Message-ID: <5C4B514A.8020500@posteo.de>
Date: Fri, 25 Jan 2019 19:11:22 +0100
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: TXing WSPR/MF on an indoor loop
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Thanks Mal ;-) Don't worry, i'll be back with a real signal soon :-)
73, Stefan

Am 25.01.2019 16:33, schrieb mal hamilton:
> DK7FC QRP- how is this possible ---is the world coming to an 
> end!!!!!!!!!!!!!!!
> g3kev
>
>
> -----Original Message----- From: DK7FC
> Sent: Friday, January 25, 2019 2:23 PM
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: TXing WSPR/MF on an indoor loop
>
> Hi MF,
>
> A few days ago i took some RF litz wire and built a loop that is now
> hanging on the wall inside my home, just 1m besides the bed :-) (no XYL
> here spoiling the fun). The loop is beaming to about 150/330 deg.
>
> After playing some days on 160m (an unusual high frequency, witch feels
> very strange. And the band is full of unknown callsigns!!) i did now
> move down to more or less low frequencies, the 630m band!
>
> About 10 nF is needed to series resonate the loop. It has about 2m x 2m
> of size. The antenna current is not stable because the WIMA FKP-1
> capacitor becomes warm during the 2 minute WSPR sequence. But the
> maximum current in the loop is 14 A. That explains why the cap becomes
> warm. A small parallel variable capacitor tunes to resonance. It is
> tuned so that the upheating capacitor runs into the resonance point in
> the middle of the WSPR sequence, then it runs out of the resonance by
> upheating further. It can cool down during the following quiet periods..
>
> 14A into a 4 square meter loop at 475.7 kHz, how much ERP is that? The
> PA consumes about 3.5 A at 13.8V, i.e. about 50 W.
>
> The system will run over the weekend, even during daylight. The signal
> generator is a Raspi which will have no internet connectivity from now
> on, so let's hope the time offset stays inside the accepted range for
> this experiment.
>
> What will the best distance be? So far the band is closed but i'm
> optimistic to crack the 1000 km distance with this QRP setup.
>
> 73, Stefan
>