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RE: To the party that just told me "less pwr" on 15M

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  • k4djg
    As I use FlexRadio (F1.5K and F3K), I haven t found a way to turn OFF AGC. If I have just missed something, will someone please set me straight, as I WANT to
    Message 1 of 10 , Sep 24 2:07 PM
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       As I use FlexRadio (F1.5K and F3K), I haven't found a way to turn OFF AGC.  If I have just missed something, will someone please set me straight, as I WANT to turn it off!

      Bob, K4DJG

      ---In wsjtgroup@yahoogroups.com, <k7aat.ed@...> wrote:


      For the record on this discussion,  I too do NOT run with AGC turned on.  I  use a SignaLink USB interface and set it to show a signal level on WSJTX of between 20 and 30dB.   I believe that is the recommended range of Joe, the author.


      Additional,  I will grant that I have not played with my radios fine filter system to see if that helps.   Been busy this weekend.  Will experiment later.


      Ed   K7AAT



      From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Carol & Fred Darrah
      Sent: Sunday, September 22, 2013 7:35 PM
      To: Bob; wsjtgroup@yahoogroups.com
      Subject: Re: [wsjtgroup] To the party that just told me "less pwr" on 15M



      There should never be a time when adjacent signals blank the graphical display while operating digital modes. If this is happening, I would think there are somethings wrong in your settings. I never run AGC. RF gain needs to be set to the lowest point you can set it, as it increases the noise levels. A check of your sound card settings is in order and if you use the Mic input be sure the Mic boost is off. The only time a signal should mess with the display is if it is very close to you in distance. Copying very weak stations is also more about the loss in your coax or switches, or even your tuner. I have used several radios and different computers and sound cards, in the past 20 years I have been on digital modes and never had the problem described.
      Fred  N9GUE



      From: Bob <wb4son@...>
      To: wsjtgroup@yahoogroups.com
      Sent: Sunday, September 22, 2013 9:14 PM
      Subject: Re: [wsjtgroup] To the party that just told me "less pwr" on 15M



      Quoting:  "The problem I have,  and one that has no solution I believe,  is that these strong +12 signals blank my graphical display,  and I assume also block much weaker signals from being decoded.  Turning down the RF gain is not going to help copying the weak stations I am trying to decode.    I cannot operate if such a station is booming in.   Fortunately it seems to be a fairly rare occurrence so far."



      First, to put this in perspective, let me give you a slightly different situation.  I'm operating during a contest and desperately want to work that rare DX station that is calling CQ in the 100 Hz gap between two KW stations with 7 element beams on 150 foot towers.  Now I might not be able to copy that rare DX station given the strong adjacent signals.  I might "wish" that the two strong stations would just go away, but I certainly have NO right to ask either of them to QSY or reduce power, or stop what they are doing for my sake.


      Second, what you see on the display is just that -- what is on the display.  It is a visual aid.  It has nothing to do with how the signals are decoded by WSJT -- fat signals on the display mean nothing other than the signal is so strong it still has energy across several bins.


      HOWEVER, and this is often the problem, if you do have one or two very strong signals, AND you have your AGC turned on, then you might have your RF gain automatically reduced to the point that you can't decode the desired signal.  There are two solutions:


      First: Turn your AGC off and reduce your RF gain to the point where your receiver no longer overloads from the strongest signals.  That has helped me many times.


      Second:  Use your filters.  Narrow the passband so that the strong signals are no longer in the passband.  Or use your notch filter to take them out.  Use of the filters almost always works.



      I'm sympathetic -- It would be a great world if all signals were -12, but they aren't.  Different paths make some weaker and some stronger.  Sometimes folks do run excessive power.  Others start sending RTTY in the JT65/JT9 area.  But it really is our job, as operators on "the other side" to do our best with the tools we have to work the ones we want.




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