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Author Topic: Amplifier fan noise  (Read 2678 times)
WM5R
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« on: July 19, 2000, 03:06:58 PM »

The University of Texas Amateur Radio Club, N5XU, has an AM-6155 ampifier on 222 MHz.  It is a rack-mounted amplifier with an Eimac 8930 tube that puts out 400 watts on 222 MHz.  Airflow is from the front of the amplifier, through the body, and out the back.  The rack is pushed up into a corner (there is literally no other place to put it) with about 9" clearance from the wall bhind it.  The amplifier actually sticks out of the back of the rack a little bit, so there's only about 6" of clearance between the back of the amp and the wall.

As this was an FAA ground-to-air unit before being converted to Amateur service, I imagine that the amplifier was just put in a separate room where nobody cared about the fan noise.  The fan noise is very loud and objectionable, though, and especially so in a small radio shack of less than 100 sq. ft.  Are there any common tricks to reducing fan noise?

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KQ6EA
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« Reply #1 on: July 20, 2000, 01:01:59 AM »

Can you vent it to the other side of the wall? How about straight up into the "attic"? Sometimes using some flexible clothes-drier ducting can help muffle the noise, but be careful you don't put too much restriction on the outlet, cutting down the airflow.
HTH, Jim  KQ6EA
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N6QTH
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« Reply #2 on: July 30, 2000, 11:30:55 PM »

I installed a remote ventilator fan in my attic that moves 100cfm through a six inch duct.  That's a lot of air and I have to admit that you can hear the air rushing through the ceiling fixtures.  But my point is that ducting through a wall or ceiling area and mounting the actual fan mechanism in a remote location can do a lot to reduce ambient noise problems.  Check at your local DIY store (Home Depot, Yard Birds, etc.....) and see what they have.  I'm not talking about those little exhaust fans that are typically installed in bathroom ceilings  -  these things look like a turbine and reeeely move some air.
Good luck..............
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PE1RLN
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« Reply #3 on: June 13, 2001, 03:01:35 AM »

Hi there,

The problem of cooling a system is very irritating and often hard to solve. A fan is often used to conduct air through cooling-radiators, but they cause a lot of irritating noise and in a shack that is exactly what you don't want.

I had a computer in a small cabinet with doors that could open. The hot air was not able to excape so the power was cut off everytime it got too hot. Therefore I made a hole in de cabinet with a fan on it. The same problem as you have dit occur: noise.

If it is possible - at my shack it was - you can make a ventialtion-shaft of sewer-pipes of about 3" diameter. You can buy curves and T-parts so you can vary how you want. A hole to the outside of the house or the room is enough. Now, place a fan in the case you want to cool and place the sewer-pipes on it. Now the air will flow through the pipes outside to wherever the hole was made.

The advantage of this system is that the thumble-dryer-hose I wanted to use first was too noisy; the air got trubulent by the ribbles in it. A straight pipe is much better.

That brings me to another idea i had and I'll put that on this forum too. Let's see if it is a good idea.

Have fun with your epuipment and keep up the HAM-spirit!

73 de Thijs, PE1RLN
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