On Tue, 21 Dec 2004 20:27:54 +0000, Ian Jackson
wrote:

However, this is not the best design for a
matching network, they are usually three resistors in either a PI or T
configuration.
Several manufacturers of precision matching pads might disagree!

Hi Ian,

I seriously doubt it, but you are free to offer examples.

73's
Richard Clark, KB7QHC

In message , Richard Clark
writes
On Tue, 21 Dec 2004 20:27:54 +0000, Ian Jackson
wrote:

However, this is not the best design for a
matching network, they are usually three resistors in either a PI or T
configuration.
Several manufacturers of precision matching pads might disagree!

Hi Ian,

I seriously doubt it, but you are free to offer examples.

73's
Richard Clark, KB7QHC



http://www.maxim-ic.com/appnotes.cfm...mber/972/ln/en
http://www.maxim-ic.com/appnotes.cfm...te_number/3250
http://www.maxim-ic.com/appnotes.cfm...mber/972/ln/en
http://www.testmart.com/estore/produ...Fsearch%2Fspec.
cfm~~MICCOM~~AGILEN~~11852B~~%20~~%20|1.html
http://www.g4fgq.regp.btinternet.co.uk/padmatch.pas
http://www.g4fgq.regp.btinternet.co.uk/padmatch.pas
http://used-line.com/b2544p1pr0-Used-pads.htm
http://www.minicircuits.com/dg03-159.pdf#search='minimum%20loss%20pad'
+ many, many more!
Ian.

--

On Tue, 21 Dec 2004 22:51:30 +0000, Ian Jackson
wrote:

In message , Richard Clark
writes
On Tue, 21 Dec 2004 20:27:54 +0000, Ian Jackson
wrote:

However, this is not the best design for a
matching network, they are usually three resistors in either a PI or T
configuration.
Several manufacturers of precision matching pads might disagree!

Hi Ian,

I seriously doubt it, but you are free to offer examples.

73's
Richard Clark, KB7QHC
+ many, many more!
Ian.

Hi Ian,

Perhaps you can share from those many, many more, those which
disagree?

73's
Richard Clark, KB7QHC

In message , Richard Clark
writes
On Tue, 21 Dec 2004 22:51:30 +0000, Ian Jackson
wrote:

In message , Richard Clark
writes
On Tue, 21 Dec 2004 20:27:54 +0000, Ian Jackson
wrote:

However, this is not the best design for a
matching network, they are usually three resistors in either a PI or T
configuration.
Several manufacturers of precision matching pads might disagree!

Hi Ian,

I seriously doubt it, but you are free to offer examples.

73's
Richard Clark, KB7QHC
+ many, many more!
Ian.

Hi Ian,

Perhaps you can share from those many, many more, those which
disagree?

73's
Richard Clark, KB7QHC

The point I was trying to make was, if the L-pad was 'not the best
design for a matching network', why are there so many about?
It gives the minimum loss for a match in both directions (with the 43and
86 ohm resistors). What works better?
Ian.
--

On Wed, 22 Dec 2004 00:19:12 +0000, Ian Jackson
wrote:

The point I was trying to make was, if the L-pad was 'not the best
design for a matching network', why are there so many about?
It gives the minimum loss for a match in both directions (with the 43and
86 ohm resistors). What works better?
Ian.

Hi Ian,

The topic is Why Match? and the context is with bench gear,
specifically a Spectrum Analyzer. It is pleasing that no sardonic
quips as to this device's suitability for antenna matching has sallied
forth. Attenuators serve a limited purpose - Isolation. They serve
this well when they don't introduce uncontrolled error. They also
serve as range extenders as do directional couplers, often with
attenuators paired with them.

In the case of using them with couplers, they insure port isolation by
insuring port loading. They buffer any deviance from an expected 50
Ohm load that may be presented by monitoring gear attached through
them to that port. This is by and large the context of the mini
circuits links you offered. The extent of this "insurance" can be
observed by computing how much load is presented to the affected
instrument when the attenuator is left open, or shorted. T or PI
configurations show a higher tolerance. An L Pad is a special case
(less general form) of either T or PI, being that one of the three
elements is replaced with either a short or an open.

73's
Richard Clark, KB7QHC

On Wed, 22 Dec 2004 00:19:12 +0000, Ian Jackson
wrote:
What works better?

Hi Ian,

In following up the links that you provided, there is a superior
reference found at the same site:
http://www.minicircuits.com/appnote/an70001.pdf
which in turn leads to a treasure trove on the topic that supports my
favorite discussion on Mismatch Uncertainty. By following the links,
they offer you articles and software to compute the accumulation of
errors (and loss) found in mismatched sources looking at mismatched
loads.

A notable quote:
"A fixed attenuator can help to lower the VSWR of cascaded
(connected) components by providing isolation between the
impedances, effectively masking the impedance mismatches."

For both mismatched source and load, one handy shortcut offered is
that the system suffers a SWR that is not the aggregation of the two,
but the multiple of the two. This is not particularly significant for
a source SWR of 2 seeing a load SWR of 2 (same result of 4 for either
addition or multiplication), but above this value and loss begins to
climb dramatically.

73's
Richard Clark, KB7QHC