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Low Power portable FM transmitter

Discussion in 'Electronic Design' started by jtspang, Nov 11, 2004.

  1. jtspang

    jtspang Guest

    Basically what I'm after is a slightly juiced up version of many of
    the FM transmitters for use in cars with a portable device (in this
    case, my ipod). I don't need to be able to adjust the frequency, and
    my only problem with the stuff on the market is the signal is too
    weak, so any nearby station (both in band and literally) gives off a
    lot of interference. I want something powerful enough in a little
    used part of the FM spectrum (i.e. ~ 88.9mHz or something) that I'll
    never get overpowered. This has the dual benefit of when on road
    trips, my buddies in the car behind me can also tune in to my ipod.
    What would be the simplest way to build this? I heard that an NE 564
    PLL chip might be the way to go, but I'm not all familiar with it.
    Thanks,
    JT
     
  2. John Fields

    John Fields Guest

    ---
    I suggest you go to

    http://a257.g.akamaitech.net/7/257/...s.gpo.gov/cfr_2003/octqtr/pdf/47cfr15.239.pdf

    and read 15.239.
     
  3. Andrew Holme

    Andrew Holme Guest

    A PLL will give better frequency stability not more power. This may help
    because single transistor VHF oscillators tend to drift.

    A little power goes a long way at VHF.

    Is your transmitting antenna external to the vehicle?

    This is a good kit http://www.northcountryradio.com/Kitpages/mpx96.htm
     
  4. Thank God for that, then!
    What miserable, crummy sh*t do you intend to inflict on the general
    population with your new toy? 24hr "Rap Music"??? No thanks!
     
  5. jtspang

    jtspang Guest


    I'm not worried about FCC requirements. This isn't intended to be a
    radio station on wheels (actually, that's exactly what's intended, but
    just a station with 1-4 listeners). I want something with slightly
    more juice than what's currently on the market, maybe 5 watts or so.
    And if it makes everyone feel better, let's say hypothetically, what
    would be the best way to do this?
     
  6. Luhan Monat

    Luhan Monat Guest

    Hi,

    There used to be a (legal) product called "Mr. Microphone" - several
    hundred foot range if I recall. It worked on the FM band.
     
  7. John Fields

    John Fields Guest

    ---
    Why not? Don't you want to listen to the radio or watch TV without
    some asshole with half a brain interfering with what you're listeng to
    or watching?
    ---
    ---
    5 watts would easily be enough to override, for miles around, anything
    legal on a channel someone might be enjoying who wouldn't be
    interested in the shit you're no doubt thinking of inflicting on them.

    Plus, your cavalier attitude about the rights of others and your
    obvious ignorance of things RF would probably result in a carrier
    drifting all over the place and modulation wide enough to cause
    splatter over several adjacent channels.
    ---
     
  8. I think the advice John gave you was pretty good. Read the law. They
    give you a lot of special considerations in the FM broadcast band, and
    low power is enough. The 5 watts you propose will cover a small city,
    under the right set of circumstances. I'm sure that's not your
    intention. This would surely draw attention to yourself within
    minutes.

    You should get 250 feet or so within legal limits. For good frequency
    stability, make sure the transmitter uses a good PLL such as the
    National LMX family. If that isn't enough, consider buying one of the
    915 MHz or 2.4 GHz transceivers on the market, and use one at each
    end.

    Frank Raffaeli
    http://www.aomwireless.com/
     
  9. Don't be to sure he doesn't want to blanket a city, a recent movie in the US
    made "Pirate radio DJs" out to be heros.

    Charles.
     
  10. Rich Grise

    Rich Grise Guest

    If that's the case, then to heck with him. Let him look it up like
    the rest of us had to. >;->

    Cheers!
    Rich
     
  11. jtspang

    jtspang Guest


    There seems to be a lot of semantics and prejudgement going on around
    here, and I don't mean just this thread. Who cares what I want it
    for, or why I'm interested in it, or what I might "inflict" on anyone
    (or no one, in this case). This is for me, and my best friend so we
    can listen to the same music on road trips in two cars.

    So please, anyone with a simple circuit using a PLL (doesn't have to
    be tunable) that accepts a stereo input I would love to see it, as I'd
    like to start building a testing different configurations. As was
    brought to my intention earlier, a 5 watt transmitter is way too big.
    I just want a max range of like 300-500 feet.

    Anyone else who wants to scold, deride, disillusion, or otherwise
    discourage this, kiss my @ss. This group is supposed to be about
    helping out one another, not browbeating someone who is more
    interested in building the circuit than using it.

    Thanks,
    JT
     
  12. Dbowey

    Dbowey Guest

    jtspang posted:

    (snip)

    << There seems to be a lot of semantics and prejudgement going on around
    here, and I don't mean just this thread. Who cares what I want it
    for, or why I'm interested in it, or what I might "inflict" on anyone
    (or no one, in this case). This is for me, and my best friend so we
    can listen to the same music on road trips in two cars.

    So please, anyone with a simple circuit using a PLL (doesn't have to
    be tunable) that accepts a stereo input I would love to see it, as I'd
    like to start building a testing different configurations. As was
    brought to my intention earlier, a 5 watt transmitter is way too big.
    I just want a max range of like 300-500 feet.

    Anyone else who wants to scold, deride, disillusion, or otherwise
    discourage this, kiss my @ss. This group is supposed to be about
    helping out one another, not browbeating someone who is more
    interested in building the circuit than using it. >>

    It appears to me that you are mistaken.

    • This group owes you nothing.

    • Your wish to be irresponsible (indifferent to others and to Federal Law)
    does not impose a mandate for others to ascede to your wants.

    Go tell your parents they should not have pandered to your tantrums, but should
    have taught you self restraint.

    You may kiss my ass.

    Thanks,
    DB
     
  13. John Smith

    John Smith Guest


    Who cares? The honest, law-abiding professionals on this group whom you have
    asked to help you break the law.


    And you can kiss our collective asses, starting with mine.

    John
     
  14. It's not prejudgment; it's based on what you yourself initially
    wrote:

    Here you have the nerve to refer to licensed stations as potentially
    causing you "interference" and you want to ensure you "never get
    overpowered."
    That would be funny were it not so monumentally arrogant.
     
  15. John Fields

    John Fields Guest

    ---
    Hey, asshole, if you're so hot for that little piece of technology get
    yourself down to your nearest public library and hit the books. Or
    get off your lazy, self-indulgent ass and find a website with how to
    do it on it.

    As you were told before, nobody here owes you a goddam thing, so if
    you have a problem with that, piss off.

    Get a fucking clue; nobody wants to help your sorry ass because you're
    an irresponsible twat who hasn't the slightest concern for the rights
    of others.
     
  16. jtspang

    jtspang Guest


    Dear god (From your posts I assume that's how you want to be
    addressed),

    I am looking other places, however, I find you get better answers by
    asking more than one source. If I could find a website that had the
    circuit I'm looking for, I wouldn't have posted in the first place.
    But I decided, instead of trying to reinvent the wheel, maybe someone
    else has already done what I'm trying to do. I'll just ask. Can't
    hurt, right? Surely the good people at sci.electronics.design can
    tell me what I need to know. And some of them can. Those of you who
    have avoided the thread but emailed me some ideas, I appreciate it. I
    posted here because I thought that it was a forum where maybe someone
    who knows about this stuff could point me in the right direction. I
    can see that I was mistaken about that. Why impart any knowledge when
    you can lecture. How does what I want impune your rights? FYI -
    where I live, that section of the FM band is empty. Hey dipshit, how
    much of your company's time do you piss away listening to static? And
    where have I said that anyone owes me anything? Disregard my first
    post, if that will assuage your guilt over aiding someone in -holy
    shit!- violating the letter of the FCC code. You must be a lawyer,
    because only a lawyer could be so narrow-minded, seeing only problems,
    no solutions. IT'S JUST A SHITTLY LITTLE CAR TRANSMITTER! So I say
    again, keep your small minded criticisms to yourself, and kiss my ass.
     
  17. Don Pearce

    Don Pearce Guest

    Look sonny. If you and your friends want to listen to the same music
    in two cars (and quite why you would beats me), then either listen to
    the same radio stations, or make yourself up some cassettes.

    You will not find anybody here with anything but the deepest contempt
    for what you propose, so don't bother arguing your case - just go
    away.

    d

    Pearce Consulting
    http://www.pearce.uk.com
     
  18. Rich Grise

    Rich Grise Guest

    People have been _trying_ to point you in "the right direction", which
    is, grownups don't build transmitters that illegally broadcast in
    reserved frequency bands. It's just that simple.

    If you do choose to do illegal stuff, nobody here wants to be an
    accessory.

    And if you and your little email pirate radio society buddies want
    to go ahead and do it anyway, then it is within your purview to
    have the wherewithal to find your own resources.

    Does this clear it up a bit?

    Good Luck!
    Rich
     
  19. John Fields

    John Fields Guest

    ---
    Capitalize, please.
    ---
    ---
    Not necessarily; all you get is, possibly, more answers. The quality
    of the information you receive has little to do with the quantity of
    information received. You, however, are between a rock and a hard
    place because you can't differentiate between good information and
    bad.
    ---
    I suspect that had you accessed a website with precisely the circuit
    you needed, you wouldn't have known it and would have eventually wound
    up here asking "Will this work?"
    ---
    ---
    Don't be absurd. If you knew how to "reinvent the wheel" in the first
    place, you would have just built your little machine and been on your
    merry way, playing "mobile DJ" for your entourage of idiots and
    polluting that 1000' circle, with no one the wiser except the traffic
    around you. As it is, you've been reduced to begging for you what you
    want and defending your position for wanting it over and over again,
    to no avail.
    ---
    ---
    So far, the only one who's been hurt in this exchange is you, so if
    that doesn't matter then you're right.
    ---
    ---
    You clearly don't _need_ to know, you _want_ to know, and Mick sez you
    can't always get what you want.
    ---
    ---
    Certainly some of us _can_ tell you, but just because we can doesn't
    mean we _have_ to. It's up to our individual discretion whether we do
    or not, and so far it looks like you're pissing in the wind.
    ---
    ---
    Perhaps you do, but judging from the fact that you're back I'd say you
    either didn't get much help or what you did get was beyond you.
    ---
    ---
    You're mistaken about being mistaken about that. The _good_ advice
    you got was to get a Mr. Microphone and adapt that to your needs.
    Another piece of good advice you got was to read Part 15 of the FCC
    rules and regs, and yet another piece of advice was to abandon the
    "project", none of which you elected to follow as evidenced by the
    fact that you're back again whining about that everybody's being sooo
    mean to you, poor baby...
    ---
    ---
    Lecturing _is_ imparting knowledge, at least to those who care to
    listen. What you want is _information_, a totally different thing.
    ---
    ---
    It's "Impugn", and your desire to break the law for your own
    convenience challenges as false my right to believe that the law
    applies to you in the same measure as it applies to all of us.
    Look it up.
    ---
    So what? The non-empty parts of the band where you live were also
    empty once. Then some folks who wanted to use part of _our_ spectrum
    got a license to do so, and are now legally on the air. Follow their
    good example.
    ---
    ---
    So far, about ten or fifteen minutes reading your crap.
    ---
    ---
    Your attitude and your refusal to want to abide by the FCC's rules
    indicates that you feel you've got something coming back to you, i.e.
    you're holding a debt of some kind over someones head and calling in
    the note.
    ---
    ---
    I'm not going do to anything to help you violate anything in the
    slightest, so you can take your sophomoric posturing and stick it up
    your ass.
    ---
    ---
    The solution is for you to stop being the problem. Get with the
    program, twerp, or get off the boat.
    ---
    ---
    Yes, I'm sure it would be a real POS if you ever got it off the
    ground.
    ---
    ---
    So _you_ say again? Geez, you must be _important_ or something...

    FYI, moron, I'll do exactly what I please, including criticise you if
    that strikes my fancy, and if you don't like it I suggest you go get a
    little attitude adjustment.
     
  20. John Smith

    John Smith Guest


    Living in Butte, Montana must have its down side, but, even there, you have
    licensed FM radio stations. The FCC lists 97 commercial and educational
    stations currently licensed and on the air in Montana. The FCC also lists 53
    LPFM stations, either currently on the air or soon to be. Then there are the
    neighboring states who, most likely, have FM stations of their own.

    Since you are a member of some sort of car club and you want to drive around
    while broadcasting, that conceivably makes all 150 legal stations an
    eventual target for your interfering trash.

    So don't give us any of that "where I live, that section of the FM band is
    empty" crap.

    John
     
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