On Mon, 15 Dec 2008 14:19:28 -0000, "christofire"
wrote:

Is this a quiz?
And then you allow:
However, I concede there may be some reason to want to combine/power-split
using balanced line but ultimately it will need to be connected to a
co-axial line - if the intention is to achieve this without use of a balun
then I wonder if this would be more of a 'nightmare'.

It must be a quiz - when I point out that Dave does not call out for
isolation (*ferrite* BalUns as have been identified through Jerry's
and Owen's correspondence) and as you do as an aside - then what is it
that you find debatable about my commonplace observation?

Common Mode doesn't disappear into the VHF/UHF. Common Mode creates a
complex impedance product that is generally unaccounted for (ignored),
and would certainly disturb phase relationships where phase
relationships are of primary importance.

The only other alternative is consuming transmission line in coils to
the same purpose. That hasn't been offered as a choice until now.

73's
Richard Clark, KB7QHC

On Sat, 13 Dec 2008 01:56:27 GMT, Owen Duffy wrote:

I refer to the diagram at http://www.vk1od.net/lost/Fig6.png which is
from an article by the then VK2ZAB (now VK3EJ) on stacking Yagis.

Hi Owen,

This illustration seems to serve other commentary as it is filled with
odd eccentricities that are not very germane to the issue you raise
below. Eccentricities aside for the moment, I have to make a lot of
presumptions about an odd arrangement of 12 radiators. Some of them
are symmetrical by groups, but not all of them are symmetrical in
toto. I presume the groups are significant; but initially, what they
are significant of escapes me.

The + and - markings in the top tier four group, along with the
commentary, is suggestive; and I have to supply experience in the
matter to know that not ALL +s are connected together (and neither are
all -s connected together). I presume this top tier is a 4-Bay, but
there is nothing to support this except the graphical allusion.

Also from experience, I would presume that connections are not
horizontally placed, nor diagonally. The impression of incompleteness
is accruing.

I have highlighted two of the diagrams with a yellow background, and seek
opinions on them.

This implies (by your statement of "two" diagrams) that along this
middle tier of radiators, we have broken away from what might be a
4-Bay; and we are examining three pairs as choices put to an unstated
problem. Here, the eccentricity of what looks like an appendix
hanging from the folded element is further disturbed by what I can
only imagine to be an abstraction for a coax feedline. Incompleteness
is compounding.

If I am to pursue my forced presumptions, I would have to say that
this middle tier lacks many more alternatives in connections and
length variations. Incompleteness has reached saturation - which is
what I think you are responding to.

Referring firstly to the left hand one:

I suggest that the figure is in error because the scenario is not ALWAYS
wrong.

My contention is that at a single frequency, the phase inversion as a
result of the left to right swap of one driven element (DE) wrt the other
can be fully compensated for by ensuring that low loss feedline to one DE
is an odd number of electrical half waves longer than to the other.

Where the low loss feedline to one DE is an odd number of electrical half
waves longer than to the other, the Yagis are driven in phase.

The outcome being that the pattern at that frequency is approximately the
same as if equal length feedline branches were used.

Well, the original author does neglect to specify length, leaving it
to the reader's imagination to "presume" (have to say it) equal feed
lengths judged by eye. Unfortunately, the third example explicitly
offers this option, but only to those connections where phasing dots
are matched. Like I said, there are many missing alternatives.

Your imposition of an extra half wavelength in one feed may be
technically accurate, but it fights with the importance of their
length - which is to be found in the lost commentary, no doubt. I can
well guess, but that same commentary may illuminate these limited
choices and explain the eccentricities. I wouldn't want to slog
through that commentary, however.

Referring now to the right hand one:

I suggest that the figure is in error because the scenario is not ALWAYS
wrong.

My contention is that at a single frequency, that where the low loss
feedline to one DE is an integral number of electrical full waves longer
than to the other, the Yagis are driven in phase.

This would be a stretch of the imagination where application has
fallen into the ditch to serve argument. If the lengths drive
frequency to match to cable proportions in wavelength that do not
serve their loads, then such solutions are hardly useful.

The outcome being that the pattern at that frequency is approximately the
same as if equal length feedline branches were used.

Note that I am not trying to excite a purist discussion about branch vs
distributed feed arrangements for phased arrays.

Am I on the wrong track?

I am wondering why you are trying to resurrect this train wreck.

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

I am wondering why you are trying to resurrect this train wreck.

I was seeking comment on the issue of asymetric branch feed topology.

It was put to me that accounting for the phase shift due to the different
branch lengths does not fully account for the time lag. My contention is
that in transforming the problem to the frequency domain, conversion of
time lag to phase lag fully and properly accounts for the different
branch lengths.

Gordon's paper was offered as evidence that my feed was "WRONG!".

Yesterday, I note that Kraus has a clear diagram of branch vs distributed
feed, and the technique of transposition to offset a half wave phase
delay.

I also note the ARRL agrees with me (http://www.vk1od.net/lost/Fig7.png
(c)), but that isn't a bullet proof recommendation!

I am now confident my critic was wrong.

Owen

On Mon, 15 Dec 2008 21:50:04 GMT, Owen Duffy wrote:

Richard Clark wrote in
:

I am wondering why you are trying to resurrect this train wreck.

I was seeking comment on the issue of asymetric branch feed topology.

Hi Owen,

That seemed to be a strain based on the illustration offered as it
wanders the field.

It was put to me that accounting for the phase shift due to the different
branch lengths does not fully account for the time lag. My contention is
that in transforming the problem to the frequency domain, conversion of
time lag to phase lag fully and properly accounts for the different
branch lengths.

Too many conversions going on there in your statement. I don't see
any transformation (conversion?) to OR from the frequency domain; and
I don't see what that would offer. Distance, "polarity," phase and
time are all hands on the same watch. Their conversion is trivial -
as you appear to be rebutting to your critic.

Gordon's paper was offered as evidence that my feed was "WRONG!".

The offeror left it you to sort it out rather than arguing their own
case, hmm?

Yesterday, I note that Kraus has a clear diagram of branch vs distributed
feed, and the technique of transposition to offset a half wave phase
delay.

I also note the ARRL agrees with me (http://www.vk1od.net/lost/Fig7.png
(c)), but that isn't a bullet proof recommendation!

True.

I am now confident my critic was wrong.

If the criticism is, as you offer above about accounting for "time
lag," as if that fell into some special category, then your confidence
is well grounded.

When I examine your other correspondence to piece together the story,
then both sides of the argument have valid points. Yours, being more
general, is more conclusive.

The second take-home here seems to be, if you wish to teach someone
how to perform a task, or build a project, you shouldn't do it with
negative examples without being encyclopedic to completion (which
invites boredom).

A proof with the free version of EZNEC was easily achieved with some
minor elaborations for the NBS Yagi. That is the beauty of modeling,
it encompasses ALL the ways to fail or succeed.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Mon, 15 Dec 2008 21:50:04 GMT, Owen Duffy wrote:

Richard Clark wrote in
m:

I am wondering why you are trying to resurrect this train wreck.

I was seeking comment on the issue of asymetric branch feed topology.

Hi Owen,

That seemed to be a strain based on the illustration offered as it
wanders the field.

It was put to me that accounting for the phase shift due to the different
branch lengths does not fully account for the time lag. My contention is
that in transforming the problem to the frequency domain, conversion of
time lag to phase lag fully and properly accounts for the different
branch lengths.

Too many conversions going on there in your statement. I don't see
any transformation (conversion?) to OR from the frequency domain; and
I don't see what that would offer. Distance, "polarity," phase and
time are all hands on the same watch. Their conversion is trivial -
as you appear to be rebutting to your critic.

Gordon's paper was offered as evidence that my feed was "WRONG!".

The offeror left it you to sort it out rather than arguing their own
case, hmm?

Yesterday, I note that Kraus has a clear diagram of branch vs distributed
feed, and the technique of transposition to offset a half wave phase
delay.

I also note the ARRL agrees with me (http://www.vk1od.net/lost/Fig7.png
(c)), but that isn't a bullet proof recommendation!

True.

I am now confident my critic was wrong.

If the criticism is, as you offer above about accounting for "time
lag," as if that fell into some special category, then your confidence
is well grounded.

When I examine your other correspondence to piece together the story,
then both sides of the argument have valid points. Yours, being more
general, is more conclusive.

The second take-home here seems to be, if you wish to teach someone
how to perform a task, or build a project, you shouldn't do it with
negative examples without being encyclopedic to completion (which
invites boredom).

A proof with the free version of EZNEC was easily achieved with some
minor elaborations for the NBS Yagi. That is the beauty of modeling,
it encompasses ALL the ways to fail or succeed.

73's
Richard Clark, KB7QHC

Hi Richard

What is the reasoning used to indicate 300 ohm line is used in (B) of the
referenced http://www.vk1od.net/lost/Fig7.png .?

Jerry

On Mon, 15 Dec 2008 23:57:39 GMT, "Jerry"
wrote:

Hi Richard

What is the reasoning used to indicate 300 ohm line is used in (B) of the
referenced http://www.vk1od.net/lost/Fig7.png .?

Hi Jerry,

It should follow the rule of being the square root of the product of
the source and load Z.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Mon, 15 Dec 2008 23:57:39 GMT, "Jerry"
wrote:

Hi Richard

What is the reasoning used to indicate 300 ohm line is used in (B) of
the
referenced http://www.vk1od.net/lost/Fig7.png .?

Hi Jerry,

It should follow the rule of being the square root of the product of
the source and load Z.

73's
Richard Clark, KB7QHC

Hi Richard

OK, on the geometric mean, but, the author surely realized *that*. I got
the feeling that I was missing something of value when it wasnt obvious to
me why 300 ohm line was used.

Jerry KD6JDJ

"Jerry" wrote in
:

....
What is the reasoning used to indicate 300 ohm line is used in (B)
of the
referenced http://www.vk1od.net/lost/Fig7.png .?

The figure is is from the ARRL Antenna Handbook.

In (b), the numbers are rounded. A nominal 280 ohm dipole via 1/4 wave of
400 ohm line gives 570 ohms at the tee. Two such branches are paralleled
for 285 ohms, which on 300 ohm main feed line line results in a VSWR of
1.05... should be acceptable.

Does that help?

Owen

Richard Clark wrote in
:

....
The second take-home here seems to be, if you wish to teach someone
how to perform a task, or build a project, you shouldn't do it with
negative examples without being encyclopedic to completion (which
invites boredom).

Richard,

That same thought occurred to me on first reading it. Teaching what not
to do has its place, but it 'dumbs down' the learner.

Explaining the concepts, and how to use them imparts empowering knowledge
more than rote learning of negative Rules of Thumb.

Still, people keep telling me that that is all old world thinking, today
you train (instead of educate) people to specific and narrow tasks, and
competency for immediate tasks (train to the need) is more important than
knowledge of principles and concepts.

I have quals to opearate a fork lift. One of the questions I was asked
for assessment was "name six places that you should not park a fork
lift". Of course, one cannot just nominate any 6 places that would be
inappropriate, it MUST be THE six places on the assessor's list. One of
them is "on a railway track". So, rather than training people to identify
hazards, and not park the fork lift in a hazardous place or way,
"competent people" know the rule to not park the fork lift on a railway
track. No doubt accident / incident driven training... a negative driver.
(I will leave you to think about 5 other stupid places to park a fork
lift!)

Owen

Keeping in mind simplicity, and , using equal length of 50 0hm
to this power splitter- all antennas should be in phase (all
Left elements , to properly phase), and that it gives 4-50 ohm loads
for one 50 ohm source. Why reinvent the wheel?? Jim NN7K


Owen Duffy wrote:
Jim-NN7K . wrote in news:9ch1l.9958$yr3.334
@nlpi068.nbdc.sbc.com:

Owen Duffy wrote:

Firstly, I didn't write the following, Jim did.

More likely, 2 - 1/4 wave (with velocity factor)50 ohm coax's to a
"Tee" fitting-- Each end also to a "Tee" fitting . ( all 50 ohm coax)
(power devider)

2x50 -----------------

2X Quarter wave | "T" fitting source 50 Ohm

2x50 -----------------

IF this is clear enough-- Jim NN7K


Jim, are you introducing another scheme, or were you trying to explain
Jerry's scheme. We sorted Jerry's scheme, he just overlooked some vital
details in his first description. (I haven't said it to date, but I
dislike Jerry's scheme, principally over its use of the balun.)

Yours is another scheme.

There are a lot of ways to do it.

The original question was over an article's diagram that stated that
unequal lines are "WRONG!".

Yours and Jerry's responses have not dealt with the original posting, but
if anything offered alternatives that might be seen to suggest the
original configuration is flawed.

Owen