I can connect a serial cable from a computer to another device or computer. Guess what, the communications works on timing. It is nothing new and has been around for a long, long time. You are making the timing out to be something incredible, when it is just the way communications works.
I now know one thing beyond any reasonable doubt: jroa is not, in any sense of the word, an expert in electronics.
Someone who throws around serial communications (on a short wire) and AM and FM and PCM with just a Wikipedia fast search should dedicate his life to anything
but communications.
jroa is about a four year undergraduate career from understanding what he is talking about. There is a reason for using a Gigahertz frequency range for GPS: its signals will be absorbed by most surfaces, so the only path from the satellite (or stratellite, if you want) to your receiver is a straight line. Also, the exact time when you receive the transmission is a function of, among others, the frequency of the signal. It is very difficult to determine the exact time when a signal starts, within, lets say, 10% of one cycle. In a 1 GHz signal, this a tenth of a nanosecond which adds 3 cm of error. On a 10 KHz signal, this is 10 milliseconds. That is, even in this hugely simplified example, a 3 kilometer error.
And if you want to calculate altitude with a signal that gives you kilometers of error, you will not distinguish between sea level and the Alps. If I did a better analysis of error, I could show you that you cannot even distinguish between the top of the Himalayas and sea level with a set of 10 KHz signals.
Just to talk about a single real life situation, amateur radio enthusiasts frequently used the 11 meter band to communicate worldwide. They had no idea whatsoever about the source of the transmissions they got until they interchanged information. Signals could bounce tens of times between, say, Europe and the US, and the number of bounces changed frequently during a single transmission.
Our use of frequencies, modulations, coding techniques, antennas, electronics and all other aspects of communications has improved dramatically every decade since before the second World War. These are not subjects where an "expert" like jroa can have a five minute Wikipedia research and give authoritative conclusions.