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.
[photo="large"]3578[/photo] 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.
[photo="large"]3546[/photo] 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:
[photo="large"]3551[/photo] 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:
[photo="large"]3550[/photo] 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:
[photo="large"]3576[/photo] 40 meter contacts:
[photo="large"]3577[/photo] 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:
[photo="large"]3552[/photo] 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:
[photo="large"]3553[/photo] 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:
[photo="large"]3547[/photo] 20 meter sweep:
[photo="large"]3548[/photo] 10 meter sweep:
[photo="large"]3549[/photo] 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.
[photo="large"]3578[/photo] 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.
[photo="large"]3546[/photo] 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:
[photo="large"]3551[/photo] 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:
[photo="large"]3550[/photo] 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:
[photo="large"]3576[/photo] 40 meter contacts:
[photo="large"]3577[/photo] 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:
[photo="large"]3552[/photo] 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:
[photo="large"]3553[/photo] 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:
[photo="large"]3547[/photo] 20 meter sweep:
[photo="large"]3548[/photo] 10 meter sweep:
[photo="large"]3549[/photo] 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.