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I just assumed 50 ohm coax was used because its a carry over from the amateur radio groups and there is lots of info from them. Certainly not as much info when applied to OTA antenna contruction and tuning.
 

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Discussion Starter · #22 ·
I just assumed 50 ohm coax was used because its a carry over from the amateur radio groups and there is lots of info from them. Certainly not as much info when applied to OTA antenna contruction and tuning.
Yes I had no idea myself but it seems to be a very very good way to Gang or stack identical antennas. To me it's like black Magic. A guy who doesn't know anything about this stuff would wonder why you can't just split the signal.

I would like to find out more about the Wilkinson power divider but for now, I like my quarter wave Transformer stub sections.
 

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Discussion Starter · #24 ·
Yurii, thanks for sharing that . That was pretty darn cool . I had no idea that all these properties were the same across different sources

Tapered section transformer? Applicable for OTA signals ?
 

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Tapered (triangular), tapered (exponential), tapered (stepped) are very widely used impedance transformers in microwaves.
Main objective to go tapered is wideband matching.

With microstrip (either printed PCB, or copper wires inside box) it is very easy to construct any desired impedance.

Unfortunately, math behind wave transformation (including Wave/4 case) is quite complicted, it involves hyperbolic cos/sin on complex numbers.
12029

12030


I did Excel worksheet for this formula, but it is not practical for real-world use:

All real-world calculations are done using circuit simulators.
Popular amateur free circuit simulator is RFSim99.

I use circuit simulators from HFSS package, it allows integration (data-exchange) between 3D models (e.g. antenna drawing) and circuit simulator.

Tapered transformers have very limited usage in coax, as nobody manufacture coax cable other than 50 and 75 Ohm.
For some special cases (powerful broadcast transmitters, radar and other military applications) it is possible to manufacture any coax line using pipes/tubes. But they are very bulky and costly for any home usage.
PCB or copper wire inside box are much cheaper.

The simplest example of tapered transformer is 2-step Wave/4 transformer, which consist of 2 sections (each Wave/8 lenght).
You can replace your 50 Ohm Lambda/4 coax line, with two sections, one 45 Ohm and second 55 Ohm, Lambda/8 each.
It will perform similar to one-piece
 

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Yuri, that was a great video. A picture is worth a 1000 words.
 
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