[Elecraft] Fwd: K3 Wide AGC threshold

[Bill W4ZV]

Bob Henderson-2 wrote:
> 
> The hardware AGC appears to be set at a level which precludes effective
> utilisation of the 100dB+ DR of the DSP system. 
> 

Hi Bob...spoken like a former Orion user!  You're absolutely correct...but
it's actually much better than it was originally.  Why?  I have no clue.

73,  Bill

Hardware AGC threshold change (HAGC Mod Kit)

http://www.elecraft.com/K3/k3_app_notes.htm  (scroll nearly to the bottom)

SMD HAGCMDKT instructions

Both through hole and SMD parts are included. Users can install either set
of parts.

	Some users prefer tuning the band with a wide filter bandwidth selected
(for example, using a 2.7 or 2.8 kHz SSB filter in CW mode rather than a 500
Hz or narrower filter). Strong off-frequency signals (above about S9+5) that
are inside the crystal filter passband can then activate the hardware AGC
circuit, reducing the level of desired signals. 

This modification raises the hardware AGC threshold from about S9+5 to about
S9+25 to +30. The new threshold still protects the DSP's analog-to-digital
converter, while providing better receive performance when wider crystal
filters are used. This is not as significant an issue when using narrow CW
filters (500 Hz and below). 

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