Voltage feeding a VHF yagi
 

Cecil Moore wrote:
That is a complete quote of your item number 1. What you said is
self explanatory. You said the current flowing onto the antenna
is equal to the current flowing down the feedline. You were wrong.

Cecil, rather than help people with questions and give them good
helpful answers you seem to just want to turn it into a peeing contest.
Even if you have to drop sentences to make it appear someone else is
wrong.

Why do you do that??? Don't you think it is more important to help the
guy asking the question than to play Cecil games??

Actually here is everything I said in CONTEXT. Tell me what is wrong
in the entire CONTEXT of what I said.

From: - view profile
Date: Thurs, Jul 6 2006 8:56 pm
Email:
Groups: rec.radio.amateur.antenna
wrote:
Tom, I didn't know that the feedline decoupling issues with J-poles
were so bad.

I'd be interested in more information about why it's such an issue.
Would a sleeve stub work better than an open wire stub? It's certainly
stupid to make the feedline MORE of an issue.



Look at what the J-pole really is.

1.) You have a half-wave end-fed antenna. There has to be as much
common mode current leaving the end of that point and flowing down the
feedline as there is flowing out onto the antenna at that point. There
isn't any exception to this rule.


2.) While that current may be small with a perfect half wave, it is
never zero. It gets worse fast of the antenna is not 1/2 wl long
electrically, or if it is thick.


3.) Now you have a 1/4 wl stub feeding that half-wave on the end. If
you perfectly floated that 1/4 wl stub, common mode current in the stub

would DECREASE as you move away from the feedpoint. But if you ground
the 1/4 wl stub, current common mode INCREASES as you move away from
the stub. This is why end-fed Zepps and J-poles model very good when a
perfect ground independent current source is used to feed them.
Unfortunately we can't do a perfect ground independent feedpoint in the

real world, so depending on the CM impedance the amount of pattern
distortion will be all over the place.


This is why Zepps, antennas that are really just the same as a J-pole,
are notorious for RF in the shack. The lack of feedlines in models are
why people who do not include the feeder or feedline matching device to

the 1/4 wl closed stub conclude they aren't so bad.


Why would anyone go through all that bother to complicate the feed
system in a Yagi is beyond me, when there are a half dozen easy
solutions that were mentioned here.


73 Tom

end of quote

So you see, you mislead people on purpose Cecil. Shame on you.

Voltage feeding a VHF yagi
 

wrote:
Cecil, rather than help people with questions and give them good
helpful answers you seem to just want to turn it into a peeing contest.
Even if you have to drop sentences to make it appear someone else is
wrong.

Pot: Kettle, Kettle: Pot.

This was a deliberate dose of your own medicine. When you
stop the deliberate obfuscation of my postings, the problem
will cease to exist.

Why do you do that??? Don't you think it is more important to help the
guy asking the question than to play Cecil games??

You are the one who taught me to play those silly games, Tom.
Just as soon as you abandon your unethical methods of quoting,
I will stop mirroring your actions back at you. You have even
reverse-ordered the dates of my postings to make them appear
to mean the opposite of what they originally meant.

I know a few technical types who could be contributing to
this newsgroup but are afraid of attack from your junk yard dog
style. Your strategy seems to be to attack everyone who disagrees
with you and try to drive them off the newsgroup.

One of the QRZ moderators advised me to stop arguing with you
because "W8JI is never wrong, even when he is completely wrong".
He made me promise not to reveal his identity. Another individual
regularly sends me technical information to use against your
irrational arguments but makes me promise to keep his identity a
secret lest he suffer one of your attacks. You have intimidated
a lot of people with your attack dog style. One wonders why, if
you are such a guru, you need to adopt such a style. How about
a kindler, gentler W8JI in the future?

I'm willing to agree to a truce which limits your and my postings
to technical information and logical arguments. Are you willing to
give up your ad hominem attacks and obfuscation of my postings?
--
73, Cecil http://www.qsl.net/w5dxp

Voltage feeding a VHF yagi
 

Cecil Moore wrote:
wrote:
Cecil, rather than help people with questions and give them good
helpful answers you seem to just want to turn it into a peeing contest.
Even if you have to drop sentences to make it appear someone else is
wrong.

Pot: Kettle, Kettle: Pot.

This was a deliberate dose of your own medicine. When you
stop the deliberate obfuscation of my postings, the problem
will cease to exist.

That's not true.

You interact with others through obfuscation and bullying. I just wish
you could control it a little bit becuase you do have useful things to
say. Sometimes people want answers to questions Cecil. The J-pole is a
good example where the focus should be on the antenna.

All of the models I've found on Cebik's site and nearly all of the
models elsewhere lack a ground or mast connection at the shorted
feed-stub junction, while most J-poles have that connection. They also
use a floating ground independent current source, which virtually no
J-poles have in the real world. I'd bet nearly all J-pole are
eventually fed by unbalanced feedlines or feedlines with finite common
mode.

The models, through pure accident or lack of basic understanding, use a
BEST case feed simulation that masks all of the problems a J-pole has
with common mode current.

No designer in his right mind would use such a lousy feed system to
feed a pattern sensitive design like a Yagi antenna, they are barely
acceptable as a omni-antenna.

73 Tom

Voltage feeding a VHF yagi
 

wrote:
You interact with others through obfuscation and bullying.

I treat others the way they treat me. I treat you the way
you treat me. You insist on turning my inclusive statements
into exclusive straw men statements so you can argue with
them. You are the only one who can change that interaction.
We just had a civil exchange over on QRZ.COM where you didn't
misquote me for a change. That could happen here.

No designer in his right mind would use such a lousy feed system to
feed a pattern sensitive design like a Yagi antenna, they are barely
acceptable as a omni-antenna.

I agree with everything you said about J-Poles in this posting
so you are apparently trying to set up yet another straw man.
One wonders why you feel compelled to try such a transparent
trick. When I disagree with you on one minor point, you react
as if I had disagreed with you on all major points. You really
need to learn the difference between "inclusive" and "exclusive".
My disagreement was inclusive of your point 1, not with anything
else you said. That's why I trimmed out everything else.

What I disagreed with you on is that common-mode current is
the same at two different points in a J-Pole system separated
by a 1/4WL stub feed system.
--
73, Cecil http://www.qsl.net/w5dxp

Voltage feeding a VHF yagi
 

The poor guy trying to learn about the J-pole probably didn't learn a
thing about the J-pole Yagi feed. He probably thinks the model on the
W4RNL site is a valid model.

Way to go!

73 Tom

Voltage feeding a VHF yagi
 

wrote:
The poor guy trying to learn about the J-pole probably didn't learn a
thing about the J-pole Yagi feed. He probably thinks the model on the
W4RNL site is a valid model.

Again you divert the issue. Will you never learn to
admit a simple mistake and move on? You were ignorant
of the definition of the word "rationalize" but you
are unlikely ever to admit it.

If you simply change your bad boy ways, the world will
be a much better place for all the rest of us.
--
73, Cecil http://www.qsl.net/w5dxp

Voltage feeding a VHF yagi
 

"Cecil Moore" wrote to W8JI:

Again you divert the issue. Will you never learn to
admit a simple mistake and move on? You were ignorant
of the definition of the word "rationalize" but you
are unlikely ever to admit it.

If you simply change your bad boy ways, the world will
be a much better place for all the rest of us.
--
73, Cecil http://www.qsl.net/w5dxp

No can do Cecil.
That goes back to his high school days and it only got worse.
The best way is to state your wisdom against his and let the in-know judge
and blind followers, worship. Too bad, but that is the reality. Makes
Freaktenna look like a school boy. Add to it pretending to be an engineer
and you get the picture.
He will never admit to be wrong (never happened yet), if he realizes he was
wrong, he will just go QRT on the subject for a while and then reemerge
shemelessly as guru on the subject, without giving credit where is due.
"Discussions" turn into obfuscating the subject, mumbo-jumbo and end with
personal attacks and ridicule. Oh, wait, it culminates with threats of
lawsuit.
Such a shame, so many decent and knowledgeable people get turned off by this
crap and ham community misses great resources.

73 bada BUm

Voltage feeding a VHF yagi
 

Yuri Blanarovich wrote:
"Cecil Moore" wrote to W8JI:

Again you divert the issue. Will you never learn to
admit a simple mistake and move on? You were ignorant
of the definition of the word "rationalize" but you
are unlikely ever to admit it.

If you simply change your bad boy ways, the world will
be a much better place for all the rest of us.
--
73, Cecil http://www.qsl.net/w5dxp


No can do Cecil.
That goes back to his high school days and it only got worse.
The best way is to state your wisdom against his and let the in-know judge
and blind followers, worship. Too bad, but that is the reality. Makes
Freaktenna look like a school boy. Add to it pretending to be an engineer
and you get the picture.
He will never admit to be wrong (never happened yet), if he realizes he was
wrong, he will just go QRT on the subject for a while and then reemerge
shemelessly as guru on the subject, without giving credit where is due.
"Discussions" turn into obfuscating the subject, mumbo-jumbo and end with
personal attacks and ridicule. Oh, wait, it culminates with threats of
lawsuit.
Such a shame, so many decent and knowledgeable people get turned off by this
crap and ham community misses great resources.

73 bada BUm



Speaking of personal attacks...
73,
Tom Donaly, KA6RUH