weirdjim
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weirdjim
Speak to me about your E/H loop antennas and what use do you make of them? HF or VHF?
Jim
Antenna/RF Technical Stuff
- Thread starter weirdjim
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Jim
The "Big" Magnetic Loop that I build from scratch is composed of 3/4 inch copper pipe in a big stop-sign octagon shape and has about a two meter diameter. It is mounted vertically with a resonant loop of around 16 inches, made out of a loop of two-wire extension cord wired directly to a section of RG-8U. The ratio is 1:5 between the loops.
I documented the build in hundreds of photos and videos and it took over three months to figure out how to assemble the thing and calculate the needed dimensions to make it resonant on 80 to 10 meters... The efficiency above 14Mhz is surprisingly high and the Q is much wider than expected. I was hoping for as little lower frequency, but it works!
The crazy part of the build is the massive capacitor I constructed of a combination of 3/4 and 1/2 inch copper tubing in a 8- element trombone style variable capacitor. In order to eliminate interference from metal and electrical fields, I made the tuning system out of plastic hydraulic cylinders built from PVC pipe and two kid's pool squirters...
It would take me all day to go through all the steps in the build, so I'll stop there. Here is a few images to start. I'll post more later, to keep this post a reasonable size:
Loop parts.
Capacitor Parts!
Gang "Trombone" Capacitor...
This is the perfect impedance for the four tubes. In order to handle the high voltage at the loop connection, more surface area is needed. That cuts the impedance in half, so I had to double the size of the capacitor...
Way too much soldering and adjustment of copper fittings...
The monster assembled!
Just right for 40 meters, but more needed for lower frequencies.
This 10,000 Volt doorknob cap brings the resonance down to exactly twice what all that copper does...
More to come. I'll show the hydraulic tuning mechanism and link to a video of it working!
I documented the build in hundreds of photos and videos and it took over three months to figure out how to assemble the thing and calculate the needed dimensions to make it resonant on 80 to 10 meters... The efficiency above 14Mhz is surprisingly high and the Q is much wider than expected. I was hoping for as little lower frequency, but it works!
The crazy part of the build is the massive capacitor I constructed of a combination of 3/4 and 1/2 inch copper tubing in a 8- element trombone style variable capacitor. In order to eliminate interference from metal and electrical fields, I made the tuning system out of plastic hydraulic cylinders built from PVC pipe and two kid's pool squirters...
It would take me all day to go through all the steps in the build, so I'll stop there. Here is a few images to start. I'll post more later, to keep this post a reasonable size:
Loop parts.
Capacitor Parts!
Gang "Trombone" Capacitor...
This is the perfect impedance for the four tubes. In order to handle the high voltage at the loop connection, more surface area is needed. That cuts the impedance in half, so I had to double the size of the capacitor...
Way too much soldering and adjustment of copper fittings...
The monster assembled!
Just right for 40 meters, but more needed for lower frequencies.
This 10,000 Volt doorknob cap brings the resonance down to exactly twice what all that copper does...
More to come. I'll show the hydraulic tuning mechanism and link to a video of it working!
I have also dabbled in EH/Poynting vector antennas made of aluminum foil wrapped around a plastic tube:
NOT MINE! Just an example from http://www.m0rzf.co.uk/EEF/index.html
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weirdjim
Ejection Handle Pulled
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weirdjim
Poynting vector.
Jim
Jim
Damn spell checker. Fixed it...
Initial Fix
Line Up and Wait
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Nice! 73