[TenTec] Pegasus/Jupe Band Scope Questn

[Duane - N9DG]

--- Steve N4LQ <n4lq at iglou.com> wrote:

> Does the bandwidth of the dsp affect the definition of the
> peaks on the scope?

Yes I'm sure that's true. If need be the filtering could be
rather broad in the interest of maintaining high speed
sweeping. 

> If so, wouldn't you need to do some demodulating?

I wouldn't say demodulating as much as simply taking the 16
bit A to D values for each tuning step of the sweep as it
sweeps across the defined range and then translate them into
8 bit values. Report those values back to the control program
just like the current S-Meter does (using a 0-255 range). I'm
sure that 256 steps of amplitude resolution is enough for
what we need or want from the sweep display in a radio.

Also there really wouldn't be a need to programatically
inject the BFO signal either. Could probably dispense with
the 1 Hz tunning steps that is DSP derived as well. Since the
first LO tunes in 2.5 Khz steps a software step size one
tenth that (250Hz) for sweeping purposes I would think could
cover just about all sweep display needs handily. With those
kinds of "sweep mode specific" DSP changes I suspect that
synthesizer lockup time would then be the next performance
limit that would be hit.

Duane
N9DG

> Steve Ellington
> N4LQ at iglou.com
> ----- Original Message ----- 
> From: "Duane - N9DG" <n9dg at yahoo.com>
> To: "Discussion of Ten-Tec Equipment"
> <tentec at contesting.com>
> Sent: Tuesday, February 22, 2005 10:01 PM
> Subject: Re: [TenTec] Pegasus/Jupe Band Scope Questn
> 
> 
> >
> > If you want to see the effects of this AGC speed
> limitation
> > download Ten Tec's control program and run it on a
> decently
> > fast PC of 2GHz or so. Set the band to say 40M at night
> and
> > then bring up the sweep panel and then click on "Sweep".
> It
> > will indeed sweep quite fast but you will also see a
> series
> > of "saw teeth" on the display. The saw toothing effect is
> due
> > to the decay time of the AGC being too long. For several
> new
> > frequencies that sweep is tuning through the AGC will
> still
> > be dropping even though there is no longer a strong
> signal
> > there.
> >
> > I've been long convinced that a *new* "mode" that is
> > specifically designed for sweeping could be done in
> firmware.
> > This mode would not do any demodulation of signals of any
> > kind. It would have essentially instant AGC decay, or no
> AGC
> > whatsoever. All that it would/should do is measure signal
> > strength and report it. If the DSP is only doing that
> then I
> > would think that it could be made to go much faster while
> > still providing a very nice sweeping action. Now I
> believe
> > that the only choice is to pick one of the exiting modes
> and
> > read its S-Meter value repeatedly.
> >
> > Duane
> > N9DG



		
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