Coaxial

What is characteristic impedance?

The RF world is full of esoteric terminology, and not least of these is characteristic impedance, or Z0. Most coaxial cables have a characteristic impedance of 50 or 75 ohms. If you want to know why 50 ohms was arrived at as a sort of standard for radio applications, you can read this post. In […]

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Antenna Tuners, Impedance Matching, and SWR

Antenna tuners seem to be some of the most misunderstood devices in all of amateur radio. In this article, I’ll try to explain what is happening when you use an antenna tuner. I’ll try not to get too much into mathematics, and I’ll also try to squash a few myths. I really don’t like the […]

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PL-259 Soldering

Do you solder the coaxial shield to the connector body when installing a PL-259 plug? What are those holes really for? I’ve been installing PL-259 plugs onto coaxial cable since I was about 16, and I’ve never soldered the body of the connector to the braid. I’ve not had any problems from not soldering the […]

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LMR-400 for Ham Radio?

I see lots and lots of posts from people extolling the virtues of using LMR-400 coaxial cable in their ham radio setups. LMR (Land Mobile Radio) cable was developed by Times Microwave Systems as a high quality coaxial cable which can be used with excellent loss properties at frequencies greater than 1 GHz. If your […]

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Coaxial Cable Length Does Not Change Antenna SWR

I’ve heard this for decades, and I first heard it when I got into CB radio when I was a kid. You’ve gotta to cut your coax to the right length if you want low SWR’s More accurately, if you are driving a mismatched load (e.g: a poorly tuned antenna) it depends where along the […]

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Why 50 ohms?

Coaxial cables, antennas, amplifier inputs and outputs, typically have either a 50 ohm or 75 ohm characteristic impedance. Why? It all comes down to the characteristic impedance value for maximum power transfer being 30 ohms, while the characteristic impedance for theoretical minimum attenuation (loss) is 77.5 ohms. 50 ohms is more or less in the […]

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