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Heterodyne conversion crystals
On Sep 3, 2:54*pm, Michael Black wrote:
On Wed, 3 Sep 2008, raypsi wrote: Hey Gary, Rocks aren't cheap hehttp://www.icmfg.com/thruhole_crystals.html Maybe in 9 land they pave the streets with gold. Personally I'd go with a programmable divider or PLL. Maybe you like retro, then I'd get some old rocks the ones you can take apart and grind them down to git's the freq's you need. And you can't grind them unless they are quite close to the desired frequency. *Grinding by hand will be too uneven, so the crystal will stop working if you try to grind it more than a tiny bit. It also relies on a big stock of crystals spread around so you can find one sufficiently close enough, something that did seem possible in the years after WWII, but after all this time attrition may have reduced the stock considerably. And realistically, they also have to be bulky FT-243 holders, since those you can open by removing screws, and the blank is held in place with pressure. *More recent holder types require desoldering the case, and figuring out how to remove the blank and then get it back in place when it's soldered in place (or something like that I can't remember how the blank is connected). One of the odd things is that if one has to buy new crystals, a synthesizer will likely be far cheaper. *In the early seventies, synthesizers made a big splash because everyone wanted lots of channels on 2m FM, and the need to have them ground to frequency (and to equipment) made it all very costly, so synthesizers despite their cost and bulk became the norm. Almost forty years later, a synthesizer for a handful of crystals would still be comparatively bulky, but would be even cheaper than in the early seventies. * * Michael *VE2BVW Believe it or not I was making a living sell rocks HI HI back forty years ago. It was like there was a freaking crystal company on every corner. There was so much competition back then the prices was chump change. The crystal companies could have put the big hurt on PLL or programmable dividers. I know the real reason crystals took a back seat, and it;s not what anybody thinks happened. 73 OM n8zu |
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