Hi Luis,
I changed the subject of the discussion.
Am 20.05.2015 14:34, schrieb VIGILANT Luis Fernández:
Hi Stefan
Which is the turn count on your
variometer ?? I can count about 10 in the internal coil but how many in
the outer coil ?
I don't know more than one can see on the image. My coil dimensions are
not relevant for you, just the principal configuration.
You can assume to have 5 pF/m, i.e. about 55 pF for your vertical
antenna. So for 475 kHz you will need L = 2.04 mH
There are many coil calculators in the web. I recommend such a simple
single layer coil. No need to spend to much effort here.
May be a variometer is not
needed as I can adjust the lenght of the antenna. Althought loosing
lenght (height) is never an advantage
a fixed coil would simplify the
test
Sure, at least for first experiments you can use a normal coil. You can
also start with a smaller coil, maybe 10 cm diameter and enamelled cu
wire. This is quickly done. But do not use ferrite or iron powder
cores! It must be an air coil.
Reducing the antenna height is not a good idea :-)
One of the reasons to
avoid using the vertical Ae hardwired to GND via coil is not to become
the Franklin lighthing arrestor of the building ! :-(
If the building is 80m high, your 11m vertical will not make a big
difference. You can also use a spark gap in parallel to the coil. I
have done the same here on my antenna, see
https://dl.dropboxusercontent.com/u/19882028/LF/20111106-19h58m31s-FF7_8466.jpg
73, Stefan
|
|
