Paul Erickson <paule@sfu.ca> asks
>I need to know how to determine if the following fans will be adequate
>for an 4cx1000/1500 amp. While I can find the cfm specs, I cannot
>find the back pressure specs.
>
>Can anyone help me out?
>
>The fans are made by Augusta Cooling Devices. Model number is 81862.
>they were bought from Mouser Electronics several years ago.
>
>Specs are:
>
>115 VAC
>200 ma
>19 W
>55 cfm
>35 dba noise
>
Eimac provides figures for required backpressure on its external anode
tubes. A simple method for measuring backpressure is provided in the ARRL
handbooks and in Eimac literature. You will need to use a pressurized grid
compartment and a squirrelcage blower.
You may find that a hair dryer (with the heat turned off) is a useful tool
for determining how much air flow and pressure you really need.
Some designs that "inhale" air through the anode, rather than pressurizing
a grid compartment, have shown success. This is worth experimenting with,
although you will not be able to measure backpressure accurately.
Jim N6OTQ
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