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[Towertalk] Need UNUN help

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Subject: [Towertalk] Need UNUN help
From: (Pete Smith)
Date: Thu, 09 Jan 2003 11:07:59 -0500
I have just been testing a quintifilar 50:75 ohm UNUN that I wound 
according to instructions from Sevick's book, figure 7-8(a). If I can get 
two of them that work well, I plan to use them to match my 75-ohm CATV 
feedline to 50-ohm everything else, without using half-wavelength multiples 
as I do now.

Using an MFJ 259B with a 75-ohm resistor on the 75-ohm port, the 
performance of the UNUN is quite good from 1.7 to about 11 MHz, with 
measured R of 48-50 ohms and X typically 5 ohms or less.  Above that 
frequency, however, the UNUN shows fairly rapidly increasing R and varying 
X (for example, at 19-21 MHz R=80-90 and X=0, for an SWR of 1.7:1, and at 
28.7 MHz R=62 and X=46 (all X signs unknown)).   Clearly this is 
unsatisfactory, but I really don't know what to do now.  Any ideas?

73, Pete N4ZR

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