recommend me a low-value resistor

Discussion in 'Wireless & RF Design' started by mik3ca, Apr 19, 2008.

  1. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    then what frequencies should I be using?

    I was trying to use my commercial radio as a form of station alignment, so that I won't screw up my TV.

    How do I know what exact frequency I am using if I don't test it on my radio?
    the colpitts equation wont help because my transmitter is done on a breadboard to begin with.

    I'm afraid if I use too low of frequency then I would be in trouble.

    the Hamilton airport is at least 15km away from me, if not, more. I can't even get my transmitter to go 1 km.
     
  2. Audioguru

    Expert

    Dec 20, 2007
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    I think airplanes use radios that are an awful lot more sensitive than a super-regen "radio" that has only a single transistor for its radio section.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Mike,
    By you "testing" your radio using components that you have selected in a somewhat random fashion, you may be jeopardizing the lives of a great many airline passengers, along with the safety of aircrews and fantastically expensive aircraft.

    This is not funny at all.

    Stop trying to build transmitters.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
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    Mike, perhaps you should read a good book or two on radio electronics instead of "easter-egging" circuits you find on the internet. A good book will explain the reasons behind component selection.
     
  5. SgtWookie

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    Mike,
    I don't wish for you to give up on electronics.
    I am highly in favor of you attempting to build a superhetrodyne receiver. I might actually send you some parts, if you can't find them locally.

    However, it would be reckless and irresponsible to suggest for you to continue transmitting as you have been. This really is not a trivial matter.

    Your superregen radio receiver has many shortfalls, and it also radiates emissions which could be interfering with various legal communication. While this is somewhat of a stretch, I most certainly would suggest leaving it at home if you were to travel near an airport.

    Wouldn't you like to build a real, honest to goodness superheterodyne radio receiver? One that would be practically immune to interference from other stations? One that wouldn't radiate RF indiscriminately? One that could pull in stations a long ways away; much further than that crappy superregen radio could?

    How about it, Mike?
     
  6. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Mike,

    You can build "experimental" transmitters; at least in the US. The stipulation is the output power is less than 100 mW [0.1 W]. Then all you need is a quiet spot on the band to "test" your transmitter. Typically people use the FM band for such transmitters, but you certainly can double check with 47 CFR to get the word from the horses [FCC] mouth. The link is one of my web pages.
     
  7. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I'm not intentially playing with random frequencies.

    Obviously, I'm doing something right, if I am able to transmit only to my superregen and not to my TV, while in the past, I was transmitting to my TV. I'm not even anywhere near an airport. My superregen receiver can barely pick up a station (Z103.5) about 80 km away from me, so it is sensitive.

    JoeJester, I wanted to transmit right after 108Mhz, simply because I can use my commercial radio to test my transmitter.

    I have read books, and they don't help much.

    I can easily adjust my transmitter frequency to make it in the center of the FM band, but I'm afraid I wil disrupt a radio broadcast.

    If only I know what frequencies are harmless to transmit on, then I will be willing to switch to those frequencies.
     
  8. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    You can transmit anywhere in the FM band that is quiet. Going outside the band is inviting trouble.

    You might want to see the frequency allocation in the FM band to know where the radio stations are authorized to transmit. Then go to each of those frequencies and see if a station is using that frequency. If there are no stations on the frequency, you can use it provided you comply with the provisions of 47 USC.

    http://en.wikipedia.org/wiki/FM_broadcasting_in_the_USA can help.
     
  9. Audioguru

    Expert

    Dec 20, 2007
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    I live about 35km from Mike and my FM band if full when I tune across it on my very sensitive home stereo and car radio.
    Mike doesn't have a very sensitive radio so he could think that a frequency is not used but a neighbour could be listening to a distant station on it.

    I tested my FM transmitter for only 1 hour on the same frequency as a low power foreign language radio station on the other side of my city. I don't know how many people I interfered with.
     
  10. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I don't know what your transmitter was interfering, but I didn't notice anything.
     
  11. JoeJester

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    You must be in a very populated area if all 101 channels are taken up. Are you in the U.S.?

    http://www.fcc.gov/eb/sed/ulo.html lists some unauthorized broadcasters. I don't think you want your name on this list Mike, as it costs money to make these listings.

    You can buy 100 mW transmitters. They sell them as items you can play your cassette, tape, or MP3 player, through the FM radio. I've seen them at best buy.
     
  12. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I'm in canada.

    I think I'll be OK to transmit on 102.7Mhz.

    102.9Mhz is taken by K-lite FM radio station, and 102.1Mhz is taken by "the edge" radio station. I don't think anyone is using 102.7Mhz yet.
     
  13. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I guess I'll have to buy an RC race car and play with it.

    I discover that they transmit on 27Mhz and/or 49Mhz, and no one has made a news report that they run on illegal frequencies, so I will work within those frequencies.

    then I will synchronize my transmitter and receiver to it so that everything will work on the same frequency. I will start with the RC transmitter and my receiver, and then when my receiver is calibrated, then I will calibrate my transmitter.
     
  14. Audioguru

    Expert

    Dec 20, 2007
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    I just finished testing FM frequencies on my very sensitive car radio:
    107.9 Interference.
    102,1 strong local station.
    102.3 interference.
    102.5 a station.
    102.7 interference.
    102.9 strong local station.
    103.1 interference.
    103.3 a station.

    The local stations are spread out and are never side-by-side. Distant stations are side-by-side because one is over here and another is over there and they don't interfere with each other.

    Some cheap model RC cars use (hee, hee) a super-regen as a "radio". Their range is across the street. Model airplanes don't use 27MHz and 49MHz. They use 72MHz and other frequencies.

    I have a video of a model B-52 bomber that is huge. It has 8 model jet turbine engines that cost $6,000.00 each. you don't want to create interference for it to crash.
     
  15. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I am nowhere near a model airplane. LOL

    Maybe I should go for 26Mhz or 48Mhz, slightly off of 27Mhz and 49Mhz so that my transmission doesnt collide with another one.

    I tried transmitting in the middle of the FM band and it did work, but only for maybe the same distance as the length of a typical home. after that, local stations flood in. So FM band transmission wasn't so great.
     
  16. JoeJester

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    Apr 26, 2005
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    Mike,

    I'm sure the Canadian equvalent of the U.S. FCC has similiar rules and similiar penalties for those who push the envelope of interference.

    I would caution you to find out the rules for your country before proceeding. Your work is already cut in half because your fellow Canadian is there to bounce those specific topics around the table with you, and of course there is these forums, to let us all be your sounding board.

    Good luck in your research. The good news is, if they don't specify an ERP, you can take your 100 mW and work on an efficient antenna system to do what you want to do ... on a not to interfere basis.
     
  17. JoeJester

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    That's typically the way it works here in the U.S. Rarely will you find two local stations on adjacent channels. Adjacent channels are usually two out of town stations, seperated by a good distance.
     
  18. SgtWookie

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    Jul 17, 2007
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