Pistolen08

Hi,

I have an idea, and want to ask a few questions to see if it's possible. My carpc has headphone + line out + mic jacks on it. The headphone jack goes from the laptop to my amp, and the mic goes from the laptop to a microphone used for my cell phone via bluetooth. I thought it would be cool if I used a modified FM modulator belkin tunecast 2 to broadcast onto a radio station so others can hear. In this case, I edited together some star trek clips relating to the borg. Would it be possible to utilize my car's factory antenna to broadcast this? Here is a picture of the antenna jack on my headunit (I'll take a picture of the antenna cable later)


This is a picture of the modified belkin's antenna output



I want to be able to listen to my music regularly, while broadcasting this "hail". Is it possible to have independant channels for headphone and line out? (example: line-out=borg hail, headphone=winamp music). I wouldn't be broadcasting over other commercial stations, and would keep it within FCC regulations. This is just an IDEA, so please don't lock it saying that it is illegal or anything. Here is the audio track I made, so you can get a better idea of what I'm talking about.

CarPC Hail

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Jahntassa

On your onboard audio card, no you can't have two seperate programs using it at once. You'd really need a second audio output, even something USB like the little turtle beach USB Audio out.

And, I suppose as long as you know FCC rules about broadcasting in commercial airspace (whether or not there is a station there or not), then we'll leave that up to you..

2k1Toaster

I want this Boarg hail!!!

Resistance is futile, you will be assimilated.

Well, except for species 8472 that is. They are pretty cool. Fluidic space and all.

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scott_fx

this would be an awesome thing to have if you're caravaning and can talk to each other using something along these lines

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2k1Toaster

My friends and I have done this before. When we drove up to denver we used 2 transmitters and a ours was hooked up to both a mic and a dvd player playing a comedy sketch and theirs a mic. We drove for about 1.5 hours and it was like we were all in the same car! We were even as far apart as about 1/5th mile and maybe a bit more, and they were still working. We were using channels that had no stations on it though somewhere in the 88Mhz range.

Pre-CarPC

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Pistolen08

Since it is a laptop, I will look into PCMCIA audio cards. So this is my plan:
Have an application running in the background (when my car is on) outputting to the PCMCIA card, which will run through the tunecast 2 and out to the antenna. The application will loop my borg hail over and over and I will be able to change the frequency (FCC regulations say no overriding commercial stations . Consequences = $10k fine and 6 months in jail). I still need to find out how to use my car's factory antenna with the tunecast 2 mod. Anyone familiar with the standards?

-Elliot

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Pistolen08

Is the jack circled in red an antenna coaxial cable? If so, I should be able to directly attach the tunecast pcb to my factory antenna and broadcast from that. Does anyone here have a knowledge of antennas? I need to know if a stock car antenna is capable of broadcasting, since they are designed for recieving. Thanks.

-Elliot

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inh

while it would work, it would not work well. automotive antennas are about as good as the foil on the rabbit ears on old tv's.. look for an antenna designed to transmit in the 88-107mhz range.. or make your own, based on wavelength, like I, and im sure others on here, do for wifi

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Pistolen08

So, if I want to broadcast at 98.7 MHz, one cycle = (1/98700000 ~= 0.00000001032 seconds) and one quarter cycle ~=0.000000002533 seconds, and at traveling at c (the speed of light), the electrons can travel ~=0.7594 km in that time, so the optimal antenna should be 759.4 m tall (2491.47 feet ~= 0.47 miles). lmao I don't think that will fit in my RSX.

On another note, the whole reason for my having this idea was to have a use for my antenna since I'm not using radio. Do you have any speculations on how far this might reach if I did just plug in my car's antenna to the pcb on the tunecast?

Here is a pic of the RSX antenna to show how small it is. I can measure it tomorrow, and maybe we can get a better idea of how far it can reach. Thanks for your help.

-Elliot

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2002 Acura RSX CarPC Worklog
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inh

hehe nice math!

what you would do is make an antenna 1/4 or 1/8th wavelength, etc etc... then again this is from someone who's only made antennas for ghz.. so 1/4 wavelegth is like an inch

it would work better than nothing, but i dunno what kinda of range you would get, honestly

Pistolen08

I am trying to keep my install look stock, so I don't want to have any antennas that would look out of place, and I don't want to remove the factory one, so it seems as though I'm stuck with it. Also, if something happens, and the FCC is knocking at my door I don't want to look suspicious lol (even though I wont be transmitting on commercial frequencies). Once I build the circuit, I can test the antenna and go from there. I just want to freak people out at red lights, etc... lol

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inh

then just get an amplifier

Pistolen08

isn't that what the tunecast mod essentially is? If you compare the power outputs before vs. after the pcb is attached, you can notice significant boosts.

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greenman100

no.



300000000/98700000=3.03m

so a quarter cycle would be about .75m, or 30 inches

Pistolen08

Wow, I was quite a bit off lol.
That sounds a lot more reasonable.
So frequency (Hz) = speed of light (m/s) / wavelength (in a vacuum).

If this is correct, the optimal antenna length for the station 98.7 is 30 inches.
Radio antennas are usually very tall, so how can this be?

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