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Re: Topband: Two Wire Beverage Query...

To: "Ford Peterson" <>,"Chuck Hutton" <>, <>
Subject: Re: Topband: Two Wire Beverage Query...
From: "Ford Peterson" <>
Date: Sun, 22 Aug 2004 15:21:53 -0500
List-post: <>
Interesting results...  Good, solid data confirming ON4UN's table 7-10 info.

After taking Tom's advice and choosing to measure the impedances correctly 
(i.e. lashing the two wires together at each end), I have pretty convincing 
evidence that my termination impedance should be about 353 ohms.  Since I wound 
it for 450 ohms, perhaps this also explains why my feedpoint impedance 
consistantly comes in at 40 ohms at most frequencies below 8MHz.

Term      Measured
Ohms    Min    Max    Sqrt(RminRmax)  Range   Error
340        338    372          355                 34        15
351        340    367          353                 27          2
360        335    363          349                 28      -11
379        327    370          348                 43      -31

My best guess based on this is 353 ohms.  This appears to be consistant with 
Table 7-10, which used meters intead of 9 feet and 12" spacing (710 ohms) 
instead of my 10" spacing (688 ohms).  So my termination transformer will get 
wound as close to (688 : 353) as I can get.

By the way, using the Autek VA1's 300 ohm mode, it was difficult to sweep and 
document the variation in SWR since all of the above values never fell outside 
the 1.14 to 1.24 SWR relative to 300 ohms.  So the Square Root of the Minimum 
times the Maximum reading over frequency was the best of the two approaches.  
In all the measurements, I swept from 600 KHz to well over 8.4 MHz.  The data 
started to fall apart at about 7.5 MHz, so I limited my sweep to about that 
spot.  None of the above data points were any where near either frequency 

Thanks for all the help.  I can now fix my beverage and forget about whether it 
is 'right' or not.  Problems in pattern will no-doubt be sourced to other 
issues, rather than termination design.


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