Re: LF: Tee- Ant. vs Loop ?

[brian hodgson <g3ykb@yahoo.co.uk>]

Hi Uwe - I would go along with what Jim says - ie if you have the space, put up some kind of vertical (T or inverted L).

 

I've never had much room for a decent LF antenna - I started off by erecting an inverted-L but since moving house I cannot even do that (small garden, bungalow, and in a conservation area !!! - not a good formula for big aerials......). I have managed to string up a modest loop  - 9.5m long by 3.5m at 1.5m from the ground (that's so small it does not even get onto Alan's spreadsheet !!). However, it does seem to put out a signal of sorts - best Dx is 600 km using 150 watts QRSS3.

 

The loop wire (single turn) is satellite coax cable - the type with the copper foil outer conductor. It has a dc resistance of half an ohm and total rf resistance of just under one ohm. RF current is about 13 amps. I match it to 50 ohms using an L-match (switched fixed capacitors for coarse tuning an d a small variometer for fine tuning).

As Jim says, the capacitors have to cope with quite high voltages and take all the current (I use several in parallel).

 

One major problem with a fixed loop is that, like a dipole, it is directional (two nulls). On the plus side - earth stakes are not needed and there is little risk of those nasty RF burns!!

 

Best of luck with whatever antenna you use - Brian 

 

Uwe Wensauer <uwe.wensauer@gmx.de> wrote:

To all ,

 

I would like to built a Tx antenne but with linited space I need at least a bulky 4 mh and variometer.

 

So I wonder if I could not use a loop antenna ( 20x 10m ) ? So I would not need such big coils ?

 

( high voltage vs. high current )

 

73, Uwe, DK1KQ

 

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