Re: Any info about making air variable capacitors, and magnetic loops?
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Here are a couple of pdf articles that might help.
Marco - KG5PRT?
On Jun 21, 2017 8:34 AM, "Michael Hagen" < motdog@...> wrote:
I have never heard an outside signal on my bit40.? Testing with a
signal generator I get signals down to or below 10uV?
I have no antenna, but a wire out the door brings in nothing but
a little more noise.
To make others happy, I could hide the loop when not
experimenting.? No one I know nowadays knows what a Ham is!
I am gathering parts for a loop.? I got 8 3/4" 45 Degree "El".? I
am going to get 2 10' sticks of the thinner 3/4" copper pipe.
If I cut to 8 pieces, there will be 2 1/2 ft. per section.? So
the loop should be 6 ft or so.
I found an online store an got the copper fitting a lot cheaper
than the Home Depots around here.? About 1$ a fitting.
There is an L and M designation.?? For the drive loop, the
hardware stores sell rolls of 1/4" copper tubing.
To get started just to receive, the little Polyester AM radio
capacitors will work.? With a real high Q, I will just tune for
noise (I hope).
I have seen people put big wire or coax in Hula Hoops. But not Tin
Foil?? To maintain High Q, you might need less resistance?
If I have any results that warrant the expense, I will buy a vacuum
variable.? But the $3 AM radio variable is used everywhere and
in a lot of low power Ham projects.
Mike, WA6ISP
On 6/21/2017 12:08 AM, M Garza wrote:
When I built my 10M loop, I used this calculator:
I liked this calculator, since it provides
approximate voltages the cap will see and I could play with
the figures to see the outcome.
Depending on the rf power, you could see several
thousand volts at the cap.? They also have a capacitor
calculator, you could use that to design a cap.
You could use coax capacitors, high voltage
caps, air variables, trombone style, or vacuum variables, just
to name a few.? Search you tube, there are a ton of examples.
I am feeding the loop with a toroid and 3 turns
of #12 wire.? Similar to VK6CS in these videos:
To connect a motor to the cap, use some kind of
insulated shaft coupler to keep the high voltage off the
motor.? Make sure to bypass the motor terminals with a 0.1uf
cap to try and keep the rf out of the motor.? I would suggest
a geared motor, ?something with a low RPM.? You could vary the
voltage to the motor, to control tuning speed.
Hope that helped some.
Marco - KG5PRT?
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