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Review of the Chameleon CHA F-Loop Portable Antenna

Discussion in 'Amateur Radio Antennas' started by Moleculo, Oct 18, 2015.

  1. Moleculo

    Moleculo
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    In March 2015, Chameleon Antenna announced the availability of their new CHA F-Loop antenna. These types of antennas are commonly referred to as "magnetic loops" (note that the term "magnetic" is slightly misused) and is certainly not a new idea. That said, Chameleon has come up with an interesting design which is geared toward the portable operator. Anyone that has regularly read my reviews knows that I'm a sucker for interesting new ham radio gear, so I bought one to evaluate. After playing with the antenna for nearly 6 months, I feel that I finally have enough "behind the wheel" time to give an honest evaluation.

    Chameleon CHA F-Loop The CHA F-Loop is available in two models: The base model uses an LMR-400 coax radiator with a unique hardline feeder support design for the coupling loop and is $365. The Plus model adds a larger diameter collapsible aluminum radiator and is an extra $110. More on the differences between the two models later. The matching unit contains the necessary variable capacitor(s) and the 6:1 reduction dial allows for smooth and fine-tuned adjustments. The toggle switch on top introduces an additional capacitor in series which is used for 40 and 60 meters. My experience has shown that under certain operating conditions on 20 meters while using the coax radiator, I am able to achieve a lower SWR with the switch in the B position. This usually happens when attempting to use the antenna indoors where there are a lot of other objects (furniture, walls, etc.) nearby. The aluminum base plate can also be mounted to a tripod as seen in the picture above. Lastly, 12 feet of RG58 coax with an integrated W2DU-style choke completes the package which all fits nicely into the included molle bag.

    Chameleon F-Loop tuner The cleverness of the CHA-F Loop is in it's break-down, portable design. The coupling loop is pre-assembled with a regular 3/8-24 UHF mobile antenna mount which is supported at the top of the radiating loop by the hardline feed. Placing the matching box at the base of the radiator results in a more omnidirectional radiation pattern but also allows you to rest the antenna on just about anything. By placing the main feedline connection at the rear base of the matching box, the coax is routed straight down or away from the radiating element, which is important to prevent it from interacting with the antenna itself. One interesting thing to note: if you want a little more directional, butterfly radiation pattern, you could suspend the antenna upside down. Of course, the aluminum radiator upgrade won't fit into the molle bag, but the two-hinge design is also cleverly designed for portability. This next picture shows how everything fits into the molle bag and how the aluminum radiator folds up for transport:



    Chameleon F-Loop Radiator Upgrade The aluminum radiator upgrade provides significant performance benefits, but does that mean you should never consider using the less expensive coax model? Remember my antenna philosophy: all antennas are a compromise of some sort; you have to choose the one that fits your needs. The coax CHA F-Loop is incredibly portable and sometimes that is more important than anything else. I used this version of the antenna for field day when space was at a premium; indeed, the ability to fit everything into the small molle bag was more important at the time than performance. For this application, I decided to just rest the antenna on the roof of my jeep while plugged into the Icom IC-7000 installed inside. Although the band conditions were tough, with this setup I was able to make several SSB contacts with some effort:
    Chameleon F-Loop Field Day It's important to understand that these antennas are not "magic" antennas. While they can work well for what they are, they are a compromise and should be viewed as such. You may often hear or read stories about the incredible contacts that operators make using these antennas indoors; indeed I made quite a few inside my den, as well. The trick to being successful under these conditions is paying attention to band conditions and carefully choosing an operating mode. The following WSPR contacts were made using the CHA F-Loop antenna with the coax radiator, 10 watts drive and the antenna inside my den, each over the course of one evening:

    30 meter contacts:
    wspr 30m cha-f loop 40 meter contacts:
    wspr 40m cha-f loop Those results aside, I was MUCH more successful using the antenna outdoors; on one particular day that had tough 20 meter conditions, I could barely get anything done with PSK31 with the antenna indoors, but moving outdoors made all the difference. Operating digital modes with this antenna in conjunction with the Elecraft KX3 in the backyard is an absolute ton of fun. Don't get me wrong; making contacts can be challenging when the band conditions are tough - but it is a blast. Changing bands takes about 5 seconds because you don't have to do anything but dial the tuning knob.

    This picture pretty much shows how I've spent the better part of the summer months playing with this antenna:
    Elecraft KX3, PC, Martini, Chameleon F-Loop antenna working PSK-31 The design of the antenna also allows for mounting in unusual places. On one day, I decided to mount it to my fence to see if I could make any local contacts. Indeed, local 10 meter contacts proved as easy as chatting on the ol' CB; I had some great QSOs with folks in the local area that just happen to hear me calling CQ:

    Chameleon F-loop on Fence with Elecraft KX3 As I said earlier, I didn't want to be too technical with this review, but I do think it is useful to show some of the analyzer sweeps I made with my Rigexpert AA-600. There are a few other articles on the web that explain how the antenna bandwidth is an indicator of efficiency (Q), but I'll let the pictures here speak for themself. Each of these sweeps were made using the aluminum radiator:

    40 meter sweep:
    Chameleon F-Loop 40 Meters plot 20 meter sweep:
    Chameleon F-Loop 20 Meters plot 10 meter sweep:
    Chameleon F-Loop 10 Meters plot Lastly, I would be remiss if I didn't discuss my experience with Chameleon's customer service. As I mentioned earlier, I purchased one of the very first of these antennas and as a result, I found a problem (I'm good at that). On the original antenna I received, it would not handle more than about 5 watts on 40 and 60 meters. While the antenna would tune up properly and present a low SWR with low power; whenever the drive was increased above about 5 watts on the lower bands, the SWR would shoot sky-high. After trying everything I could think of, I decided to contact Chameleon for support. The quick response from them indicated that some of the first models had a problem caused by the mounting method used for the variable capacitor which caused it to arc once certain power levels were introduced. They asked me to return the antenna and I had a new working version in my hands within a few days. I have not seen this problem since and kudos are in order for how well Chameleon handled this issue.

    In summary, the Chameleon CHA F-Loop is a very clever, well-made antenna that is geared toward the operator that requires convenience and portability in a small package. If you have the funds and means to use the aluminum radiator upgrade, you will definitely experience a nice difference in performance. You need to understand that these types of antennas are no substitute for a full-sized antenna, but you can have a ton of fun, for sure. You will have much better success using CW or digital modes like PSK-31 and you should definitely try WSPR with with these antennas. Keep an eye out for good band openings - when you combine QRP with a compromise antenna, you definitely need to do anything you can to improve your odds. Over the next few months, I plan on taking the antenna in its molle bag with the Elecraft KX3 on a local backpacking trip. Because the antenna takes less than 5 minutes to set up, I keep finding new ways to experiment with it and am constantly drawn to trying new things. The price of this antenna isn't cheap, but nothing about the construction of it is, either. I'm pretty happy with the purchase and plan on keeping it to continue exploring what I can accomplish with it.
     

  2. fourstringburn

    fourstringburn
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    Nice review. I was expecting this to be a receiving antenna only. I'm looking into trying a magnetic loop receiving antenna soon.

    According to manufacture specs, this antenna is now rated at 25 watts SSB or 10 watts CW.

    Maybe the matching unit could be beefed up to handle 100 watts. Either way it seems to work as intended with the contacts you made.
     
  3. Moleculo

    Moleculo
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    You would need a pretty sizable capacitor to handle the voltage requirements of 100 watts, which could be in the neighborhood of 5000 volts. While that's certainly doable, it will start to impact the portability. You should also remember that even at 10 watts, there's quite a bit of voltage present at the base of the antenna. The unit comes with a nice warning sticker on top to let you know that the metal contacts on the matching box are hot while transmitting. I had to find out for myself, so of course I touched the metal switch on top while transmitting and got a nice zap! I would hate to think what that would feel like at 100 watts.
     
  4. Robb

    Robb
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    Was the martini yours; or was it supplied in the kit as an adjunctive assembly aid?

    BTW; what did you pay for the antenna - if you don't mind the question?
     
    #4 Robb, Oct 18, 2015
    Last edited: Oct 18, 2015
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  5. Moleculo

    Moleculo
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    Haha - that Martini was either Tanqueray or Beefeater with a little good quality dry vermouth and an olive. That pic was likely taken on a Sunday (martini day) with the grill lit behind me.

    I paid full price for the antenna: $475+ tax with the upgraded aluminum radiator.
     
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  6. 2RT307

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    Very nice review! I like the portability of the coax unit. Could make for fun listening on my SDRplay when I travel.

    73,
    Brett
     
  7. 2RT307

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    Moleculo, have you played with this as a receive only antenna with your setup, and transmit with your "normal" antenna? I'm in a pretty noisy environment at my shack, and wonder if the magnetic loop might be a better way to go. I have the ability to run an rx only antenna on my FTdx-3000, and could still run my delta loop or end fed random wire as my main tx antenna. Could also use it as receive only for my SDRplay, and transmit with the FTdx-3000/regular setup.

    73,
    Brett
     
  8. Moleculo

    Moleculo
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    I have used it as a RX only antenna indoors in the sense that I set it up for a while just to monitor, switching back and forth between my dipole at 42'. As you might suspect, the dipole at height could easily hear things that the indoor magnetic loop could not. Once you move outside with the setup, things improve for the loop. I don't think I would want to permanently use a configuration like you're describing.
     
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  9. 2RT307

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    Cool. I know it's a compromise from any full size antenna, but thought the quietness of it might help me. I am just ok with my current setup, and looking to improve it.
     
  10. Chameleon Antenna

    Chameleon Antenna
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    To successfully operating a CHA F-LOOP or a CHA F-LOOP Plus from indoor, fews things must be observed.

    1. The quality of RX and TX of the unit will depend if a metallic material has been used to cover the roof and/or the walls of the building. If it's the case then the performances of the unit might be very low as barely nothing will get in or out of it.
    2. If you're living in a high density area and your antenna is located at the first floor or even worse at the basement of the building, the RX and TX will also greatly suffer. So try to get as close as possible from window or an outside wall.
    3. Install you unit as far you can from noise generator devices like large computer, flat screen TV, games machines like X-Box and PS4 and AC system.
    4. If you live in a two story building then operate the loop from the upper higher floor if possible. You'll reduce the noise level and the RF blockages produced by all the stuff that is a ground level and which will prevent your RX and TX to get out properly.
    With a good antenna location you should be able to achieve the following with a CHA F-LOOP or CHA F-LOOP Plus







    Cheers,

    Carl
     
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  11. Moleculo

    Moleculo
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    That's a very good point and one that I often assume people understand, but often don't consider. My house is a typical wood frame construction. However, it uses stucco for the external surface, which means that that the whole house is wrapped with chicken wire. It really does severely affect indoor antennas. On the other hand, it might be possible to make the whole house radiate if I wanted to, lol.
     
  12. 2RT307

    2RT307
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    I've been up in my attic, and there's a reason I don't have any antennas up there. Aluminum tape everywhere, the big honking heater that is metal, ventilation tubes with aluminum tape, etc. Never thought about tuning up the stucco house though, Moleculo! :)

    73,
    Brett
     
  13. Captain Kilowatt

    Captain Kilowatt
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    I had an AM TX house that was basically a Faraday cage. It was cement block construction with quarter inch hardware cloth metal screening under the gyproc. This was done to help safeguard against lightning as well as limit the RF getting into things. Yeah I know. Ironic. Cell phones lost service the minute you stepped inside and closed the door even though you could see the tower. Whenever we used HT's to communicate between the tx house and one of the remote towers we had to leave the door open or the signal was very poor even though we were only a few hundred feet apart. Some older houses had aluminum foil in the walls as insulation and getting a portable radio to work was nightmare unless you sat it on a windowsill.
     

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