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Re: LF: Re: A simple ULF/MF diplexer?

To: "[email protected]" <[email protected]>
Subject: Re: LF: Re: A simple ULF/MF diplexer?
From: Rik Strobbe <[email protected]>
Date: Fri, 26 Aug 2016 18:53:06 +0000
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Thread-topic: LF: Re: A simple ULF/MF diplexer?
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 

73, Rik  ON7YD - OR7T
Van: [email protected] <[email protected]> 
namens DK7FC <[email protected]>
Verzonden: vrijdag 26 augustus 2016 15:18
Aan: [email protected]
Onderwerp: Re: LF: Re: A simple ULF/MF diplexer?

Hi Rik,

OK, a picture tells more than 1000 words:
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: [email protected]<[email protected]>  
> namens DK7FC<[email protected]>
> Verzonden: vrijdag 26 augustus 2016 13:46
> Aan: [email protected]
> 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

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