[Elecraft] Auto Notch Revisited.

[GRANT YOUNGMAN]

The Icom’s manual notch is inside the AGC loop, but not the auto notch.

The early (Version 1) Orion firmware had the auto notch inside the AGC loop, and it was one of the many great features of that radio.  In AM mode, you could punch in audo-notch and it would remove the carrier to let just the sideband energy drive the AGC — which often made uncopyable low-modulation percentage AM signals readable.  And of course, auto-notched interfering carriers would not affect AGC.  When Ten-tec completely rewrote the software (Version 2) they moved the auto notch outside the loop, and there were universal complaints (at least compared to how the notch worked in V1 firmware). It’s unfortunate that there were other factors that eventually led to the rewrite. 

Obviously there are design tradeoffs, and I don’t fully understand them all.  But it does seem that it’s feasible to put a manual (e.g. non-adaptive) notch inside the AGC loop without doing too much damage to IMD or other specs. Maybe even do it as a menu selectable option if there are performance tradeoffs.

Grant NQ5T


On Jul 31, 2014, at 9:23 PM, John_N1JM <johnn1jm at gmail.com> wrote:

> The trouble with the K3 notch is that it is outside the agc loop(audio notch)
> unlike the Icom radio. It may notch out the tone but not the carrier. A huge
> signal will still swamp the receiver. You will get arguments that this is
> better on receiver imd performance but I think I could live with receiver
> imd degradradation for the small if not brief time I would use the  inside
> the agc loop notch.
> 
>> 
>> On 7/31/2014 3:12 PM, David Cole wrote:
>>> Hello,
>>> I find I must also agree with the complaints regarding notching...  I
>>> just cam from a Icom 756 P3, and the notching was far superior to the
>>> K3.