA RXL arrives in two boxes, the 36 inch heavy loop in one flat box and the PRE-AMP and Bias T with mounting hardware in another.

First impressions are positive, especially of the loop itself which is constructed of heavy rigid aluminum (powder coated) and mounted to the left and right sides of the pre-amp box with screws and lock washers.

The pre-amp box which is quite heavy can be positioned atop a flat surface outdoors – included in the hardware box are four silicone bumpers that help with this, though the antenna which is quite heavy still tended to flop over and thus the preference will be to mount on a mast or similar.

Many readers probably know from my previous reviews that I operate numerous premium-grade receivers.  The list is long, but includes the latest in high-tech receivers, the ICOM IC-R8600, along with classic premium receivers such as a Watkins Johnson 8711A and 8712P, and Cubic CDR-3280.

I chose for my tests a Rockwell/Collins badged 51S-1, the classic tube receiver known for its low noise characteristics and high sensitivity.

Some years ago, my local high-noise environment led me to abandon traditional longwire antennas for a Wellbrook 1530/LNP.  Later I added a W6LVP loop.  These feed 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. My W6LVP is on a tripod with an overall height from ground of about 12 feet.   This antenna has special filters to prevent strong medium wave signals from bleeding into HF.

From the start, let me point out that my testing of the CHA-RXL was only on HF, not LF.  There has been some robust discussion on the loop antenna group at Groups.io in which the low frequency performance of the Chameleon was criticized.  Anyone wanting to read that debate should go to https://groups.io/g/loopantennas and do a search for Chameleon.

I chose a number of frequencies in the 31, 25, 22 and 19 meter bands as well as one 21 MHz and 27 MHz frequency, roughly between 1830 and 1930 UTC.  Propagation conditions have varied.  My location in Maryland is quite noisy and each day is a battle with electric lines and various noise sources from neighboring houses.

Results from my first test, pitting the Chameleon against the Wellbrook can be seen in Video No. 1.  Overall, the CHA-RXL is very sensitive, able to go head to head on most frequencies.  But the CHA is the noisier antenna.

CHA-RXL v Wellbrook

Then it was on to a comparison of the Chameleon to the W6LVP loop.  Results of this test can be seen in Video No. 2

CHA-RXL v W6LVP

So, some observations. While doing a good job keeping up with the Wellbrook on signal level, the Chameleon falls behind when it comes to noise.

This can be seen on certain frequencies more than others, for example, reception of VOA on 15,580 kHz where the Wellbrook is far quieter, and on 15,300 kHz where Wellbrook is both quieter and delivers more signal.

Similar can be seen on 15,140 kHz (Cuba).  Perhaps the most striking example is WWV on 15 MHz where the CHA struggles while the Wellbrook far exceeds the competitor in clarity and signal level.

The difference is more difficult to discern on some much stronger signals, for example 15,770 kHz and the VOA frequency 11,610 kHz.  On BBC on 11,810 kHz, the Chameleon actually sounded to be delivering more clearly than the Wellbrook.  The same on 11,955 kHz.  But then 11,975 kHz showed the Wellbrook winning the point again.

On 15,300 kHz it seems as if the CHA and Wellbrook are equally matched in terms of signal level, but the Wellbrook still wins out on clarity.  But on 11,995 kHz the CHA seems to be clearer while the Wellbrook has more noise.

On 31 meters and 9,460 kHz which is a main frequency for Voice of Turkey the CHA performed quite well and was clear while the Wellbrook was noisier.  On 9,635 kHz, the CHA and Wellbrook seemed about evenly matched.

Down on 49 meters and 6,070 kHz Toronto the CHA seemed clear and less noisy than the Wellbrook.  Up on 7,490 kHz the two antennas seemed to be evenly matched with the CHA seeming to bring in the signal better.

Back up on 25 meters, at 11,850 kHz the CHA did quite well, but the Wellbrook won the contest.  On 11,985 kHz, one of the stronger signals on the band the Wellbrook won by just a smidgen.  Up on 13,670 kHz it was the Wellbrook winning on signal strength though the antennas seemed evenly matched on clarity.  At 13,740 kHz the Wellbrook blew the CHA away on signal, which can be seen on the S-meter of the Collins.

At 9,675 kHz it seemed an even match on clarity but the Wellbrook won on signal strength.  A bit higher on 9,845 kHz the difference was very difficult to discern.   And back at 15,580 kHz VOA from Botswana the CHA seemed to win the match.  At 15,130 kHz the Wellbrook won on clarity and signal strength.

Finally, back to 15,000 kHz WWV the Wellbrook won on signal strength but seemed evenly matched with the CHA on clarity.  And on 13,630 kHz, a China frequency, the CHA seemed clearer.

Then it was on to CHA and W6LVP comparisons. I should note what everyone knows about the W6LVP loop, which is that while it has shown itself to be a very quiet antenna, the sacrifice comes on signal level.

On 11,800 kHz, a comparison of these two antennas did not reveal much.  But then things started getting more interesting.  On BBC 11,810 kHz the CHA shows far more noise than the W6LVP even though the CHA has more signal level.

Here are the rest of the comparisons along with my assessment of which antenna wins out [* are instances where the W6LVP wins but by a closer margin].

• 11,810 kHz W6LVP 9,420 kHz W6LVP
• 11,640 kHz W6LVP 9,685 kHz W6LVP *
• 11,670 kHz W6LVP 9,790 kHz Tie
• 11,780 kHz W6LVP 9,855 kHz W6LVP
• 11,900 kHz W6LVP 6,195 kHz W6LVP*
• 11,965 kHz W6LVP 6,070 kHz W6LVP*
• 13,630 kHz W6LVP 3,330 kHz CHA
• 15,000 kHz W6LVP 11,810 kHz W6LVP
• 15,580 kHz W6LVP
• 21,525 kHz W6LVP *
• 27 MHz (CB) W6LVP
• 20,000 kHz W6LVP

So, what conclusions to draw?  Clearly, the Chameleon CHA-RXL competes better against the Wellbrook 1530 antenna than it does against the W6LVP, where differences are most striking.  W6LVP wins almost every contest, which is why it is preferred by so many people whose listening takes place in noisy environments.

This does not mean that W6LVP loops don’t come with compromises.  Signal levels on W6LVP antennas are reduced to such an extent that some people, including me, place pre-amps back on the line to make up for the signal loss – this has to be done carefully so you’re not then re-introducing too much noise.

Is the seemingly noisier CHA antenna due to the material used in construction of the loop?  I don’t know the answer to that.  The CHA is one rugged piece of aluminum in comparison with the smooth and light tubing on the Wellbrook and PRO-1B.

It should be noted that W6LVP uses wide-diameter coax for the loops – LMR 400 and even LMR600.  I find there is a slight but noticeable difference when using the wider diameter coax on a W6LVP, but not necessarily a major improvement.

Which brings us around to the pre-amp box of the CHA itself.  Much larger than the Wellbrook and W6LVP, this too has been discussed on the Groups.io loop antenna group, so I won’t repeat that here.

Like Wellbrook, Chameleon can be expected to revise its pre-amp so anyone considering purchasing the antenna should be aware of this and act accordingly.  As my comparisons show, where the CHA falls short is in the noise area rather than signal level, something Chameleon is aware of from other reviews.

One of those reviews, by Dave Casler, can be found here.

It raises another matter that Chameleon is surely aware of, namely the QC on the screw threads on the mounting plate for the pre-amp box.  I too noticed a minor threading issue on the pre-amp box I received, making it somewhat difficult for me to mount the pre-amp box on a tripod.

The review by Casler, by the way, stated that the CHA seemed to have a “slight edge” on SNR on a 40 meter frequency.  This was comparing the CHA to a MFJ loop.  On 20 meters, he asserts that the two antennas were “not that different” but later observes that the CHA appeared to be picking up more noise, particularly noticeable in the 31 meter band.

Another review can be found at Ham Radio Crash Course You Tube channel.

Demonstrations there by Josh (40 and 20 meters) show the CHA compared to a STEPPIR and an End-Fed Half Wave.  Another comparison in 31 meters showed the CHA competing nicely with the STEPPIR, and doing well also in medium wave.

Summary

The CHA-RXL certainly makes the market for HF loop antennas, dominated as it has been for years by Wellbrook and the PRO-1B, along with the W6LVP, more interesting.

This is a professional grade antenna, and rugged with its powder-coated large diameter loop, heavy pre-amp box which is mountable (though you will need a strong tripod for it).

I think Chameleon could improve the Bias-T box, which currently consists of open connectors on a black plastic box – I would prefer to see a box similar to Wellbrook and the W6LVP preamps.

The big question, of course, is whether the CHA-RXL is worth the $500 or so cost when it comes to noise reduction, while retaining sensitivity.  This is without a doubt a sensitive loop that keeps up with Wellbrook and W6LVP on signal level.

But my overall assessment is that it is also noisier in most cases than the Wellbrook, and especially in comparison with the W6LVP, even when that antenna is re-boosted with an amplifier unit such as the RPA-1 or RPA-2.

A key critic of the Chameleon, who posted both in the Groups.io loop antenna group, and also commented on the initial SWLing Post overview of the CHA, has dinged the antenna for its LF performance suggesting that Chameleon has more work to do to improve its pre-amp. But that critique focuses on LF.

If Chameleon can upgrade its pre-amp to address what appeared to me in my tests of the antenna to be generally noisier reception in comparison with the Wellbrook and W6LVP, it will be more competitive with those providers, making the $500 or so price of a CHA-RXL more palatable.

My thanks to Chameleon for providing the CHA-RXL to me.  I certainly look forward to being able to test any newer modified pre-amp the company may come up with in the future.