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Re: [wsjtgroup] Re: TS-2000 Question

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  • Bill VanAlstyne W5WVO
    Agree 100% with everything Gary says here. I used to run a TS-2000 on WSJT modes (on 6 meters), but now run a K3 on both 6 meters and HF. The difference is
    Message 1 of 3 , Dec 7, 2010
      Agree 100% with everything Gary says here. I used to run a TS-2000 on WSJT modes (on 6 meters), but now run a K3 on both 6 meters and HF. The difference is night and day.
      You said you are running “WSJT65-HF”. You have the names of two different software products in there, Randy – “WSJT” (developed by Joe Taylor, K1JT) and “JT65-HF” (developed by Joe Large, W6CQZ). Since you did add the “-HF”, I’m going to assume you mean “JT65-HF”.
      First, there is a dedicated email reflector for JT65-HF that you might like to know about. It is a Google group, and you can find it at http://groups.google.com/group/jt65-hf.
      Reception on most HF bands is noise-limited, so receiver sensitivity is seldom an issue. The thing you want to do is limit the gain of your receiver such that the band noise can be heard, but not be heard LOUD. This will help increase the dynamic range of the receiver. You can do this using the preamp (off), attenuator (on), and/or RF gain (turned down), either separately or in combination, to reduce the gain of the receiver appropriately. Generally speaking, the lower the frequency band, the more noise you will have, and the lower the gain of the receiver should be.
      Having said that, receiver dynamic range comes into play on HF (where it usually doesn’t on VHF) because of the presence of extremely strong signals within the receiver IF passband. When a very strong signal exceeds the ability of a receiver stage to pass it in the linear part of its gain curve, harmonic distortion will result. If AGC is turned on, the strong signal in your IF passband will cause a reduction in receiver gain to a point where weak signals may not be detectable. If AGC is turned OFF in the presence of a very strong signal, the dynamic range of the receiver will be exceeded and you will hear a lot of distortion products -- phantom/ghost signals all across the band, and so forth. Not pretty. The best thing is for very strong and very weak signals to coexist in the same passband without producing any harmonic distortion OR blocking (reduction in sensitivity). The degree to which this is possible is called the receiver’s dynamic range.
      The TS-2000 receiver is NOT KNOWN for its high dynamic range. (That is putting it very charitably. See any of the ARRL Labs or Sherwood Engineering reports.) You can help it out by keeping its gain adjusted to the minimum necessary, but if you are serious about HF operation (as opposed to VHF/UHF, where the TS-2000 does a much better job), you will probably want to upgrade your transceiver at some point to one with better dynamic range performance.
      Bill W5WVO
      From: Gary
      Sent: Tuesday, December 07, 2010 04:36
      Subject: [wsjtgroup] Re: TS-2000 Question


      I have a Navigator and am not overly impressed with the soundcard chip
      in it. It is not stable in freq, so it is hard to get a good clock.
      Maybe I just got a klunker.

      I don't have a TS-2000, but what I suggest should apply, generally. As
      far as the settings for JJT65 it depends on the band and the signals you
      are trying to decode. For general operations (fairly good signals down
      to say -20), I usually don't use any pre-amp on 20 m and below, maybe
      some on 17 and above. Be sure to set the A/D (input audio) to get about
      0 dB with noise in the bandwidth of the receiver and no signals. If the
      signal is really weak, yiou can try a pre-amp on 80 thru 20, but it
      probably won't help too much. For normal ops, set RF gain in the high
      range. Leave attenuation off unless you are getting really saturated
      with a close by signal and can't decode it. Highly unlikely. Again,
      these are general recommendations and there will probably be a lot of
      differing opinions. If you have a lot of noise, sometimes the noise
      blanker or noise reduction can help, but in general I find with digital
      signal demodulation it sometimes reduces the probability of
      demodulation. The radio designers put these controls there for us to
      play with so go ahead and experiment. :)

      As far as AGC, since JT65 is constant amplitude it doesn't really matter
      too much if you use fast, slow, medium, or whatever. If you want to try
      to decode a really weak signal (less than -24 or so) turn off the AGC
      and then adjust RF gain to get the best SNR as seen on the waterfall.
      This may help in some really marginal decodes.

      73 Gary W5GW

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