[Elecraft] Price Comparison and Comment

[Bill Tippett]

Hi Don,

At 08:47 PM 5/4/07, Don Wilhelm wrote:

>I did ask Wayne about the AGC (with respect to the roofing filter 
>selection) and he indicated that the AGC was developed in hardware 
>before the A/D conversion and there is additional AGC action created 
>in the DSP.  As I understand it, it is similar to that which you 
>describe in the Orion.

         If it is like Orion's I'll be happy!

>Yes, from a receiver performance standpoint, only the A/D overload 
>problem counts (and it is critical), but from an operating (AGC 
>pumping) standpoint, there can be undesired performance in the 
>presence of strong signals that pass through the roofing filter even 
>though they are filtered out by the DSP because they will reduce the 
>overall gain of the receiver.  Quite apart from the receiver specs, 
>it does show up during operation and the AGC pumping can be a real 
>problem for weak signal reception regardless of the total dynamic 
>range of the receiver.

         I'm not sure I agree.  If analog AGC is
not activated, there is no analog gain change or
pumping.  According to the note I posted from
Doug Smith, the DSP can internally handle AGC
within the ballpark of 100 dB (noise floor to S9+40).
It first filters signals digitally and then applies AGC
only to signals appearing within the selected DSP
bandwidth, so there is no pumping by signals
outside the DSP bandwidth...unless I misunderstand
...which is completely possible of course!

         All I can say is I have never experienced
the problem in Orion.  I've got to get ready for a
symphony concert now so hopefully all will be
answered in the fullness of time!

                         73,  Bill