Saturday, November 25, 2017

Polyvaricon Variations -- Polyvaricons Are Not all The Same


When I built the first prototype of the iPhone DC receiver, I just reached into my junk box and used a polyvaricon capacitor for the main tuning control. It was marked PL 051.  I was really pleasantly suprised at the stability of the Variable Ceramic Oscillator circuit.  I could tune the entire 40 meter band with complete stability -- Juliano levels of stability. 

By the time I put the second version into its box (see above), I used a different polyvaricon (the one pictured below).  It worked, but with this part the receiver drifted noticeably.  So this morning I pulled it out and put in a second PL 051 Polyvaricon.  Viola!  Eccolo!  Success.  Drift eliminated.  Rock stable.    

 Has anyone else noticed variations like this in the stabilty of polyvaricons?  

 The dial in this version is an Archer device that has been kicking around in my junkbox for more than 20  years.  I think it was given to me by my old friend Pericles HI8P -- this adds a tremendous amount of soul to this new machine).   The box is an old Bud aluminum chassis.  Man, this thing sounds great.  I will try to post a video soon. 


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2 comments:

  1. sarmaNovember 26, 2017 at 11:22 AM

    I have a varicon(whether poly?) as used in SONY ICF-sw-11that was made in Japan (not China)and when i had minor issues with it and removed for cleaning up,
    it has proved to be made from PTFE

    I was happy.

    The logic "not all polyvaricons are same"Stands well.
    73s
    sarma
    vu3zmv

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  2. W3JDRNovember 26, 2017 at 8:57 PM

    Bill

    I noticed that nice looking HP8640 signal generator on the bench, but I seldom see sensitivity results for your receiver designs. How xbout it? While you're at it, how about some RF overload data for the mixer we've been discussing off line?

    Joe
    W3JDR

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