To my ears, this AGC change is a MAJOR improvement! It didn't take any extensive testing to reach that conclusion. The difference is immediately obvious.
As mentioned previously, with low values of slope and high values of threshold, loud signals "blank out" with the current firmware release, so the most aggressive combinations can't be used now. Threshold 15 and slope 0 seem to work pretty well though. I am listening to 20 meter cw now with two K3's. Rig 1 has the new firmware, with threshold 15 and slope 0. Rig 2 has threshold 8 and slope 0 with the current mainstream firmware. Rig 1 sounds MUCH cleaner, both on the loud W1AW code practice signal, and on the 7O6T pileup. The pileup is not too deep on any one frequency, so it's not the ultimate test, but signals do sound much cleaner on rig 1. If more aggressive values of slope and threshold can be accommodated without the blanking effect, the improvement will be even greater. Elecraft is definitely on the right track here. Thanks for working on this issue! Dave Hachadorian, K6LL Yuma, Arizona -----Original Message----- From: Wayne Burdick Sent: Sunday, May 06, 2012 4:06 PM To: Elecraft Wayne Burdick - N6KR Subject: K3 AGC improvements (MCU rev 4.50 / DSP 2.74) Hi all (everyone is BCC'd on this), As I mentioned, we've made some improvements to the K3's DSP AGC. No hardware changes are being made this time. This is strictly a firmware change to the MCU and DSPs. One change will benefit the AGC at all settings: elimination of the interpolation errors in the AGC onset curve. This by itself adds some clarity to signals. The other change allows the AGC THR parameter to be set to a higher value -- up to 20. The original default (5) put the threshold for AGC onset to around S2 or S3, and the max was 8 (about S4-S5). A setting of about 11 now puts the threshold around S7, and the new max of 20 puts it around S8-S9. Any signals below the threshold should not activate DSP AGC at all. (Hardware AGC is not affected by the changes; it still kicks in around S9+20 dB.) Two interesting side-effects of raising the threshold: (1) noise blanking may seem to be much more effective than before; (2) QSB on weak signals may be more noticeable. ********** IMPORTANT: Please set AGC SLP (slope) to something above 0, for now, as this appears to cause problems. Setting AGC THR above 8 will *temporarily disable* auto-notch and noise reduction. The switches and NR level control will still behave the same, but they will have no effect unless you set the threshold back to 8 or lower. We may make the threshold per-mode in a later release so that, for example, you could set a high threshold for CW but still have a threshold of 8 or lower for other modes, allowing NR and auto-notch to still work in this case. The reason autonotch and NR must be disabled for high-threshold AGC is that the dynamic range of signals can be an order of magnitude higher. We'll be experimenting further to see if NR and autonotch can be modified to still allow their use with high thresholds. But generally speaking, pileup conditions in CW (the principle target) don't require the use of NR, and autonotch doesn't apply to CW. *********** Keep in mind that it may be difficult to reproduce the conditions under which in-band IMD has been reported. Most operators have claimed it was caused by "dozens" (maybe even hundreds!) of signals in the S5 or lower range, all practically on top of each other. This effect has gotten worse in recent years due to the prevalence of spotting. Short of actually heading for a DX QTH, you may not be able to reproduce the conditions accurately. But it is true that some operators prefer a higher AGC threshold in general, while allowing AGC to remain turned on. You'll now have that capability with the K3. This has been touted as a difference in favor of some other radios. Not any more :) The new firmware is attached. As with a beta release, you'll need to unzip (extract) the files and put them somewhere easily located, usually on the desktop, then tell K3 Utility where to find it. You must load all of the new code, so use the "send all" option. Make sure after loading that your MCU is at rev 4.50 and both DSP and AUX DSP at 2.74. Please test the new code in a variety of conditions. If you have two K3s, please put the new firmware on one of them, set them both up identically, and compare them by switching the antenna between the two radios. Assuming it passes your own tests, feel free to pass it on to anyone who you think might benefit from it, including those planning DXpeditions (or even *at* a DXpedition, if they're willing and able to try a new firmware load). Also, by all means post your observations to the Elecraft reflector (or elsewhere). If all goes well, we can release this as beta code next week. 73, Wayne N6KR ______________________________________________________________ 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
