[BC] BE AM-1A Transmitter Air filter Heads-up!!

[Broadcast List USER]

I think it is very cool you built a transmitter.  I considered it.  I  
worked for Viacom, and our DOE, Frank Kramer, REALLY wanted to do it.   
Eimac made and I think still makes cavities, so it isn't that much of  
an insane project.  Today, it would be easier since monitoring and  
control circuits would be MUCH easier than in the days of relays.

However, I have to point out that K&N filters are NOT good filters --  
and my reason to write.

K&N filters allow for more horsepower and more airflow by allowing  
more air to go through the filter.  They do this by not being as good  
at filtering.

They used to have statistics on their web site stating that a normal  
air filter filters out 98% of the dust and grit in the air, and K&N  
filters blocked 96%, only 2% more engine damaging dust and grit gets  
through.

This became a HUGE thread on the Hummer List, back when there was only  
the Hummer and HMMVEE, not the "Wanna Be" other models.  I pointed out  
that going from 2% grit going through to 4% grit getting through was a  
100% increase, not a 2%.  Sadly, far too many people are arithmetic-ly  
impaired.  Hey, this isn't math, it is simple arithmetic.

The reason the K&N filters lasted longer was because they were not  
being blocked by stopping smaller particles.

Remember, the filter that is doing the best job is the dirty filter.   
The dust on the filter is helping it do its job.  The dust is also  
blocking air, but that is a different issue..

I would run away from any vehicle or engine that has a K&N filter  
installed on it.  For racing, OK, I get it.  You sacrifice engine life  
for horsepower.  That is why many race engines have no air filters at  
all.  If your engine has to last eight seconds...

That being written, my wife and I have allergies.  I ran a Honeywell  
"Electronic" air filter for years.  I didn't like the idea of it  
creating ions and discovered 3M makes HEPA filters to replace the  
cells in the Honeywell unit.  Just turn off the power.  Now, we clean  
the metal pre-filters once a month, change the HEPA filters about once  
a year, depending on dust, and we even have one of the 3M three month  
filters in the one-inch filter space in the air handler itself that we  
change about every 18 months.  It isn't really that dirty, but hey,  
why not?

Those metal filters in the front do most of the heavy lifting, and the  
HEPA backs them up.

Putting pleated HEPA filters on a transmitter would extend the filter  
change interval quite a bit, AND let much less grit and dust through.

--chip

On Apr 6, 2010, at 6:28 PM, broadcast-request at radiolists.net wrote:

> Message: 8
> From: "Craig Healy" <bubba at dukes-of-hazzard.com>
> [...]
> The secondary filters were put directly on the input of the 2hp  
> blower used
> to cool the final tube.  Initially I used a pair of Fram filters.   
> The part
> number was for a common Chevy truck with a 350 engine.  Some time  
> after that
> I swapped them for a pair of aftermarket K&N filters.  They did flow  
> better
> and lasted much longer.  And, they were able to be cleaned and  
> reinstalled.
> [...]
> The 2 original Fram blower filters lasted six months or so before
> the pressure differential was 2" or so.  The K&N lasted years.
> [...]
> Craig Healy
> Providence, RI