[Elecraft] Re: S meter operationg

Thu May 2 18:09:00 2002

As several pointed out earlier, the S Meter voltage is derived from the AGC loop
voltage when the loop is closed (AGC on). When AGC is off there is no S meter as
a result. This is how just about all current ham rigs are currently designed. 

Jesse suggested just taking the linear, open loop, voltage and correcting it in
a software table to derive the s meter display. This will not work because the
open loop linear signal level voltage will quickly reach its upper limit, well
in advance of the maximum s meter display, preventing an accurate software based
display. 

There are definitely many other ways to approach S meter design. We won't be
changing the K2 design in this respect since it is more than adequate for most
uses, be we will certainly look at alternatives in the future.

73, Eric  WA6HHQ
=======

[email protected] wrote:
> 
> I am offering this hoping it will have a positive impact.
> 
> If the current design does not support an S meter function when the AGC
> is turned off, perhaps the entire S-meter/AGC function needs to be
> re-designed.
> 
> Personally, I do not need a meter to tell me a signal is strong or weak,
> but it does help somewhat in generating signal reports.
> 
> Regards,
> Frank Kamp
> 
> lhlousek wrote:
> >
> > Dear Dr MC,
> >
> > You wrote:
> >
> > "In general, there is no reason why the S-meter should not work when the AGC
> > is turned off. One can disconnect the AGC control point and leave the meter
> > still connected to measure the AGC voltage. You only need to disconnect the
> > control line, not the line to the S-meter. This way, the S-meter still works
> > but the AGC does not."
> >
> > As you point out this works in some designs but in the K2 and other designs I am familiar with the S meter is in the AGC
> > control loop so that its response is calibrated when the loop gain is taken into consideration.  If you open the loop
> > after the meter the meter will be overly sensitive.
> >
> > Lou   W7DZN
> >
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