Is it a viable thing to do or not? I understand it's difficult to synchronize broadcast transmission, but with today's digital technologies, it seems there should be a way to nail it down with some inexpensive components which will keep the BCB AM signal in bounds of relevant distortion, narrow-band filters, etc., at each TX in a limited (say 5 units) constellation.
The goal here is to develop a wireless network where the audio is all in sync at any receiver passing from one TX to another, thus allowing coverage of maybe 6 miles radius ... enough for this island, terrain notwithstanding.
I've done a slew of research on this, but haven't come up with a truly viable solution so far. If the components are too expensive, are there circuits, pie-pan, Pringle-can backyard solutions I haven't seen yet that I can build to do the job? ... stuff like that??
I believe you are right, Ken, that there must be a very smart and home-do kind of a way of syncing multiple-AM transmitters. I want to see fiber-optics employed in the process. That's my contribution.
I predict this idea will be almost ready for market by Tuesday, once everybody thinks of different ways of doing it.
I really miss Boeing's surplus store. You could pick up miles of fiberoptic cable for next to nothing. IIRC, they even had a fair selection of optical converters and transceiver parts.
But, alas, no more 🙁
Howdy,
Carl brought up the optical cable idea so I went and found this:
http://www.amazon.com/FiiO-Digital-Analog-Audio-Converter/dp/B0053VKP8S/ref=pd_cp_e_1
Seems like a relatively inexpensive solution ... Is anyone here using this type of unit for getting audio from their digital audio out to the TX?
Now, if you can just find the reverse of that D/A converter you could link them together to send the audio program over fiber.
Perhaps a stereo amp with a TOSLINK output.
But then again I don't think TOSLINK goes far enough to be useful.
"Now, if you can just find the reverse of that D/A converter you could link them together to send the audio program over fiber."
Find an old mini-disc recorder or DAT machine. There's your "reverse".
RFB
Thing is even light has a propagation delay, via air, space or through a fiber.
Such a setup would still require delay compensation even for a 6 mile long/radius link.
The only time I ever saw any non-delay propagation was a demonstration of 4 orchestras all linked via a unique satellite system from 4 different nations around the world. This was back in the late 90's. I remember it well, the conductor was that oriental guy with the long hair, always laughed when he would conduct an orchestra cuz on emphasis during a piece his hair would swing wildly like a rock concert goer!
They were all linked up through this ultra no delay satellite system with the conductor in Chicago on a camera, and the orchestras linked also with camera and audio and he conducted all 4 orchestras at once through this system and there was no delay in the audio or video.
Was quite impressive.
Have not seen anything else like it since.
There was rumor some years ago about the bass player of Iron Butterfly and his father developing some new form of communications that was not using normal radio or light to transmit, and that the demonstration was using that technology. Some even have said the reason why that Iron Butterfly bass player suddenly disappeared along with his father is because of what was involved in the technology..to be "exotic"...or more commonly referred to as..beyond normal understood physics and that both were about to spill the beans.
The only form of communication I am aware of that has practically no delay..and was sort of referenced to in another thread..is faster than light communications, or "subspace" communications. Don't laugh, I know as I was there, the labs out at Los Alamos worked on such things back in the mid 80's, shortly after that, the mystery of Iron Butterfly's bass player around 95.
RFB
Funny how things show up. The recent sales flyer from MCM lists the A/D (P/N 33-11635) and D/A (P/N 33-11630) fiber convertors at $34.49 each. Not cost prohibitive.
These offer L/R line level audio input to TOSLINK or coaxial digital output and the opposite, TOSLINK or coaxial input to L/R line level audio output.
The A/D convertor supports up to 48kHz sample rate. The D/A convertor supports 32, 44.1, 48 and 96 kHz sample rates.
There is no mention of distance limitations of the TOSLINK fiber but again, as I understand, TOSLINK fiber is for short distances using a plastic fiber optic medium.
Put up a good AM Part 15.219 installation that
really sounds great and goes far.
Then: AM DX minimalists have discovered in the
last five years or so, that Sony makes some very
inexpensive little AM/FM portable radios. Shirt
pocket size. I think some of these cost around
$20. They are good DX radios. Get a bunch of
those.
Then, IF - IF 88.1, 88.3, 88.5, and 88.7 MHz in your
area have a hole to put a signal, go get a Maxell
P-13 FM transmitter. I've seen them for $13 to
$20 dollars. Actually get a bunch of those.
Go out in your neighborhood. Hook the Sony radios
ti the Maxell transmitters. Put them on little parachutes,
use a slingshot and let them fly out to who knows
where. Then you will have a bunch
of little FM transmitters repeating your AM. Because
the fidelity won't be all that great, run a talk or oldies
format.
You guys have got to know I am stating this with a
bit of humor. The problem will always be the same.
Where to put them, and how to power them. I also
don't know if the P-13 transmitters still exist.
(ACTUALLY THEY DO - your DOGGRADIO editor.)
I own one. It's not the greatest FM transmitter in the
world, but I do like mine. I've had very good luck with
it. But I understand that the quality control may be
poor. You sort of have to mess with it to get it
to work right.
I have actually tried to do this. Someday I will try again
just for the fun of it. That's actually what my solar
power project was supposed to provide energy for -
back last year.
Bruce, DOGGRADIO STUDIO 2
AND
THE MOLE 520 AM UNDER GROUND RADIO
"Now, if you can just find the reverse of that D/A converter you could link them together to send the audio program over fiber."
No need to convert from analog to digital separately here ... I own a studio, the audio generally remains in the digital domain until it passes to the TX, in which case it needs to be converted to analog.
I wasn't really considering optical solutions for sync'ing, but for best audio reproduction at a base station TX.
So, I know radio stations and network facilities sync stuff all the time, otherwise data transmissions would fail.
I also have tried to investigate using GPS clock for sync. This is working with at least one Part 15 setup I know of, but I haven't discovered how it works.
What sort of scheme is used, how is the GPS time signal extracted from a GPS unit, how does it align signals from sources,...? Etc., etc. I haven't succeeded in discovering that stuff so far.
If i had the money.
I would build my TIS style site
Use a GPS timebase CQuAM Tx
optimod 9200 fed by a 320D
the rest of the studio would be all digital right up to the D/A at the input to the aphex 320D
microwave (1.2 or 2.4ghz) AV security transmitters with highly directional antennas. up to 1W is legal and then you throw a high gain directional antenna on it and you are transmitting for miles. i think that the video channel might have enough bandwidth to broadcast the carrier to all the local broadcast band transmitters this eliminating 'flutter' from multiple transmitters.
The carrier would have to be baseband modulated on the 1.2 or 2.4 Ghz carrier. I don't think it's gonna work simply feeding RF carrier into the video input.
RFB
why not? im pretty sure video bandwidth for a color signal is about 6mhz.