I forget whether you are correct about memory being the second thing.
As for CONELRAD, this semi-duplicates my other submission, stations that were assigned to one of those frequencies for normal operation would be part of the emergency news network. In addition other stations that were _close_ to those frequencies would be utilized (after the minor transmitter re-tuning needed).
Station density was such that any location would be within range of any of several stations on either frequency.
Each station would be on the air for a short period, then power off while each of it's 'neighbors' cycled on.
With semi-random switching between transmitters, and a comparatively short 'on' time for any given transmitter, RDF-based navigation was made very difficult.
The emergency news stations were of comparatively high power (I _think_ 25kw minimum, many were 'legal max' 50kw stations) in conventional operation, so that each had a fairly large service area, even during daylight hours. In a war emergency, they may well have been capable of running at significantly higher levels. High-power stations _are_ an advantage -- transmitters can be further apart (causing larger RDF errors when the active station changes), and each station can operate less often, because more stations can reach any given location.
***** Moderator's Note *****During a previous life, I was a broadcast engineer, and although your explanation makes military sense, I'm going to contradict _my_ previous remarks and think aloud here.
Consider:
- Cycling an AM transmitter on and off might seem easy in our modern world, but don't forget that they were working with vacuum tubes and power levels sometimes exceeding 70,000 watts (In the U.S., a station's power rating is the _output_ power, not what goes _in_ to the transmitter: at those power levels, many of the units have to be _water_ cooled). It can take several minutes to turn such a transmitter on, which doesn't make sense if the CONELRAD stations were supposed to switch on and off again and again.
- Most U.S. AM broadcast antenna arrays are designed to put signal nulls in specific directions, to "protect" other stations that share the same frequency. In other words, most AM stations are "Directional", and have multi-tower arrays. Because of this, the antennas are highly reactive, i.e., they are _very_ sensitive to frequency excursions away from their design center. Retuning such an array, even assuming that the directionality of the antennas wasn't considered, is a time consuming, error prone job that DJ's and station managers just aren't trained for, especially during an emergency: even if the output phasor coils were pre-set to switch via relay, the transmitter would have to be retuned for the new reactance anyway, or it would have to be equiped for multi-frequency operation at the factory.
It sounds like a system designed to fail: too much complexity, too many changes, too much of all the wrong ingredients for an emergency communications network. Also, there's the cost: special-assembly transmitters and phasors, custom antenna engineering, out-of-hours maintenance and a more failure-prone signal during the regular day when managers are trying to meet the payroll.
OK, we need a history lesson: who's out there that can cite the authoritative references?
Bill Horne Temporary Moderator
(Please put [Telecom] in the subject line of your post, or I may never see it. Thanks!)