> Very interested findings - Fred has a graph of AGC action with AGC > THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
That graph is nearly identical to the information that Jack Smith, K8OZA originally presented two years ago: http://cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm The following table comes from Jack's work: > From the data, my estimate of the threshold settings is: > > AGC THR Corresponding Input > Signal Level > 2 -117 dBm > 3 -110.5 dBm > 4 -105 dBm > 5 -103.5 dBm > 6 -102.5 dBm > 7 -101 dBm > 8 -99 dBm The K2 AGC curve is also presented for comparison. K2 does not have a well defined threshold like that of the K3 but some AGC action (the curve departs from 1:1) begins at around -85 dBm and settles at slope similar to the K3 SLP=09 or SLP=10 (about 1.5 dB audio change for 10 dB RF change) at an RF level around -70 dBm. As a second point of comparison, Sherwood's Receiver Performance Table shows the FT-1000D has an AGC threshold nearly 10 dB higher than the K3 *with the FT-1000D preamplifier enabled*. Since the FT-1000D preamp is at least 10 dB, that represents an overall 20 dB higher ACG threshold (around S8/S9 with preamp off and S6/S7 with preamp on). It seems clear that the K3 would have much better "pile-up performance" if range of AGC THR were expanded by as much as 20 dB either by increasing the "step" (5/6 differ by only 1 dB) or by increasing the number of options. 73, ... Joe, W4TV On 12/9/2010 9:07 AM, Barry N1EU wrote: > > > Cady, Fred wrote: >> >> I made some measurements and have posted the results for your perusal >> and information at www.ke7x.com. >> > Very interested findings - Fred has a graph of AGC action with AGC THR=8 > labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : > > So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 > or s9 by simply reducing the RF Gain control? Can anybody estimate what > settings of the RF Gain control would accomplish that? > > Barry N1EU > ______________________________________________________________ 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
