[GreenKeys] filters, dead or alive

[David Freeman]

My experience was the opposite. I always had better luck with passive filters than active filters way back when I was building experimental TUs. Perhaps it was just my lack of ability but I found that active filters tuned with a Q equal to passive filters would "ring" on static crashes causing more printing errors. That said, the Dovetrons don't use LC circuits and they work very well. I'm sure most newer TU designs don't use LC circuits either.

Dave, WW8S




On Sun 7/16/2006  7:52 PM, "WB6BLV" <wb6blv at inreach.com> wrote :

> 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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