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Tech Notes

How to Order CTA, LPQRA & CRA Crystals

For the CTA (All Serial Numbers):

Use fundamental series resonant in HC-25 holders for plug-in crystals and HC-18 holders for solder-in wire lead crystals. To determine the crystal frequency, divide the operating frequency of your CTA transmitter by 2. Order this frequency in megahertz.

Example: Operating frequency is 26.15 MHz. 26.15 / 2 = 13.075. Crystal frequency is 13.075 MHz.

To order from Sentry MFG.: The holder is SCM-25 Sentry part 1669 for plug-in and SCM-18 Sentry part 2030 for wire lead.

For the LPQRA (Serial Numbers 1063 thru 1636):

1st oscillator crystal is a 3rd overtone anti-resonant with a 5 picofarad load in an HC-25 holder. To determine the crystal frequency, add 10.7 MHz to the operating frequency of the LPQRA receiver.

Example: If your LPQRA receiver operates on 26.15 MHz, the crystal frequency should be 36.850 MHz. (26.15+10.7=36.85)

To order from Sentry MFG.: The case is SCM-25 Sentry part 1850

The 2nd oscillator crystal for LPQRAs S/N 1063-1636 is an 11.155 MHZ fundamental anti-resonant for a 32 picofarad load in an HC-25 holder.

To order from Sentry MFG.: The case is SGP-25 Sentry part # 2002.

For the LPQRA (Serial Numbers 1-1062 and 1637 to the present):

1st oscillator crystal is a 3rd overtone anti-resonant crystal with a 5 picofarad load in an HC-18 holder. To determine the crystal frequency, add 10.7 MHz to the operating frequency of the LPQRA receiver.

Example: If your LPQRA receiver operates on 26.15 MHz, the crystal frequency should be 36.850 MHz. (26.15+10.7=36.85)

To order from Sentry MFG.: The case is SCM-18 Sentry type 2492

The 2nd oscillator crystal for LPQRAs S/N 1-1062 and 1636 and higher is an 11.155 MHZ fundamental anti-resonant for a 20 picofarad load in an HC-18 holder.

To order from Sentry MFG.: The case is SCM-18 Sentry part 2108.

1st and 2nd oscillator crystals are available from:

International Crystal Manufacturing
10 North Lee St
Oklahoma City, OK 73102

800 725 1426
e-mail: info@icmfg.com

Note: If you are in a rush, crystals may be ordered on an emergency basis for twice the price.

For the CRA in TV VHF Channels (Serial Numbers 884 and higher - in black cases):

Note: All crystals are 5th Overtone Series Resonant in a HC-25 holder.

Channel Aural Frequency Crystal Frequency
(covers high or low offsets)
2 59.75 MHz 70.45000 MHz
3 65.75 MHz 76.45000 MHz
4 71.75 MHz 82.45000 MHz
5 81.75 MHz 71.05000 MHz
6 87.75 MHz 77.05000 MHz
7 179.75 MHz 63.48333 MHz
8 185.75 MHz 65.48333 MHz
9 191.75 MHz 67.48333 MHz
10 197.75 MHz 69.48333 MHz
11 203.75 MHz 71.48333 MHz
12 209.75 MHz 73.48333 MHz
13 215.75 MHz 75.48333 MHz

2nd OSCILLATOR: HC-25 FUNDAMENTAL ANTI-RESONANT FOR A 32 PF LOAD AT 11.155 MHz.

For the CRA in TV VHF Channels (SERIAL NUMBERS 1-883 - in grey or beige cases):

Note: If your crystal has solder-in leads, order HC-18 holders rather than HC-25.

Channel Overtone Series Frequency
Channel 2: HC-25 5th overtone series resonant 81.15000 MHz
Channel 3: HC-25 5th overtone series resonant 87.15000 MHz
Channel 4: HC-25 3rd overtone series resonant 50.35000 MHz
Channel 5: HC-25 3rd overtone series resonant 60.35000 MHz
Channel 6: HC-25 5th overtone series resonant 66.35000 MHz
Channel 7: HC-25 3rd overtone series resonant 52.78333 MHz
Channel 8: HC-25 3rd overtone series resonant 54.78333 MHz
Channel 9: HC-25 3rd overtone series resonant 56.78333 MHz
Channel 10: HC-25 3rd overtone series resonant 58.78333 MHz
Channel 11: HC-25 3rd overtone series resonant 60.78333 MHz
Channel 12: HC-25 5th overtone series resonant 77.05000 MHz
Channel 13: HC-25 5th overtone series resonant 79.05000 MHz

2nd OSCILLATOR: HC-18 FUNDAMENTAL ANTI-RESONANT FOR A 20 PF LOAD AT 21.855 MHZ.