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[AMPS] Re: Blower

To: <>
Subject: [AMPS] Re: Blower
From: (Frank Donovan W3LPL)
Date: Sun, 28 Feb 1999 08:13:18 -0500
Hi Dave,

Three of my 3-1000Z amps use an older Dayton equivalent of the
2870 rpm 4C443, the other  three amps use the equivalent of the
3160 rpm 4C446.  The 4C443 is significantly quieter than the

I would't recommend the 4C012, it's static cutoff pressure is quite low
and there's a good likelyhood that you are getting only about 10 CFM
across your 3-1000Z rather than the recommended 35 CFM minimum.
Have you ever measured your static pressure?  It's a trivial measurement
to make.

Sub-1800 rpm blowers have a much lower cut-off static pressure
(0.42 and 0.59, vice 0.80 for the 4C443 and 1.04 for the 4C446).

The 2200 rpm 4C006 looks like an attractive alternative with a 4 inch
wheel and 1.58" cutoff static pressure.  Might be interesting to try
this one
as an alternative to the higher rpm blowers.   It does have a note that
must be operated with no less than 0.5" of backpressure, a little
of the blower outlet would increase the backpressure if needed.

I had no difficulty locating additional 3-1000Z tubes for a reasonable
This reflector was very helpful in that regard.  After 25 years of
service and
500,000 DX Contest QSOs, I only had to replace two tubes.  The amps
are now all producing 1500 watts output with 80 watts drive and 3400
volts.  They're ready for the next 500,000 QSOs!


-----Original Message-----
From: David A. Pruett <>
To: Frank Donovan W3LPL <>
To: <>
Date: Sunday, February 28, 1999 2:35 AM
Subject: Re: Blower

>Reverse engineering your description, it would appear that you are
>either a 4C763 or a 4C443.
>My 15M 3-1000Z (my only 3-1000Z at this point) was my first ever
>amp and it was built from what I had on hand.  The blower is a 4C012
>has proven to be OK.  The specs are adequate but not much margin for a
>3-1000Z; 36 CFM at 0.3" SP.
>Did you find enough 3-1000Zs to re-tube W3LPL?
>Good luck to your crew next weekend in ARRL SSB.  We will be QRT -
still in
>the middle of a station rennovation here.  Good thing my
>profit-sharing check arrived this week.  Maybe now I can get stuff done
>Thanks for your info.

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