I've had a few obstacles that I've never been able to overcome in relation to my objective to accomplish covering a two and a half mile stretch of roadway - legally.
My primary concern is reception on car radios, and I'm not particularly concerned about reception in homes because once I get a stream going then the locals (and the world) can just listen on their computers, or Rukos, or other streaming receivers..
Tybee Island, where I live is a tourist spot, my station programming is geared primarily as a resource for tourist information.. like a constantly updated brochure on air, combined with current information of interest to the locals.
My biggest problem is that ground mount install(s) is unfeasible for my situation.. so my options all involve elevated installs - which creates the problem of radiating grounds.. You see where I'm coming from..
The result of a legal elevated install being a range of maybe a few blocks, but that's it.. I can bend the rules a little and accomplish better, but I really don't want to go that route, especially since this is a business venture ( it involves local advertising) and I would hate to establish something with a risk of being shut down for an illegal operation.. It certainly wouldn't sit well in public perception.
So, I decided that the best way to go about it was to install several elevated transmitters with no ground, each covering their limited general area and accepting a brief dead spot between each transmitters range... So, while driving a car along the main two mile stretch and listening to the tourist information it would fade in and out..
Yeah, it kind of sucks, but at least it would be 100% legal, as well as accomplish the primary objective..
Plus, the dead spots disadvantage has a silver lining.. With the remote transmitters all having to be fed via internet feed, the synchronization wont be an issue.. So what if the audio feeds are not synchronized? cause there a dead spot between each area anyway!
Yeah it's far from perfect, but it will at least serve the purpose..
Any views??
How do you plan to feed the xmtrs? (power and audio) Any leads to the source(s) is gonna mess ya up..
If possible you should also try carrier current in the chance that your particular electric lines allow reaching most or all of the target area.
Possibly carrier current on one frequency, radiant signals on other frequencies.
I know, frequency hopping isn't going to appeal to listeners, but we're kind of stuck with the current rules.
There was an article a few years ago. Similar setup-tourist town located on the East Coast.
This guy worked a deal with his City Fathers. He was able to mount "repeaters" on utility poles along the main drag. Coax was strung to interconnect the "repeaters".
The coax was connected to each "repeater" as well as a master transmitter/exciter. The master/exciter was your basic Part 15 AM. The RF along with DC power was fed to the coax. Each "repeater" was a single transistor with appropriate input and output coupling; input of RF and power from the coax, output to a whip antenna.
Each "repeater" had a drive adjustment to set the power level. He had about six or so "repeaters" and was able to cover a fairly large area. Each "repeater" was exactly synced in frequency and audio as they all received the same input from the master transmitter/exciter.
Somewhere I have a schematic of the system.
Solar power each unit and rent a sideband from a local FM radio station to get content to them..
out of curiosity - what brand transmitter?
I ask because there is an installation in a coast town here in NorCal that has a gang of Hamiltons pretty much sitting on top of each other, and boy do they get out...
How do you plan to feed the xmtrs? (power and audio) Any leads to the source(s) is gonna mess ya up..
I'll utilize the little roku units with a shoutcast stream to feed the audio, transmitter locations and power provided by local shops in exchange for free advertising.
I don't know what you mean by "any leads tothe sources going to mess you up.." ..?
If possible you should also try carrier current..
I already have 3 transmitters as well as a fourth one coming soon.. I think the best route for me to take is to utilize what I already have, and have familiarity with..
....mount "repeaters" on utility poles along the main drag. Coax was strung to interconnect the "repeaters".
I perceive no likelehood of obtaining permissions to string coax for 2 miles along the main drag.. and if I did see that as a possibilty, then I would probally use such a method to link the Rangemaster units.
Solar power each unit and rent a sideband from a local FM radio station to get content to them..
Cost prohibitted.. I can hardly afford my cigarettes and beer!
what brand transmitter?
Currently, two Rangemasters.. one which I bought used on ebay last year, but it arrived with a flaw.. works fine for aprox. 10 seconds then all power goes out, I'm going to inquire with Kieth on repairing it. I also have a third Rangemaster to arrive soon, which Artisian graciously held for me a month so I could work up the funds, which I have accomplished..
So, that's three Rangemasters, and 1 SStan3000
...a coast town here in NorCal that has a gang of Hamiltons pretty much sitting on top of each other, and boy do they get out...
I highly suspect that to be a questionable install to say the least.. Sounds striking familiar to what was described in a couple NOUOs from a couple years ago.
Thanks for the replies.. Just to clarify the scenerio of my objective.. I'm talking about setting up 4 transmitters, ungrounded, each which cover their own limited individual area, each far enough from each other to cause interference with each other.. All with the same audio feed, all transmitting on the same frequency.
That way, when a tourist sees in a local publication, or on a flyer, or a sign: "For Tybee Island Information tune in on 1700AM" .. Then in most parts of the island they will be able to do just that..
No, the coverage will not be solid, but they will be able to listen in most of the primary locations of the island.. Thus, the primary objective is accomplished.
It's not all that I had hoped for,but it seems to be a preety good backyard mechanic solution, with no additional expenses I can't afford, and it's legal..
Basically, it can actually get the show on the road instead of the dilly-dallying I've been doing with it the last couple years.
I could (and actually have) covered this entire island and parts of the next with a clear and bold signal using only one single Rangemaster.. but the installation wasn't legal, so I ceased it.. I've been running around in circles ever since trying to determine a legal way of doing the same thing to no avail..
So now,finally accepting realities, I've consider this method to be the closest thing to it.
End80's plan will be a good test of theory.
Below is a NEC analysis of two Part 15 AM ground-mounted setups using 3-meter antennas separated by 2 km, with co-phased carriers on 1700 kHz radiating equal power. The net groundwave radiation pattern from the combined system is shown for a perfect ground plane.
The broadest lobes there are offset from the directions that are +/-90 degrees from the axis on which the two radiators lie. The lobes will be stationary and as shown only if the two carriers are co-phased as they leave those antennas
If they are on the same frequency but not co-phased, the lobes will be stationary, but in different directions than shown. If the two carriers do not use exactly the same frequency, then the lobes will constantly rotate around the radiation center of the system.
In a real-world environment the lobes will not be as deep as shown by NEC, due to cancellation/re-radiation from other vertical conductors in the coverage area, and due to a non-perfect ground plane.
There can also be other effects if the modulation of each transmitter is not in sync, and properly phased (all transmitters must have the same relative modulation polarity).
It will be interesting to see if the performance of such a system was/is ~accurately predicted by NEC.
Rich(F) the estimates of radiation patterns using multiple same-frequency transmitters is useful and informative toward Rich(P)'s End 80 Project, but I'm very worried about his situation of having no ground method for his transmitters.
From experience I've learned how vital at least a minimal ground scheme is to getting a strengthy signal within a meaningful footprint.
I hope you (Rich(F)) will post a second part with your thoughts about how Rich(P) can do something ground-wise given the necessity of an elevated install.
Connecting co-linear, ~1-1/2 meter vertical conductors to the r-f output connector and to the chassis ground of an elevated Part 15 AM transmitter is one possibility that could meet FCC §15.219(b). In such a case the antenna is a (very) short, center-fed dipole, which is a balanced antenna not needing/using a connection to r-f ground.
Possible and maybe probable issues with this are that the loading coil in the transmitter may not have enough range to resonate that antenna, and that it will be relatively narrow-band, more difficult to tune, and to stay in tune.
Not such a good answer, I guess.
PS: The net radiation pattern shapes and characteristics from a pair of such systems using dipoles would be the same as shown in the NEC analysis, for those conditions.
Thank you Rich(F) for providing a technical answer to the (grounding) problem faced by Rich(P).
This might be ridiculous, but what might happen if Rich(P) communicated with the FCC, explained what he was doing, and asked for an approval or a waiver or some kind of thumbs-up for the planned service to Tybee Island?
With only conjecture to go by, there might be no response, or a response might be very bureaucratic, simply quoting rules and giving no hint of special concern. Or maybe the coast guard, national guard, DHS and FCC would arrive with battleships.
There I have revealed my negative expectation of government service to anything less than a monied enterprise.
Never invite the refereee into the game.
Rule #2, Adhere to Rule #1
i tend to agree with wdcx's rules. I had great experiences with the FCC, but that was a differnt time, a different place (Silicon Valley I think gets a lot of free passes...)
Rich Powers hasn't posted in this thread since my posts here.
I hope that is not due to my posts.
His real-world results could be useful for his goals.
I'm only guessing as usual, but I suspect that Rich(P) is simply pre-occupied with other Tybee Island business and will pass by this thread sooner or later.
Guessing some more, I think he'll find the fact that we are discussing the ground problem and other aspects as being helpful and maybe useful.
It's too interesting a project to go undiscussed.