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very small low power simple transmitter (ideally single chip)?

Discussion in 'Electronic Design' started by megoodsen, Aug 18, 2006.

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  1. Rich Grise

    Rich Grise Guest

    See how that screws up the natural flow of the threae? Sheesh!
    Only if they can receive it on their FSM! ;-)

  2. John - KD5YI

    John - KD5YI Guest

    You are correct about antenna gain. The FCC spells out many of the test

    I cannot answer your question about RF modems without much more study of the
    regulations. Most likely they are manufactured to meet some other part of
    the regulations and have probably been submitted to the FCC for approval. In
    some of these cases, it is illegal for the end user to tamper with any part
    of the device, including attaching an external antenna.

    Presumably you mean 13 nW. I estimate that the signal strength would be
    about -115 dBm at the receiver (isotropic source in free space) at 300
    meters. I wouldn't try it.

    That band is regulated in other parts of the rules. I do not remember the
    appropriate section. I am certain that higher power is permitted for those
    specific frequencies.

    See (a) above. There are exceptions listed elsewhere in part 15. For
    example, they allow 100 mW input power to the final stage in a transmitter
    on the AM broadcast band (with not more than 3 meters of antenna, lead-in,
    and ground combined). In the 88-108 MHz (commercial FM) band, 250 uV/m at 3
    meters is allowed. The OP asked about the 144-146 MHz band which is alloted
    to licensed amateur use (covered by Part 97 rules). Unlicensed operation in
    that band is limited to 150 uV/m at 3 meters per the above table.

    It is important to wade through all applicable regulations to discover what
    is permitted.

    Cheers to you, too.
  3. John - KD5YI

    John - KD5YI Guest

    Part 95 (
    covers the 72 MHz R/C frequencies. As you can see, power output can be up to
    0.75 watts (95.210). That's high power!

    See 95.201 through 95.225 (R/C Rules).

    Note that an R/C transmitter must be FCC certified. You may make no
    modifications to the transmitter.

  4. John - KD5YI

    John - KD5YI Guest

    Read Title 47 and decide for yourself. In the meantime, I will ask them if
    there is a reward for reporting lawbreakers such as yourself.

  5. John - KD5YI

    John - KD5YI Guest

    Hi, Mark -

    AFAICT, only on the commercial AM broadcast band.

    I have a feeling that the belief that 100 mW is legal came from the FCC's
    rule that you may transmit using 100 mW on the AM broadcast band (510-1705
    kHz) which is very popular with the hobbyist home broadcasting group and it
    got erroneously applied to all frequencies.

    By the way, the FCC says

    "Sec. 15.219 Operation in the band 510-1705 kHz.

    (a) The total input power to the final radio frequency stage (exclusive
    of filament or heater power) shall not exceed 100 milliwatts."

    Note the reference to filaments indicating it is a rather old rule. In
    addition, note that it is *input* power to the final stage. With less than
    100% efficiency in the final, it will be less at the antenna (which, at 3
    meters for antenna, lead-in, and ground) will give very low radiated power.

    AFAIK, this is the only reference to 100 mW in the FCC regulations. However,
    I have not been through them all and I may someday be corrected.

  6. Tim Auton

    Tim Auton Guest

    I think the only important bit of that quote from the FCC is this bit:
    "Except as provided elsewhere in this subpart". Elsewhere in the subpart
    you'll find the limits for the ISM bands, RC frequencies etc. and they
    are of course much higher.


  7. is the address to report suspected illegal use of RF
    equipment to the FCC. I contacted them to ask where to report the
    people spamming cell phone jammers and is where I was
    told to make reports.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  8. John - KD5YI

    John - KD5YI Guest

    My comment was in the same vein as Luhan's. I should learn how to put in
    smiley faces, I guess.

    If I were to report Luhan, I would also have to report all those other
    lawbreakers who drive around with their headlights on.

  9. I wasn't suggesting you report him. Like I said, it is the link if
    there is a real need to report anything to the FCC.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  10. Rich Grise

    Rich Grise Guest

    In what state is it illegal to turn your headlights on?

  11. Yep, that's a good transmitter circuit. If you need longer batery
    life, you can add a 74HC14 and set it up as a short pulse oscillator,
    say 10 seconds on, a minute or two off.
  12. The state of insobriety?

  13. megoodsen

    megoodsen Guest

    In fact, yes I do have the appropriate licence for operation on 144MHz
    (and all others) amatuer bands.

    I doubt the cat has though, and he will be the one 'transmitting'...

    I suspect at the RF output levels the cat will be transmitting, he
    won't need one. Here.

    I asked originally for a simple circuit, knowing this sort of thing
    would have been done already, why re-invent the wheel...

    And just a comment following the er, expansion of the thread.

    As far as I know the FCC is only the American radio regulatory body.

    There IS life outside the US of A you know!!
  14. Alan

    Alan Guest

    Have a search for animal tracking collars/transmitters. Usually a
    simple one or two transistor crystal controlled oscillator circuit
    normally used at about 152MHz so easily modified for 2m.

  15. Rich Grise

    Rich Grise Guest

    Well, I suggested looking into key fob transmitters, that you could
    hack into and bypass the button with a little CMOS pulser, but you
    seem to have ignored my suggestion.

    RS has a transmitter/receiver set (the receiver is like a coffee timer,
    but without the knob) for about $15.00. Or they did when I went there
    a few years ago.

    Good Luck!
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