How to make simple RF on/off Switch....?

Discussion in 'General Electronics Chat' started by RRITESH KAKKAR, Aug 28, 2010.

  1. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    :confused: I want to make Rf switch having no Basic Idea, I have Listen about The RF Transistor Pls Help...................!
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Can't be done. The transistor is only the beginning. There is a great deal to learn before you can successfully build an RF switch. How much time do you have?
     
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  3. Potato Pudding

    Well-Known Member

    Jun 11, 2010
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    The simplest RF switch is a regular switch with a voltage resistor line that forward biases an RF signal diode.

    Transistor switching for RF is much more complicated.

    This is assuming that you only want to turn a RF signal line on and off.

    If you want to do the actual switching at RF speeds, then some type of very high speed CMOS IC would probably be simplest. You might lose any AM, but I if you aren't interested in Signal Amplitude it would be worth trying.
     
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  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    What type of switching are you trying to do? If it's just a transmitter/receiver pair to turn something on and off then it won't be that big of a deal however, as mentioned, if you're trying to make a switch that can select between different sources it gets a bit more complex depending on the frequency involved.

    In other words can you give us some more specifics as to what you're trying to acomplish?
     
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  5. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I have Study Transistor In Basic Electronic In 1 Year (BTECH) & Having Knowlege How to Bias In Simple Circuit But Having no Idea In Transmiter/Receiver Circuit So pls Help............!
     
  6. tom66

    Senior Member

    May 9, 2009
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    You will need to find a transmitter/receiver on a band which is legal for use in your country. Likely, it will be the same band used for remote controlled toys or wireless door bells or something like that. In fact, you could take a wireless door bell apart and use the transmitter and receiver pair as your switch.
     
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  7. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I want to ask How To make RF switch As I have seen Circuit But having Problem in Understanding it pls Tell...............!
     
  8. tom66

    Senior Member

    May 9, 2009
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    Why don't you buy a wireless door bell thing on eBay (for about $10 US), take it apart and learn? You'll probably find a custom chipset in there, but maybe you can find something about those chips and build it into your design.
     
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  9. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I thick You are not getting me I want Make & Understand Rf circuit That's why I am asking for Help...............!
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    What you want is neither quick, nor simple. You do have to start somewhere though so let me suggest that you start with basic AC circuits. On this website is an excellent place to start. If you can understand the basic operation of a bandpass filter made of an inductor L and a capacitor C you will have made substantial progress. Are you willing to make that level of effort?
     
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  11. bertus

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    Apr 5, 2008
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  12. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Considering the number of threads I've seen you start, many about the very basics, it's as if you're trying to shove years worth of education into a few days.

    It just doesn't work that way. AC/DC theory alone is a full semester course and you've got to have a good grip on that before you move on to simple transistors and the like. Even full engineeering students often don't start designing and constructing simple circuits until their 2nd or 3rd year and RF theory is almost a subject in itself.
     
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  13. gootee

    Senior Member

    Apr 24, 2007
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    For switching an RF path on/off, or routing RF to different paths using RF switches, do a google.com search for PIN DIODE RF SWITCH. They usually use Pin Diodes that are DC-biased to make them switch a path on or off, for RF. (There might be one or two Application Notes at agilent.com, among other places, that might cover Pin Diode RF Switching.)
     
    Last edited: Aug 30, 2010
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  14. gootee

    Senior Member

    Apr 24, 2007
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    Concur. And if you haven't already mastered the usual electrical engineering major's core course sequence of: analytic geometry, calculus, ordinary differential equations, and basic signals/systems theory (i.e. transfer functions, Fourier Transforms, and LaPlace Tranforms, etc), and probably also courses in engineering physics, basic circuit analysis theory, transistor circuit analysis and design, and engineering electromagnetics, then everything electronic will probably seem MUCH more difficult than it really IS. I'm not saying that you can't learn it another way. It's just that there will be many things that will all seem like special cases when in reality they are part of a larger unified body of theory, the knowledge of which would make everything much easier to learn, understand, and apply.

    I have to disagree that RF theory is "almost" a subject in itself. It is definitely that, and much more. It can be like a whole other world, sometimes appearing to be a "black art" to non-practitioners, even if they have electrical engineering degrees. Computer simulation capbilities are starting to help a lot with that. But it's still a very involved area of knowledge and practice, where experience can still matter a lot, because closed-form mathematical descriptions and solutions are simply impractical for all but the most-trivial situations.

    [Edit:] Rritesh, I DO NOT want to discourage you from asking questions! After seeing some of your other threads, just now, it sounds like you ARE studying electronics as a formal student, currently. So asking questions about things that interest you, "at the moment", is GREAT! Eventually, I think, your "seeking" and your education might converge and you will achieve a "critical mass" in some area(s) of inquiry that you have been pursuing, and you will experience great satisfaction(s). My hope is that the rate of occurrence of such experiences will suddenly grow exponentially for you, and you will reach a point where you feel unstoppable in your ability to learn and understand! It's a beautiful thing!

    (Aside, for ALL "engineer" types: ) Just remember that learning "interpersonal communications" is (gasp!) AT LEAST as important as learning technical subjects. A person might know ALL of the right answers, technically, or might have the best idea EVER. BUT, it will all be for almost NOTHING, and possibly LOST FOREVER, if that person cannot COMMUNICATE with, and EFFECTIVELY _persuade_, OTHER people, about their idea(s)! Besides, you don't want the loudmouth idiots to screw things up and still get all of the money and hot women, do you?! NO!! So _ALSO_ learn, extremely well, to communicate with other people, even to "play them like violins" and motivate them and persuade them to take action based on your ideas, maybe _especially_ the non-technical people. And then SPEAK UP! It's the ONLY way to make sure that things get done the "RIGHT" way. (And the money and hot women couldn't hurt, either.)
     
    Last edited: Aug 30, 2010
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  15. marshallf3

    Well-Known Member

    Jul 26, 2010
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    RF isn't so bad, at least not to me because I've worked with it for over 40 years starting with basic receiver technology. I still cringe at anything much over 500 MHz though, component layout becomes so critical that a few hundredths of an inch error in a PCB layout can mean the difference betwen success and failure and you really only learn by making a lot of failures.

    I do however delight in designing 2.4 GHz antennas for oddball coverage situations.
     
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  16. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    Okkkk I will Go through It..........!
     
  17. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Another good point made, however jumping back and forth between a multitude of vastly different technologies all at the same time usually ends up as a giant blob of confusion, kind of like trying to read a novel by reading whatever page it opens to when you pick it up.

    I'd suggest forming a good starting point. Buy an inexpensive multimeter, a 9V battery with a snap connector, a bag of clipleads and a small assortment of common value resistors along with a potentiometer or two then use this along with a book chapter on basic ohm's law to get a feel for the equations, proving each one to yourself by simulating it with your parts. When you've got that down buy a wall pack that outputs an AC voltage, a few rectifiers and some various sized filter caps then again, with the book on the proper chapter, put into practice some of the formulas for AC theory. Next you'd get a few NPN, PNP transistors and get that down, etc etc.

    Of course at the same time you're going to need to integrate some knowledge of physics along with every step so you can understand WHY things work as they do. Just take things one step at a time, and don't try to move on until you've mastered the previous theory.

    In time you can get a ProtoBoard and try your hand at a simple one transistor amplifier. Move at your own pace but don't try to jump ahead, for if you don't understand the basics that all came before it you're just wasting your time by jumping ahead to try and figure out how to modulate the output of a 20 GHz klystron.
     
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  18. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    I want to share With You That In My 10 Class I have Made Electronics Voting Machine With 7- Segment Display Using 100's Of Diode & Now In B-Tech first Year I Have Again Made It with 200's Of zener Diode & For Counting Votes I have used 4017 Decade counter & constructed Counter Without Ic (7432 & 7490 ) That's I was asking Rf Control Ckt. For making it Wireless.......!
     
  19. smartyram

    Member

    Aug 5, 2010
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    So how much time did you spend in soldering 100's and 200's of diodes into a PCB? And you also made counters without using ICs? How productive was that? Seriously Ritesh, I cannot believe a word of what you are saying. Coming from the same country as yours I know how projects are done in 10th grade. Blindly soldering components from circuit diagrams found in books or internet and praying that everything works.

    Your question is like I know how to fix a bicycle puncture and am now ready to make a motor cycle form scratch. The fact that you ask such a question shows how lazy you are. If you spent five minutes googling about RF theory you would have got first hand information about what you are up against.

    Answering your queries is a waste of time and bandwidth.
     
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  20. smartyram

    Member

    Aug 5, 2010
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    I disagree. People who ask questions like these can never be motivated. Humans fall under certain categories and it is extremely rare for them to jump from to another. The category that asks questions without doing there homework is basically looking for free lunch. They feed on innocent good Samaritans who take the effort of helping them.
     
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