>> However, measuring cfm requires elaborate test equipment.
This is not so. It requires nothing more than a large plastic bag and a
stopwatch. One can calculate the volume of the bag, put it over the air
exhaust in such way as to not let any air to escape around the bag, and then
simply measure the time until the bag is fully inflated. One or two seconds
can be allowed until the blower reach full speed. Of course, this test
should be made without HV present, because the most convenient place to put
the bag is over the tube chimney. What you get is real CFM figure in the
I stumbled upon this idea reading an excellent article by George T.
Daughters in May 1996 QST.
73 de Mike, YO3CTK
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