A small ferrite core inside a coil realizes the magnetic loop antenne to be tuned.
No expensive vacuum glass capacitors - which are often used in this type of antennes - are required. The antenna is designed for the 80m band and is constructed in a way that portability is garanteed.
Two fixed value high capacitors (120 pF / 10 kV) are used; this type of capacitors can easily be found and are not expensive.
Richard has used this antenna with SSB RF powers up to 100 Watts and that is a lot for this type of antennas. I would keep great distance from this antenna while using this amount of power. (Magnetic) fieldstrengths are enormous in the near field of this antenna. Take care !
The complete story:
http://www.v2g.nl/site/images/stories/downloads/projecten/Portable%20magnetic%20loop%20antenne.pdf
This article was published earlier in the "QRP Nieuwsbrief 132, December 2009"
The pdf file is NOT FOUND. Looks like an interesting design.
ReplyDeleteCheck out this URL -
ReplyDeletehttps://a19.veron.nl/wp-content/uploads/2016/02/Portable-magnetic-loop-antenne.pdf
This seems to work - Although it is in Dutch -
I downloaded this on Feb 27 2018