Using Tuner to Determine Line Input Impedance
 

On Jun 3, 2:17*pm, dave wrote:

http://ytdp.ee.wits.ac.za/smithchart.pdf

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8763

I don't run Linux Dave. Is there a Windows version? Meanwhile I am
going at it manually with a Smith Chart. At multiple frequencies this
will take some time.

Dykes AD5VS

Using Tuner to Determine Line Input Impedance
 

From: dykesc
Date: Wed, 3 Jun 2009 Time: 10:57:52

I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.


Is this any help?

http://www.wy2u.com/

Scroll down to "Electrical / Electronic Engineering Links" and click on
"L/C Impedance Matching Design Tool"

--
73
Ian, G3NRW

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
On Jun 3, 2:17 pm, dave wrote:

http://ytdp.ee.wits.ac.za/smithchart.pdf

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8763

I don't run Linux Dave. Is there a Windows version? Meanwhile I am
going at it manually with a Smith Chart. At multiple frequencies this
will take some time.

Dykes AD5VS


you can do it with an Excel Spreadsheet..

You know that at "match" the impedance looking into the tuner from the
antenna is the conjugate of the impedance looking into the antenna from
the tuner.

If you assume your transmitter is 50+j0 ohms (not a good assumption..
but you could make it closer to being so by putting a 10dB pad between
Tx and tuner, for instance)

Then, you calculate what the impedance the tuner is using the L and C
values (I assume it's a series L and a shunt C) ... you'll either have:

TxR plus L, shunted by C
or TxRshunted by C, then series L

A spreadsheet like XLZIZL does it in a flash.

Using Tuner to Determine Line Input Impedance
 

On Jun 4, 2:10*am, Ian Wade G3NRW wrote:

Is this any help?

http://www.wy2u.com/

Scroll down to "Electrical / Electronic Engineering Links" and click on
"L/C Impedance Matching Design Tool"

--
73
Ian, G3NRW

Thanks Ian. That is the type of calculator I am looking for. However,
this one requires both source and load impedance as input. I am
looking for one that will allow you to specify the source impedance
(50+j0), fill in the capacitor and inductor values, and then tell you
what the matched load side impedance is.

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
I am
looking for one that will allow you to specify the source impedance
(50+j0), fill in the capacitor and inductor values, and then tell you
what the matched load side impedance is.

That is a trivial problem. What configuration?
What does the schematic look like?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Using Tuner to Determine Line Input Impedance
 

On Thu, 4 Jun 2009 09:19:42 -0700 (PDT), dykesc
wrote:

That is the type of calculator I am looking for. However,
this one requires both source and load impedance as input. I am
looking for one that will allow you to specify the source impedance
(50+j0), fill in the capacitor and inductor values, and then tell you
what the matched load side impedance is.

The source code is at:
http://www.hoflink.com/~mkozma/match19cb.html
which, if you can follow the design and make your own changes, should
be ammenable to your needs.

73's
Richard Clark, KB7QHC

Using Tuner to Determine Line Input Impedance
 

"dykesc" wrote in message
...
On Jun 4, 2:10 am, Ian Wade G3NRW wrote:

Is this any help?

http://www.wy2u.com/

Scroll down to "Electrical / Electronic Engineering Links" and click on
"L/C Impedance Matching Design Tool"

--
73
Ian, G3NRW

Thanks Ian. That is the type of calculator I am looking for. However,
this one requires both source and load impedance as input. I am
looking for one that will allow you to specify the source impedance
(50+j0), fill in the capacitor and inductor values, and then tell you
what the matched load side impedance is.

Hi dykesc

I may be missing something. But, if the objective it to learn if the
local 105 MHz signal is actually introducing error into your impedance
measurement, only a few Smith Chart Polts are needed. You know the path (on
the Chart) the shunt reactance will have taken while being adjusted to make
a "match". You also know the path the series reactance took. Start from
the Chart center and move the impedance along the circles of constant
resistance for the series reactor. Move along the circles of constant
admittance for the shunt reactance. When the Xc and Xl are both known, and
you know which is closest to the "transmitter", it seems that a "program" is
unnecessary. What am I mising?

Jerry KD6JDJ

Using Tuner to Determine Line Input Impedance
 

Jerry wrote:
"dykesc" wrote in message
...
On Jun 4, 2:10 am, Ian Wade G3NRW wrote:

Is this any help?

http://www.wy2u.com/

Scroll down to "Electrical / Electronic Engineering Links" and click on
"L/C Impedance Matching Design Tool"

--
73
Ian, G3NRW

Thanks Ian. That is the type of calculator I am looking for. However,
this one requires both source and load impedance as input. I am
looking for one that will allow you to specify the source impedance
(50+j0), fill in the capacitor and inductor values, and then tell you
what the matched load side impedance is.

Hi dykesc

I may be missing something. But, if the objective it to learn if the
local 105 MHz signal is actually introducing error into your impedance
measurement, only a few Smith Chart Polts are needed. You know the path (on
the Chart) the shunt reactance will have taken while being adjusted to make
a "match". You also know the path the series reactance took. Start from
the Chart center and move the impedance along the circles of constant
resistance for the series reactor. Move along the circles of constant
admittance for the shunt reactance. When the Xc and Xl are both known, and
you know which is closest to the "transmitter", it seems that a "program" is
unnecessary. What am I mising?


Fine, for doing a couple or three. Now do it for a dozen measurements
at different frequencies, especially if you have to convert L and C into
Z for each measurement. A program or spreadsheet is nice to have,
because it automates the tedious calculation.

Heck, if you have a RS-232 interface to the antenna tuner, you can
automate the whole process. Quod fecit.

By the way, the assumption that the run of the mill ham rig has a 50 ohm
resistive output impedance is not necessarily valid. In practice,
nobody cares.. they just adjust until the reflected power is minimized.
But if you're trying to use the tuner as a measuring instrument
(essentially, the variable part of an impedance bridge), it's important.

Using Tuner to Determine Line Input Impedance
 

dykesc wrote:
On Jun 3, 2:17 pm, dave wrote:

http://ytdp.ee.wits.ac.za/smithchart.pdf

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8763

I don't run Linux Dave. Is there a Windows version? Meanwhile I am
going at it manually with a Smith Chart. At multiple frequencies this
will take some time.

Dykes AD5VS


RF Cafe has one that uses Excel. www.rfcafe.com

Using Tuner to Determine Line Input Impedance
 

On Thu, 04 Jun 2009 11:47:31 -0700, Jim Lux
wrote:

By the way, the assumption that the run of the mill ham rig has a 50 ohm
resistive output impedance is not necessarily valid.

By the way, this comment above is another assumption in that it lacks
a quantifiable. I find it offered quite often as a negative assertion
to which the several many posters who offer them never provide an
actual value to prove what the run of the mill ham rig is, much less
is "not." Rarer, indeed, is any effort put forward by those posters
to show they have attempted to quantify their own equipment.

As there are posters here who have performed this work, shown their
data, and such data follows conventional design considerations (which
is easily revealed within the page cited at http://www.wy2u.com/);
then these assumptions dressed in denial are rather unprofound proofs.
As this topic has been visited many times, and as it quickly descends
into equally unsupported claims (although often annotated with vague
references and citations that are quickly demolished); I doubt
anything said here is going to sway those assumptions.

As an amusing exercise (I anticipate none will tread down this path),
the page at http://www.wy2u.com/ offers a means to test your own rig's
Source Z - if, in fact, you can cope with translating your tuner's
settings into picofarads and nanohenries, and if you can obtain a
known mismatch. These impediments are Herculean to most,
unfortunately.

73's
Richard Clark, KB7QHC