| Author | Message | ||
     BryanJ |
I was wondering if I could build the transmitter with an oscillator that is larger than 1Mhz; something like a 5Mhz, and how many miles would you saw that it would sent if it had a 25 foot antenna. Also, where would I find a 5Mhz oscillator that would work for the project (for a reasonable price)? | ||
| Simon Quellen Field (Sfield) |
One megahertz is the frequency, not the power. Raising the frequency would not increase the range. We selected 1 Mhz because it can be received on a cheap AM radio. If you used a higher frequency, such as 5 Mhz (which is in the 60 meter short wave band), you would need a short wave radio to receive it. When I sent messages from San Diego to Texas using one of these, I selected 28.322 Mhz for several reasons. First, it is a common frequency, so off-the-shelf oscillators are not difficult to come by. Second, it is a legal frequency to use if you have an entry-level Amateur Radio license, so I would maximize the number of people who might be able to talk back to me. Third, it is in the 10 meter band, so the E layer of the ionosphere can reflect it. This means that I can bounce the signal off of the ionosphere, and thus reach the other side of the world. The drawback was that the receiver for the 10 meter band is more expensive than the $5 AM radio you can use with 1 Mhz. The little transmitter is legal to use in the AM band because it puts out so little power. If you wish to send the signal farther, it is really easy to get an amateur radio license (a few dollars and a simple written test you can practice on the Internet -- all of the questions and the answers are published, so you can just memorize them if you want). With a license, you can use bigger antennas, you can use higher power transmitters, and you can use many frequencies that can go around the world. | ||
| Anonymous |
But how to increase the range? I want to send messages only inside a city. | ||
| Simon Quellen Field (Sfield) |
You need a license to transmit city-wide. Go to the ARRL website to get a license. Then you can use 28.322 Mhz and an easily obtained amplifier. | ||
| Anonymous |
I live in Viet Nam so i think if i transmit something in 1Mhz, no one can know... So, why we have to use 28.322 Mhz, why is not 1Mhz? And is it cheap to do it? | ||
| Simon Quellen Field (Sfield) |
The reason for choosing 1 Mhz was that there are very cheap radios that can receive that frequency. If you have such radios where you live, then it is likely that the AM band is being used by people who would object if you put out a strong signal that interfered with them. Governments usually protect and regulate the airwaves, and license certain frequencies for amateur use. Using frequencies other than those you are allowed to use can get you into trouble, unless the power is so low that it is effectively limited to your own house, and thus will not interfere with anyone else. That is why our design is legal, even though the frequency is normally used by radio stations. The 10 meter band (in which 28.322 Mhz resides) is governed by international treaty, and so I know that you can get a license to use that frequency with power high enough to cover the entire globe, and extend into outer space. | ||
| Anonymous |
How much a 28.322 Mhz AM radio tranmitter? | ||
| Simon Quellen Field (Sfield) |
Ok people -- how many of you want 28.322 Mhz oscillators but are finding them difficult to find? Should I offer them in our catalog? I can probably have them made for the same price as the 1 Mhz oscillators. How many readers have amateur radio licenses? | ||
| Anonymous |
I BUILT A COMPUTER CONTROLLED TRANSMITTER BUT IT WONT WORK I CHECKED EVERYTHING BUT IT WONT DO ANYTHING THE LED WONT LIGHT UP OR ANYTHING THE PORT DOESE WORK CAUSE IT USED TO HAVE A INFRARED MOUSE SO WHAT COULD THE PROBLEM BE? BY THE WAY HOW FAR WILL A 53.2659MHZ OSCILLATOR TRANSMIT? | ||
| Simon Quellen Field (Sfield) |
It sounds like you are using the wrong port. The software lets you select which port to use. Try another port. It is also possible that you have made a mistake in the construction, such as a short circuit or a solder bridge. Check everything over carefully. An oscillator for 53 Mhz will be limited to line-of-sight operation except under unusual circumstances. That frequency does not skip off of the ionosphere like 28 Mhz does. | ||
| Anonymous |
so...what port should i use? my computer only has one port that is a male connector in that the transmitter fits on. | ||
| Simon Quellen Field (Sfield) |
On a PC, the ports are called COM1:, COM2:, COM3:, etc. Find out which port the infrared mouse was using. That will be the port associated with the connector to which you have attached the transmitter. You might also be having trouble if the software for the infrared mouse is still active, and still controlling that port. You might want to disable the infrared mouse software while using the port for other hardware. | ||
| Anonymous |
how do i disable the infrared mouse? | ||
| Simon Quellen Field (Sfield) |
You will have to read the manual, or contact the manufacturer. | ||
| Anonymous |
i got the transmitter to work and i also downloaded the cwget program to decode the signals. were do i conncet the am radio? do i connect it the microphone or the input in jack. also is the sound in input jack stereo or mono so i can get a suitable cable to connect it in | ||
| Simon Quellen Field (Sfield) |
You can try each of the inputs (microphone or line-in) to see which works best for you. A mono plug will work in a stereo jack, so you can use either mono or stereo as you choose. | ||
| Anonymous |
I foud an oscillator that is 1843.200KHz. How much is this in MHz and could this oscillator work for transmitting and what kind of receiver would be needed. | ||
| Simon Quellen Field (Sfield) |
The prefix "kilo" means "thousand". The prefix "mega" means "million". Thus, you have a 1.8432 Megahertz oscillator. This frequency is in the middle of the 160 meter Amateur Radio band. You need a General Class license to transmit in this band. The General class requires one extra test beyond the entry level test needed for being a licenced radio amateur. That said, the test is still pretty easy (my daughter got her General Class license when she was 15, and I'm sure there are kids younger than 6 who have General Class licenses). Since normal AM radios only go up to 1.7 Mhz, you will want a shortwave radio to receive at this frequency. If you look up "simple shortwave receiver" in Google, you will find many simple circuits you can build. Or, you can modify our Three Penny Radio" for shortwave reception by adding a capacitor in series with the tuning capacitor, to raise the frequency. The added capacitor can be another variable capacitor from our catalog. | ||
| Anonymous |
I would like to know if, in the computer-controlled transmitter project, a JENRA 49.860 MHz oscillator can be used without a license. (P.S. It was found in a toy walkie-talkie) Also, would a 9 position male D-Sub connector work instead? | ||
| Simon Quellen Field (Sfield) |
First of all, the part labelled "49.860" is most likely a crystal, not an oscillator. An oscillator will have more than two leads. Next, as long as you don't interfere with other communications, and are willing to accept interference with your own communications, you are generally protected under Part 15 of the FCC regulations, although you should read those regulations yourself to be aware of the limitations. See the FCC web site (go to "http://www.fcc.gov" and search for "part 15"). I would be surprised if your computer had a connector of the wrong gender. Trying to plug a male into a male will not work. | ||
| mei |
is it possible to encode what one transmits, so as to only have one's friends to communicate with? | ||
| Simon Quellen Field (Sfield) |
Certainly. You can use any of the common encryption schemes, or you can invent your own. Suppose you scramble the alphabet and write the result as a word on a piece of paper. Then do it again, and write the new word on the next line, and so on until the paper is full. Now make a copy of the paper, and give your friend the copy. No one else in the world has this series of scrambled alphabets. Now, whenever you need to send an 'A', send the first letter of the first line on the paper. Then cross out that line, so you never use it again. If the next letter is a 'D', count over 4 letters on the second line, and send that letter. Then cross out that line. Keep doing this until you have sent your entire message. Your friend receives the first letter, and decodes it by noticing that it is the first letter on his decoding page, so it must be 'A'. He continues to decode this way, until he has the whole message. Because you are crossing out the lines and never using them again, no one can decode your message but you and your friend. You can do all of the tedious parts by writing a computer program. You can exchange your decoding pages (called "one time pads") by carrying the file by hand or mailing it to your friend. You can make years worth of them and still fit it all in a small file. | ||
| mei |
how can one encode the signal being emitted from the transmitter so as to only have friends able to listen?...OR is it even possible to--speak into a mic-- have the sound signal scrambled(or radio signal), sent out and have a friend recieve(a somehow descrambled signal or sound wave)a meaningful conversation, as oppossed to meaningless noise? | ||
| Simon Quellen Field (Sfield) |
The previous message contained a long description of how to do that, in answer to your first question. All of the methods within your budget use computers to do the tedious parts. Look up "PGP encryption" on Google to find free programs to do it. Record your voice using a sound card. Encrypt the sound file with PGP. Send the encrypted data over the radio link as dots and dashes. Your friend will receive those, convert them to a computer file, run the PGP decryption program on the file, and listen to it. There are other ways, but I think you will find most of them difficult to realize, or too expensive. Look up "scrambling circuit" on Google. | ||
| Anonymous |
A few questions. 1. I have two 9-pin ports label "IOIOIO A" and "IOIOIO B"; which one do I use and which port (COM 1 or COM 2) is it? 2. I tried putting them into the ports anyway and the LED just went on solid without me sending any message with the Transmitter Program. What should I do? 3. I was using the command line version of the transmitter program and when I started it up, the first line said " Can't open 'com1:' " What should I do? | ||
| Simon Quellen Field (Sfield) |
The manual for your computer should tell you which port is com1 and which is com2. If you don't have a manual, you can probably find one on the web. It should be easy to tell which is which, however. Attach a serial device (such as a modem) to a port and see if you can talk to it as com1 or com2, using a terminal program such as HyperTerminal. When you do determine which port to use, and the program is running, the LED will flash. It is OK if the LED is on solidly before the program is running. When you have the transmitter connected to com1, the program should stop telling you that it can't open com1. | ||
| max Unregistered guest |
A got a few questions: Where can I buy a 1.000 Mhz oscillator besides in your catalog? If radio shack sells them, do you know the product number? What is the radio shack number for a 14 pin socket, and what is the radio shack number for a general purpose circuit board? Also, can you give me very specific step-by-step instruction for making an antenna? Could you tell me how, and not just tell me to use the antenna book you suggested before in one of my previous posts? Thanks! P.S. Is the oscillator in the computer controlled transmitter the same one reffered to in the "AM transmitter from simple parts"? Thnx again! P.P.S Have you written any other books besides "Gonzo Gizmos"? | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 32 Registered: 12-2004 |
I don't think Radio Shack sells oscillators. You might try another electronics part retailer. You can look up Radio Shack part numbers on their web site. They have a search box where you can type in what you are looking for. The antenna does not need to be outside, but the bigger it is the better it will work. I have already discussed how to attach the test lead to the wire leading up to a rooftop antenna. It's that simple. The oscillator in both projects is the same one. | ||
| David L. Rice Unregistered guest |
Hi! My son is using your circuits for a science project and I built one first to make sure it would work for him. It seems ideal since he has very limited soldering experience. I have been able to make the cw mode of the xmit program work very well, but when I attempt to use the hig and low tone modes I receive something that sounds like 60 cycle buzz. I'm certain my the computer I'm using is fast enough to perform the functions of turning on and off the com port. .what am I missing here? ( I have used both a 25 mhz and a 1.6 mhz oscillator. Thanks in advance for any solutions you may have. | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 159 Registered: 12-2004 |
You could verify the frequencies with an oscilloscope, but the buzz should be all you need. The idea is to amplitude modulate the signal, so a cheap AM radio can receive it. It sounds like you are there. | ||
| Anonymous |
i am ready with all my hardware parts +.but i am not getting the programme required to transmitt and receive the messages. could you please help me? | ||
| sandip puraneindia Unregistered guest |
i am ready with all my hardware parts +.but i am not getting the programme required to transmitt and receive the messages. could you please help me? | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 164 Registered: 12-2004 |
You will have to provide more information about your problem. Are you having difficulty downloading the program? If you have downloaded it, are you having trouble running it? If you are running it, are you having trouble determining if it is powering the oscillator? Have you checked that your serial port works by using HyperTerm (built-in to Windows)? Are you sure you have connected to the right serial port? An inexpensive tool like this serial line tester or this cheaper one will help, although you might want to find a 9 pin version, or use a 9 pin to 25 pin adapter. | ||
| Anonymous |
The C++ Program Doesnt Work!!! There is a compile errpr | ||
| JasonDalton Unregistered guest |
Hi Simon, I enjoyed your article in Make magazine. What a great mag for people who like tinkering with stuff. Why did you take the computer controlled radio off your site? are you moving things off that will get put into Make or another publication? Thanks for your help BTW earlier, everything worked out great eventually. | ||
| JasonDalton Unregistered guest |
Silly me, i didn't notice you had created a new section. Way to go simon! | ||
| Kushal Unregistered guest |
i got a 48 mhz oscillator does it will work for the project of computer controlled transmitter. | ||
| Simon Quellen Field (sfield) Senior Member Username: sfield Post Number: 372 Registered: 12-2004 |
You will need a receiver that is capable of receiving AM signals at 48 Mhz. That may be hard to find. We sell the 1 Mhz oscillator in our catalog because cheap AM radios can receive the signal easily. | ||
| kushal Unregistered guest |
thanks for telling me | ||
| Jonathan Blissett Unregistered guest |
Hello, Please could you tell me if a 100mhz oscillator work for the computer controlled radio transmitter project. Thankyou | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 421 Registered: 12-2004 |
It is highly unlikely that you will find a receiver that can receive AM signals in the middle of the FM band. | ||
| kushal Unregistered guest |
hi simon am kushal i am from india i got the 28.322 mhz oscillator but can i get morse code on normal radio it has three mode MW FM and SW or will i need to buy that expensive short wave radio. and tell me how to built that 28.322 mhz computer controlled transmitter with full information .and tell me what other things wil be needed . | ||
| sfield Unregistered guest |
The traqnsmitter is the same no matter which frequency your oscillator uses. If your receiver can tune to that frequency, then try it once you get your license. There are many shortwave bands, and not all cheap shortwave recievers can receive all the way up in the 10 meter band (28.322 Mhz). Try the 1 Mhz version first. | ||
| kushal Unregistered guest |
yes i have license and i did the 1 mhz version i got sucess. but in of my radio is of philips company and and it has seletion in shortwave from 60 meter band to 19 meter band is this the problem for which i am not able to get morse code from 28.322 mhz oscillator . and which radio should i use. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 432 Registered: 12-2004 |
The Ramsey FR10C should work fine. My ICOM will do a better job though. | ||
| kushal Unregistered guest |
in this ramsey fr10c i wil get 10 m band | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 433 Registered: 12-2004 |
That's why it is called the FR10C. But go for the ICOM -- you'll like it much better. | ||
| kushal Unregistered guest |
but what is the cost of icom | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 434 Registered: 12-2004 |
$10,499.00 as of this writing. | ||
| Norman A Alcantara (Glvertex_nhor) New member Username: Glvertex_nhor Post Number: 1 Registered: 5-2005 |
Simon Quellen Field: I am wondering how the Transmitter discussed in Scitoys can send a text messages.because the tutorial did not mentioned anything about sending a text messages. How can I send a Text Messages to my cellphone using the simple transmitter? Norman | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 440 Registered: 12-2004 |
You have a cell phone that understands Morse Code? And listens to the AM broadcast band at 1 Mhz? I've never seen one of those. Our transmitter sends messages in Morse Code to a receiver connected to another computer. You type your text message into our program, and it gets transmitted to the receiver, and decoded by the receiver's computer, showing up as text on that computer's screen. No cell phone is needed. | ||
| Norman A Alcantara (Glvertex_nhor) New member Username: Glvertex_nhor Post Number: 2 Registered: 5-2005 |
No, I dont a have a cellphone like that. That is the reason why Im wondering about it. Ok now I understand transmitter to transmitter via a computer I thought I can used this to send a text message to a cellphone device. Ok It means that if I build 3 transmitter, and those 3 are online and I will try to send a Text messages,So the other 2 transmitters can received my messages? It is possible to control the transmittion, like for example only one transmitter can only receive my messages? norman | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 441 Registered: 12-2004 |
Just so there is no confusion: Transmitters transmit. Receivers receive. Radios are said to be "on the air", not "online". You control who receives radio signals by changing the frequency. Each transmitter would transmit on a different frequency, and in this way each receiver can be tuned to the frequency of the transmitter they wish to listen to. This is why receivers have little round knobs that can adjust the frequency they receive. If you don't want anyone but your friends to understand what you are sending, you use a thing called a code, where you agree on different meanings for words. For example, to prevent the enemy from knowing that they were working on armored vehicles, the army used the word "tank" so that people would think they were building water tanks. The code word eventually made it into the language, and we call armored vehicles "tanks" to this day. | ||
| Norman A Alcantara (Glvertex_nhor) New member Username: Glvertex_nhor Post Number: 3 Registered: 5-2005 |
I see your point, now I understand. But Im having trouble understanding your program Because it is written in C++ im using VB and Java language are there any available Program written in VB or Java to transmitt a Message? and my second problem is how far can a 1.00 Mhz Oscillator can reach? and if i will try to extend more my Antena is there any possibility to further more my nerwork? | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 442 Registered: 12-2004 |
C++ is not difficult to learn, especially if you already know a couple other languages. Having another tool under your belt is a good thing. We share the airwaves. If everyone was sending radio signals at 1.0 Mhz over long distances, no one would be able to communicate. To prevent that, the law and international treaties limit the amount of power you can use without a license. This means that for any serious application where you want good signal to noise ratios over any reasonable distance, you will want to get a license. The good news is that it is very easy to get a license. Go to the ARRL web site to learn how. | ||
| Norman A Alcantara (Glvertex_nhor) Junior Member Username: Glvertex_nhor Post Number: 4 Registered: 5-2005 |
Ok I will study C++, My last question before I proceed building my own transmitter. What if incase that there are two persons trying to transmitt a Text Message in a transmitter what will happen to their messages after receiving it? for example Person A is sending "Hello" and Person B is sending "Bye Bye" at the same time. And received their message like this "Bye Hello Bye" or "He Byello Bye" etc. What do you think? Norman | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 443 Registered: 12-2004 |
If two transmitters are sending different messages but on the same frequency using AM, you will hear both at the same time, like two people talking to you at the same time. In FM, you will only hear the strongest signal. With two people talking at once on the same frequency, the Morse Code decoder will have a difficult time figuring out what is being said, just as you would. That kind of interference is called QRM. | ||
| Norman A Alcantara (Glvertex_nhor) Junior Member Username: Glvertex_nhor Post Number: 5 Registered: 5-2005 |
I see, So there is any solutions to Solve QRM? or To control QRM and retrive the message as is like what they sent? And How can i switch my Transmitter/Transceiver From AM to FM? Thanks a lot. norman | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 447 Registered: 12-2004 |
You solve interference by moving to a different frequency. Changing from AM to FM is like changing a bicycle into a submarine. You basically start over, and build an FM transmitter. There are lots of circuits on the web, Google for "simple fm transmitter". | ||
| Norman A Alcantara (Glvertex_nhor) Junior Member Username: Glvertex_nhor Post Number: 6 Registered: 5-2005 |
Ok thanks for ur help Simon, How long it will take to receive your products here in the Phillipines? 2 to 3 days? (Message edited by Glvertex_nhor on May 27, 2005) | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 451 Registered: 12-2004 |
That's the time it takes for U.S. shipments. I would expect longer for the Phillipines. Let us know. | ||
| Anonymous |
Simon, You say that the oscillator for the am transmitter is like the ones from a computer. Are there oscillators off of a computer that I could use to make my transmitter or would it not be the right frequency? Thanks | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 515 Registered: 12-2004 |
Modern computers use oscillators that are thousands of times higher in frequency than 1 Mhz. It is unlikely that you will find an oscillator in consumer electronics equipment that will be in the AM band. But brand new oscillators are not that expensive. See our catalog. | ||
| Anonymous |
Thanks I will probably place an order soon. | ||
| erin r erikson (Freakydoo) New member Username: Freakydoo Post Number: 1 Registered: 7-2005 |
can this system be used to control a radio controlled car? which programs might work best? | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 588 Registered: 12-2004 |
If you want to have your computer control the car it's even easier than the transmitter project. Just use a CMOS switch like the 4066. Use the computer's parallel port to control it. Replace the switches in the remote control with the 4066. Use a simple BASIC program to send bits to the parallel port. | ||
| erin r erikson (Freakydoo) New member Username: Freakydoo Post Number: 2 Registered: 7-2005 |
cool quick response. but forgive my ignorance do you know where I could find a visual represention of the proccess you just explained. | ||
| erin r erikson (Freakydoo) New member Username: Freakydoo Post Number: 3 Registered: 7-2005 |
ok i wasn't sure what the cmos switch was but i looked at a picture so i'm good with that. but i'm still lost on the proccess. | ||
| priya Unregistered guest Posted From: 61.1.212.232 |
I want to modify a radio that can communicate to a nearby place (ex. to get information from a nearby located place were the database is stored)without towers, for which i would like to use FM trasnmission.Can i know if it`s possible & how I`m a final ComputerScience student(B.E). | ||
| priya Unregistered guest Posted From: 61.1.212.232 |
I want to modify a radio that can communicate to a nearby place (ex. to get information from a nearby located place were the database is stored)without towers, for which i would like to use FM trasnmission.Can i know if it`s possible & how I`m a final ComputerScience student(B.E). | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 653 Registered: 12-2004 |
The simplest way is to hack a pair of FRS radios. They sell for as little as $17.50. Use a transistor to switch the push-to-talk button, and a sound card to send and receive the audio. Encode the data using a telephone modem. | ||
| Anonymous Posted From: 69.239.60.130 |
I'm trying to build a robot and I'm wondering if I could use the computer controlled transmitter to transmit morse code to an on-board receiver (which would have a pic microcontroller to decipher the morse code). I'm thinking that maybe i could tell the robot what to do using simple commands. Thanks. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 659 Registered: 12-2004 |
Sure, go for it. You can use any code that is convenient for you. You can make up your own code if you want better error detection and correction, or faster response. | ||
| physics boy (Physicsinaction) Intermediate Member Username: Physicsinaction Post Number: 21 Registered: 7-2006 |
Can our 1Mhz oscillator be used as a receiver to receive like radio . I mean can it be use to make a radio. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1513 Registered: 12-2004 |
No. But we have a coupld radio receiver projects if you want to do that. | ||
| physics boy (Physicsinaction) Intermediate Member Username: Physicsinaction Post Number: 22 Registered: 7-2006 |
I see your radio projects they are great but the downfall comes for me is that they need a ground I want to build a receiver that runs only on it`s own battery power and can just turn on LED when picks up simplest signal (Range could be about 1 to 2 meters ) a buzz or anything like that from the crystal oscillator the oscillator I am using is 30MHz. | ||
| Alex Roberts (Whoo_mythbusters) Senior Member Username: Whoo_mythbusters Post Number: 169 Registered: 9-2005 |
A ground can just be a piece of metal. Get some tin/aluminum foil, about a foot or so should work, then connect your ground on our radio to that. The radios will work without the ground, but performance is greatly compromised. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1516 Registered: 12-2004 |
The Three Penny Radio needs no extra ground or antenna. But it won't work at 30 Mhz. | ||
| physics boy (Physicsinaction) Intermediate Member Username: Physicsinaction Post Number: 23 Registered: 7-2006 |
Through some enhancement on the project can it be made to receive that frequency. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1518 Registered: 12-2004 |
No. The chip works at frequencies up to about 2 Mhz. | ||
| physics boy (Physicsinaction) Intermediate Member Username: Physicsinaction Post Number: 24 Registered: 7-2006 |
I was trying to build your project of computer controlled FM Transmitter . The thing I observed which I don`t understand is that I connect pin 5 and pin 4 of serial port to a LED and write a program which turn on and off DTR after 300ms interval I receive the buzz on radio at frequency about 103 Mhz why it happened can you explain and also the range was very nice more tan I got on 1Mhz oscillator. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1526 Registered: 12-2004 |
First off, there is no FM transmitter project on my site, computer controlled or otherwise. There might be in the future though. The reason you are hearing noise at 103 Mhz is that you are splattering radio waves across all frequencies. It is called noise. You should be able to pick it up all over both the AM and FM bands, and in between, as well as over shortwave bands and TV bands. This is why we have to keep the power way down, so as not to interfere with other communications. A better designed transmitter will have a filter on the output, so instead of square waves, we have a pure sine wave that uses much less bandwidth, and does not stray outside of its designed frequency. | ||
| scott (Ichyc) Senior Member Username: Ichyc Post Number: 128 Registered: 6-2006 |
why don't you just make a sine wave generator then it wont go out of it's frequency. | ||
| Manuel Perez (Prz22) New member Username: Prz22 Post Number: 1 Registered: 3-2009 |
Hi, excuse my ignorance, but... How can i recieve(syntonize) a 1Mhz frecuency from a Short Wave Radio or a cheap AM Radio ? Thanks | ||
| Theresa Simmons (Theresa) Senior Member Username: Theresa Post Number: 113 Registered: 1-2008 |
See "http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html". 1 megahertz is right in the middle of the frequency range that an AM radio is designed to receive. Any amplitude modulated signal at that frequency will make sound in an AM radio. | ||
| Patrick (Firewire) Senior Member Username: Firewire Post Number: 122 Registered: 12-2007 |
If you can't get a hold of a receiver that can receive 1 Mhz, then just use an oscillator with a higher frequency that your radio can receive. But I'm better off using FM transmitters. This is a good site to start with. It contains pictures and diagrams of simple FM circuits (1, 2 ,3 ,4 transistor FM transmitters) which you could receive using a pocket FM radio receiver, or that of your mobile phone (some mobile phones have FM radios in them). |
