Crystal Specifics — information on Overtone crystals – formulas for crystals – and more– this page is being worked on starting August 10th 2021
FT243 CRYSTAL GRINDING INFORMATION:
I havent gotten around to experimenting with crystal grinding (yest). There is a very good article or two on the QRPME web site. You might want to try it yourself as it is doable by an average joe (I think).
I have a bunch of projects ahead of me. I just sold off most of nettyelectronics.com inventory to Nelson and Im still re-organizing everything around here. I do want to try my hand at grinding some FT243 crystals. It is my understanding that you can move them some to get a target frequency. The QRP Me web site has some specifics on methods of grinding.
VHF RADIOs AND Crystals
You will need the formula for the crystals in order to come up with the frequencies required. What I can do is search my database for anything close to those frequencies. With vhf gear..the crystals will be “overtone”crystals and the radio multiplies the signal with circuitry and on the receive frequency..the IF frequency will be factored into the calculation.
Transmit crystals are generally easier because they are straight multiply of their frequency.
I cannot make crystals as in manufacturing them. Bomar in USA or Crystek in UK does that and usually costs about $50 per xtal. — If you need any furthur info/tips feel free to contact me again. 73 earl ve3ab
DRAKE CRYSTALS ie SPR-4 and CRYSTALS above 20 mhz (in General)
The manual for the SPR-4 does not go into deep specifics about the crystals. (I need a formula). This is because the user would order from Drake (in the past). The crystal marked 25.09 would in all likelyhood be an overtone type crystal. Crystals above 20 mhz are almost always overtone types. Perhaps it might be a third overtone type. One thing you could do is pull one of the crystals for the upper bands and measure it..or.. talk to some discussion groups on Facebook or on the web somewhere and ask around and find out the formula. Perhaps a Drake discussion group on groups i.o or facebook. I will keep this information on file in my book for future demands as well. Let me know how you make out. Often the information is in a manual under “crystal ordering information” — it is in the drake 2b manual that way with a forumala. Maybe I could have missed it in the SPR-4 manual. 73 earl ve3ab
EXAMPLE of a Formula for the DRAKE 2A receiver (I have a 2A here at VE3AB)
I have some of the formulas here in my reference book as I collect information as I go along. A popular radio I have crystals for is the Icom IC22. I have plenty of crystals for the IC22 and some other popular radios. CB radios have formulas as well.