drawde 11 Posted September 1, 2022 I picked up a job lot of crystals to use with my old 27MHz Acoms Techniplus radio gear. I tested them and they all worked as expected. They were in need of new labels, so I printed some up. When I took the old labels off, the frequencies printed on the metal casing were as expected for all of the transmitter crystals, but for three of the receiver crystals the frequencies printed on the metal casing were different to the frequency marked on the labels, and the printed frequencies were not ones I was familiar with. See table below: Channel Colour Expected Frequency Marked Frequency 1 Brown 26.995 26.540 2 Red 27.045 26.590 5 Green 27.195 26.740 The job lot also included some crystals without labels, with frequencies printed on the casings that I'm not familiar with. They are: Tx 26.690 and Rx 26.690 Rx 26.800 Rx 27.175 Does anyone know what's going on here? 1 Share this post Link to post Share on other sites
M 800STD 586 Posted September 1, 2022 Are they split bands? Share this post Link to post Share on other sites
drawde 11 Posted September 1, 2022 Ok I figured it out. I noticed that the difference is always 0.445MHz, and when I googled that I found an article that said that receiver frequencies are always 0.445MHz lower than the transmitter frequency (it didn’t say why though), and that different manufacturers label them in different ways. That solved everything except the 27.175MHz crystal which I’m happy to leave as a mystery 1 1 Share this post Link to post Share on other sites
sosidge 624 Posted September 1, 2022 2 hours ago, drawde said: Ok I figured it out. I noticed that the difference is always 0.445MHz, and when I googled that I found an article that said that receiver frequencies are always 0.445MHz lower than the transmitter frequency (it didn’t say why though), and that different manufacturers label them in different ways. That solved everything except the 27.175MHz crystal which I’m happy to leave as a mystery You got to the bottom of the frequency offset on the RX crystals. They aren't always marked that way. 27.175 would be a yellow/green "split" crystal as alluded to above. 1 Share this post Link to post Share on other sites
Wooders28 4703 Posted November 5, 2022 On 9/1/2022 at 8:05 PM, drawde said: That solved everything except the 27.175MHz crystal which I’m happy to leave as a mystery Sold a full set of splits a while back, and just found the pic I took for ebay. (Actually bought these, when I got back into RC ,and went to run at a club with my Futaba Attack R. Some looked confused, when I asked about the 'peg board'.....🙄🤣) As above, yellow/green split. Share this post Link to post Share on other sites