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Electronics Store for parts for AM transmitter

Discussion in 'General Electronics Discussion' started by chickens1127, Mar 15, 2010.

  1. chickens1127

    chickens1127

    12
    0
    Nov 22, 2009
    I need a store, NOT RADIO SHACK, which has these three items fairly affordably.

    1. 1000ohm to 8 ohm audio transformer
    2. 1mhz crystal clock oscillator
    3. 22 guage insulated wire
    4. And this is a small order, but affordable shipping to the mid-alantic USA
    I realize #1 and #3 are at RadioShack, it's just there's a project which I bought $10 worth of parts for, and I could never finish it so they'd probably say "Finish what you started" vs Internet, I tell them, and they're fine.
     
  2. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Does that make any sense to you?

    If your goal is to save money, you will have to buy it from Radio Shack. If you have a beef with the local store, drive to another store, pay cash and tell them that you do not want to provide them with your phone number (I never do).

    If you buy from any place online, you are going to get hit with a shipping change. They have to ship it to you and it costs money.

    For what you are doing, www.Jameco.com may be your best bet, but for what you are looking for, you will end up spending more money than RS.

    ---55p
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    That wire appears to be 22AWG, but within nylon insulation. That means it's fine for an antenna, but possibly a poor choice for winding a coil (because the insulation will keep the turns spread apart).

    That TTL oscillator has 4 pins.

    If you're building an AM transmitter, I'm not sure that an oscillator with TTL output creating a square wave is exactly what you require.

    If the wire you need is for an antenna (basically a long piece of wire strung up somewhere) then the gauge is not important. If it's for winding a coil then it is far more important (possibly critical).

    If the 1000 ohm to 8 ohm transformer is to couple the output of something to headphones, then you may be able to get away with something else (e.g. if you're breadboarding this and you have a small signal transistor and a selection of resistors lying about...

    Showing us the circuit would help us help you. (also knowing how you're constructing it).
     
  4. chickens1127

    chickens1127

    12
    0
    Nov 22, 2009
    Now, this is the BASIC circuit. I'm making some changes, possibly a second input, some switches and such, and make sure it is at the top of the FCC allowed 100mW of power, getting me hopefully a mile and a half or more/
    http://scitoys.com/scitoys/scitoys/radio/am_transmitter.html

    P.S. Could I get away without a transformer? I saw an audio transformer on Jameco that wasn;'t 1000 ohm to 8 ohm, so it wouldn't work, right?


    Thanks, you guys are much nicer then the jackasses over at Electro Tech Forums, and they are arguing whether AM or FM gets better range, which AM obviusly does, and not answering my posts!

    Radio Shack also has an audio transformer, which was linked for the product page. It's 273-1380, and it has no mention of ohmage, so I assume it would work since the author linked it.
     
    Last edited: Mar 16, 2010
  5. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    Ouch, that's as simple as it gets.. Maybe it works, but it sure leaves a few things to be desired.
    1st, that oscillator doesn't only transmit at 1MHz but also at 3, 5, 7, 9 and so on, wasting power & thereby range, and you can forget all about FCC compliance.
    2nd, the modulation achieved must be miniscule with the 11:1 transformer, being fed from a headphone output, also limiting range.
    3rd, I wasn't aware that a TTL oscillator could be fed 9V, with modulation on top, and still survive.. TTL's circuits usually die when fed over 7V.

    Most any low-ohms audio transformer would work in that circuit I believe.

    But I'd try to spend a couple of extra transistors to make a real modulatable output stage, plus a 5V regulator for the oscillator .
     
  6. chickens1127

    chickens1127

    12
    0
    Nov 22, 2009
    Thanks a lot! You guys are really helpful.

    I know it's quite simple. I am currently trying to find a 1.5-1.7 mhz chip since I want to broadcast up in that range, becuase if you use 1mhz the arial is going to be too short and you're going to get a decent amount of harmonics. I'm looking at chips with a 5v supply, so I was thinking either 9v w/ 5v regulator or 3 AA/ or 3 AAA and hopefully get that other half a volt from the inputs

    So, one last question. Would you happen to have a link that would help me with #1? I was nearly sure that the chip can only do ex. cycles, and couldn't go higher or lower, but yet again, I'm a newbie.
     
  7. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Looking at that website, I am shocked that the person is recommending that. Maybe they are planning to use something other than the 5V square wave oscillator that everyone here is assuming. But with a 5V square wave oscillator that is a HORRIBLE circuit, one that I would not recommend building and one that I believe will be violating a whole stack of FCC regulations.

    If you are intent on building it, why not buy the parts from the website that is recommending it? They sell complete kits with almost everything included. If you are a beginner, take the easy path and start with a kit rather than trying to buy the parts separately. You will likely end up spending more money doing it your way rather than buying a kit from the company. That way you have someone to turn to when it does not work.

    ---55p
     
  8. chickens1127

    chickens1127

    12
    0
    Nov 22, 2009
    Yea, with second thoughts, it might be too rediculous to get all these parts. I have always had my eye on:
    http://www.bobhobby.com/store/ramsey-493964-B0002NRJCM-Ramsey_AM1C_AM_Radio_Transmitter_Kit.html

    I found it on a website with free shipping, so that's where I'd buy if I did. Any comments, questions, or concerns on it? You have to build it, which looks fairly easy.

    My question is, for 9.95 more I could get an AC adapter. Do you think this thing blows through batteries? It's 9-12 volt, so if I went without adapter, would I be OK? I'm kinda worried, since the price on this could baloon, with a $10 antenna + if anything breaks, etc, etc= $60.

    I'm kinda cheap, so I might buy it if I can scrap up the money by working for my parents
     
  9. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Depending upon your age, level of experience, access to tools, experience and ability with soldering, it may be a good kit or it may be too advanced for you. I would definitely not start with it as the first kit. I would definitely not consider it if you have had problems with other kits.

    Have you considered that your problems with Radio Shack you mentioned in your first post may be a reflection of your current abilities rather than their fault? You may need to think about starting small and growing those skills rather than jumping to something bigger.

    ---55p
     
    Last edited: Mar 16, 2010
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    The answers to those questions would be easier if we knew:

    a) How long you intend to operate this (if it's only to be used occasionally for a short time, then batteries would be OK. If you intend to keep it running to (say) pipe music from your computer to radios in the house then I'd go with the mains adapter.

    b) how much experience do you have in building electronic projects? Do you have a soldering iron? Do you know how to solder?

    c) what range do you need. If it's just inside the house or really short range, then I'd go for an FM transmitter.

    d) what stability is required? Do you care if you have to tune your radios occasionally to get the best reception. If you do then you need something with good stability (I don't know about this kit). Try looking up kits for wireless FM microphones as an alternative.

    e) Do you really need an antenna? I can't imagine it costing $10. I'd start with a random length of wire (say a couple of inches to a couple of feet).
     
  11. chickens1127

    chickens1127

    12
    0
    Nov 22, 2009
    Well, I've done electronics kts before, one or two w/ soldering, fairly easily. That whole thing with I never finishing projects was I was building an airsoft gun and could never come up with a good hop-up system,so it really didn't have much to do with electronics.

    I want to run it fairly constant, and I swear I have an AC adapter just like that from my ham radio.... Pains me to buy it when I may have it.

    I wanna get as much range as possible. On the website, it says 1/4 mile with their antenna under optimum conditions. People have taken this same radio, built a nice antenna with radials ($15-20) and get a good 2-3 miles. All I want is 1 1/2 miles max, so a good vertical load antenna would be perfect

    I might get the kit, may not.
     
    Last edited: Mar 16, 2010
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    Low frequency like the AM band doesn't benefit greatly from fancy antenna design unless you've got a serious engineering budget. A 1/4 wave is 75 metres at 1 MHz, and I seriously doubt you'll be making an antenna that large.

    Just try a long wire. And try to run it approximately orthogonal to the direction you wish to transmit.

    Are you trying to build this to communicate with a friend? I'd always be a little sceptical of claims about range of transmitters.
     
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