When I ask people about their objection to the modern, mini crystals in a vintage holder, the usual answer is that they feel the modern crystals should not be used in tube equipment. In other words, they think the modern crystals are fragile and won't hold up.
The FT-243 crystals that I rebuild with modern, miniature crystals work very well in almost all vintage tube equipment. That is the main reason people buy them, and many, many hams are using them in that way without problems. I sell some for solid-state equipment, but the majority of the FT-243 units go to homes with tube gear.
One application that may not be well-suited to these crystals are the one-tube, power oscillator homebrew projects. Those work the crystals very hard, with high current through the crystal. Even then the problem is usually crystal heating rather than failure. It is important to know that these rigs can kill original FT-243s too!
But multistage tube rigs are generally fine. In those cases where the oscillator design is pulling a lot of current through the crystal, series resistance on the order of 20 50 ohms can help.
If you'd like an independent review of the modern miniature crystals, see the article in Electric Radio magazine May 2005 by G3UUR. Here's a summary:
Materials science expert Dr. David Gordon-Smith, G3UUR conducted some very tough tests on these crystals using a high-powered Pierce power oscillator circuit and discovered that they were quite rugged. In some cases they can actually prove to be MORE reliable than the old World War Two era FT243 crystals. The crystalline structure is more pure and less prone to failure.
Steve WD8DAS
sbjohnston@aol.com
http://www.wd8das.net/
http://af4k-crystals.com
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