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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 8th Jul 2019, 2:46 pm   #21
Jon_G4MDC
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Default Re: 4 port Wilkinson combiner / splitter question

Here is the MW/LW hybrid coupler. Found deep in the shed.
Board has a corner that got cracked at some time.
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Old 9th Jul 2019, 1:39 pm   #22
Chris Wilson
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Default Re: 4 port Wilkinson combiner / splitter question

Oooh, big pots! I'll show you mine later just doing the cabling tonight. Thanks Jon, is it for sale....?
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Old 9th Jul 2019, 4:46 pm   #23
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Default Re: 4 port Wilkinson combiner / splitter question

Haha sorry Chris it's a bit of history to me so not for sale.

Happy to discuss the making of something similar though. It works just like the 600 Ohm
ones for POTs using 3 windings on each transformer.
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Old 9th Jul 2019, 11:21 pm   #24
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Default Re: 4 port Wilkinson combiner / splitter question

Quote:
Originally Posted by Skywave View Post
Many, many years ago I read of an approach to address that issue by Pat Hawker in an issue of his Technical Topics. When using an LPF, the idea was also to have an HPF, its input connected to the input of the LPF and the output of that HPF terminated in a resistive load. The essential idea is that the reflected HF components, rejected by the LPF, are accepted by the HPF and are consequently dissipated in its resistive load. That prevents them (ideally all; probably, in practice, most of them) from appearing at the output of the driving RF source.
I've never tried that idea, but I can see that it has some validity.
Al.
It's a valid method if you are simply interested in making the pesky energy at harmonic frequencies just go away.

However, there is another approach. If it is reflected with the right phase delay it winds up back at the merrily switching PA device and gets re-chopped. Some of the harmonic energy gets converted to the wanted output frequency and with care this can be made to be of a helpful phase and combines with the wanted output. The other products keep getting reflected back and re-chopped until they eventually make it out as wanted output. The overall efficiency climbs. I have a 120MHz PA running comfortably over 80% efficiency, including matching losses, filter losses, and detectors on a directional coupler. Perfect class C has a theoretical max limit of 66.6666%

Once you can play this game over a moderate bandwidth, you qualify as a mage of the 8th order and get a free pointy hat with 'Wizzard' written on it, (in crayon).

David
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Old 11th Jul 2019, 10:27 am   #25
Jon_G4MDC
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Default Re: 4 port Wilkinson combiner / splitter question

That could be a good wheeze for a band as narrow as the 136kHz allocation.
Then the combiner could be quite narrow band too.

I have also made quadrature hybrids from bifilar wound ferrite inductors with capacitors across the ends of the windings.
Never for a frequency as low as 136kHz but why wouldn't it work? It's fine at 50 and 70MHz.
That range was never available from a certain company. I therefore called this the winger coupler.
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Old 13th Jul 2019, 11:01 am   #26
Chris Wilson
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Default Re: 4 port Wilkinson combiner / splitter question

Quote:
Originally Posted by Jon_G4MDC View Post
Haha sorry Chris it's a bit of history to me so not for sale.

Happy to discuss the making of something similar though. It works just like the 600 Ohm
ones for POTs using 3 windings on each transformer.
Thanks Jon and i quite understand! I may have a go at a transformer combiner next, just for the experience.
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Old 13th Jul 2019, 11:03 am   #27
Chris Wilson
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Default Re: 4 port Wilkinson combiner / splitter question

Quote:
Originally Posted by Radio Wrangler View Post
Quote:
Originally Posted by Skywave View Post
Many, many years ago I read of an approach to address that issue by Pat Hawker in an issue of his Technical Topics. When using an LPF, the idea was also to have an HPF, its input connected to the input of the LPF and the output of that HPF terminated in a resistive load. The essential idea is that the reflected HF components, rejected by the LPF, are accepted by the HPF and are consequently dissipated in its resistive load. That prevents them (ideally all; probably, in practice, most of them) from appearing at the output of the driving RF source.
I've never tried that idea, but I can see that it has some validity.
Al.
It's a valid method if you are simply interested in making the pesky energy at harmonic frequencies just go away.

However, there is another approach. If it is reflected with the right phase delay it winds up back at the merrily switching PA device and gets re-chopped. Some of the harmonic energy gets converted to the wanted output frequency and with care this can be made to be of a helpful phase and combines with the wanted output. The other products keep getting reflected back and re-chopped until they eventually make it out as wanted output. The overall efficiency climbs. I have a 120MHz PA running comfortably over 80% efficiency, including matching losses, filter losses, and detectors on a directional coupler. Perfect class C has a theoretical max limit of 66.6666%

Once you can play this game over a moderate bandwidth, you qualify as a mage of the 8th order and get a free pointy hat with 'Wizzard' written on it, (in crayon).

David
I thought I had read of recombining, but I am nothing like ready to try this, the wizard's hat is a long way off, I am still wearing my dunce's one <LOL> Very interesting though. Thanks.
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Last edited by Chris Wilson; 13th Jul 2019 at 11:09 am.
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Old 13th Jul 2019, 11:21 am   #28
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Default Re: 4 port Wilkinson combiner / splitter question

Chris: The LPF circuit which you posted at the start of this thread can be adapted to form the leg(s) of the Wilkinson combiner.

The C-L-C topology used in the lumped combiner circuits is a narrow-band approximation to a quarter-wave line: by increasing the number of elements in this lumped circuit you get closer to modelling the behaviour of a true transmission line. I guess it's a practical matter of whether you're happy to wind a few coils to make this combined 3-way hybrid / LPF?



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