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[TowerTalk] RadioWorks line-isolator spec.

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Subject: [TowerTalk] RadioWorks line-isolator spec.
From: (Chuck Counselman)
Date: Tue Jan 28 14:32:13 2003
At 9:35 AM -0500 1/28/03, Mike Wetzel W9RE wrote:
>To add to your RadioWorks info, I had 3 of their baluns...and found 
>that the baluns exhibited a very high swr on 10 [meters]....  The 
>baluns seemed ok below that frequency (21 Mhz).  I informed them and 
>they ignored me.

About three years ago, suckered by RadioWorks' advertising which 
seemed to say that the common-mode-choking impedance of their 
so-called line isolator at 3.5 MHz was _extremely_ high, of the order 
of 100 kohms, I bought two of these devices.

In fact the complex impedance at 3.5 MHz is about ( 0 + 800 j ) ohms. 
Yes, zero ohms resistance plus eight hundred ohms reactance.  The 
uncertainty in this complex value is a couple of ohms in the real 
part and a few percent in the imaginary part.  In other words, at 3.5 
MHz the device is a 37-microhenry inductor with a very high Q, 
greater than 400.

An exchange of email with RadioWorks' proprietor Jim Thompson 
eventually revealed his justification for advertising "100 kohms." 
In the parallel L-R circuit having the same impedance at 3.5 MHz, the 
value of L is about 37 microhenries and the value of R is about 100 

Since the complex impedance of such a device varies with frequency in 
the 3.5-MHz range like that of a _series_ L-R circuit, not at all 
like a parallel L-R circuit, I told Jim Thompson that I thought his 
advertising was misleading.  He ignored me, too.

-Chuck, W1HIS
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