[Boatanchors] Toroids

[mikea]

On Thu, Mar 26, 2009 at 06:39:25PM +0000, Telegrapher at att.net wrote:
> Is there any way to determine characteristics of toroids?
>
> I've got some here, large types, that only have a number like
> A-759135-2, Turquoise in color, B-957020-3 which is kind of an
> orangish-brown and D-093075-3 which is brown. Different dimensions and
> i don't know whence they came from. Heavy little donuts to say the
> least.

If you've got a spectrum analyzer with tracking generator, as some here
are fortunate enough to, you could wind each with a 1:1 set of turns and
see where the transformer effect tails off. You could also hook the same
toroid-plus-turns up to a siggen with levelled output and to a scope or
RF voltmeter, and see where the transformer effect tails off.

That doesn't say much about the RF power levels the toroid will handle
before saturating, but the siggen plus an RF amp plus the scope or RF
voltmeter will tell you that. If I recall correctly, larger toroids
saturate at higher levels than smaller ones, for the same material.

I've got a bunch of Ethernet baluns (RJ-45 to BNC) with toroids that I
need to characterize; I foresee a little time spent winding one, and
more spent with the HP 8640B and a scope this weekend. I'll report on 
how this works in practice. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin