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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IC-7000 current consumption

This article describes measurement of an Icom IC-7000 current consumption during SSB telephony transmission.

The capture is of an IC7000 running 100W PEP with compression off. I have read copy as loudly and consistently as I could with barely a breath, so it is an overestimate of current consumption. There was small ALC deflection, but not so much as to effectively provide compression. Compression will draw higher current, depending on the level of compression. Note too, that like many Icom radios, the IC7000 draws a relatively high current key down with no audio (4.5A here).

IC7000 current consumption
IC7000 current consumption

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