My email address is email@example.com.
I know you’re looking for info beyond what’s already been posted, but in case you haven’t run across it, Steve Hicks wrote a white paper several years back that included a discussion of the AGC-T algorithm (under “Gain Control Considerations”):
BTW, I hope you share your offline questions and answers. AGC/AGC-T comes up frequently, but it’s an important concept and I know that I, and probably others, would benefit!
Hopefully this idea will be implemented one day and we'll have it as an option. It is number 2 on idea list by user votes currently.
Regards, Al / NN4ZZ
al (at) nn4zz (dot) com
SSDR / DAX / CAT/ 6700 - V 1.10.16
I went back over Steve Ellington's video which I found useful in the past. I still don't feel AGC is working like it used to but I guess so much of what AGC does depends on band conditions.
It seems to me that AGC slow is almost peaceful for slow to medium CW. There's not enough time between elements for the noise to come back up. When fast, the noise is almost as prominent as the CW signal. From peace to chaos. For high speed CW a faster mode is probably appropriate.
Still not certain I'm setting AGC-T properly but I'm thinking I'm in OK shape. I did not change the threshold between slow/fast mode change.
Here is the associated audio file: SlowFast.mp3
If anything, I would like to have an adjustable mode maybe. In the case of this sample, a little slower might have cleaned things up even more. Another thing, seeing the effect as in the graph above actually helped me hear the affect. Not unlike the panadapter helping me find find a weak signal in the noise. I sure wish there was more control over the AGC and some sort of graphical representation of the setting right on the panadapter.
1) Visual cues (clues?) as to where the AGC-T setting should be placed. I believe the current AGC-T is arbitrary based on what a person thinks they are hearing or seeing on various meter arrangements. If not a visual cue right on the sacred (or fragile?) panadapter how about something like an indication on the S-meter or a dedicated meter for AGC.
2) Automatic Automatic Gain Control... if you can't give us a visual cue then give us an automatic setting. Work some magical mathematics and set an optimum AGC-T. Keep the Fast/Med/Slow/Off and add AUTO to that list. Make it so the AUTO setting can transfer to the fast/med/slow setting so we can tweak from there.
Enough from me on AGC. I know these suggestions were proposed over the yeeeaaarrrrssss and are probably around #2000 on a list of 10,000.
My next question in my series of dumb questions is about RF Gain. According to the manual, setting RF Gain involves checking the signal level without an antenna (dummy load ok?) and with an antenna. If the difference is less than 8 dB increase in noise on the antenna then additional RF Gain is appropriate. How much?
Dummy Load 0 dB -121.0 dBm Antenna -10 dB -108.0 dBm +13.0 above dummy load 0 dB -119.5 dBm + 1.5 above dummy load 10 dB -123.0 dBm - 0.2 below dummy load 20 dB -124.5 dBm - 3.5 below dummy loadHere are my RF Gain my questions:
1) Going from dummy load to antenna (0 dB) only showed 1.5 dB increase so additional RF Gain is indicated. How much? I thought if I added 10 dB the difference would be +11.5 dB but instead it is -0.2 dB from dummy load.
2) The whole scale looks backwards to me. As I increase the RF Gain from -10 dB to +20 dB the noise drops from -108 to -124 dBm. How does adding 30 dB of gain (-10 to +20) translate to a 16.5 dB drop in the noise level? How does that drop in the signal strength as indicated by the meter translate to an increase in the noise I hear in the headphones?
Not really questioning if things are working right. I'm assuming they are. Just looking for an explanation to help me understand what I'm seeing. In the meantime I'll be pulling out the handbook and doing some web searching to see if I can't find an explanation.
I know as soon as I hit the submit button I'll see my mistake but here it goes...