Chameleon P-Loop 2.0 & A Real Shark Attack- K6UDA Radio Episode 46

I'm on San Salvador Island in the Bahamas testing out the new CHA-P Loop 2.0. Made a 3,000 mile QSO with Dr. Balun back in California. You also get to see a little bit of my dive trip and an honest to goodness shark attack by not one but two sharks.

 

Well, the shark attack was neat.

 

Bob

Next why dont you test the new F Loop with the new remote rotor and tuner.

Glad your feeling better.

Ian

 

K6UDA

Thanks for the video. Nice job.

Tom
KB9UFE

 

Bob, a nice video and over view of your ham radio experiences on San Salvador Island.
I've had a go at building mag loops of approximately the same dimensions as the CHA-P Loop 2.0 and I too have had disappointing experiences on 40mts. I was using RG213 with the braid and core shorted together as the major loop. I had a look into this lack of performance and found the '66Pacific' site where they had a link to an ' antenna calculator' (the site address is
www.66pacific.com/calculators/small-transmitting-loop-antenna-calculator.aspx). The calculation showed showed that the efficiency of my antenna on 40mt was 10%. Which isn’t too good if you’re only working QRP 5Watts into it! According to the same calculator if I doubled the diameter of the primary loop to 7.2mts and tripled the conductor thickness to 30 mm the efficiency would soar to 73%. As it stands my mag loop is acceptable for 18MHz with a 76% efficiency. And these results are born out by the experiences you have had on 20 and 18mts.
73
Tony VK3CAB

 

Good video Bob beautiful place.
73
Glyn M6XXX

 

That's the problem with all these manufactured loops--they aren't really right for any frequency but supposedly can cover a lot of them, even if they do it poorly on most of them.

You might get away with a 1.5 or 2-turn loop on 40m and not have to double the size--just bundle the loop together on itself--either 1 full turn or maybe 1.5 depending on how you do it. I haven't seen a reliable calculator for that type. Uniform currents can be a challenge though.

Loops are cool though, but far more rewarding for the homebrewer than anything I bought out of a box.

 

Tony, I would think a 22 foot diameter loop would be practical for portable operation. Are you thinking feet vs meters or circumference(as the calculator uses) vs diameter?

 

Are you serious? My 7-foot diameter 40M loop is just "small" enough to carry about 25 feet out into my back yard to set up! 22 feet might require a forklift of some sort!

All of these commercial STLs that use braided coax are responsible for the bad reputation that they garner---if they would only get their act together and use solid and continuous copper or aluminum tubing with a proper vacuum variable the results would be far, far superior.

I can't imagine ever using one of these Chameleon or Alpha or Alex Loops unless I was into digital or CW modes they are so inefficient!

 

Here is another alternative small magnetic loop:

http://www.carasmfg.com

 

Oh! the embarrassment and me living in a metric country too! Of course I should have realised the 7.2 mts is circumference not diameter. Even so having a primary loop of 2.3 metres diam. presents some challenges when working portable. My mag loops are suspended on a cross of 27mm UV stabalised PVC water pipe. The top of the cross supports the primary and secondary loops and the left and right arms hold the RG213 primary out so that it forms a reasonable circle. The ends of the primary loop are terminated in PL259 connectors which in turn screw into SO239 sockets. This makes for a good solid connection.The variable capacitance is a paralleled two gang 420pF (? or there about) with a 6:1 vernier drive. I also have a high voltage 50pF fixed capacitor that can be brought into series with a wander lead to lower the capacitance and get the antenna down to around 20MHz. The whole thing is mounted on top of a pointed broom handle which can be pounded into the ground and the PVC tubing slid onto the end. I find the mag loops extraordinarily sensitive in adjustment, highly directional but great fun to play with. A colleague of mine is making one out of 25mm copper pipe and with a primary loop of around two metres diam. Good luck to him!
Tony VK3CAB

 

That's what I was saying, I think he mixed diameter with length, the 66pacific page calculator uses FEET of loop length, not meters in diameter. Either way homebrew is the way to go with low resistance construction as it will be a cold day in Miami before I pay $400 for 20 feet of coax and a capacitor for a manually tuned loop. No offense to anyone's fine products. Five feet is the minimum diameter for a 7mhz loop for about 25% efficiency, all else being ideal, with 10mhz up being much better.

 

Yeah, another case of people mixing up diameter with circumference.

Coincidentally, my homebrewed 40M loop is 22-feet in circumference which equates to right about 7 feet in diameter. I've been working great dx with it since I finished building it recently and it can handle 600+ watts PEP. For me, this is the way to go with my STL as I like to chase dx and want the best results I can achieve from my condo backyard. No, I don't use digital modes or CW at all but if I did something less QRO capable would suffice.

I know what you mean about paying hundreds of dollars for a bit of coax, tripod and a boxed air variable cap, too. For the same amount of money one could build at least one or even two much more efficient STLs with vastly superior performance. The key is good construction, a continuous conductor (not coax braid!) and a vacuum variable capacitor. While one built this way would not be "foldable" it could still be made light enough to carry or use in a portable application. Soft copper HVAC tubing or solid shield Heliax is your friend here.

The 66pacific.com calculator is OK but I prefer the KI6GD Loop Calculator instead---it allows one to input other parameters such as shape and conductor type which also have a bearing on the operating specifications---although all online calculators are a rough guide at best.

Anyone interested in using or building a STL should read VK5KLT's well-written 32-page article for further small loop enlightenment; I find it most illuminating:

https://www.nonstopsystems.com/radio/pdf-ant/article-antenna-mag-loop-2.pdf

73, Jeff

 

Perhaps but not necessarily. Not everybody has time or capability or inclination to build their own magnetic loop antenna. And some manufactured antennas do offer good performance and do not cost hundreds of dollars.

While I am certainly not against homebrewing and do my share, I also am in support of those who support themselves and their families and the economy in general by producing and selling a good product. This is what drives our system.

 

People are free to make their own choices and spend their money as they wish; true, many don't have the capability or inclination to build their own STL. But if they do, they'll understand why I continue to promote them as great DIY antennas for us in restricted antenna situations.

One thing that really annoys me about all of the STL manufacturer's claims and advertising is that they continue to promote the term "magnetic loop" when the only thing about them in that regard is their near-field radiation. After the signal is beyond that they radiate and receive like any other antenna in the electrical plane as well as the magnetic plane.

Small transmitting loop or fractional wave antenna is much more accurate term to use but many will insist on promoting erroneous information as usual...