Ham Radio - The Chameleon Antennas power compensator for magnetic loops.

THIS^

Someone wiser than myself (and I can't put my finger on exactly who right now maybe W8JI ?? ) talked about how there is this holy trinity with antennas; Efficiency, Bandwidth, Size . You can optimize any two at the expense of the third. Truer words were never spoken. Probably you can really only optimize one while compromising with the other two. Lots of snake oil out there but nobody has gotten around this law.

 

Endlessly accessorizing the most expensive ham-stick should be the other name for this outfit .
And others like it .

I have to admit I bought one of there 1st versions some yrs. ago [ in storage & out of production , so can not give model ] .
Gave some thought to if I could find another cheap enough , I might make a dipole with 2 most expensive hams sticks

 

Consider a "couple" of factors
1. round or disc-shaped objects are similar to "a single shorted turn coil" in the near field of an inductor (loop) and have a specific effect in an RF circuit or antenna;
2. self-resonance of 500pf doorknob capacitors can be near the HF frequency range, which when placed in the near field may increase the coupling between the loop and the disc of the doorknob in the HF range;
3. the doorknob lowers the overall loop system Q because it is sharing the field with the loop, but the doorknob also radiates, so it isn't as lossy of a technique as a resistive or lossy dielectric component would be for lowering Q;
4. the effect may be somewhat diminished at lower or higher frequencies, depending on the loop geometry and components.

 

Well, anyone who doubts the ability of magloops to put out a good signal should read my carefully-conducted WSPR examination of such an antenna. No 'magic', no human bias, just pure results:

https://mw1cfnradio.blogspot.com/2018/06/magnetic-loop-careful-what-you-believe.html

 

Good work there, John. I like the interesting triangular feed system--I gotta try that! I don 't know where that meme came from, 'Magloops are nothing more than dummy loads.' Maybe they've never successfully used one/made one. I know the military has been using magnetic transmit/receive loops for decades. I believe there's a commercial magnetic loop array in Bern at Bernradio they use for ship-to-shore communications.

 

It's simple. No need to spend 15 minutes watching a video. To make a small antenna as efficient as possible, you want to make the current as uniform as possible over the length of the antenna by using as much capacitance as possible at the ends of the antenna. That's all that this "power compensator" (their name for a capacitor) is doing. You want to use an antenna that is physically small compared to the wavelength only when you have no other choice. It's a little bit better than a leaky dummy load.

 

That would be true for the capacitor between the ends of a loop. This capacitor is only connected to one end of the loop and not even used as a capacitor because the other endof the capacitor is not connected to anything. So this capacitor does nothing as a capacitor. It's just a parasitic "load" on one end of the loop, thus lowering the Q. And that will also lower the current through the loop and the voltage across the tuning capacitor, allowing more power to be input to bring the radiated power to the same level as without the "power compensator". This is just a fake product, sold to make money and to make you feel good.

 

There is no PHYSICAL connection, but the other plate of the capacitor DOES couple to the loop and affect its performance. Otherwise, I agree with you completely. W8JI has a very good explaination of "magnetic loops" on his website: https://www.w8ji.com/magnetic_receiving_loops.htm

 

That is exactly what I meant with "It's just a parasitic "load" on one end of the loop". If this device had been a metal disc, it would have had the exact same effect.

 

I agree completely

 

So far it looks like everyone agrees its a HV cap with one end attached to the loop on one side of the tuning cap inside the box. The other end is just left hanging in the air.

Sure there is some stray capacitance to ground, to the loop and to the tuning cap in series with this 500pf cap. Maybe this stray is 50 pF ( just a guess). These two caps, the stray capacitance and 500pf in series give a total capacitance of 45 pF. I think the experiment would benefit from a field strength (FS) measurement made with 5 Watts and a FS measurement at the maximum power that the compensator is rated for.

If there is a way to measure loop current that would be nice to have as a check. Both measurements would be made when tuned to match the signal source.

 

If you watch the video he verifies everything to be working except for far field results.
1. The tuning cap did not arc with higher input power
2. The addition of the cap did not reduce near field signal strength at the same input power
3. Adding more input power with the cap resulted in higher near field signal strength.

I would like the debunkers to explain how this thing increases near field signal strength but does not increase far field signal strength.

 

He measured the same field strength at the same input power with or without the extra cap.
He measured higher field strength with higher input power and no apparent bad effects.
I would like it explained how these results show a "parasitic load".

 

His measurement is completely unreliable because of the short distance to the antenna. His field strength meter picks up everything, including standing waves on the outside of the coax to the antenna. Measuring the E field too close to the antenna and cable means nothing. The theory of resonant circuits is quite clear and proven: lower Q means lower voltage. So if he can output more power with this "compensator" without arcing on the cap, it simply means that the Q of the resonant circuit is lower than without the compensator. The only thing that influences the Q of a resonant circuit is electric or magnetic loss. So this "compensator" must introduce some sort of loss on the resonant antenna.
I would like to see this measurement repeated in the far field, which is for an electromagnetically short antenna, at least 2 lambda away from the antenna.

 

Sounds great , maybe we can get him to to that. He is active on YouTube and responds to his subscribers.