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.