[HomeBrew] Torroids in vacuum tube circuits

[jeremy-ca]

For HF the powdered iron works great from microwatts to kilowatts. A T-50 or 
T-80 size is convenient in a receiver project.

The best thing about toroids is their self shielding characteristics. This 
means that interaction between adjacent coils is minimized even at 1/2" 
spacings allowing compact and efficient construction.

Carl
KM1H


----- Original Message ----- 
From: "James Kearman" <jkearman at att.net>
To: <homebrew at mailman.qth.net>
Sent: Friday, August 24, 2007 12:14 AM
Subject: Re: [HomeBrew] Torroids in vacuum tube circuits


> ** Please do NOT cross-post messages when posting to HOMEBREW **
>
> rrfowler at bellsouth.net wrote:
>> Can't remember if this has been discussed before, but has anyone ever 
>> tried using ferrite or iron core toroids instead of solenoidal air wound 
>> coils in plate and grid tuned circuits before?? I have been pondering 
>> building a HB vacuum tube receiver and would like to use them in the 
>> preselector (RF amp) tuned circuits. Anyone with this experience???
>
> The powdered-iron cores are used in the output pi-L networks of high-power 
> HF amplifiers to get the inductance needed for 160 M in a compact 
> enclosure. RF doesn't see the core, only the inductance. Assuming you stay 
> within the current limits above which a core may saturate, and the applied 
> peak voltage isn't high enough to cause breakdown between individual 
> turns, there's no reason you can't use them in tube circuits.
>
> 73,
>
> Jim, KR1S
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