From: Rik Strobbe <rik.strobbe@kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: LF: Re: A simple ULF/MF diplexer?
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Date: Fri, 26 Aug 2016 18:53:06 +0000
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Subject: Re: LF: Re: A simple ULF/MF diplexer?
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Hi Stefan,

the picture makes clear what you intend to do.
A possible pitfall could be the behaviour of the 1.3H coil at 475kHz (self resonances).

73, Rik  ON7YD - OR7T
________________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.org> namens DK7FC <selberdenken@posteo.de>
Verzonden: vrijdag 26 augustus 2016 15:18
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Re: A simple ULF/MF diplexer?

Hi Rik,

OK, a picture tells more than 1000 words:
https://dl.dropboxusercontent.com/u/19882028/ULF/ULF_MF_Diplexer.jpg
While drawing the picture i saw that i had to correct my idea. The
transformer should be in series and i have to think about the lower
series C. Another thing is that the MF transmitter should act as a
shortcut for ULF so the transformer does not act as a (saturated) L. So
the picture is updated.

73, Stefan

Am 26.08.2016 14:36, schrieb Rik Strobbe:
> Hi Stefan,
>
> if you can keep both transmitters from feeding power into each other it should work.
> But one thing to keep in mind is that the 2nF parallel capacitor needed on ULF will reduce the overall (antenna + parallel C) resistance at 475kHz significantly.
> It is not clear to me what configuration you intend to use, but maybe you should try to avoid that the 2nF cap is drawing a lot of 475kHz current.
>
> 73, Rik  ON7YD - OR7T
>
> ________________________________________
> Van: owner-rsgb_lf_group@blacksheep.org<owner-rsgb_lf_group@blacksheep.org>  namens DK7FC<selberdenken@posteo.de>
> Verzonden: vrijdag 26 augustus 2016 13:46
> Aan: rsgb_lf_group@blacksheep.org
> Onderwerp: LF: A simple ULF/MF diplexer?
>
> Hi all,
>
> I would like to run some transmissions on MF WSPR but i also like to run
> a longer transmission on 2.97 kHz. In the current ULF TX installation
> i'm using a parallel 2 nF capacitor anyway. This is just -j167 Ohm on
> MF. I could series compensate it with 65 uH (which is just j1.2 Ohm at
> 2970 Hz :-) ) to ground. The 65 uH could be parallel compensated for MF,
> using 280 nF. Then i could add a ferrite transformer to apply the MF RF
> across the 65uH/280nF parallel circuit. The large loading coil of 1.3 H
> will be a high impedance, hopefully, as long as there is no internal
> resonance on MF due to its own winding capacity.
> The 2 nF capacitor will have to handle the sum current of ULF and MF.
> QRO is not possible on MF i think but it will handle a few watts which
> is fine for WSPR. Hmm, worth a try?
>
> 73, Stefan
>
>
>