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Wall Loop 20m.

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by PD7MAA, Feb 15, 2016.

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  1. PD7MAA

    PD7MAA Ham Member QRZ Page

    This max. size magnetic loop antenna for 14 MHz with a totall circumference of 6m. ( 19.68 feet ) is designed to attach to a wall . Not sutable for reenforced concrete walls . It has a no tune bandwidth of more than 300 KC with a centre swr of 1 : 1.1 The 150 pF parallel capacitor was the best value in my situation ( brick wall ) but can be replaced by a 250 pF tuning capacitor in order to find the lowest SWR at resonance. First contacts gave good reports in Europe. For max. performance be sure that the 'hot' side of the antenna points to the window. A test was made with 100 Watts without arcing however 5 Watts are more than enough for indoor use...
    The top capacitor is made of twisted antenna wire or a piece of 25cm RG-213 coax and is cut for tuning to the frequency . This antenna can also be build on a fibre frame for field or attic use.

    wall loop 14 MHz.jpg walloop capacitor (Small).jpg 20m. walloop 150pF at feedpoint (Small).jpg feedpoint with line choke (Small).jpg
    Last edited: Feb 15, 2016
    AE4LH, KD6RF, AK5B and 1 other person like this.
  2. KC8YLT

    KC8YLT Ham Member QRZ Page

    This looks like a good antenna project. Thanks for sharing!
  3. KH6AQ

    KH6AQ XML Subscriber QRZ Page

    Very nice! This is great antenna for apartment dwellers and you might like to write an article for one of the magazines or eham to let more know about it.
  4. VE3DXK

    VE3DXK XML Subscriber QRZ Page

    Can this loop be used outside, close to the ground (on wooden fence, for example)?
  5. PD7MAA

    PD7MAA Ham Member QRZ Page

    Yes . You only need to make the connections waterproof HI. A diamond shape base fed version should also be possible.

    73 John PD7MAA
  6. AK5B

    AK5B Ham Member QRZ Page

    That's really cool, John. One of the things I love about these antennas is the way we can try out all sorts of clever and ingenious variations to adapt them to a particular situation.

    Yes, it is the ultimate stealth antenna!

    Although it is hard to tell from the photos I suppose you must have used enameled wire for that twisted pair capacitor, right?

    73, Jeff
  7. G0VKT

    G0VKT Ham Member QRZ Page

    Hi John,

    Curious as to how you came up with the idea. It's an STL with a (sort of) gamma match perhaps? It will make an interesting comparison antenna to try at my mobile home (I will be experimenting with EFHWA's over the coming months). Can build it with what's in the junk box!

    73, Paul.
  8. KH6AQ

    KH6AQ XML Subscriber QRZ Page

    Shunt capacitor, and shunt inductor, matching methods step up the feedpoint impedance and are often used on low band mobile antennas.
  9. PD7MAA

    PD7MAA Ham Member QRZ Page

    Hello Jef

    The wire used is 1.5 mm PVC covered stranded copper wire . If you use transformer wire you must use a coax capacitor of aprox. 25 cm at the top.

    73 John
  10. PD7MAA

    PD7MAA Ham Member QRZ Page

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