At 08:23 AM 7/25/2006, you wrote:
>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
This has been a problem for many decades. I built a Crud-O-Ject back in
the 70s and still use it. Here is an old note from the Topband reflector that
is a better summary than I can do from memory.
--John W0UN
To: topband reflector <<mailto:topband%40contesting.com>topband@contesting.com>
Subject: Re: Topband: eliminating radio hum/hiss
From: GALE STEWARD <<mailto:k3nd%40yahoo.com>k3nd@yahoo.com>
Date: Fri, 6 Feb 2004 06:01:41 -0800 (PST)
List-post: <<mailto:topband@contesting.com>mailto:topband@contesting.com>
Since several expressed interest, I looked thru my
files last night and came up with the following
articles for building a speech bandpass filter. The
first is by Ed Wetherold, W3NQN. His article "Passive
Audio Filter for SSB" is in the Technical
Corrospondence section of the Dec. 1979 QST, page 50.
The other appropriate article is by Bob Myers, now
W1XT. This article "The Crud-O-Ject" can be found in
the Feb. 1972 QST, page 11. I have built both of these
and they do a great job of eliminating the hum and
hiss. I still use them on a daily basis. Most of the
active filters will also do the job also. I have a
real fancy CW & SSB active audio filter that I built
years ago. It also eliminates the hum/hiss crud but
the audio filters just seem a lot simpler. I just
install them in the audio line and forget about them.
As far as I know these articles are not available
online. I can supply paper copies if anyone needs them
if you send me an SASE.
K3ND
G. Steward
282 Perkasie Ave.
Quakertown, PA 18941
73, Stew...
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