Design / build project: Guanella 1:1 ‘tuner balun’ for HF – #2

Second part in the series…

 

Common mode impedance

When baluns are used with open wire feed lines to wire antennas on HF, most commonly the main purpose is to suppress common mode current, to ensure that the current in one wire of the feed line is equal but opposite in direction to the other wire at that point.

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Design / build project: Guanella 1:1 ‘tuner balun’ for HF – #1

This is a project to design and build a Guanella 1:1 (current) balun for use on HF with wire antennas and an ATU.

First part in the series…

 

For use with a tuner, the most important design criteria are:

  • high voltage withstand;
  • high common mode impedance;
  • generous power handling given our 400W PEP limit, possibly 1kW in the future.

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WIA 4:1 current balun – further explanation

4-101a

I mentioned in my article WIA 4:1 current balun that the use of a single toroidal core in the above graphic compromises the balun. This article gives a simple, but more detailed explanation for the technically minded of why the shared magnetic circuit ruins the thing.

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Foundation manual on power measurement

My article Foundation watts explained triggered some discussion on the thorny issue of compliance with power limits of the LCD.

One correspondent was confident that the Foundation candidates are properly trained, which leads to examining the training materials.

SWRMeter

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Do SWR meters make you stupid

Eric Nichols, KL7AJ, published a manifesto entitled “SWR Meters Make You Stupid” announced on eHam in March 2010. Eric is clearly a disciple of Walt Maxwell (W2DU SK), his first announcement states By popular demand, my complete treatise on transmission lines. Approved by Walt Maxwell, W2DU as if Walt’s blessing was an imprimatur from the ham radio church.

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Common mode current and coaxial feed lines

An antenna feed line is intended to convey energy from the transmitter to the antenna, and usually without giving rise to radiation itself.

The term “common mode” comes from consideration of the currents on an open two wire line, and it refers to the net  or unbalance current, ie the current that would give rise to external fields, to radiation.

This article looks at the equivalent common mode current in a coaxial transmission line.

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A/B comparison test on 40m

An extended test comparing signals received in Florida from three nearby stations in Australia was conducted 21/12/13, a low elevation path of more than 14,000km.

The A/B comparisons were performed on statistics gathered from the W4HBK grabber, in this case measurements of the noise and each of two transmissions of 1min of steady carrier every 5min over a half hour.

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