[Boatanchors] SX-115 Xtal oscillator question

Paul Vasek w2ec at bmjsports.com
Mon Oct 15 21:47:53 EDT 2007


I'm just starting to work on an SX-115 that needs some cleanup and a little TLC restoration. The oscillator crystals for WWV thru 10 meters were not installed in their sockets but had come loose. In sorting them out in order to ensure they were all there, I found a strange situation involving one crystal. In the SX-115 there are four 10 meter band segments, each 500kc wide, consisting of band 10-1 (28.0mc to 28.5mc), 10-2 (28.5mc-29.0mc), 10-3 (29.0mc-29.5mc) and 10-4 (29.5mc-30.0mc). According to the schematic, the oscillator xtals should be: 10-1 = 34.505mc, 10-2 = 35.005mc, 10-3 = 35.505mc, 10-4 = 36.005mc.
   
  Heres my problem, I found the correct crystals for bands WWV, 80, 40, 20 and 15 meters, plus those for 10-2, 10-3 and 10-4. I do have an additional crystal left over for band 10-1, howevr it is 33.505mc, NOT 34.505 mc as needed for band 10-1 (28.0mc to 28.5mc). Since I don't have the radio working yet I can't just plug in the crystal and see what I get when I select band 10-1. Doing the math it looks like a 33.505 crystal (assuming the circuit will oscillate OK) will have band 10-1 operating on 27.0mc thru 27.5mc, which is pretty much the 11 meter CB band, what a co-incidence. 
   
  So I either have an SX-115 with a crystal that was mismarked 33.505mc instead of 34.505mc 40 some years ago, or someone modified their SX-115 to cover the 11 meter/CB frequencies. I'm guesing the latter, so does anyone have a spare 34.505mc crystal for an SX-115 in case I need one?
   
  73, Paul W2EC


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