[R-390] Alternative to IERC tube shields?

[Renée Deeter]

If you desire to run an AC fan at reduced speed place a Capacitor in 
series....1 to 3uf at 400V works great...no heat...and it preserves the 
impedance of the fan.
Renée

John Vendely wrote:
> When noise is a primary concern and a modest volume of air suffices, a 
> simple expedient is running a 220VAC muffin fan at 110V.  It's simpler and 
> more efficient than the cumbersome "solution" of a dropping resistor, which 
> adds heat when you least want it.  It's quiet, and in many situations even a 
> small airflow will provide a worthwhile temperature reduction.   One 
> occasionally encounters a fan which simply won't run at such reduced 
> voltage, but in most cases, it's no problem.  I've employed this simple 
> trick on several occasions with adequate results.
>
> 73,
>
> John K9WT
>
> ----- Original Message ----- 
> From: "2002tii" <bmw2002tii at nerdshack.com>
> To: <R-390 at mailman.qth.net>
> Sent: Monday, August 17, 2009 12:16 PM
> Subject: Re: [R-390] Alternative to IERC tube shields?
>
>
>   
>> Bob wrote:
>>
>>     
>>> And while I haven't done any testing to prove it, I would
>>> think that adding a bit of forced convection cooling would help a lot.
>>> Thanks to cheap and quiet brushless muffin-type fans it is easy to try
>>> at least.
>>>       
>> Definitely a big improvement.  But where do you find these "quiet
>> brushless fans"?  I guess quiet is in the ear of the behearer.  In my
>> view, all the cooling fans I've ever met are "quiet" only when
>> evaluated in a small room with a window air conditioner running.  I
>> generally use oversize fans and slow them way down to reduce the noise.
>>
>> A noiseless option is to build a chimney about 3-6 feet tall (~ 1-2
>> meters for the metrically inclined) that is fed from vents in the top
>> or top-sides of the radio, leaving appropriate bottom and/or
>> bottom-side vents for air intake.  Give thought to the
>> convection-driven air circulation.  Sometimes, one needs to block off
>> some vents and/or make some new ones.  Typically, the chimney for a
>> 390 or SP-600 would be 30-40 square inches in cross-section.  I build
>> them out of corrugated box cardboard, with shallow pyramidal
>> transitional sections. You'd be amazed by how much air such a thing can 
>> move.
>>
>> Best regards,
>>
>> Don
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>>     
>
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