Category Archives: transmission lines

Diode ring mixer

A picture says a 1000 words.. this is an ancient mixer on e-bay recently, I have one for experimentation. It looks well designed (baluns to keep the mixer balanced, and tight twists), and is from a military device (UFT 721 … Continue reading

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Transmission line transformers (TLT)

Worryingly, there are comments here: http://www.eham.net/articles/24502  that are simply wrong, and cause a lot of confusion to people trying to understand this topic. “In order for Z0 to matter, in the TEM mode, one must use a relatively long transmission … Continue reading

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More dielectric constants

Since these are so hard to find, I’m going to record all findings. According to a 1961 document called Plastic-Film-Dielectric Capacitors by C. B. Charlton, high density polyethylene is 2.2, and low density polyethylene is 2.25. Polystyrene is 2.55. Polycarbonate … Continue reading

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More on transmission lines

PTFE has a more constant (!) dielectric constant over a reasonable frequency range (not that the 4 ohms delta of Kynar from 1MHz to 100MHz is a particularly significant amount), and apparently PTFE’s constant is about 2.1. Farnell sells wire … Continue reading

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Transmission line calculation tool

Since the steps were too much, this excel file was created. In the spreadsheet, the green values can be entered, and it will calculate the characteristic impedance, and the twists per inch for a given twist pitch angle. It will … Continue reading

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Twisted pair transmission line

For constructing transmission lines, coax is useful because it is available in 50 and 75 ohms. For transmission line transformers, the coax can be used, but it is quite thick. Twisted pair or parallel pair wires can be useful in … Continue reading

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