[CQ-Contest] Noisy shack? Here's the cure

David Hachadorian K6LL at adelphia.net
Mon Jan 17 19:44:14 EST 2005

A while back, I acquired an Ameritron AL-1500 amp. 
Naturally, for contesting use, I set the blower on MAX, 
and it sounds like a Hoover vacuum cleaner! I tried an 
electronic noise-cancelling headset, and it reduced the 
noise quite a bit, but introduced some high frequency 
hiss of its own, and the noise reduction was only 10 dB 
(per headphone spec).  The blower could still be heard 
droning away.

I recently tried a new approach, building a headset 
from scratch, based on a 30dB industrial hearing 
protector. It's a little ugly, but it sure does work! 
Here's the deal:

1. Buy a Peltor H10A hearing protector (about $25)

2. Buy two little speakers from Mouser (253-5405) $4 

3. Use sticky-back Velcro to mount the speakers in the 
hearing protector. Unless you have ears like Dumbo, 
there's plenty of room in there. Dumbo may have to 
pluck out some foam to get more clearance. Just run the 
wires over the ear cups. I used speaker wire from the 
99 cent store, but RG-174 might be nicer.

4. Buy a Heil HC-4 or HC-5 element (about $33)

5. Take a one foot piece of #14 copper wire and solder 
a copper penny to one end. Glue or Velcro the HC-4 to 
the penny. Twist the other end of the wire around the 
headband wires of the hearing protector.

6. Glue some of the acoustic foam that comes with the 
HC-4 over the mike aperture to protect it.


I can just barely hear the AL-1500 blower.

The speakers sound great, plugged into the headphone 
jack. I'm picky about headset audio, and these little 
speakers are winners!

The headset is comfortable, but my ears do get rather 
hot. It helps to lift the earcups now and then to let 
some air in there.

My buddy W7WW also built a set of these, and reports 
that they are the best-sounding headphones that he has 
ever heard with the 1000MP. Apparently the MP has some 
sort of headphone drive issue? Anyway, he reports 
plenty of audio at low settings of the AF gain control. 
He has TWO AL-1500's, and a window A/C. His shack 
sounds like a boiler room.

That's about it. It's ugly, but for about $66 it knocks 
ambient noise down by 30 dB. I think it definitely 
helps in copying those super-weak signals.

Dave Hachadorian, K6LL
Yuma, AZ

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