-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
11 meter Magnetic Loop antenna
- Thread starter NF822WNY
- Start date
I think this is going to be the way to go super compact and can handle the power...My hair is already turning grey, dont need it to fall out too. Thanks for the input fellas! 73's
It depends on how close you are to it. Stick the numbers into here and it'll tell you if you're in compliance with FCC exposure limits.
http://hintlink.com/power_density.htm
In the second table of results at the bottom it'll say: Does the Area of Interest Appear to be in Compliance?
Last edited:
Compact, light weight, broad band width, QRP is where magnet loop shines. If I remember right a 4 watt input is 400 volts at the tuning cap. So as you want to add power the price of the cap even if it is an air variable and not a vacuum variable get's heavy and expensive fast due to voltages. Losses drop off quickly when you start to build them with fairly large copper tubing and solder everything instead of using coax with connectors etc.....Anyone that is familar with Alpha's multiband loop antenna package and how compact it is can see the allure. They are also cheap and easy to build if you keep the power input on the low side. People will use them for QRP contesting int he field or to use indoors when lightning is a real risk. Depending on the size and what you make it out of it they do not scream "antenna" if you sive some place you can not mount an antenna even to a balcony etc....
IN my mind the biggest safety issue is arcing or touching the exposed tuning cap etc if you do not enclose it. When 4 watts in equals 400 volts at the tuning capcitor you can see how input power can get deadly quickly. On top of that since all wire or tube stock has resistance and you have large high voltages heat can become an issue real quickly too.
They can be really broad band if not worried about efficiency drops. It does not take much capacitance change to change the tuning. That said you have to re-tune anytime you make a tiny freq. change. It is not at all hard to keep SWR at 1.5:1 or bellow 2:1 even really pushing the bandwidth more than you should. Obviously great SWR does not equal really effeceint antenna but it should keep most radio's and amplifiers happy.
There is a guy on youtube that has built a 1000 watt magnetic loop and the capacitors where ordered from Russia to keep cost down.
IN my mind the biggest safety issue is arcing or touching the exposed tuning cap etc if you do not enclose it. When 4 watts in equals 400 volts at the tuning capcitor you can see how input power can get deadly quickly. On top of that since all wire or tube stock has resistance and you have large high voltages heat can become an issue real quickly too.
They can be really broad band if not worried about efficiency drops. It does not take much capacitance change to change the tuning. That said you have to re-tune anytime you make a tiny freq. change. It is not at all hard to keep SWR at 1.5:1 or bellow 2:1 even really pushing the bandwidth more than you should. Obviously great SWR does not equal really effeceint antenna but it should keep most radio's and amplifiers happy.
There is a guy on youtube that has built a 1000 watt magnetic loop and the capacitors where ordered from Russia to keep cost down.