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Re: LF: EA5DOM vertical

To: [email protected]
Subject: Re: LF: EA5DOM vertical
From: DK7FC <[email protected]>
Date: Wed, 20 May 2015 15:02:16 +0200
In-reply-to: <[email protected]cal>
References: <[email protected]cal>
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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

73, Stefan
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