"Oliver Gebele" wrote
i am using a Collins-Filter with 2 variable
capacitors and a switched inductor (Pi).
Obviously there are infinitely many possibilities
to match an antenna.Are there any preferred
possibilities? And how would i adjust my box
to do this? (Maybe there are already links on
the internet that i did not find.)


======================================

Matching networks, with 2 C's and 1 Coil, can be either Pi networks or
T networks. The Pi network, with the coil in series, also behaves as
a low-pass filter and for this reason it is to be preferred. But the
T network has more convenient and therefore less expensive values of L
and C. So for economic reasons manufacturers sell more T than Pi
networks. Pi-networks have considerably larger coils and capacitors,
but in general they are equally efficient when working between the
same transmitter and antenna impedances.

As has already been pointed out, with a T network, 2 series C's and a
shunt coil, least loss nearly always occurs when the coil, in
conjunction with the C's has it's lowest inductance. But component
settings are quite uncritical.

Problems occur only when one or other or both of the capacitors are
very near to their minimum settings, ie., little more than stray
capacitance remains in cicuit. The capacitors may then arc over
(which is immediately apparent). Or the coil turns may become
overheated when attempting to run 1 Kwatt or more (which may take a
minute or so when operating CW or FM).

I mention overload circumstances only because the effects and worries
are too often exaggerated in these newsgroups. So don't lose any
sleep! Even if half the power is lost in your tuner your signal
strength falls by only 1/2 of an S-unit.

To become familiar with series T-Match Networks download program
T_TUNER from website below. Any impedance R+jX can be matched to any
other R+jX. But usually the Tx or generator impedance is a purely
resistve 50 ohms which simplifies understanding of what's going on.

Other practical programs, from the very few I've seen, only manage to
match two purely resistive impedances. Which with radio antennas
seldom exist.

Download program T_TUNER in a few seconds and run immediately. Go from
"Index" to "Download Progs from Here" page and run immediately.

There are several other programs of various sorts which include
operation and component values of T and L-match transmitting circuits.
If you are accustomed to calculating how many rolls of wallpaper are
needed to re-decorate your shack then you will feel at home.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

VSWR isn't a REAL problem! Deal with it!

VSWR is real and ENGINEERS and Ham Radio operators make transmission
lines and antennas work; while Physicists wonder if it's real or
uncertain. [My 80 meter antenna has a VSWR of 30:1. It works just
fine!]

=====================================

Anything will work after a fashion. It's no proof of anything.

It is not realised by many amateurs and engineers that the so-called
SWR meter does not measure SWR. It merely indicates whether or not
the transmitter is loaded with its design resistance. Which, of
course, is useful.

The meter not located in the right place to measure SWR on the
feedline. The feedline on which it is imagined SWR is measured does
not exist.

To measure SWR on any line a moving voltmeter is required. SWR is
simply max volts divided by min volts which occur at a distance apart
of 1/4-wavelength if the line is long enough, and requires no
knowledge of line impedance or its terminating impedances, or of
anything else about the line.

In other words, SWR is just something for Old Wives and "clever"
people to plagiarise and waffle about, on newsgroups and in the
magazines, and so continue to mislead themselves together with the
unfortunate learners, CB-ers, and the novices.
----
Reg, G4FGQ

"Reg Edwards" wrote in message
...

VSWR isn't a REAL problem! Deal with it!

VSWR is real and ENGINEERS and Ham Radio operators make
transmission
lines and antennas work; while Physicists wonder if it's real or
uncertain. [My 80 meter antenna has a VSWR of 30:1. It works just
fine!]

=====================================

Anything will work after a fashion. It's no proof of anything.

It is not realised by many amateurs and engineers that the so-called
SWR meter does not measure SWR. It merely indicates whether or not
the transmitter is loaded with its design resistance. Which, of
course, is useful.

The meter not located in the right place to measure SWR on the
feedline. The feedline on which it is imagined SWR is measured does
not exist.

To measure SWR on any line a moving voltmeter is required. SWR is
simply max volts divided by min volts which occur at a distance
apart
of 1/4-wavelength if the line is long enough, and requires no
knowledge of line impedance or its terminating impedances, or of
anything else about the line.

In other words, SWR is just something for Old Wives and "clever"
people to plagiarise and waffle about, on newsgroups and in the
magazines, and so continue to mislead themselves together with the
unfortunate learners, CB-ers, and the novices.
----
Reg, G4FGQ

================================

In other words, ENGINEERS make transmission lines and antennas work by
copying what was done last time.

Nothing has changed since Oliver Heaviside, 1875 - 1925.

If anybody mentions G5RV I shall cry.
----
Reg, G4FGQ

Reg Edwards wrote:
"Reg Edwards" wrote in message
...

VSWR isn't a REAL problem! Deal with it!

VSWR is real and ENGINEERS and Ham Radio operators make

transmission

lines and antennas work; while Physicists wonder if it's real or
uncertain. [My 80 meter antenna has a VSWR of 30:1. It works just

fine!]

=====================================

Anything will work after a fashion. It's no proof of anything.

It is not realised by many amateurs and engineers that the so-called
SWR meter does not measure SWR. It merely indicates whether or not
the transmitter is loaded with its design resistance. Which, of
course, is useful.

The meter not located in the right place to measure SWR on the
feedline. The feedline on which it is imagined SWR is measured does
not exist.

To measure SWR on any line a moving voltmeter is required. SWR is
simply max volts divided by min volts which occur at a distance

apart

of 1/4-wavelength if the line is long enough, and requires no
knowledge of line impedance or its terminating impedances, or of
anything else about the line.

In other words, SWR is just something for Old Wives and "clever"
people to plagiarise and waffle about, on newsgroups and in the
magazines, and so continue to mislead themselves together with the
unfortunate learners, CB-ers, and the novices.
----
Reg, G4FGQ


================================

In other words, ENGINEERS make transmission lines and antennas work by
copying what was done last time.

Nothing has changed since Oliver Heaviside, 1875 - 1925.

If anybody mentions G5RV I shall cry.
----
Reg, G4FGQ



G5RV
73,
Tom Donaly, KA6RUH

On Fri, 24 Jun 2005 20:51:54 +0000 (UTC), "Reg Edwards"
wrote:
Nothing has changed since Oliver Heaviside, 1875 - 1925.
Nothing has changed since Ptolemy (85-165) - Oliver, who's she?

On Fri, 24 Jun 2005 17:04:26 -0700, Richard Clark
wrote:
Ptolemy (85-165)
Something from his Almagest, Book 1, that is vaguely descriptive of
someone we all know and love:
"Well do I know that I am mortal, a creature of one day.
But if my mind follows the winding paths of the stars
Then my feet no longer rest on earth, but standing by
Zeus himself I take my fill of ambrosia, the divine dish."
This epigram follows the table of contents as something of a
self-dedication (also a mannerism we are familiar with).

Ptolemy also reduced much of his theory of Astronomy and Optics to
geometric construction techniques in many Handbooks and offered scads
of tables of observations - some of which were condemned by Newton:
"[Ptolemy] developed certain astronomical theories and discovered
that they were not consistent with observation. Instead of
abandoning the theories, he deliberately fabricated observations
from the theories so that he could claim that the observations
prove the validity of his theories. In every scientific or
scholarly setting known, this practice is called fraud, and it is
a crime against science and scholarship."

There still remain some high Q resonances with that condemnation.

Well, the validity of that accusation has to be judged in light of
Newton's own flamboyant fudging of "observed" times for the speed of
sound forced-fit into his own theoretical work. Those errors are so
stunning that Isaac must've thought no one would ever discover them
while reading his sleeping pill.

There've been a lot of grave robbers that have come down the pike
since that fall from grace in the garden.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
. . .
Ptolemy also reduced much of his theory of Astronomy and Optics to
geometric construction techniques in many Handbooks and offered scads
of tables of observations - some of which were condemned by Newton:
"[Ptolemy] developed certain astronomical theories and discovered
that they were not consistent with observation. Instead of
abandoning the theories, he deliberately fabricated observations
from the theories so that he could claim that the observations
prove the validity of his theories. In every scientific or
scholarly setting known, this practice is called fraud, and it is
a crime against science and scholarship."
. . .

How ironic! I recall an article in _Scientific American_ many years ago
which presented credible evidence that Newton himself fudged his data.
The author argued, and gave examples to show, that some of Newton's data
were much too accurate and consistent for the techniques and equipment
he used.

Roy Lewallen, W7EL

On Thu, 23 Jun 2005 15:06:33 -0700, Wes Stewart
wrote:

On 23 Jun 2005 12:29:51 -0700, "Brian Kelly" wrote:

Inductors are lossy. Capacitors are not. Use the tuner settings which
provide a 2:1 VSWR match or better with the least possible amount of
inductance. In other words use the least amount of inductance you can
get away with.


First all should note that this is a pi-network. Suggestions to use
an MFJ (tee-network) tuning procedure are wrong.

Here is a random example made up on the spur of the moment.

Assume the load is 20 +j50 @ 14 MHz. SWR = 5.2

Also assume that the tuning capacitor(s) Q = 500 and the inductor Q =
200, both typical values.

A nearly optimum solution, from a match and loss standpoint is:

Cin = 140.3 pF, L = .958 uH, Cout = 333.6 pF.

The input z = 49.69 +j0.03 or SWR = 1.006 , Loss = 0.09 dB.

Now, let's force the inductance to a lower value.

Cin = 422 pF, L = 0.67 uH, Cout = 471.3 pF.

The input Z = 49.6 -j0.04 or SWR = 1.008 but the loss = 0.18 dB.

The loss doubled when the inductance was lowered.

All of this is easily calculated using a free tool: XLZIZL.xls.


Does anyone know what kind of network is in the TenTec 247?

I have one and noticed it will tune most bands with three different
inductance settings.


--
73 for now
Buck
N4PGW

.... and, while I may have misplaced the place where this happened (I could
have heard this when I was at U of Manchester), it seems that an extensive
set of early measurements of c were deliberately "sorted" and produced an
expected value and std that was outside of the actual value of c. When the
logbooks containing all of the measurements were consulted many decades
later, it was found that if one used all of the measurements the actual
expected value of c was within the expected error.

It is late and I have not quite said everything right. The (old)
published expected c and its std were well outside of the actual c. When
the old data was used in its entirety, the newly calculated expected c and
its std encompassed the actual value of c. (Note "expected" has a
technical meaning.)


The moral is to keep a complete log and be honest. It is much more easy
to do both when one has numbers. Before some of my work at Ohio State, one
had to extract numbers from strip chart recordings using slave labor.

Mac (who should be in bed) N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Roy Lewallen" wrote in message
...
Richard Clark wrote:
. . .
Ptolemy also reduced much of his theory of Astronomy and Optics to
geometric construction techniques in many Handbooks and offered scads
of tables of observations - some of which were condemned by Newton:
"[Ptolemy] developed certain astronomical theories and discovered
that they were not consistent with observation. Instead of
abandoning the theories, he deliberately fabricated observations
from the theories so that he could claim that the observations
prove the validity of his theories. In every scientific or
scholarly setting known, this practice is called fraud, and it is
a crime against science and scholarship."
. . .

How ironic! I recall an article in _Scientific American_ many years ago
which presented credible evidence that Newton himself fudged his data.
The author argued, and gave examples to show, that some of Newton's data
were much too accurate and consistent for the techniques and equipment
he used.

Roy Lewallen, W7EL

Nothing has changed since Oliver Heaviside, 1875 - 1925.

If anybody mentions G5RV I shall cry.
----
Reg, G4FGQ


G5RV
73,
Tom Donaly, KA6RUH

===============================

Bwwaaaaaaaaaaaaaaa

Thanks Tom, I feel better now.
---
Reg.