Yes, finding oddball crystals is a challenge. I very much doubt that you will find 52.5 (or 55, for that matter) MHz crystals as standard stock items, so your choices are limited. If you can't find them as off-the-shelf or surplus items from the usual sources (including ebay), you'll have to have them made.
So, your next question would be: Who makes custom crystals? The number of good answers is unfortunately diminishing with time, as vendors disappear. About the best recent discussion I've seen is a couple of years old:
Scroll down near the bottom of the first page. A poster "drussell" offers a comprehensive list of potential vendors. Warning: Custom crystals tend to be rather expensive. You may spend as much or more just for the crystal than for a nanoVNA. :)
In discussions with potential vendors, let them know that you would be happy with a third-overtone crystal, if they ask. Fundamental-mode crystals for that frequency range exist, but are incredibly expensive. Plus, the TR50x gens already use third-overtone crystals. No need to pay a surcharge on top of a surcharge.
Good luck!
-- Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 12/31/2020 12:16, Attilio wrote:
Hi everybody,
where can i find the 52.5 MHz crystal? It is hard to find!
Thanks and happy new year
Attilio
