On Fri, Dec 18, 2009 at 11:09 AM, Wes Stewart [via Elecraft] < ml-node+4187383-231954...@n2.nabble.com<ml-node%2b4187383-231954...@n2.nabble.com> > wrote:
> "The more you turn RF GAIN back, the higher the S-Meter will read." > > Well, that's the way it should work, but I can assure you that with my K3 > with the factory default RF Gain calibration, turning the control > counterclockwise from max would cause the S-meter to increase at first, then > *decrease* and then increase again as the control reached minimum gain. > > That is why I've said repeatedly, NOT ALL K3s BEHAVE THE SAME WAY with > respect to RF gain and AGC. > > If you do not have a 50 uV signal source and you haven't run the latest > variant of the RF Gain calibration routine, then you are at the mercy of the > default settings. > > This endless discussion of the "proper" way to adjust your RF gain, > attenuator, preamp, et cetera is pointless when there is this variation. > > Look at Jack Smith's analysis here: > > > http://www.cliftonlaboratories.com/elecraft_k3_and_manual_rf_gain_control.htm > > and pay particular attention to the chart of gain reduction v. control > volts. To be sure, this is a simulation, but Jack is a smart guy and his > lab measurements to back this up are second to none, plus I asked someone at > Elecraft whether this was accurate and the reply was, "pretty much". > > Now introduce into this FET characteristic variations that > are---well---variable, such as Gm having a 2 to 1 tolerance, and you should > be able see how easily one radio can be different from another. > My S-Meter increases monotonically with reduced RF Gain...from S0 at Max clockwise to S9+55 at Max counterclockwise. I made the assumption that everyone has done the new RF Calibration Utility implemented August 11 beginning with version 3.25 (and subsequent updates). I've also calibrated my S-Meter with an XG1. I'm not sure how current Jack Smith's note is but I see his Test Setup was dated 12 January 2009, so I'm not sure if his comments are still valid for the new RF Calibration Utility. Someone asked about my AGC settings. Here's what I'm presently using but I do vary them from time-to-time: AGC-S = 020 (but I seldom use AGC-S) AGC-F = 100 AGC THR = 006 AGC SLP = 013 AGC PLS = nor AGC HLD = 0.20 (only applies to AGC-S) AGC DCY = Soft To be honest I don't really find the AGC settings to be all that critical for my operating, which is 100% CW on 160m (until 10m opens up again). I can regularly copy weak DX signals that others have trouble hearing and I generally have low error rates in contests, so the K3's AGC can't be all that bad. Sometimes I do try turning AGC off for very weak signals but to be honest I've never been able to notice much difference. I never use NR but do have NB on most of the time (DSP t1-6, IF NAR5) outside of contests since I have some local electric fence noise. I have a variety of headphones (Heil BM-10, 2 old Heil ProSets, Extreme Isolation EX-29 and Etymotic ER6). AF GAIN = LO works well for all of these with tons of gain available. I have excellent hearing (hearing test last September) but I don't hear the 12 kHz artifacts some claim to hear. Perhaps it's because I prefer low pitch settings (300 Hz for DX and 400-450 Hz in contests). I seldom need to touch controls on the K3 in contests except for the VFO and occasionally WIDTH, which makes this rig the easiest I've ever used in contests. I also never use RIT but prefer operating in SPLIT mode simplex so I can use the big VFOA knob. FWIW & 73, Bill W4ZV -- View this message in context: http://n2.nabble.com/Noisy-K3-receiver-tp4184529p4188628.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
