From: Chris Wilson <dead.fets@gmail.com>
Date: Tue, 9 May 2017 14:31:21 +0100
Message-ID: <1728082795.20170509143121@gmail.com>
To: Andy Talbot <rsgb_lf_group@blacksheep.org>
In-Reply-To: <CAA8k23SLs1pG26YV3450ipaziCFT=chKYWT9gSNnT2tUb6r1cw@mail.gmail.com>
References: <876597267.20170406161946@gmail.com> <B2AC21BCC3B544A5B26196BB6CEAA956@gnat> <8316279A81E04D0BBDCB4504B46041BE@StevePC> <D764E29331804232821ED4B647CEBBAF@gnat> <CAA8k23Q=ntzqCtQbuKGiQ=PWuuBHyRk16qPduDWOdxnEt7cHLQ@mail.gmail.com> <90CAB3E9321F4885BB239619EB9D7F7D@gnat> <CAA8k23SLs1pG26YV3450ipaziCFT=chKYWT9gSNnT2tUb6r1cw@mail.gmail.com>
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Subject: Re: LF: Re: Re: Re: Wilkinson combiners
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Status: RO

Hello Andy,
09 May 2017


I would like to try the transformer coupling, what turns ratio should
I use please? I will not try and be too clever and impedance match
there as well, i will leave the impedance matching transformer outside
by the loading coil for now, so as not to introduce too many
variables. Should I be OK winding on a stack of three FT-240 ferrite
toroids in 77 material that are in the combiner right now? And
finally, apart from the math to work out if a toroid might saturate at
a given power level, is their an instrument test to see if that is
occurring in real time? Thanks.


Best regards,
 Chris  2E0ILY                          mailto:chris@gatesgarth.com


 >> Why not keep it simple, and do it like the Decca transmitters?  
 >> Forget complicated splitters/combiners with messy deliberate
 >> isolation.  You are combining identical signals so that sort of design is not required.

 >> BEFORE any low pass filters, take each output of each transmitter
 >> module to separate identical primary windings on one, normal ferrite
 >> transformer core.  Use a single secondary to take the combined power
 >> off through a low pass filter to your antenna.   (But do size the
 >> core and turns for the TOTAL power to be generated)

 >> As both transmitter modules will be delivering identical outputs,
 >> the voltage induced in primary 2 coil from Tx module 1 will be
 >> exactly equal to the that delivered to it from Tx  module 2 (and
 >> vice versa)  so with both transmitters operating correctly, the
 >> outputs will sum in the secondary.    you are adding teh currents
 >> delivered by each stage, from an equal voltage delivered by both.  
 >> You are, to all intents and purposes, connecting the transmitters in
 >> parallel to multiply the current delivered in total

 >> You can use the combining transformer for impedance matching if
 >> wanted - for example the Decca ones  have direct drive to the
 >> primary windings via a tank circuit and each of the ( In their case
 >> three) primary to single-secondary turns ration ratio sets the impedance transformation.

 >> Isolating combiners like Wilkinsons only come into their own
 >> properly when non-identical signals need to be summed while keeping
 >> the two sources isolated.    Intermod testing in receivers is a
 >> particular case in point, where the two test signals have to be
 >> summed without generating their own intermod products caused by  the
 >> output of one source leaking into the (probably non-linear) output
 >> of the other.  If that happened, self-generated IMPS that could swamp those being tested-for.

 >> Andy  G4JNT


>  


-- 
Best regards,
 Chris                            mailto:dead_fets@gmail.com