[GreenKeys] filters, dead or alive

[Eugene Hertz]

I've often thought of that same question.  Has anyone ever produced boards for the st6 that use op amp active filters? 

Eugene

>-----Original Message-----
>From: WB6BLV [mailto:wb6blv at inreach.com]
>Sent: Sunday, July 16, 2006 07:52 PM
>To: GreenKeys at mailman.qth.net
>Subject: [GreenKeys] filters, dead or alive
>
>I notice that most here seem to run passive filters 
>rather than active ones using op amps. Is there 
>some advantage to using these older LC circuits? 
>For me it has always been much easier to just 
>adjust a single pot to set the filter right on the money. 
>Filter gain, Q, and of course center frequency are all 
>set with ease in most active filters, using three resistors. 
> 
>For MARS I had a set of passive filters made by 
>Grant Storey, and they worked well, but not as well as 
>simple active filters. 
> 
>Sidenote - yes actual shift is the critical parameter for 
>HF vice actual frequency for VHF AFSK. That is why 
>the URA-8A (CV-89) will work well on HF using the 
>lower in frequency tone pairs. Anybody running the 89 
>in diversity mode? Getting dizzi from the 'flippin line'? 
> 
>John 
>WB6BLV at inreach.com 
> 
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