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Author Topic: RF transformer confused schematic  (Read 2278 times)

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Offline kendalll

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RF transformer confused schematic
« on: March 24, 2016, 11:50:40 pm »
I'm confused by the schematic symbol for this RF transformer drawn as a choke. But if you look at the pin names, and the location of the dots, it looks like it's actually a 'standard' configuration transformer. Anyone know why this is? I posted in the RF section figuring maybe you guys might have run into this before.

Does anyone know why it's shown this way in the schematic for the ETC1-1-13? http://cdn.macom.com/datasheets/ETC1-1-13.pdf

 

Offline rfeecs

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Re: RF transformer confused schematic
« Reply #1 on: March 25, 2016, 12:39:00 am »
It's a transmission line transformer balun they are spec'ing like a power splitter.  Pin 1 is the input.  Pins 3 and 5 are the outputs.

Refer to figure 3a:
https://www.minicircuits.com/pages/BalunApplicationNote.htm
 

Offline G0HZU

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Re: RF transformer confused schematic
« Reply #2 on: March 25, 2016, 02:01:47 am »
Google for 1:1 "current balun"   :)
 

Offline German_EE

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Re: RF transformer confused schematic
« Reply #3 on: March 25, 2016, 04:25:40 pm »
The schematic is incorrect anyway because a dot is normally used to indicate the start of a winding. One coil has two starts and the other coil never starts at all.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline rfeecs

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Re: RF transformer confused schematic
« Reply #4 on: March 25, 2016, 04:47:33 pm »
In this case, the dot indicates the polarity.  They are calling pins 1 and 2 the primary and pins 3 and 5 the secondary.  Secondary dot pin 5 is in phase with primary dot pin 1.  Pin 3 is 180 degrees out of phase.
 

Offline Richard Head

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Re: RF transformer confused schematic
« Reply #5 on: March 29, 2016, 06:36:12 am »
The drawings a cock-up. No wonder you are having a problem understanding it!The dots indicate the relative phasing of the windings and there should be a single dot on each winding, not two on one winding.
 


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