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[Amps] Re: re cooling of coils (Ian White, G3SEK)

To: "amps@contesting.com" <amps@contesting.com>
Subject: [Amps] Re: re cooling of coils (Ian White, G3SEK)
From: Will Matney <craxd1@ezwv.com>
Date: Mon, 06 Sep 2004 03:16:13 -0400
List-post: <mailto:amps@contesting.com>
Ian,
I would think a set of louvered holes at the input for the blower air in the chassis would do it. That is if they were aimed in different directions from one to the other. This would make the incoming air streams sort of bounce against each other making it turbulent I would think.


Will Matney


Will Matney wrote:


What is poor, is those junky 11 meter solid-state "contesting amps" floating around with better cooling than any amateur amplifier made now! The innards may be junk, but by cracky they do add the fans to them. I've seen as high as four 4-3/4" high output muffin fans mounted on a 1kW model.



Hams - especially the new generation of "baby broadcasters" - want amps that sit quietly on the table. In contrast, CB "amp contesters" actually *want* to hear those mighty engines roar. In both cases, the maker aims to please the market.


Many modern amps share the same through-flow air system as the Alpha amps. A particular sound-reducing feature is that the blower is buried deep inside the box.

This system is very good for cooling 'external anode' ceramic tubes, and it also promotes a general airflow around every component in the amp, but its weakest point is cooling the transformer. Although the transformer sits in the full incoming air stream, the airflow there is quite smooth, not turbulent, so the heat transfer is poor.

The cure for that is to add the optional Muffin-type fan on the air inlet. It doesn't increase the total airflow much - its main purpose is to make the incoming air very turbulent, so the transformer is cooled much more *efficiently* (along with most of the other components on the power-supply side). But the price for that is a noisy fan, right onto the rear of the amp where you can hear it.

I don't know what type of fan they supply, but low-noise Muffin-type fans are available that are at least 10dB quieter than the regular type.


-- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek



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