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power loss in tuner ?

Jul 17th 2016, 00:37

AB3FN

Joined: Jun 5th 2007, 14:11
Total Topics: 0
Total Posts: 0
It seems obvious that some power loss will occur in an antenna tuner, and it also seems that many factors determine the loss, e.g. SWR, resistance in the inductor(s) and wiring, frequency, Q of components, etc. Although we could, hypothetically, use high quality instruments to measure the loss in any specific situation, how would the loss be calculated?

For example, assume that we know the frequency, component values, purely resistive losses of wiring, etc., how would we calculate the theoretical loss.

Given today's modern equipment, I doubt losses are high enough to worry about in most circumstances. But perhaps this matters more when running QRP, or when building miniature tuners or matching networks from scratch.

Thanks in advance for your comments, thoughts, guidance.
Jul 18th 2016, 14:06

WB1GCM

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
See our past Product Reviews of Antenna Tuners. We publish a loss chart. Most of the time, losses are under 10%, sometimes only 1 or 2 %. A loss of 10% is less than a 1 dB loss, which does not make a difference at the other end.

However, if you are loading up a very short antenna, with an impedance that is very low, you will have a much higher loss. Many tuners exhibit a 30% loss with a 12 Ohm load. At the legal limit, that's 450 Watts that's lost in the tuner. That much power lost means something inside the tuner will fail, quickly. That's why it's important to read our reviews.

As far as calculating the loss, there are too many factors involved to easily calculate that. If good quality components are used, the loss will be less.

Bob Allison
WB1GCM
ARRL Lab
Jul 18th 2016, 20:23

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
http://fermi.la.asu.edu/w9cf/articles/tuner/index.html
Estimating T-network losses at 80 and 160 meters

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