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34269Re: [Heathkit:Yahoo] Waveform characteristics of an SG-8 RF signal generator?

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  • bobfburns2000
    Jul 4, 2014
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      Hi Ray
       
      I would be surprised if the output on any band was sinusoidal. There is no ALC on the oscillator so it will run from cut-off to saturation which will always result in some harmonic output.
       
      To see the true output waveform your scope should have a frequency response of at least several times the frequency that you are observing.
       
      Check the waveforms at the control grid and cathode of the cathode follower to ensure that it is not making the situation worse.
       
      The manual makes reference to harmonics of the output during the calibration phase of testing.
       
      73

      Bob

      Bob F Burns G3OOU
      C Eng, FIET, MSE
      G-QRP 6907
      Crystal Palace Radio & Electronics Club: www.g3oou.co.uk
      Technical web site: www.qsl.net/g3oou
      @BobFBurns on Twitter: http://twitter.com/BobFBurns
       
      In a message dated 04/07/2014 15:54:08 GMT Standard Time, heathkit@yahoogroups.com writes:
       

      I have an SG-8 picked up from a hamfest. 
      I brought it up slowly with a variable AC supply.   It works after a fashion, but looking at the waveforms on my Tektronix 485, the SG-8 thru the various ranges, produces substantial waveform distortions mostly in the bottom half of the cycle, often showing a double hump or dip there.   This is with the output terminated or unterminated.  I do not see any significant low frequency hum in it's output. 
       
      Is this a normal characteristic of the SG-8?  Or, is there some suspect component that needs to be looked at?
       
      Also, the internal modulation doesn't seem to be working. 
       
      Tube substitutions doesn't seem to help.
       
      Any experienced suggestions?
       
      Your attention is appreciated.
      Ray, W4BYG
       
       

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