[CQ-Contest] hiss

[George Fremin III]

On Tue, Jul 25, 2006 at 04:15:25PM -0700, Tree Tyree N6TR wrote:
> 
> K8BB writes:
> 
> > 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.
> 
> I have the same issue - and still hear things others can't at the high end.
> 
> Two solutions I have seen:
> 
> 1. Back before we had audio filters, there was a circuit in the older handbooks
> called something like a crud-o-ject.  It was a passive audio filter that had
> some big inductors in it - and really did a good job eliminating hiss.

I use a very simple R/C low pass filter.  It uses one resistor and one
capacitor. I do not recall the values I ended up using I just played
around until I was happy with the sound.

I did look at the noise with a software audio spectrum analyzer on my 
computer to see where the hiss was - it was well above the audio passband of 
the receive audio as I recall - this also gave me a starting point for 
component values.

http://www.qrp.pops.net/filter1.htm

and

http://www.muzique.com/schem/filter.htm

might be useful - I am sure there are other sites with information 
if you do a search.



-- 
George Fremin III - K5TR
geoiii at kkn.net
http://www.kkn.net/~k5tr