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

Discussion in 'Amateur Radio News' started by KB7TBT, Nov 3, 2019.

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  1. NH7RO

    NH7RO Ham Member QRZ Page

    Kudos for your astute observations; many good points in your meaty post. ( The emphasis added above is mine)

    Via no-holds barred optimization it is possible to create a small "lizard-like loop" that can roar like a Komodo Dragon---but that requires the best components at greater expense and size not always feasible with the vast majority of manufacturers.

    The sole exception might be Ciro Mazzoni's massive TIG-welded Midi Loop---perhaps Ciro could rename his "The Dragon" since it practically breathes flames by comparison!

    73,

    Jeff
     
    Last edited: Nov 5, 2019 at 6:11 PM
  2. N4RL

    N4RL Ham Member QRZ Page

    It seems like the point of this is to make a trade off that lowers Q, and thus allows for minor frequency adjustments without retuning, while increasing power to try and offset diminished performance. Is that how others see it?
     
  3. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    Well, the lower Q also lowers the radiated field strength. The relation between produced field strength and applied power is linear. So if this device lowers the Q to allow you to push more power into the antenna to eventually reach the same field strength, then the only thing gained is the extra money in the pockets of the manufacturer...
     
    N6SPP likes this.
  4. VE3VXO

    VE3VXO Ham Member QRZ Page

    "while increasing power to try and offset diminished performance. Is that how others see it?"

    He said his air variable could handle up to about 15 watts of RF power before it would arc. With the addition of the hockey puck capacitor he could run 30 watts. So this "compensator" made a 3db improvement in the power handling capacity, but the question is did he realize a 3db increase in the far field strength? It's fine to dump more power into an antenna but if he added 3db of loss then it isn't going to make any difference in being heard. In terms of QSY without re-tuning, until you get north of 1/4 wave circumference for the size of the radiator, the Q is going to be so high that you won't be able to move much at all without re-tuning, hockey puck or no. It is a fact of life with small transmitting loops that you are always re-tuning them. Where broadening can help is when the Q gets so high that you can only use CW because the bandwidth is too narrow for phone. In that case the answer is to raise the radiation resistance by using a larger circumference, NOT broadening the response by adding loss.
     
  5. W7SJP

    W7SJP Subscriber QRZ Page

    I sure appreciate what you do for the hobby--I know it's mostly a labor of love. It'll be sad to see you stop producing this, but I can understand the reasons.
     
    K7LZR likes this.
  6. VE3VXO

    VE3VXO Ham Member QRZ Page

    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.
     
    KR3DX likes this.
  7. KD0CAC

    KD0CAC Ham Member QRZ Page

    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 ;)
     
  8. KQ6XA

    KQ6XA Ham Member QRZ Page

    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.
     
    Last edited: Nov 6, 2019 at 8:09 PM
  9. MW1CFN

    MW1CFN Ham Member QRZ Page

    W7SJP likes this.
  10. W7SJP

    W7SJP Subscriber QRZ Page

    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.
     

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