----- Original Message -----
From: "Harold B. Mandel" <ka1xo@juno.com>
To: <Amps@Contesting.com>
Sent: Saturday, July 23, 2005 11:05 AM
Subject: [Amps] Protecting Blowers
> Many of us use fans and blowers whose exhaust ports
> are open into the amplifier under-chassis plenum and even
> into the Anode compartment where their airflow cools
> the tank circuitry, and worry about RF fields damaging
> the blower.
>
> In one of AG6K's articles mention is made how an
> RF "event" welds the squirrel-cage shaft with the
> RF amperage absorbed by the blower.
>
> A simple yet effective protective measure is to
> attach a section of aluminum window screening across
> the fan ports leading to the RF compartments, with care taken
> to see that it's well grounded.
>
I need to address this issue with a 8169 project. The blower is rather
large and the exhaust mounts directly under the socket, six inches away
on the bottom cover to the rf deck. Just how large an aperture can I get
away with here? I was planning on a plate with four holes about the size
of a half-dollar to match the pattern of the air socket undercarriage.
Should I not be directly under the socket?
> Running an additional heavy conductor such as a tinned
> braid to the fan enclosure also helps keep the RF on the
> skin of the fan instead of on and in the armature and
> bearing surfaces.
>
> Lastly, bypassing the fan motor leads with some disc
> capacitors can't hurt.
>
> Respectfully,
>
> Hal Mandel
> W4HBM
> _______________________________________________
>
Mike k1ern
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