[TenTec] Problem on 160 meters, Whats up?

[Bob McGraw - K4TAX]

Reading the responses, this is my basic reason for advocating using a 1:1 
current balun for at least 90% of all applications.   Yes, the beads over 
coax is a very good workable application. For the life of me I don't 
understand why tuner manufacturers insist on installing 4:1 baluns in their 
boxes as they create more issues than correct solutions.

In general if your antenna is a folded dipole providing some 200 to 300 ohms 
impedance at resonance, this is about the only good justification for a 4:1 
balun.  Other than myself, I run across very few folks using a folded dipole 
associated with their stations today.

Most think that if they use 450 ohm line they should make an attempt to 
match the line Z.  I find this approach to be more incorrect than correct. 
Under these conditions, line Z has little to do with the application of a 
balun where electrical line length has a greater factor becoming a partial 
wavelength matching section.

Likely the cause of the problem at 600 watts is balun failure or an arc 
taking place somewhere within the system.

73
Bob, K4TAX


----- Original Message ----- 
From: "Jim Brown K9YC" <k9yc at audiosystemsgroup.com>
To: <tentec at contesting.com>
Sent: Wednesday, March 18, 2009 10:25 AM
Subject: Re: [TenTec] Problem on 160 meters, Whats up?


> On Wed, 18 Mar 2009 08:38:46 -0600, Dr. Gerald N. Johnson wrote:
>
>>The higher power is saturating the core of the balun. One of the hazards
>>of tuning through the balun.
>
> Yes, very likely. There are several very different things called baluns. 
> The
> one in antenna tuners is a transformer, so 100% of the transmitted power 
> is
> in the core. Very likely to saturate with high power, heat, distortion.
>
> Another VERY different thing that is CALLED a balun is really a common 
> mode
> choke. Put a bunch of ferrite cores around coax, or wind a bunch of turns 
> of
> coax through one or more ferrite cores. Those are common mode chokes,
> commonly (wrongly) called "current baluns." But when done well (enough 
> turns
> to have a high enough choking impedance), they work VERY well.
>
> 73,
>
> Jim Brown K9YC
>
>
>
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