[TenTec] Old vs New = crunch time

[Dr. Gerald N. Johnson]

On Sat, 2010-02-06 at 19:26 -0500, Ronald Hands wrote:
> Dr. Gerald N. Johnson wrote:
> > But that relaxation oscillator has one good feature. It starts and stops
> > fast, so it doesn't hang behind fast keying. A low pass filter on the
> > speaker can help it a lot. I'll have a circuit that I did over 20 years
> > ago up on a web page in a while.
> >   
> It probably achieves the same effect as my MFJ DSP filter (I think it's 
> a model 784b), which does a terrific job of smoothing the Corsair II 
> side tone and also adds other bells and whistles such as selectivity and 
> heterodyne deletion.

Except my passive LC filter introduces no DSP artifacts to the audio. No
hum either. It does demand more power from the audio output stage
though.

> I've heard others complain that their outboard DSP 
> units introduced a disconcerting amount of delay in the side tone 
> signal, but I didn't notice that effect with the MFJ, even when using a 
> keyboard.

In the Orion's DSP users can choose the number of stages in each filter
with the caveat more stages means more delay but steeper filter skirts.
I hear its possible to get enough delay to make tuning awkward because
the careful user has tuned 100 Hz further than the DSP output and then
has to back up to get the desired pitch. Trading delay for precision and
steep skirts is a constant trade off in DSP applications.

> The MFJ unit also boasts very robust audio.  That I was able 
> to buy it secondhand at a very attractive price also added to its charm.
> 
> -- Ron
> VE3SP
> 
Maybe I'll get that filter of mine posted soon. I did get it scanned.
Need to make it into a .pdf next probably. Soon as I find the scans
again.

73, Jerry, K0CQ