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[TowerTalk] Baluns/tutorial/notes applied to the AV640

To: towertalk@contesting.com
Subject: [TowerTalk] Baluns/tutorial/notes applied to the AV640
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Date: Sat, 22 May 2010 18:49:02 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I changed the subject line due to the AV640, but with the question of 
the Guanella balun and the other experiments, maybe I should have left 
it as it was?

On 5/22/2010 2:56 PM, Jim Brown wrote:
> On Sat, 22 May 2010 18:51:14 +0100, Steve Hunt wrote:
>
>    
> I think that's what I said. If we recognize the Guanella balun as two
> common mode chokes, the differential voltage is across the common mode
> impedance of each core. Doing the math, for 1500 watts keydown, that's 275
> volts across 5,000 ohms, which is 15 watts. Applying a reasonable duty
> cycle for CW or SSB, that's something like 5 watts when you're
> transmitting.
>
>    
So if I take to "individual" current baluns wound on #31 mix and connect 
the inputs in parallel with the outputs in series, I have two 
independent chokes with no common magnetic field serving as a 4:1 
balun.  Even though the chokes may be in very close proximity and even 
on the same axis with say a half inch to inch spacing between them they 
are still independent as the flux is contained almost entirely within 
each individual core. If I understand that correctly that is the 
difference between the Guanella balun and the experiments run by W8JI?

If this be the case, I wonder if replacing the conventional 4:1 balun in 
the AV640 with this arrangement would *possibly* eliminate the power 
limitations of the AV640 and particularly on 6 meters. At the least I'd 
think it would certainly increase the power handling capability by a 
notifiable amount.  OTOH I've run the thing to 800 PEP on 6 with nary a 
problem. I've also run the duty cycle on HF far beyond the listed 
ratings with no problems.

73

Roger (K8RI)
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