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LF: Re: A simple ULF/MF diplexer?

To: "[email protected]" <[email protected]>
Subject: LF: Re: A simple ULF/MF diplexer?
From: Rik Strobbe <[email protected]>
Date: Fri, 26 Aug 2016 12:36:26 +0000
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Thread-topic: A simple ULF/MF diplexer?
Hi Stefan,

if you can keep both transmitters from feeding power into each other it should 
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 
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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