Scott gets the cigar!!!  Yes, in the late 40's and into the 50's, 126.18 was the Air Force "tower common" frequency. Hence, the larger number if those crystals, vice some of the others for ARC-1, ARC-4, ARC-3 and other era equipment. When Mil and civil air homologated the VHF spectrum, the 100 khz channel spacing came into being.  Thence to 50 kHz and 25 kHz.  I read its now 12.5 kHz in Europe.
On 04/28/2022 7:48 PM [email protected] wrote:


Just a guess, but maybe a common interplane freq.? (126.18 MHz), or maybe on HF using the fundamental.  If for VHF, it would follow there be an equally common receiver mixer crystal.

I have a bunch of them around, and 7010 is quite common here as well.


Scott W7SVJ


From: [email protected] <[email protected]> On Behalf Of Doran Platt
Sent: Thursday, April 28, 2022 4:41 PM
To: [email protected]
Subject: [MRCA] Trivia Question


With your kind indulgence,  I ask the following:

Why do we find a proliferation of surplus CR-1-A crystals cut for 7010 kHz?

K3HVG