Temporary loss of a satellite signal has been covered by some GPS frequency synch hardware by reverting to a built-in, high-accuracy oscillator. A rubidium-controlled "atomic clock" oscillator is one possible option (link below).
One of these units would be needed for each AM co-channel transmitter in the synched AM system.
Thanks for posting the link to Spectracomcorp. Yep, each TX site would need one of those puppies. Would you happen to have an idea on the cost for those?
RFB
This thread is taking on a life of it's own!
But in reply to your question, RFB, yes, you could have 2 different audio sources and drive 2 different transmitters. They could overlap programming, but you couldn't drive 2 transmitters with the same audio source.
So it makes 2 or 3 transmitters possible, but more than that gets problematic.
That's why I'm looking at extending the useable range of a single audio source with a hotspot. And still waiting for the initial equipment to be delivered.
The comparison of AM transmitter synching to video synching got me to thinking back to the 90s when I became very much involved with the task of calibrating our new video system which was an outgrowth of our much older audio service.
The Amiga Computer had a video output which was 100% NTSC and could be be employed to produce graphics and animations straight to video tape with quality so high that many TV stations used Amiga's.
NewTek became the Rolls Royce by bringing the Video Toaster plugin card that turned the Amiga into a video switching system for high end production.
To fill a need Digital Processing Systems produced a timebase corrector card and a waveform monitor/vectorscope card, all of which still resides in the same room with KDX Worldround Radio, although it hasn't been turned on since 2005.
I remember discovering that television signals have a strong similarity with FM radio signals, in that the "main channel" signal is the black and white carrier, with black being the "floor" level, and every rise in signal above that forming the gray-scale with white being 100% modulation. The color is a sub-carrier, the same as stereo.
Setting up the video chain by calibrating timings and levels was as much a part of producing a video taped program as was running a camera and having talent on the set.
That all makes me wonder what kind of "fine tuning" controls could be designed into a part 15 AM transmitter to at least allow manual manipulation of all the parameters. Could we invent a "poor man's synchronizing method" that could be adjusted with meters, a scope and tweaking tools?
"But in reply to your question, RFB, yes, you could have 2 different audio sources and drive 2 different transmitters."
Ok..so that would be 2 completely different audio sources, or programing, but not necessarily TX B running the same program as TX A shifted by 12 or 24 hours then?
Or does that mean that each TX must run completely different programs regardless of overlapping..ie each TX sees program sourcing from isolated "studios" or sourcing even if in the same room?
RFB
"I remember discovering that television signals have a strong similarity with FM radio signals, in that the "main channel" signal is the black and white carrier, with black being the "floor" level, and every rise in signal above that forming the gray-scale with white being 100% modulation."
For video feeding a video recorder or video monitor..yes.
But for a transmitter, it's the opposite.
Black (zero IRE with sync) is 100 percent PEP. White (100 IRE) would be about 50-60% PEP. Normal black setup (7.5 IRE) with sync and color burst is about 95% PEP.
RFB
Oh man, I did NOT know that about TV transmitters!
But let me share one experience that I miss.....
Watching a TV show on a waveform monitor is like watching dancing ghosts.
The strange stretching and shrinking of signals that look like a mixture of clouds and a dust-storm with circular scribbles as though applied by a baby god.
For comparison, imagine "listening" to a radio program by watching the audio editor waveform streaking up and down like a seismograph. Not in a hundred years will that work.
Let's go back to the drawing board. What is the problem we are trying to solve?
"Watching a TV show on a waveform monitor is like watching dancing ghosts."
Have you ever seen CG characters (letters) in a video waveform monitor looking at the vertical fields? The horizontal fields are even more ghostly!
An even more fantastic display is watching the PEP power meter on an analog television transmitter when feeding it with the "bounce" test signal, which goes from zero IRE black to 100 IRE white! The meter needle bouncing like a teeter totter!! That is used to check the DC stabilizing of the H and V sync pulses which are at -30 IRE.
RFB
What I'm thinking in this discussion is that, if rewired a certain way, TV test equipment can provide that window to another world we have always looked for in pseudoscience and paranormalogy.
We could find, for example, that we are surrounded all the time by other dimensional beings that want, more than anything else, to eat us alive.
That's only one possibility.
Watching a TV show on a waveform monitor is like watching dancing ghosts.
Just to note that a TV show cannot be watched on a waveform monitor -- as far as getting an accurate picture display of the image scene scanned by a TV camera. That waveform monitor is used for other technical purposes.
The only ~accurate display of the original televised scene occurs when that TV waveform is displayed on a TV receiver/monitor compatible with the TV camera/source generating that video waveform.
Also to note that this topic, while interesting, is not very relevant to the performance of synchronous AM broadcast systems.
The talk of gps syncronation and use of an atomic clock reminded me of a previous thought. I was pondering the idea of - if - all programing was pre-recorded material, then maybe a computer at each location utilizing atomic clock software to sync the time precisely on both of them.. and then with a batch file or something; have both pc's start their identical playlist at the exact time, then both of the xmtr audio feeds would be synchronized.. or so it seems.
I had mentioned this idea sometime back, but the theory got shot down. I can't remember why.
What I liked about rich's recent transmission was the "while interesting" portion.
Further, I would argue that discussion of TV waveforms is distantly related to the subject of AM transmitter synchronization.
The reason your post is important is that without it I couldn't have put this post.
As to your most recent input, Rich Powers, I am thinking along similar lines and am working on an idea that is still in formulation which coincides with what you have described.
As soon as I organize my thoughts I'll be here with a related post.
Meanwhile, help yourself to the holiday snacks.
You and you're nonexistent snacks and cookies has caused me to have a craving.. I'm going to 7-11 for some Chips Ahoy.
"Also to note that this topic, while interesting, is not very relevant to the performance of synchronous AM broadcast systems."
Well...perhaps not a direct relevance, but similar relevance to the issue of synchronization.
Both require a reference.
Both require timing.
Both require monitoring.
And both require adjustment to obtain synchronization.
The stray off subject isn't really. More like relevant comparison side note.
IE..to make the subject matter a bit more interesting and start the creative juices flowing to develop an approach for a Part 15 AM multi-transmitter synchronization system, to which the details of phase correcting and time duration/pulse width constants have to be...well synchronized.
Does any of that make relevant sense? 😉
RFB