Random sounds on 75 meters this afternoon...

[Paul, K2ORC]

I just wanted to check in to say, after listening to that audio clip, how much I miss the northeast AMers.  Ay yi yi.  

Still in Va. Beach and and occasionally listen for the gangsters on a random wire and the FRG100, but sadly all I seem able to hear are 4-land slopbuckets which is too depressing for words.

73
Paul, K2ORC

[steve_qix]

Hi Paul,

That sounds like an excellent idea. I have a short audio sample that I believe demonstrates it very well. It was recorded a few minutes before Tim joined Dave and I on 75 meters. If you listen to the MP3 file, you'll immediately notice that it sounds like Dave is using a poorly adjusted limiter, but in fact, he was not. The limiting effect was the AGC in Power SDR version 2.0.8 responding to his audio peaks. Note the gain reduction that immediately follows each word. The screenshot of the audio sample taken in Audition shows the gain change between each word as Dave is speaking.

http://members.cox.net/w1aex.fn31/PSDR_AGC_AM.mp3

Perhaps Steve QIX can confirm that this is the effect he is referring to. I would have to say that this is an extreme example, and I have no doubt that my AGC-T level was not optimal, but it is a strange anomaly.

Rob

Actually, that wasn't too bad.  You'd really have to know what the station in question sounds like for "real", but you could hear the background come up a bit when there was no modulation.  If you put the AGC on fast, and turn up the AGC-T a bit, it will be REALLY bad.  Lots of pumping and artifacts like that.

[W2NBC]

 Interesting on the AGC action on newer versions of the PowerSDR.. Here is a recording of my recently finished cheap SDR general coverage kit .. (fun working with surface mount!).. The PowerSDR version is the most recent 2.0.16 Beta set up to work with softrock... AGC T is set nominally (at 80)..

opinions?

http://dl.dropbox.com/u/17340243/come%20and%20go.mp3

take care,
Jeff

[KM1H]

I heard parts of that same transmission and didnt even realize who it was until the ID. Didnt stick around as I was working on taming birdy generators throughout the house.

Carl

[W1AEX]

opinions?

That sounds (and looks) very smooth Jeff. I lifted a small sample and looked at it with Audition. It shows no variation in gain with modulation. The screenshot shows a flat-line between words instead of the rising gain symptom. Was that recorded using AM or SAM? I think I'll install 2.0.16 this weekend and see how it looks.

73,

Rob

[Opcom]

Man, that was retched. Think about that next time your at a fester wondering how that sweet looking used microphone on someone's table might sound on your station.

Any used mics I get that I can't take apart and boil on the stove for an hour get tossed directly into the garbage.

I always called the crud in mikes "moustache dandruff". My friend Jack calls it "radio breath". Either way it's nasty. An ultrasonic bath will do wonders for all but the element itself.

[WA1GFZ]

"I love you sweet lief"   B.S.

[w1vtp]

Hi
I'm not aware of the AF pumping the AGC on my Flex.  I believe I can put an unmodulated carrier on and vary the AM modulation % and the output will accurately track the mod level.  I'll have to take a function osc home from work to check this out.

I do have a custom setting where I really draw out the hang time for several seconds but have found that the "Long" setting that PSDR offers is OK with me.  Sounds like a nice evening project when band conditions go bye bye.

Al

[Steve - K4HX]

It's how fast you vary the modulation level that's the issue.

Hi
I'm not aware of the AF pumping the AGC on my Flex.  I believe I can put an unmodulated carrier on and vary the AM modulation % and the output will accurately track the mod level.  I'll have to take a function osc home from work to check this out.

I do have a custom setting where I really draw out the hang time for several seconds but have found that the "Long" setting that PSDR offers is OK with me.  Sounds like a nice evening project when band conditions go bye bye.

Al

[WA1GFZ]

I don't know about the Flex rig but HPSDR there seems to be a lot more audio gain than nesessary using PSDR. I tried SSB last night and was way over modulated until I went into the EQ and set the main level pot way back. I was using an EV664.  I was running "6" on the compression setting.
High audio gain and a fast time constant would make things go crazy.