Re: [TenTec] Argonaut II/Delta II crystal filters

[Bob Towers <mm0rkt@beeb.net>]

Dr. Gerald N. Johnson wrote:
> On Wed, 2007-08-01 at 11:14 +0100, Bob Towers wrote:
> > I'm not exactly happy with the Jones filter on my Argonaut II.
> >
> > a) the centre of the bandpass shifts up frequency (on USB) when I 
> > tighten the bandpass width
> > b) the narrowest width setting is about 700Hz: I could do with 500Hz or 
> > narrower.
> > The manual warns against adjusting the two sets of 4-pole filters unless 
> > you have a network (spectrum, surely?) analyzer, which I do. Anyway, the 
> > adjustment pots are all locked in position with some sort of fixative.
> Network analyzer is a spectrum analyzer with signal source to measure
> the pass band characteristics. It could probably be done with a noise
> source and the spectrum analyzer or manually using a signal generator
> and detector, though that might be slow to get the necessary detail.
> > Has anyone had a go at adjusting the filters?
> >
> > If so, I would appreciate some advice - which might be, of course, don't 
> > try and fix it!
> > 73
> >
> > Bob
> > MM0RKT
> I'd be inclined to go with an external DSP audio filter if the inherent
> selectivity wasn't quite narrow enough. But I tend to prefer wider
> rather than narrower so I can tell what's going on around the QSO I'm
> copying.
>
> 73, Jerry, K0CQ
>
> _______________________________________________
> Thanks, Jerry, for the advice.
I've recently picked up a Timewave DSP-9+ for a silly (=cheap) price and 
I'll give it whirl. Been using it on the K2 and I'm quite impressed. I 
had a Datong FL3 some years ago and sold it, like a fool....
73

Bob
MM0RKT