On Aug 7, 2005, at 7:01 PM, m.ford wrote:
>
> ----- 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.
-- Not true. Unless lubricated every couple of years, the motor
bearings in the SB-220 simply run out of lubricating oil and the
bearings become brakes.
>>
>> 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?
It's not a problem because the serious RF is above the chassis, not
below it. .
> 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.
I would use one hole, the same size and shape as the outlet.
>
> Should I not be directly under the socket?
I doubt that it would matter much since the 8169 anode cooler is the
choke point.
>
>> ...
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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