Variable caps and MW loops.

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bigbassman
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Variable caps and MW loops.

Postby bigbassman » 30 Jul 2012, 14:25

I'm in the process of building a MW loop using a 3 ft Hula hoop and 9 turns of stranded speaker wire.All good so far,but I've noticed that everything I've picked up so far seems to be concentrated at the one end of the V/caps travel ie almost wide open.The cap is a dual-gang 375 & 260 pf.Am I right in thinking that the vanes and body of the cap are separate from each other? That might sound very basic but I've found continuity between the vanes of the 375pf section and the body.I've also noticed no interference at all when I touch the cap. with my hand.
The loop seems to work as I'm in S.Co Down,and I can get Radio Clyde 2 in Glasgow on 1152khz clearly,but still can't understand why everything is focussed with the cap wide open.Any pointers? Hope I've made myself clear :)
1 X PRO 2006 1 X DX-394 1 X GRE PSR 282 1 X UBC780XLT with ProScan 1 X Pro43 2 X Uniden UBC9000XLT Tristar777 LCL 2740.

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26CAB40
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Re: Variable caps and MW loops.

Postby 26CAB40 » 30 Jul 2012, 14:34

Are you using a coupling loop ?
You may have to play around with the value of the capacitor.

http://www.mds975.co.uk/Content/aerials1.html
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bigbassman
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Re: Variable caps and MW loops.

Postby bigbassman » 30 Jul 2012, 14:50

Yeah,the coupling loop is a single turn around the hoop on top of the others.Which is better do you think,this one or a small loop about 1/5 the diameter of the main loop?I've seen the latter used more often.Cheers.
1 X PRO 2006 1 X DX-394 1 X GRE PSR 282 1 X UBC780XLT with ProScan 1 X Pro43 2 X Uniden UBC9000XLT Tristar777 LCL 2740.

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26CAB40
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Re: Variable caps and MW loops.

Postby 26CAB40 » 30 Jul 2012, 15:32

bigbassman wrote:Yeah,the coupling loop is a single turn around the hoop on top of the others.Which is better do you think,this one or a small loop about 1/5 the diameter of the main loop?I've seen the latter used more often.Cheers.


Suck it and see I think, if it's easy enough to try both, do so.
The plastic rod on the tuning knob trick should stop the hand-capacitance issue though.
"It's worth whatever they're willing to pay"


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