Re: [Amps] toroid filament choke?

[Tony King <amps@w4zt.com>]

At 10:13 AM 10/27/2004, k7fm wrote:
> Will said:
>
> "You have to keep in mind the current surge there until the heater warms up.
> The colder the heater is, the more current it draws. I would use a conductor
> with at least 750 cir mils per ampere. For 3 amperes, that equals out to be
> about 16 AWG wire for the minimum"
>
> The filament choke should not take into account any surge current, and there
> is an advantage in limiting the wire size to limit surge current.  By
> limiting the wire size, the smaller wire will limit the surge current and
> protect the tube.  Since the choke is presumably in the slipstream of air, a
> significantly smaller size of wire can be used.  If there is no other means
> to protect the filament surge current, then this is an opportunity to
> protect the tube and wind a smaller choke.
>
> Since chokes always seem to be just large enough to not fit where you want
> them to, take advantage of downsizing.

Very interesting guys!  I was thinking that with a step start on the 
filament, the surge would be of little consequence anyhow. Keeping the 
choke smaller would certainly make it easier for constructing the input and 
even more desirable for those folks that are thinking of a retrofit to desk 
top amps.

Based on Rich's earlier comments I would think you could easily go smaller 
than #16 wire on the choke and reduce the physical size or at least get 
enough inductance for 160 in the same package. What do you think the target 
inductance should be for effective use on 160?

73, Tony W4ZT


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