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The best range ( RF power ) — Parallax Forums

The best range ( RF power )

markustermarkuster Posts: 184
edited 2009-03-20 01:07 in BASIC Stamp
Hi,

I need to turn on and off a motor with two Basic Stamps.

One Basic Stamp at the transmitter and the other one at the receiver.

But my problem is that I need 15 miles ( very long range)

Do you know where can I buy long range transmitters?

Thanks, Mark

Comments

  • FranklinFranklin Posts: 4,747
    edited 2009-03-18 22:11
    More info? Is there anything between these two points? Phone lines? You can do this but I don't think it will be cheap.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • SRLMSRLM Posts: 5,045
    edited 2009-03-19 00:25
    I'm going to steal a page from Mike's book, and post his link: http://www.digi.com/products/wireless/long-range-multipoint/xtend-module.jsp

    Note that the 40 miles is for line of sight, with 3000 ft being the range in urban situations.

    This link may help too: http://forums.parallax.com/showthread.php?p=759557
  • FearTurtlesFearTurtles Posts: 89
    edited 2009-03-19 00:55
    What SRLM will do it so long as it is clear line of sight and about 19' clear Fresnel zone. I think Fresnel is the right word. It is the clearance between the line of
    sight and any object at center distance. With those transmitters you can legally use a 6dbi antenna at max power. But for long distance I would reduce the power level and increase the gain of the antenna to 15dbi. This will result in the same effective power with less interference. Anyway this is about the only solution with out the need of a Licence. If you do have clear line of sight you can also opt for 2.4 gig or 5 gig equipment. You should be able to find 2.4 gig equipment cheaper then the 900mhz. 900 mhz just penetrates trees better.
  • markustermarkuster Posts: 184
    edited 2009-03-19 03:15
    Hi,

    The best solution I found at digi.com is the Xtend module.

    But there are buildings between the signal (between the antennas).

    So, I need more power.

    I know it is almost impossible to find a product but If you know about any other alternative
    will be very useful .

    thanks, Mark
  • SRLMSRLM Posts: 5,045
    edited 2009-03-19 03:41
    You could always use the classic method of repeaters: radio towers in strategic locations that take in data on one frequency and automatically retransmit on another frequency. That way, it's like you have a middle man. ARRL has thousands on their frequencies, but I think it's probably frowned upon to use them for lots of data transfers. Otherwise, your best bet (and probably only solution) is to become a licensed ARRL operator and use one of the lower frequencies. Those radios can reach thousands of miles.
  • roadrunner3groadrunner3g Posts: 36
    edited 2009-03-19 09:21
    if you have internet at both ends you can try remote desktop (free) or goto my pc ($$$), then you only need 1 stamp chip. just program it to use the debug termanal so you know what the chip is doing.
  • FearTurtlesFearTurtles Posts: 89
    edited 2009-03-19 13:19
    An alternative is to get a amateur radio licence and use 2 meters. There is a communications system APRS which will allow you to send short text messages that might work for you. You have to test for the licence and pay a small fee but they sell books with all the possible answers to the test so its not really that hard. This idea is something that I have been toying with. My question though can a basic stamp handle receiving a 25 or so letter text string sent at 1200baud. It might be better to use a propeller chip instead.
  • FearTurtlesFearTurtles Posts: 89
    edited 2009-03-19 13:38
    Just to add that accually doing this under an amatuer radio licence might be illegal if this is a commercial project. It does not sound like 900mhz will work for you. I don't know how remote the motor is but you might play around with wifi and a directional antenna to see if you can pick up a signal anywhere. This might require a tower to get above some objects but if lets say there is a hotel with wifi near by maybe you can arrange to use thier Internet connection. I mean its not like you will be surfing the web and using a large amount of bandwidth.
  • manzanamanzana Posts: 24
    edited 2009-03-20 00:13
    Why not use a cell phone? Run the audio into Stamp. I dial a GoPhone with my BS2 and it is amazing. Just need some cheap Radio Shack relays.

    manzana , AB4OB , ham 47 years
  • NR1XNR1X Posts: 111
    edited 2009-03-20 00:41
    Not too long a go ken gracey posted a project that would do just what you want!!! it used radio modems and hand held radios .. packet radio is the way to go. as long as your not going to be using it too make money in any way. all you need is an fcc licence.Tech class is easy to get and well worth it for anyone.. packe t radio can also be internet linked and infact is ..
  • FearTurtlesFearTurtles Posts: 89
    edited 2009-03-20 00:54
    Where is the fun in using cell phones? LOL Thinking about it you could probable use a cell phone with direct-connect easy enough too. Just let the Stamp generate one of two tones to indicate motor on or off.
  • FearTurtlesFearTurtles Posts: 89
    edited 2009-03-20 01:07
    And accually all he would need is a reciever at the motor end if he has some other means of knowing if the motor is on or off. He might even get away with using 11 meters. That would really keep the cost down. And no licence either although I think 2meter APRS/Packet would be more reliable.

    KD8CUN Pat
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