Or rather, what is the significance of this:
A few hints; it was found (written on a wall) at an old, mountain top transmitter site. We are renovating this site and it was underneath an old old alarm panel from the 1970’s that I removed. It reads 468 ÷ 45 = 10. and the 468 is significant.
Once upon a time, a person could go to the TELCO demark and get all of the inside numbers for the CO and any number of COs in the area. They would be scribbled on the wall next to the equipment along with many other numbers. This was especially helpful when doing emergency troubleshooting on a circuit that was down. Try to do that these days and the most likely result is an unanswered phone. Most of the smaller COs are not normally manned unless there is a trouble ticket in the process.
Amateur radio operators should recognise this one — 468/f where f is in MHz gives you a fair approximation in feet for the length of a halfwave dipole.
That’s right. This was found on the wall at WSPK, which signed on the air in 1947. It was a part of the Rural Radio Network and received of it’s network program feed over 44.5 MHz from Alpine, NJ (W2XMN).
FM broadcast radio was on 45MHz at one time.