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Author Topic: Do Ham's READ?  (Read 5723 times)
K9YLI
Member

Posts: 872




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« Reply #15 on: December 30, 2011, 07:12:10 AM »

How about making the standard answer to all questions a copy and paste  canned answer.

  ""Go to the hand book year xxxx , chapter x , page xx."""
or  year xxxy  , chapter y, page yy"

make them read...  then  after  5 days.. start with the usual answers.
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K8AXW
Member

Posts: 3900




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« Reply #16 on: December 30, 2011, 08:58:40 PM »

Quote
"Don't I want to use a 9:1 balun to go from 450 ohms to 50 ohms?"  And, of course, on paper, the short answer is YES, but the long answer involves what the REAL required transformation...Then we get into the type of core, and how to insulate the wire, and by the end of the thread.  In the end, I think we leave the poor guy more confused than not.

When I ask a question like this I would like to get a YES, and the way you make one is like this out of that.  If you want to ad a lot of theory, fine but give me the short version first.

However, what usually happens is you get an answer saying that there are several ways of building that balun and this and thus must be considered. 

THEN, it hits the fan and from there on everyone who has an opinion on how a balun is to be made get into it and adds their opinions.  This is when the originator of the question gets snowed in with the BS.  He walks away all glassy eyed and still doesn't know how in the hell to make a balun!
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NA0AA
Member

Posts: 1042




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« Reply #17 on: December 31, 2011, 07:16:13 AM »

[quoteWhen I ask a question like this I would like to get a YES, and the way you make one is like this out of that.  If you want to ad a lot of theory, fine but give me the short version first.

However, what usually happens is you get an answer saying that there are several ways of building that balun and this and thus must be considered. 

THEN, it hits the fan and from there on everyone who has an opinion on how a balun is to be made get into it and adds their opinions.  This is when the originator of the question gets snowed in with the BS.  He walks away all glassy eyed and still doesn't know how in the hell to make a balun!

And of course, if you pick up a comprehensive book on baluns, you will discover that there are indeed several ways to skin that cat, and frankly, not even real experts agree on everything about them.  Let alone the experts here on-line.

That being said, I'd guess that about 90% of all balun needs are solved with either a 1:1 or 4:1, but then there's voltage and current designs, etc.

And then you find rebels like me, who own baluns and don't use them!  Well, OK, I have a couple in use, but they are built into hardware, not free-standing.
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NA0AA
Member

Posts: 1042




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« Reply #18 on: December 31, 2011, 07:58:27 AM »

And it's not that there is not room for some healthy debate, but a new amateur is far more likely to be simply overwhelmed by information that he/she is not yet qualified to evaluate, offered by on line experts of uncertain [for the most part - and I include myself in the 'well meaning fool' category] qualifications.

And, as you know, this is surely not limited to this forum or to amateur radio.

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K8AXW
Member

Posts: 3900




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« Reply #19 on: December 31, 2011, 08:55:06 AM »

WOU: 
Quote
And, as you know, this is surely not limited to this forum or to amateur radio.


Again, you're correct.  Which is something I learned only within the past couple years.  Prior to this I considered this problem more or less a "computer geek" problem.

I was at a hamfest once back when I was really getting started in computers.  I needed a video card and found one that looked like what I needed.

However, there was something I needed answered before buying the guy's video card.  When I asked a question, another guy standing there listening to the conversation, chirped a rebuttal to the seller's answer.  Then the two of them started this back and forth.

I interrupted their conversation reminding the seller I was interested in buying his card.  As he started to talk the other guy interrupted again and the two went back to their "discussion."

I interrupted them once again, this time I was getting mad and tried once more time to find out what I needed to know about the video card. No luck!

I then walked away and the last I saw them they were still arguing over some detail or theory or other BS.  I hope he still has that video card.

This is when I decided to get my own computer education and minimize the need to ask someone else.
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K0JEG
Member

Posts: 669




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« Reply #20 on: December 31, 2011, 09:39:21 AM »

"Sticky" threads might help. I see them in other forum software for frequently cited or well written articles that are useful for newcomers.
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N3OX
Member

Posts: 8847


WWW

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« Reply #21 on: December 31, 2011, 11:00:03 AM »

When I ask a question like this I would like to get a YES, and the way you make one is like this out of that.  If you want to ad a lot of theory, fine but give me the short version first.

Some things do have simple answers.  Take pretty much anything about a half-wave dipole:

Q: What kind of wire or tubing should I use for best performance?
A: Doesn't matter one bit.  Put up something that stays up in your weather.

Q: What kind of insulators should I use?
A: Doesn't matter much.  PVC, polyethylene cutting board, varnished wood, glazed ceramic.  Just don't use anything that absorbs water or conducts electricity.

Q: How should I connect the coax?
A: Doesn't matter.  Solder, wire nuts, PL-259/SO-239.  Just needs to be reasonably strain relieved and not constantly drip water onto your coax.

Q: How high does the dipole need to be? How far away from other objects/metal?
A: It doesn't matter.  Higher and in the clear is better, but a dipole is a good antenna even if it has to be low and cluttered.

Q: My SWR is too high, what should I do?
A: If the SWR is lower at the bottom of the band, trim off some length.  If the SWR is lower at the top end of the band, add some length.  If you can't get low SWR at all, your dipole is broken and you should look for bad connections.

=======

For a basic dipole, EVERYTHING is simple.

Some things do not have simple answers no matter how much you want there to be a simple answer.  Baluns are one of those things, at least if you want it to actually make a difference and you don't just want to pretend the balun is doing something.  Core type and size number of turns, coax or twisted pair and the insulation type... it often all matters.

And you can't just give advice willy-nilly and expect it to work.  A balun that works great and totally fixed someone's RF feedback problem on a 75m half wave center-fed dipole used at full legal limit SSB with a non-worst-case feedline length for common mode might burn and crack in five minutes of 1kW 80m RTTY operation on a 60 foot high OCF dipole.

Can I use an air core balun?  It depends.  Can I use this ferrite I found in my junk box?  It depends.  Do I need a balun?  It depends.  What core material?  It depends. 


Commercial companies will happily sell you a vastly overbuilt balun with high common mode impedance and high power handling  for a hundred bucks, and for people with plenty of funds or something like a single ladder-line-fed antenna, that can sometimes be a good solution to all the complexity.  But for most applications they probably cost ten times more and weigh ten times much as is necessary.  If you have a couple beams and four dipoles then the cost starts getting really ugly.

Quote
This is when I decided to get my own computer education and minimize the need to ask someone else.

It's a good idea.  And even when you do ask others, a "trust but verify" attitude really pays off.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KC2OYZ
Member

Posts: 128




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« Reply #22 on: January 04, 2012, 06:20:23 PM »

I have no room for books - all filled up with radio gear.  Grin
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