I think this may only apply to Rangemasters and probably also the Procasters as a way to expand range.. I actually had forgotten all about method to expand range until just now seeing it again: http://www.am1000rangemaster.com/pdf/synctransmitters.pdf
But it seems there was an instance somehow, somewhere, sometime, that such an install didn’t fly with the FCC.. Anyone have any recollection or knowledge of this?
Multi-Unit Busts
Not sure but I think those take down’s were over setups where more than one transmitter and antenna system were clustered together in a small space, in effect creating a combined ERP like that of a stacked FM antenna array which will produce a greater field strength than that from individual units separated apart by some distance. I’ve never heard of a case where a synchronized set of transmitters separated by a good distance got tagged for that reason of having synchronized systems separated by some distance, but clustered on the same roof top or in a 20 foot radius..I believe so.
RFB
Right RFB.. the FCC has no
Right RFB.. the FCC has no stance on the use of multiple transmitters – and since the FCC link pertaining to this matter is at the moment for some reason giving an error, here is a copy of it:
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Publication Number: 708832
Rule Parts: Publication Date: 04/05/2007
Keyword: Multiple, Low Powered Transmitters
…..
…..
Question: Are multiple transmitters addressed in the Commission’s Part 15 Rules?
Answer: There are no specific regulations that address the use of multiple Part 15 transmitters. In 1987-1989, the Commission revised its rules for unlicensed operation (GEN Docket No. 87-389). In the original Notice of Proposed Rule Making, the Commission proposed to prohibit the use of multiple transmitters to extend coverage area. However, the final Report and Order in this proceeding did not adopt that prohibition. In paragraph 137, the Commission stated that it concurred with the comments that multiple devices should be permitted provided, the individual transmitters comply with the rules and any emission resulting from the simultaneous operation of the individual, non-coordinated transmitters complies with the rules.
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But back to my question concerning the ZeroBeat method.. I guess I misinterpreted the diagram, I thought that it indicated a cluster on one roof..
So what is that diagram showing then?
Connections thru separate telephone lines to remote locations? — or what?
I don’t get it.
Multiple transmitters are
Multiple transmitters are fine… but, of course, depends on your inspector. I was inspected in Surfside Beach at Surfside 1640. The inspector arrived as a result of a letter I sent to them detailing our operation… when he did, our stuff was exactly as described and, even with our great signal, was left alone to prosper. But again, depends on the inspector…
PS: two rangemasters were literally 50 feet apart in once instance.
Odd
“So what is that diagram showing then?
Connections thru separate telephone lines to remote locations? — or what? I don’t get it.”
Basically what it is describing is using leased telco lines in a dual pair..or two leased telco lines, one for your balanced audio, the other for the reference pulse.
Problem is..unless you got very good equalized telco lines (expensive), that reference pulse won’t work very well through standard telco lines because the frequency response through a regular twisted pair telco line is extremely narrow and won’t pass the 10khz or so reference pulse..thus why it states equalized or wide-band telco lines must be used.
But again, leasing such lines isn’t cheap even these days…and that’s if the telco company even messes with that anymore. ISDN would work, if the telco company offers that anymore too!
RFB
Equalized Telco Lines
For a remote studio connection to a public station FM transmitter 5-miles away, we had two lines. One was equalized to above 15kHz which was our mono audio, and the other was a full time link (could not be hung up) for the remote control, which worked on pulses….. except it did bring back meter readings, so I’m not real sure the bandwidth involved.
The audio was spectacular, and at first cost $50.00 a month, but all at once and overnight it went up to $500 a month!! Our programming studio soon went off the air.
Facing Reality
Indeed. It will cost some $$$$ no matter how one looks at it, approaches it or wishes to no end for it all to be cheap and done with pocket change.
Beyond the simple wire or outdoor antenna sitting in the back yard, if you want an elaborate synchronized setup..your going to have to spend the bucks.
There is just no way around that. Better to face the reality of it than to try to ignore it and reach at thin air cheap solutions that will create more problems and more expense anyway.
I say it again..who says Part 15 is cheap?!
RFB
The Rangemaster website has
The Rangemaster website has all sorts of interesting references on it. We should mine their documents and make a section on here for folks getting started.
Check out the documents under miscellaneous:
http://www.am1000rangemaster.com/downloads.html
The zero beat method is for these transmitters to be literally quite far apart. Far enough apart that you either don’t have an AM signal or barely do at that point. We are talking 1-3 miles in most installs between each of these.
Synchronizing audio spot on at this distance isn’t going to happen easily or cheaply, if at all. Still waiting to hear anyone actually doing one of these systems today.
Your cost effective transport options between sites would be:
1. Internet (cable, DSL or fiber)
2. Wireless (900mhz, 1.2Ghz, 5Ghz)
3. Telco leased lines
Internet is the least costly to get started with. Probably doable in most places at $20 per site per month (under residential plans or special deal with internet provider)
Wireless is iffy. Can be done very well, but requires line of site up high typically tower locations, which aren’t cheap. Been years since I priced tower space. Likely cheaper than it use to be. Wouldn’t expect less than say $100 a month per tower. But, if you are covering a long valley, a high tower on the hill could service all your remote transmitters and be one bill.
Telco leased lines are somewhat exotic and probably traditionally tariffed, meaning way overpriced legacy stuff.
No matter what you choose, need something on the technical side to pull this off reasonably fast, clean, lag free, etc.
To do this, would work with internet provider to put you on your own VLAN in some sort of private channel bonding your sites close together in their network, switching, etc. What you don’t want is three intenet connections that all route to some main point 5 states away. Doing this might be good also to isolate the sites from the general internet, hackers, etc.
The method I see many folks doing with replaying a shoutcast stream from remote server will work, but absent the VLAN / local network tie together, your packets are on the internet, bound to get delayed, lost, etc.
One thought I had to this
One thought I had to this repeater system was to setup a local network on transmitters spaced at 1-5 miles apart (3 to 5 of them).
Interconnect them over internet (cable) but in a VLAN with emphasis on point to point. Meaning the hops or steps from one transmitter site on the network should be in terms of 1-5 hops tops and millisecond time for packets from site to site should be equal from all points and ideally < 10 milliseconds (prefer under 5 ms). This would also have our mixing/studio site on the same network with same requirements. There are tons of linux tools out there to do all sorts of stuff. Haven't found the right tools yet but the concept: Multicasting. Multicasting allows for essentially broadcasting like radio. I believe the checksums, renegotiates, etc. go out the window. If there isn't data there, the stream might go silent or render a sound artifact. The other loose idea I have is is a pipe solution. Linux is known for piping functionality. In simple terms, you have data or in this instance sound on your mixing computer. The sound instead of playing on that, gets piped for audio output to your other sites. I am doing this pipe thing with nothing more than socat and mplayer right now across a LAN with two computers. A third option although even less clear is using a voice server like Teamspeak or Mumble with a high quality bit rate/codec. Mumble is 70k rate by default. Believe that can be bumped up to 128k. Essentially you run mumble client at all transmitter sites. The mumble server runs elsewhere central to things. Jack or Sox probably enable piping of music stream to mumble. I like the mumble / teamspeak idea as they are low latency for voice communications. Any solution like these is going to require an audio stacking solution - way to control audio through various programs in set order. Jack and Sox are often used for that. On top of those you would run your mixing console software (looking for a text based simple solution) and on the end you'd have another tied-in audio mixer/compressor/etc. Yep, I am working on it 🙂
The internet doesn’t support
The internet doesn’t support multicasting. You could build an intranet or hotspot that did.
And therr are no guarantees of packet delivery or order on the internet, it would be tough to synchronize using it.
Best way without a hard wire, I believe, would be point to point radio.