[1000mp] audio filters for the Mark V

[Harry Yingst]

Actually some of the "old timers" may not hear it.

I know my High frequency hearing is not what it used to be.

Many of us Vets had our hearing messed up while in the Military as
well.






--- "Ian White, G3SEK" <G3SEK at ifwtech.co.uk> wrote:
> J. Mc Laughlin wrote:
> >    I do not know what "the hiss" is
> 
> Just to clarify this point: the "hiss" that everyone talks about is 
> noise at audio frequencies *above* the roll-off of the IF filters.
> 
> The noise originates in the IF stages after the filters... maybe in
> the 
> 455kHz analog notch filter, which is never completely disabled, only 
> de-tuned.
> 
> It isn't a serious hindrance to communication, but it is quite 
> noticeable in unmodified FT-1000s, and also the FT-990.
> 
> Some people don't care about it, while others find it very
> irritating. 
> (I certainly do, because it's a constant reminder of another stupid 
> design error that Yaesu refuse to recognise, and that kind of thing
> bugs 
> me. YMMV, of course.)
> 
> The audio lowpass filters will kill the hiss completely, but you have
> to 
> adjust the audio cutoff frequency whenever you switch IF filters. The
> 
> Inrad IF amplifier mod masks the IF noise, but causes a permanent 
> degradation of close-in IMD performance.
> 
> 
> -- 
> 73 from Ian G3SEK
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=====
Harry - AB2PN

-


	
		
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