[CQ-Contest] hiss

[David Hachadorian]

----- Original Message ----- 
From: <k8bb at comcast.net>
To: <CQ-Contest at contesting.com>
Sent: Tuesday, July 25, 2006 1:23 PM
Subject: [CQ-Contest] hiss


>I notice that most amateur transceivers, even most (all?) 
>high-end units,
> have quite "hissy" audio amplification. I find this 
> particularly irritating
> but I have ignored it or otherwise dealt with it until it 
> doesn't bother me
> anymore. However, I have *excellent* hearing and I would 
> like to keep it
> that way - pumping high-freqency, white-noise hiss (even 
> very low level)
> through my headset until I become desensitized to it is 
> not looking out for
> a healthy future. :-)
>
> Anybody use an audio filter to get rid of your rig's audio 
> amplifier noise?
> I have a Heathkit HD-1418 audio filter on one of my radios 
> which is a most
> excellent variable audio filter, but the audio amplifier 
> in it is not much
> cleaner than my rig. I have also seen the SCAF-1 by Idiom 
> Press that is
> intended to help low-level filter blow-by (etc.) but 
> supposedly also helps
> fix "white noise" hiss and stuff. Anybody use one? Does it 
> work for this
> purpose?
>
> Can anybody offer an alternative solution for somebody who 
> still has
> very-wide-frequency hearing? I am not really looking for a 
> "ham radio audio
> filter" as much as I am looking to improve the 
> poor-quality audio coming
> from the audio amplification stage of my receivers.
>
> Thanks!
> Don Chisholm K8BB
> Pontiac, MI

Many rigs have a line level audio output, picked off before 
the final audio amp, for use with phone patches or rtty 
decoders. You can run that to the LINE IN jack of a 
soundcard and listen to the audio output of the sound card 
on headphones or amplified speakers, which are usually 
pretty good audio amps.

Also, sometimes the hiss coming out of the radio's audio amp 
is constant, and does not vary with the position of the 
audio gain control. In that case you can add attenuation 
before the headphones (~120 ohm resistor), and improve the 
s/n ratio at normal listening volume.

Dave Hachadorian, K6LL
Yuma, AZ











































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