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Re: My own Leila experience (was: AO-40 AGC study)



Does "everything" really drop 10dB?
I wonder aloud because my personal Leila experience has been as follows (I guess I'm admitting to having Leila experiences...so much for the 5th!)
1. Siren nearly always appears 4-5kHz above my RX freq
2. Notch is at least 5kHz wide, below the siren freq.  Can't assess how wide above the siren freq.
3. Siren/Notch will last for >30 seconds

This happens much much more frequently than the "nominal case"
1. Siren right on top of my RX freq
2. (can't comment on notch width)
3. Siren/Notch lasts about 5-8 seconds

The first case is Incredibly FRUSTRATING because unless you do tune up in RX, the siren is far enough out of my RX passband (at least mine, and I know others too) that you can't hear it.  It just appears as if the downlink suddenly went down 10dB or more, and for a long time. Of course the problem with not hearing the siren is that you may try to talk thru it...I can't tell you how many folks just keep on going while the notch is in place, and of course I can't copy a thing because I don't have 10dB margin on RX :-)

So I'm not sure what a typical Leila signature is.  Based solely upon my own personal experience, Leila is a poor shot (off frequency), sloppy (notch placement doesn't match siren) and overly persistant (does the notch really need to stay in place for 20-30sec???).  Please note that I am by no means anti-Leila, but the operational implementation seems to be a bit off.  That's OK though, it's a first attempt!

Plus, my initial impression with Leila was that the siren would sound, and then if the offending uplink didn't reduce power, THEN the notch would be placed.  Either my understanding is incorrect, or it does not work as advertised.  

Overall it's my feeling that a significant number of operators may be trying to force their way thru Leila without knowing it.  That can't help the AGC statistics.

Scott NX7U


> 
> From: Estes Wayne-W10191 <W10191@motorola.com>
> Date: 2003/01/15 Wed AM 11:26:35 EST
> To: amsat-bb@AMSAT.Org
> Subject: Re: [amsat-bb] AO-40 AGC study,please read it!
> 
> Has anybody identified the cause(s) of sudden drops in the AO40 downlink signal strength?  I'm talking about when everything is working fine, and then the signal SUDDENLY drops by ~10 dB for ~30 seconds, and then SUDDENLY returns to "normal".  The duration of the drop is longer than a typical LEILA attack, and I can't hear a LEILA siren when I tune up and down a few kHz.
> 
> What do you guys with panoramic receivers see in the passband when everything suddenly drops 10 dB?  Has anybody noticed a geographic pattern when this occurs and doesn't occur?  I suppose this could be caused by an extremely powerful SSTV or RTTY station.  Or perhaps the offending signal is NOT a ham?
> 
> Wayne Estes W9AE
> Mundelein, IL, USA
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