[Elecraft] K-3 Contest agc settings

Mon Sep 8 09:35:39 EDT 2008

I have found that I tailor the AGC to the types of signals I am 
working with.  Jacks articles were a big help with understanding what 
is going on ( cliffton labs ).

If I am play with weak DX signals, I tend to keep the AGC levels a bit 
  hard, meaning louder.  Low signals low, high signals high.  I have 
also used this, and RF gain together in a contest, to dig weaker 
signals out between the big guns.

When in the midst of lots of big guns, I have to flatten the signals 
out so that my ears are not shorted out by the big signals coming in.

David Wilburn
K4DGW

H Kohl wrote:
> Ed ....
> 
> If I understand what I think you said, the agc settings are
> dependant on:
>     Pre-amp on/off and / or Attenuator on/off
>     The DSP filter width
>     Which 1st IF filter is active
> 
> and .....
> the AGC SLP and THR settings are, for the most part a
> well kept secret and not to be shared.
> 
> However mine are SLP= 8 and THR= 4 and, to me, it
> sounds pretty close to the K2.  I don't use NR much on
> CW because of what it appears to do to the received CW
> signals.
> This is with MCU 2.34 and DSP 1.81, which may affect
> how those two settings are set.
> 
> If SLP= 8 and THR= 4 are bad settings, please tell me
> why.
> 
> 73    Hank    K8DD
> 
> 
> 
> ----- Original Message ----- From: "Ed Muns" <w0yk at msn.com>
> To: "'Mike Kasrich'" <aj9c at indy.rr.com>
> Cc: "'Elecraft'" <elecraft at mailman.qth.net>
> Sent: Sunday, September 07, 2008 11:51 AM
> Subject: RE: [Elecraft] K-3 Contest agc settings
> 
> 
>>> If you are a contester please respond off list.
>>
>> I chose to reply to the list because this is a topic of interest to many,
>> whether contesting or not.
>>
>>> What AGC
>>> settings are you using?  In sprint last night I used the K-3
>>> (first real contest) and I was less than thrilled with rx
>>> performance.  Close by stations seemed to overload the rx.
>>> Something I didnt have with my MKV with the inrad mods and
>>> filters.  Been fiddling with the settings but obviously dont
>>> have it right.
>>
>> All my operating is contesting and I've used two K3s for a year now.  At
>> home, there are several local contesters just a few miles 
>> line-of-sight off
>> the back lobes of my Yagis.  At 1.5 KW they saturate my S-meters.  Still,
>> they are unnoticeable when outside my filters and I'm usually run the
>> default AGC settings.  Most people have reported just the opposite
>> comparison between the MKV and K3, i.e., they prefer the K3 RX in 
>> contest or
>> crowded band conditions with strong signals nearby.
>>
>> The PREamp has more impact on RX overload than the AGC in most cases.  On
>> the low bands, you may even need to engage the ATTenuator.  Don't make 
>> the
>> AGC do all the work by slamming it with too much signal strength.
>> Certainly, you can optimize the AGC for different conditions by 
>> changing the
>> threshold and slope.  For many it is a matter of personal preference more
>> than an absolute "correct" setting.  You will probably want higher
>> thresholds on the lower bands due to the noise level.  The slope is a
>> trade-off between reducing gain for strong signals and still having
>> discrimination between different signal strengths.  If you keep the
>> front-end tamed down with appropriate PRE and ATT engagements, then 
>> you will
>> find the AGC gives you fine control over the range of signal strengths
>> rather than relying on it alone for dealing with the very strong signals.
>>
>>> filters in rig 2.8, 1.8 and 250
>>
>> Remember your "250" filter is really 370 Hz at the -6 dB points, so you
>> might have it engage at DSP bandwidth of 350 or 300 Hz.  But even at 350,
>> the cascade effect will produce an overall bandwidth of less than 300 Hz,
>> which is a bit narrow for CW contesting, IMO.  At DSP WIDTHs of 
>> 400-500 Hz,
>> your roofing filter will be the 1.8 kHz, if you have it configured
>> "normally", so that doesn't give you IMD protection for the DSP with very
>> strong signals located between your DSP and crystal filter widths.
>>
>> (I should point out that some K3 ops don't subscribe to the K3 design 
>> that
>> deploys the crystal filters as roofing filters that are set wider than 
>> the
>> DSP WIDTHs to protect the DSP.  Instead they prefer the passband shape of
>> the crystal filter and effectively eliminate the DSP filter by 
>> configuring
>> their K3 filtering to have the crystal filter engage at DSP bandwidths
>> GREATER than the crystal filter.  Until the DSP WIDTH is reduced to well
>> within the crystal filter bandwidth, the crystal filter is dominating the
>> passband shape and filtering.  Of course, the DSP will still provide 
>> steeper
>> skirts at a point well below the passband.)
>>
>> 73,
>> Ed - W0YK
>>
>> P.S.  Thanks for the Sprint Qs!
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: Elecraft at mailman.qth.net
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
> 
> ____________________________________________________________
> Make more on your investments with qualified asset management. Click now!
> http://thirdpartyoffers.netzero.net/TGL2241/fc/Ioyw6i4ulIRaB5K0PWBazTvoDcbraYe7ekPFGhkhT1cWPPgui57Yhd/ 
> 
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
> 