Talk:Antenna tuner

This article currently is fairly specific to amateur radio, rather than being "encyclopedic". This is not suggesting that the current information is not useful, merely that the article covers a very narrow view of its subject to the exclusion of the majority of the topic material. 75.140.243.0 (talk) 14:36, 9 January 2009 (UTC)

DIAGRAM ERROR

Inductor and capacitor need to be swapped from the cited image http://en.wikipedia.org/wiki/File:Basicnetworkatu.svg . Diagrams further down in the article, specifically the equivalent circuit diagrams, are correct. Furthermore, external references such as http://home.sandiego.edu/~ekim/e194rfs01/jwmatcher/matcher2.html and http://leleivre.com/rf_lcmatch.html agree with the latter article diagrams. — Preceding unsigned comment added by 76.104.2.80 (talk) 21:09, 8 September 2012 (UTC)

FORMULA ERROR

Here are the formulae copied and pasted from the article...

XL = {(Rsource+jXsource)([Rsource+jXsource]-[Rload+jXload])}0.5

and

XC = (Rload+jXload){(Rsource+jXsource)/([Rload+jXload]−[Rsource+jXsource]}0.5

In the Xc formula, the parantheses are unpaired. I have had to guess what the real meaning is. Here are my interpretation in Excel: (is this right?) Rsource = b2 jXsource= b3 Rload = b4 jXload = b5

XL = SQRT(((B2+C2)^2)-(B4+B5)) XC = =(B4+B5) * SQRT((B2+B3)/((B4+B5)-(B2+B3))) the square root is taken across that entire term. (?)

Also, if the sum b2+b3 is negative, then there is an error (root of a negative number). This can happen if the jXsource is capacitive and large. Or an error can arise if b2+b3 is larger than b4+b5. duh. Baruchatta (talk) 20:31, 25 January 2008 (UTC)

Need Real World Advice

This article needs some real world advice on how to use an antenna tuner. For example, all of the "how it works" examples show how to match one resistor value (1000 ohms) to another resistive value (50 ohms). BUT IF MY ANTENNA WAS RESISTIVE (RESONANT) I WOULD NOT NEED AN ANTENNA TUNER! I would like to see advice on how a reactive antenna (too short or too long, capacitive or inductive) is matched to a transmitter. Also, if an antenna is resonant at one frequency, what is its resistance and reactance at another frequency. For example, if an antenna is resonant at 5 MHz, what is its values at 3 MHz? --Baruchatta (talk) 14:50, 25 January 2008 (UTC)

This article could use some discussion about how to build an antenna tuner. It might be useful in this to mention complex conjugate matches. --ssd 04:44, 21 October 2005 (UTC)

How to

This article used to have a section on how to use an ATU, which I wrote. That has since been removed because "The section on the use of ATUs has been removed becuase [sic] WP should not be how to guides" I expect that also means they should avoid becoming how to build guides as well.

Sigh, I personally think both of these would add value to the community and should really be allowed to stay. This article is now terribly complicated with much math and very little use to someone who might actually want to find out any practical information on ATUs. For the record I think the math section is important as well. But not more than how you may typically operate one.

J3gum 05:46, 12 March 2007 (UTC)

I agree that the tuner article needs more info, the author should look at the literature

http://fermi.la.asu.edu/w9cf/tuner/tuner.html

and look at the mathematics in dispute.

I have added some comments about the PI configuration , which is better then the T configuration. Missing parts are :show matching in the Smith diagram and comments about values and voltage/current handling needs of the components. The "Single side band" Collins book shows the real and imaginary Z values of a whip antenna and some thoughts about the need.

Ulrich L. Rohde N1UL , Jan 2009 —Preceding unsigned comment added by 67.84.179.142 (talk) 22:49, 18 January 2009 (UTC)

I had added that while modern solid state power stages do not like an SWR above 1.5, in reality an antanna VSWR of 2 means 11 % of power is refelcted, 11 Watts out of 100 supplied, 89 Watt send forward in the antenna. Tube amplifiers using the Collins filter could easily tune this out. I hope this sataement does not get removed again. Ulrich L. Rohde, N1UL —Preceding unsigned comment added by 67.84.179.142 (talk) 02:27, 17 February 2009 (UTC)

Here's the likely reason it was remove (and I didn't do it, so I'm just guessing). VSWR (any level) does not cause any line loss. Reflected power is not lost. The reflection will be re-reflected by the source. The only loss that will occur is the additional trips back and forth over the lossy transmission line. If the line is of relatively high quality (low loss) the useable VSWR can be relatively high. J3gum (talk) 03:57, 24 September 2009 (UTC)

Somethings wrong in the calculation

In the calculations complex numbers are changed into non-complex numbers.

X_L = j 217.94 Ohms

But later

X_L = 2πfL

L = X_L/(2πf) = 1.239 μH

is incorrect, because there is no "j" in the formula:

L = X_L/(2πf) = j 1.239 μH

Z=R+jX = j*j 217.94 Ohms = - 217.94 Ohms

Quality and importance ratings

I think this article is much better than it was a few months ago, if not, I have wasted a lot of time. Is the C quality rating something that gets re-evaluated from time to time? Also, I can't understand why this topic, with over 100 visits a day and lots of interest in the ham community is considered of the same importance as Antarctic call signs and other low importance designated topics. Does anyone know if these ratings are reviewed and if so how it happens? JNRSTANLEY (talk) 21:04, 23 October 2014 (UTC)

What is "backlash current"?

I am not able to find any references that describe "backlash current". Is this another way to describe reflected power? If we are to use this term in the article, I think people need to know what it means, otherwise use more commonly understood terms. JNRSTANLEY (talk) 13:48, 3 April 2018 (UTC)

I agree. I feel this term should not be used, as you say the accepted terminology in radio is "reflected power". Edited introduction to remove this term and improve clarity. --Chetvorno^TALK 19:08, 3 April 2018 (UTC)

Article size

The article seems to be much too big for a single encyclopedia entry. Perhaps it should be split into several smaller articles.107.242.121.7 (talk) 03:43, 16 October 2019 (UTC)

Proposed Rewrite of Section

I am proposing that the entire section "Types of L-networks and their uses" be replaced with the following text and graphic. The present graphic, which I originally prepared, and which has been usefully modified by others, is nevertheless somewhat misleading in its labelling, requiring a lot of rather convoluted explanation with multiple footnotes. Please let me know if this more concise rewrite is an improvement, or make suggestions for improving it.

Types of L-networks and their uses

The 'L'-network can have eight different configurations which are shown in the diagrams at the right.

All eight possible ‘L’-network circuits and there use

Circuit selection

If the load impedance is plotted on a Smith Chart, it will fall into one of the four regions shown. In each region are numbers indicating which circuit can be used to match an impedance in that region. For example, an impedance that falls within the small right circle labled R>50 can be matched using circuits 1 or 3. For a complex impedance falling anywhere in the chart either 2 or 4 different circuits could be used so additional criteria may be used to decide which circuit to choose. This chart was made with 50 ohms at the center. For matching to to other values of R such as 75 ohms, that value should replace 50 everywhere in the Smith Chart.

Additional selection criteria

The low pass circuits shown in the top row (1 and 2) use one inductor and one capacitor. Normally, low-pass would be preferred with a transmitter, in order to attenuate possible harmonics. The high-pass configuration shown in the second row, (3 and 4) may be chosen if the components are more convenient, or if the radio already contains an internal low-pass filter, or if attenuation of low frequencies is desirable – for example when a local AM station broadcasting on a medium frequency may be overloading a high frequency receiver.

In some cases it may be desirable that the circuit either pass or block DC currents. Thus the series (horizontal) component should be either an L or a C. In addition, it may be useful for the phase shift across the network to be either advanced or delayed.

In automatic tuners typically either circuit 1 or 2 is chosen. Many commercial autotuners can switch the C to either the left or right side of the inductor, thus both circuits 1 and 2 are available without additional components. As shown by the green and red sections of the Smith Chart, these two circuits can cover all possible loads, provided the minimum and maximum values of the inductor and capacitor are sufficient.

Loads such as a small transmitting loop may be highly inductive. The impedance will fall well into the L dominant region of the Smith Chart. They can make use of circuit 6 although most designs feed them via an even smaller coupled loop. Short vertical antennas such as used for HF mobile, are C dominant and can be easily matched with circuit 8. However with both of these examples, there are three other circuit options.

Measuring instrument limitations

Older SWR meters do not indicate complex impedance, so they are not very helpful for determining which circuit to use in an L network. Antenna analyzers, however, can separately show the resistive and reactive parts of the antenna impedance, and are suitable for selecting the orientation of an 'L' network. The most convenient of these analyzers are able to plot the complex impedance on a Smith Chart display. When an instrument indicates the complex series impedance, but not the shunt (parallel) equivalent, formulas or a calculator can be used to make the conversion to the parallel values. When complex impedance information is not available, a circuit can be chosen by assuming that a high impedance can be matched using circuit 1 and a low impedance using circuit 2. However where there is a significant reactive component, this simplified rule may fail.

Q and Phase shift

Unlike more complex networks, the L network does not allow independent choice of operating Q and phase shift. High Q leads to more loss and a narrow operating bandwidth. It is made greater when the load impedance differs greatly from the impedance to be matched. Phase shift can be made to either lead or lag by circuit choice, but like the Q, its value is determined by the impedance ratio. Phase shift is only important if two or more loads are to be fed, such as in AM broadcast directional arrays.

references (m,n, and o) can be deleted. Additional sources can be added, suggestions welcome)

JNRSTANLEY (talk) 16:07, 22 June 2022 (UTC)

References

Beware of Calculation error at section "3.3.1.1 Theory and practice"

I understand that the section wanted to describe how to "make 1000 Ohm load appears as 200 Ohm" from the input impedance point of view. All of the 4 diagrams describes the idea/concept of adding "inductive or capacitive" components at the 1000 Ohm load correctly, however the 3rd and 4th diagram have calculation mistakes, the newly calculated inductances does not let me arrive at the final (200 + j*0) Ohm .

I am guessing the writer wants to give an idea of how the computation goes, not emphasizing on mathematical accuracy. (E.g : Equivalent impedance of parallelizing inductor (j409.82) and capacitor (-j5200) should be (+j444.88)inductive. )

Correct me if i am wrong. :) Hope it would help others out. Douglas Koo Chen Soon (talk) 17:00, 6 July 2022 (UTC)

Douglas, thanks for catching this error. That it has gone so long without being detected tells me that very few folks work through the math in this section. As part of further simplifying this article, I propose the section "Theory and practice" be replaced with the following. The math is simpler and the method one which is very easy to apply:

Theory and practice

T-network match for a partly reactive load

An example of matching with the low pass T network is shown here. The load measures 200 -J75 ohms representing both a resistive and capacitive part. Conceptually, the -j75 ohms can be cancelled by adding a series inductor with +j75 ohms reactance. This leaves a pure 200 ohms to be matched. This is done with a 100 ohm Quarter wave impedance transformer, consisting of two inductors with +j100 ohms reactance and a shunt capacitor with -j100 ohms. The quarter wave transformer uses reactances that are the geometric mean of the two resistances to be matched. The output inductor of the quarter wave network can be combined with the inductor used to cancel the reactance of the load. The final network will have +j100 ohms for the input inductor, -j100 ohms for the capacitor and +j175 ohms ofor the output inductor.

I will wait a few days for feedback and if no one objects I will replace the section as above or with any modifications that others suggest.

JNRSTANLEY (talk) 16:00, 7 July 2022 (UTC)