Folks, I have received several requests from folks wanting to know how to optimize their AGC Threshold. It is only inferred in the manual. If you want the best weak signal detection that your K2 can deliver, I recommend doing the optimization. A bit of discussion first, then how to do it (no meters other than your ears are required) --
Real optimization depends on what you want to accomplish. Certainly you don't want the AGC to be activated by internal receiver noise because that would mean your K2 would never achieve its full gain (and sensitivity) potential. OTOH, you may choose to have no AGC action with no input signal (but above your local ambient noise) - the only problem doing it that way is that you have to be able to inject that amount of noise during the adjustment, but if you have a constant S-3 power line noise level at your QTH, you don't want the AGC to respond to that noise because it will de-sensitize your receiver. If the S-meter is responding to the noise, you can be certain the AGC is active and reducing the gain! So choose a condition from the above paragraph as your AGC/no AGC Threshold point (I set up others K2s for the internal noise condition - I don't know what the local noise level might be) - for internal noise only, just disconnect the antenna, for local noise level, choose a time and a band with no signals when your ambient noise level is correct for making the adjustment. The procedure is easy - turn the RF GAIN all the way up, PREAMP on, and the AUDIO GAIN up enough so you can clearly hear the noise then switch AGC on/off by pressing both the AGC and PRE/ATT buttons. Adjust the AGC Threshold pot just to the point where you find no difference in the noise levels. Once you have found that point, the adjustment is done - measure the voltage at U2 pin 5 for future reference. Then re-adjust CAL S LO and CAL S HI (and in that order - they interact) so your S-meter will read correctly. Enjoy all the sensitivity (and apparent audio) that your K2 can deliver. 73, Don W3FPR _______________________________________________ Elecraft mailing list Post to: [email protected] 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
