Posted by
juergen piezo on
Feb 02, 2010; 8:40pm
URL: http://elecraft.85.s1.nabble.com/Attenuator-and-RF-Gain-Settings-tp4503505.html
Hi Lance
This issue is a real problem for me. If I turn the AGC off I need too use the noise blanker. This ruins the K3's strong signal handling performance. Normally I dont need to use the noise blanker. However with the AGC off, electric fence pulses are loud as hell because the pulse stretching blanker is not on with the AGC off.
This problem with the K3's producing noise with AGC on is real problem. On my 40 meter 4 square I basically have a very low noise floor S1 -S2. With AGC on I am getting QRN that the K3 AGC makes thats not really at the level that the K3 is reporting. Yes there is QRN there, but its residual with occasional pops, not the S5 and S7 QRN crashes that the AGC produces. This is not a S meter calibration issue either. Like you my QRN level jumps up mysteriously. With the AGC is off this QRN is not there. I have the threshold set at 2. Even with the ATT on this QRN is being made much more apparent with the AGC on. I hope Elecraft has a fix for this because the K3 is unusable for me in its current form on the low bands.
In the 160m CW contest, because of the QRN I had too use my TS850 and lowly IC735 which seemed too cope much better in mild QRN conditions. The K3's AGC under these conditions was making the band sound like I needed to disconnect the antenna very soon!
John
This is a very interesting thread. I am seeing a similar RF gain/AGC issue on
my K3 (I posted a description of this effect on 1/31). While I have also
defaulted to presetting the AFG and use the RF gain to control receiver
performance, I have noticed issues with the AGC on the K3 that make it
behave differently than other radios that I have tried. The K3 has both
hardware and DSP/firmware AGC.
Strong signals (over S9) cause the AGC to behave normally but weak signals
(DSP/firmware) behave oddly with an apparent, and I say apparent, noise
issue. Audio quality of weak signals with the AGC on also seems to be
slightly compromised as compared to operation with the AGC off.
Perhaps weak signal performance of the K3 with AGC on needs some
DSP/firmware modification. In the meantime, I am using the rig in a similar
fashion as Barry and other have described.
Lance, NR7N
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