Crystal Specifics — information on Overtone crystals – formulas for crystals – CRYSTAL GRINDING ..and more– this page is being worked on ALWAYS… noted 24 March 2023
FT243 CRYSTAL GRINDING INFORMATION:
I have started custom grinding ft243 crystals. So far..Ive ground up 3 in the 40 meter band. They all work. I have tested them with my Drake 2NT transmitter and my test oscillator. I am going to make a little movie for the my YOU TUBE channel in the near future (noted: Mar 25 2023) 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 used 600 grit emery cloth sandpaper and I taped it to my table top (no glass used) and I ground them up in frequency. At first..they worked in my solid state tester but they wouldnt work in my 2NT transmitter until i gave them a final careful buffing and I cleaned the quartz well with alcohol and then had to reseat the quartz slab a few times to get it working and BEHOLD..THE crystals worked.
The QRP Me web site has some specifics on methods of grinding with instructional video.
MARCH 24 2023 — i have ground a few ft243 crystals now. All 3 of them worked BUT.. i had to clean the quartz piece very well with pure 99 pct alcohol and i had to play around a few times repositioning the quartz slab in the holder and it worked. I tested these 3 crystals on 40 meter band using my Drake 2NT transmitter AND full output with these modified rocks.
I also played around with one of 3rd planet solar custom made ft243 holders complete with trimmer capacitor. I used a 7.110 mhz rock. When mounted in the holder the capacitance of the trimmer made the rock change up to over 7.111 mhz and i could swing the frequency up to about 7,1135 mhz. I will be posting pictures and perhaps include this topic in a video to come in a couple of weeks time.
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
BELOW: EXAMPLE OF INFO ABOUT CRYSTALS below right: EXAMPLE of a Formula for the DRAKE 2A receiver (I have a 2A here at VE3AB)
this below info i picked up off a forum of CB radio. The fellow is looking for a
11.325 mhz crystal. A different fellow wrote me about this same crystal today. I
generally just search my databases and try and find a match in frequencies. I dont go in as great
detail as a manufacturer of crystals would go into when manufacturing a specific crystal.
ON THE FORUM– QUOTE—-
I need to source an 11.325 MHz crystal for my Cobra 2000.
It’s part# X3 QX-086, 11.325 MHz in the SAMS manual, but that’s all it tells me.
I can have one cut locally as a one-off, but they are wanting all sorts of data like ESR,
f stability, calibration tolerance, load capacitance, shunt capacitance, storage/op temperature
range etc etc., and have probably never heard of a Cobra 2000 before.
Barkett Electronics have them, but don’t ship outside the USA.
There are 2 ebay sellers, which can be easily found, who are selling lots and will ship to 43 division.
But they appear to be smaller type 49 holders, rather than the original type 51.
Anyone with experience of these? Any significance in the 11.3258 MHz?
The 2nd picture shows where it goes on the board using the outer 2 holes
for the leads.
Are the 2 inner holes there to accept the smaller type holder?
Radio is in storage right now, so can’t see the solder side of the board.
Hope these pics post OK.
Thanks & 73’s
LAFAYETTE HE-90 VINTAGE CB CRYSTAL INFORMATION
transmit crystal can be a talkie crystal because the transmitter is about as simple as you can get. If you want channel 23 you put in a crystal for 27,255 mhz.
Receive is very weird because it is only a single conversion receiver, but uses a non standard IF frequency of 1.650 Mhz, which is really wide banded…
So for your receive crystal, you would need one that had a frequency either 1.650 above the transmit frequency, or 1.650 below the transmit frequency.
For channel 23.
The transmit crystal would be 27.255 and
The receive crystal could be either 27.255 – 1.65 =
27.255 + 1.65 =
please note to above however— most crystals above 20 mhz are overtone crystals. So in the above example: 27.255 crystal if placed in a crystal oscillator used with a frequency counter to measure the oscillation frequency.. it would measure as : 27.225 divided by 3 or 9.075 mhz
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.