[TowerTalk] analysis request

[Jim Lux]

>
> Can one assume that each clamp on represents a single turn choke,
> with whatever reactance is rated for the ferrite, at the operating
> frequency?
>
> One analyst has suggested that it's the lossiness of the ferrite, not
> the inductance per-se, which is important.

You've got to look at the material to find out if the inductance or
resistance at the frequency of interest will dominate.  You also might want
to figure out how much power is being dissipated in the ferrite, especially
for some "off nominal" situations where there might be significant power on
the outside of the coax.. broken/shorted antenna; out of design band
operation; etc.
A worst case (but not necessarily plausible.. ) would be that the entire Tx
power is being run through those chokes.

A lot of the "EMI filter" type ferrites (like those you see for making a PC
meet Part 15) do rely on lossiness, rather than inductance, since the power
is small.

Typically, some manufacturer (not necessarily the one of your ferrite parts)
will have some data on a similar part with similar (enough) geometry and
similar magnetic properties to get a handle on it.

For what it's worth, one of the techniques for identifying unknown ferrites
is to figure out what frequency the resistive component starts to dominate
the inductive, and from that you can determine the general class of
material.

>
> I'm off to look for the mfr's specs on this stuff....but would appreciate
> the thoughts of anyone inclined to model this.
>
> Jim/N2EA
>
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