>I *think* I have read (here?) that there is a big difference between
the physics of
>pressurized and unpressurized systems in this respect. Is there anyone
out there
>who understands this and can comment?
>
>73, Pete N4ZR
There is a big difference in cooling efficiency between the turbulent
air that comes directly out of the blower, and the same volume of smooth
flowing air coming out of a long duct. However, that doesn't negate all
the advantages of mounting a bigger blower remotely.
Another very effective method of cooling is to blow air directly into a
sealed anode compartment. Most of the air flows upward through the anode
cooler and is vented directly to the outside through a chimney ABOVE the
anode cooler. There is NO chimney between the base and the anode cooler.
Meanwhile 25-30% of the air flow is allowed to bleed downward through
the tube socket to cool the base seals. This method reduces the back
pressure on the blower, and allows it to deliver much more air than the
conventional base-upward layout. It has been used very successfully for
decades in VHF and UHF amps - so much so, it is regarded as "the normal
method".
73 from Ian GM3SEK
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Pete Smith
>N4ZR
>Sent: 16 March 2013 11:39
>To: amps@contesting.com
>Subject: Re: [Amps] Coupling a blower to an air system socket
>
>I *think* I have read (here?) that there is a big difference between
the physics of
>pressurized and unpressurized systems in this respect. Is there anyone
out there
>who understands this and can comment?
>
>73, Pete N4ZR
>Check out the Reverse Beacon Network at
>http://reversebeacon.net,
>blog at reversebeacon.blogspot.com.
>For spots, please go to your favorite
>ARC V6 or VE7CC DX cluster node.
>
>On 3/15/2013 9:04 PM, KA4INM wrote:
>> On 03/15/13 16:58, Alan Ibbetson wrote:
>>
>>> For minimum airflow resistance for a forced air cooled amplifier it
>>> would seem the blower needs to discharge in a straight line directly
>>> into the underside of the valve socket. This leads to a fairly tall
>>> structure with the blower underneath the RF deck.
>>
>>> What is the "right" way to make the physical connection between
>>> blower and air system socket? Rigid ducting? Something resilient
like rubber?
>>> Or (what intrigues me) how about a fabric transition duct as shown
in
>>> several places here
>>
>>> http://users.pipeline.com.au/~burst/stc.htm
>>
>>> The "floppy" fabric seems attractive as a way to take up minor
>>> (major?) misalignment between the blower and RF deck if they are
>>> built as separate units and should help isolate any blower
vibration.
>>> A competent seamstress (seam-master) would be able to take
>>> differences in duct shape and size in their stride too.
>>
>>> Has anyone got a feel for the pros and cons of the use of fabric
>>> rather than more rigid blower couplings?
>>
>> I should think the difference is negligible and not worth the
bother.
>> Many successful amplifiers using all kinds of air cooled tubes have
>> been built with the system where they are simply pressurizing the box
>> under the tube/s with the air passing through or around the tube/s
above.
>
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