[time-nuts] 5070B once more.... (actually 5370A fans)

[Lux, James P]

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Richard 
> (Rick) Karlquist
> Sent: Thursday, May 21, 2009 9:26 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] 5070B once more.... (actually 5370A fans)

>   get a bit cooler and some a bit warmer.
> 
> This is incorrect.  ECL components require a minimum airflow 
> velocity that is rather high.  The purpose of the large fan 
> is to maintain this velocity.  If a smaller fan is used, the 
> ECL components will get hotter, even though the air flowing 
> past them is not much hotter.  When you say the fan didn't 
> make any real difference in cooling inside the unit, did you 
> measure the temperature of the ECL DIP's?  "Modern" fans obey 
> the same laws of physics as the original equipment.  They 
> don't magically produce more airflow for less noise.

It's not necessarily magic. It's things like better blade design that gets you same air performance with less noise.  I used to work for a company which made fans for use in the theatrical/entertainment market (so quiet is important).  We went through dozens and dozens of different blade/housing configurations to find ones that were both quiet and performed well. 

Unfortunately, it's a task that is not made simpler by CFD modeling.. The relationship between flow and sound production is so complex that empiricism (i.e. trying lots of ideas) is cheaper (unless you're designing propellors for nuclear submarines).

And, once you have a design that works, you have to be careful about patent infringement.  Each "muffin fan" vendor has patents on their particular blade design.




  It 
> would also be a mistake to assume automatically that all HP 
> equipment is overdesigned.  I remember one logic analyzer was 
> referred to internally as the "logic furnace", which had a 
> high failure rate.

And there's the 8663A signal generator as well. 


> 
> Rick Karlquist N6RK
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, 
> go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>