Hey guys! I am in college now and I live in the dorms which is actually an old hospital! I got permission to mess with some of the stuff left in the building and I have my eye on the things that are in the ceiling. You know those little 4 antenna hubs. Any way I wanted to know if I could somehow wire them up so that I can run my rc car all over the building using the hubs as antennas? Also I have a 900MHz wireless pinhole camera I strap to the car and drive around but the range indoors is bad could I somehow use the same antennal hubs as repeaters for the camera to? Thanks.

 

Figure out what frequency of signal was sent to the antennas.

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I'm no electronics god, i just talk too much.

 

Hmm that may require strategically borrowing a frequency counter but I don't think that will help because they have been disconnected/turned off and I don’t know where the control system is. Any clues?

 

Thurn the whole hospital upide down?

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Il give you shocking experience.

 

I don't think it will work.
The antennas aren't all just in parallel. They must be using splitters to keep the proper impedance match to their transmitter. Splitters cause attenuation so the hospital's pager system must have used a high transmitter power to feed all the splitters. The car's transmitter is low power and by the time it gets reduced by the splitters then each antenna's output would be far too low.

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Uncle $crooge

 

What if a signal amplifier were to be used at each hub? Or could I use just one near my dorm so I can at least get better range with the car? I guess it might be simpler to just boost the power directly from the remote rather than mess with the hub right? What about the camrea can I do any thing to boost its range?

 

You could add a single high-power amplifier or use amplifiers at each hub if you can match the impedances.
Then you can make a wagon for your car to carry a big battery and amplifier for the camera's transmitter.
You will have the RF cops at your door in no time. :wink:

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Uncle $crooge

 

I forgot about leagle stuff.... What is the max my car/transmiter can put out in W? I will try to boost it a little higher but try to keep it in limit. If I am a bit overpower say <1mW in a out of the way place do you think I could tinker a little with over powering the transmitters? I guess the other logical question is, can I aply for a licence so I can have more power? A nother question is, can I hock up the transmiter (controler) to the metal hand rails and get more range? Or even better, everyone in the building has wireless networks........ That would be fun!

 

No. Doing so would change the parameters of the antenna (resonant frequency, radiation pattern, ect).
Your best bet is to use them as is, at the frequency they are designed for.

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Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

So what would be the best/legal way to get more range? The wireless network souds fun but would be expensive and complex what about the power boost for the controler?

 

Government defines the absolute maximum transmitting power, and that can affect the range. Just increase the power of the transmitter or increase the sensitivity of the car.

same thing.

Why not just buy an RC car from a store and play with it?

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-=: The best low-priced components to troubleshoot with are the speaker and the LED :=-

 

Thats what I am doing! I just want it to go farther than it does now. What is the point in straping a camrea to a car if I cant even drive it around the building without folowing it? I mentioned the wireless network because no matter where you are in the building, you have a strong wireless conection. Run the car from over the network!

 

Does your school have a network analyzer? If so, you could hook a couple of the antennas up to it, and determine their frequency response, impedance, etc. (you're looking for the frequency range where the antenna impedance is about the same as the line impedance--probably 75 ohms).

Chances are, there's a frequency somewhere in that region that you can legally transmit on; if not, you can always use stub-matching to get acceptable performance at further-away frequencies.

 

I don't think I will bother with using a network because that will cost some big money just to play. I need to stick to the $10 recever and transmiter mods because what do I do with all of this when I am out of school? "Hey look my car runs on a wireless network!" "Wow, thats cool but there arn't any wireless networks in this town." "I know.... "