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6 votes

Antenna tuning confusion - help!

Tuning at the antenna will give you the most accurate antenna characteristics, but a good VNA can cover up some of the inaccuracies from tuning at the end of the coax instead. However, you have to ...
user10489's user avatar
  • 6,415
6 votes
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What is the apparent AC voltage source caused by a mismatched impedance on the antenna or transmission line?

This would usually take a course in Transmission Line Theory, but we can give you the mechanical solution really quickly. Behold: THE SMITH CHART (in impedance form): Wow. A mandala! A fractal! What ...
Marcus Müller's user avatar
5 votes
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Understanding how antenna mismatch can damage a transmitter

There are a few parts to this, it's good to keep them separate. 1. Antenna impedance Antennas are complicated beasts, they connect the circuit world of voltage, current and power, into the ...
tomnexus's user avatar
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3 votes
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Lumped Solution for Impedance Matching vs. Ferrite Transformer

The statement above is...? True or false, depending on the losses of these components at any given operational frequency, and the bandwidths you need to achieve, as well as the impedance curve of ...
really not Constantine A. B.'s user avatar
3 votes

What is the output impedance of a typical solid state ham transmitter?

For efficiency the transceiver output impedance is much different from its rated load impedance. For modern 100W TRX expect an output impedance of a very few Ohms. An example: A tranceiver has a ...
Pete Singleton's user avatar
2 votes

Resonant 80m End Fed Halfwave Antenna With Counterpoise - Questions

Originally, I built an 80m EFHW, 130.5 feet long cut for approximately 3.58Mhz. I attached a 49:1 UnUn at the feed point 13 feet above the ground with coax back to the shack. I did not use a ...
Raonoke's user avatar
  • 131
2 votes

Understanding how antenna mismatch can damage a transmitter

– let's say we modify the antenna so its radiation resistance is only 15 ohms. Current increases to 330 mA, total power to 10 W, but only 1.7 W is radiated, with remaining 8.3 W lost as heat. I ...
Kevin Reid AG6YO's user avatar
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2 votes

Input impedance of a shortened dipole antenna

ZecosMAX: The calculation that doesn't really tell you specifically what you need to do for a dual-band antenna can simply be found here: https://www.66pacific.com/calculators/coil-shortened-dipole-...
Louis Seaman's user avatar
  • 1,025
1 vote

How do you decide on number of turns for twisted gamma match?

It seems to me a "twisted gamma match" is a way of getting a small magnetic coupling to the primary loop, with some extra resistive losses. There's no harm in trying it out, that's the ...
tomnexus's user avatar
  • 11.3k
1 vote

I would like to know more about designing broad bandwidth transformers and current baluns using binocular cores

The best reference is from Jim Brown, K9YC. http://audiosystemsgroup.com/RFI-Ham.pdf is a well-respected and accurate reference. Check out the documents available at http://k9yc.com/publish.htm and ...
Mike Waters's user avatar
  • 7,986
1 vote

SWR reading problems

The process is a bit more complex - first you need to calibrate the internal SWR meter, then you need to read it on the antenna. the manual says: Calibrate for SWR (Standing Wave Ratio) SWR ...
tomnexus's user avatar
  • 11.3k
1 vote

Antenna tuning confusion - help!

You are asking two questions, tune the antenna, or tune the coax/antenna system for low SWR. Or tune for best performance/tune for lowest SWR. They aren't mutually exclusive, but pretty hard to ...
Jimbo47's user avatar
  • 86

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