John, Your recording has substantiated the cautions that I have mentioned. First, attempts to evaluate the K3 AGC response with no signals on the band will lead you in the wrong direction. Secondly, you apparently have the AF Gain well advanced, perhaps even at maximum. Third, you have demonstrated that at low threshold settings the AGC can be activated on receiver noise alone. That fact is demonstrated by a reduction in noise when the threshold is lowered. Reducing the RF Gain has the effect of reducing the range of the AGC.
If you want signals to "pop out of the noise" using real signals on a real band, try setting the Threshold to maximum and set the Slope to minimum. Set the attenuator on and preamp off for 160 meters (unless you are using an inefficient receiving antenna). Start with the RF Gain set at full clockwise and turn the AF Gain up only until you hear a moderate, but tolerable amount of band noise. You may wish to reduce the RF Gain a bit and advance the AF Gain, but keep the band noise received to a moderate level. Try it and see what happens. Again, reducing the AGC Threshold is going exactly the wrong way. 73, Don W3FPR On 10/9/2010 8:15 AM, John Chappell G3XRJ wrote: > Don, > Thank you for your responses and for your efforts on your webpage. > > However, I should have made it clear that I'm not in a noisy environment > and just to make it absolutely clear I've made another recording without > antenna connected to the K3. > Main and RX antenna physically removed, pre Amp off. > Att Off, SSB Bandwidth Normal .... > Recording made in LSB mode rather than my normal CW because it > demonstrates the point more clearly. > > Recording here http://www.g3xrj.com/Recordings/K3_agc_part2.mp3 > > Finally I must point out that I'm not saying the K3 is a noisy receiver > but rather, whatever the AGC does in its present incarnation in the > digital stream, has the effect of increasing the 'rf gain' from 12 > o'clock to nearly 3 o'clock on overall system noise. > > 73 > John G3XRJ > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
