[TenTec] Built in SWR meter bannans

[Rick - DJ0IP / NJ0IP]

Charles,

Thanks for the information.
My story was in the 1980 and we didn't have a web back then.
Information on baluns and chokes was scarce.
I burned up commercial baluns rated 2KW or more running just 400w.

I always opened to check and see what had happened.
I always found the insulation of the wire had broken down.

So I cleaned up the mess and began winding my own using Teflon covered wire
and the bits salvaged from the old baluns.
I have never burned up one of my home brew baluns and I've built quite a few
in the meantime.
Also, I have stopped buying commercial baluns because if I build them
myself, I know what's inside.  No more surprises.  

Most of the burning up was due to using them with Openwire fed antennas.
I found the better solution was to switch to a proper symmetrical link
coupled matchbox where you don't need a baun.
I also found it was better to use a 1:1 balun than a 4:1 balun when using
the asymmetrical matchboxes.
I found this out by trial and error.
In the meantime I've learned from reading a book by DL1VU and from studying
Steve's (G3TXQ) web page on the topic that it is indeed better to use 1:1
baluns for that purpose, even though most matchbox manufacturers still use
4:1 baluns.
Here's a link to "Tuner Balun Ratio: 4:1 or 1:1 ?:
http://www.karinya.net/g3txq/tuner_balun/ 

MY ONE BIG QUESTION MARK HERE IS, POWER RATING ?

I have googled quite a bit but just can't find a source that says how much
power you can run through the various core sizes.
I guess it's application dependent so they don't rate them, but it sure
would be nice to find a chart somewhere saying something like for 100w, use
1.4", for 500w use 2.4", for 1 KW use 2x 2.4", etc.  I would like to see
some kind of guide line but I have not come across one.  By the way, the
values I stated here are what I personally use, but I have no clue if they
are correct or not.  I stop at two because we're only allowed 750w and I
choose to stay legal.

73
Rick, DJ0IP


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Charles P.
Steinmetz
Sent: Wednesday, April 24, 2013 2:23 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Built in SWR meter bannans

Rick wrote:

>I had so much trouble burning up baluns back in the 80s that I have 
>switched to using only Teflon insulated wire for my chokes and baluns.

Baluns don't normally burn up because the insulation isn't adequate.
Rather, they burn up because the common-mode current is higher than the core
size and mix can tolerate (or, much less frequently, because the wire used
is too small).  Overheating is a symptom of too small a core, the wrong
ferrite mix for the frequency(ies), too few turns, and/or too small a wire
gauge.  There is lots of information on the web.  When in doubt, use a
bigger core (after making sure you are using the right ferrite mix for the
frequency, sufficiently heavy wire to handle the power, and enough turns to
get the common-mode impedance that you need).

Best regards,

Charles






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