I am very interested in fm transmitter.But I have not enough knowledge to construct such a fm transmitter circuit on my own really .I have no chance to buy a fm transmitter from other countries around the world because my country has no "clear money exchange system " to take relationship with on-line stores.
I have constructed short range fm transmitters and I had successs on them
But I don't satisfy with their "range" .So I searched long range transmitter circuits on internet.But I can't find what I want so far.So Could someone help with this problem?.I want to design & construct a long range fm transmitter having the transmitting distance of up to five miles around .I would use that circuit to broadcast songs as an amateur .( My country has no "hard " limitations on transmitting ) I will use that transmitter at my "countryside".So who could give me a helpful hand with this my "big dream " crazy? .
Please.RFC coils are not allowed there in my circuit design because these RFC coils could not be bought any where in my country .
With . Thanks a million,
Mg Myo Ko
myokoko19@gmail.com
I want to design & construct a long range fm transmitter having the transmitting distance of up to five miles around .I would use that circuit to broadcast songs as an amateur .( My country has no "hard " limitations on transmitting ) I will use that transmitter at my "countryside".So who could give me a helpful hand with this my "big dream " crazy? .
Please.RFC coils are not allowed there in my circuit design because these RFC coils could not be bought any where in my country .
Quite a mouthful KE5FRF,
I'm sure he'll appreciate all that information.
I forgot about the the fact of limiting RF output power and antenna constraints. If he did use HF, his desired distance could be aggrandized and surpass what he originally expected. However, he seems to be implying about the standard FM radio bands for broadcasting and I'm not sure if 5 miles could be achievable under the FCC conditions they enforce. Well, I guess he'll just have to get his amateur radio license, eh?Then he could use one of those mini QRP CW HF transceivers and go across the world like you have. With 1W it seems hard to believe, but you must have been at the top of the sunspot cycle; hopefully we'll get more soon. Sunspots would improve his distance range too.
It is pretty hard to imagine an FM transmitter with a five mile range that does not use inductors. You might want to consider removing or disguising your email address in your post. The spambots will find it an pound your inbox relentlessly. What is your country by the way?[/QUOTE
First of all,I want to say "thanks" Papabravo ,for your time.Most of them who reply my thread are considering that I don't want inductors included in my circuit .I don't really mean like that. What I do not really want is RFC component like VK200 tosk .Those are very rare in my country .
Dear Papabravo, I really appreciate your words suggesting not to add my e-mail address in my threads .Thanks for that again! My country is Myanmar.Have you ever been to my country ,Myanmar, before,Papabravo?Looking forward your incomming suggestions for my circuit design with great hope!!
Sincerely
Mg Myo Ko
If you cannot buy any parts it is difficult to give advice on a design. If it were possible for you to get the Rohm BH1414 integrated circuit, this would be an excellent starting point for your transmitter. This IC does all the hard work of generating a good carrier with stereo modulation. Here is the data sheet:
https://www.electro-tech-online.com/custompdfs/2009/10/bh1414k-1.pdf
In America, this part costs about $5US.
This IC will generate a very low level of power, so it will be necessary to add amplifiers to boost your power. It will probably be possible to find circuit schematics for simple amplifiers on the net, but again, you need to explain what parts you have access to.
You will need to use many RF inductors in your circuit, but you can make these easily yourself with solid copper wire.
I will try the book you suggest ,MikeMI. I have said that I have very little knowledge about circuit .Dear MikeMI the very first step of my design is to configure out a transmitter circuit with a output wattage as much as possible.I don't mean Inductors ,I really mean RFC coils ( so-called chokes) like this one VK200 tosk component They are very rare in my country,Myanmar .Dear MikeMI ,Can't I build a transmitters circuit using transistors and other radio components because tubes that you said are also scare and very complicate to handle ? Forwarding your warmly suggestions to my circuit design MileMISimply put, you cannot build a high power transmitter without LC tuned circuits. Coils are easy to construct; Capacitors rated for high-frequency RF currents are a tougher problem, but could be fabricated using parallel-plates and air dielectics.
To get the range you want, you will need a transmitter capable of producing ~1 to 10W of RF output presumably at ~100mHz. To get that you will need a tube and a high voltage power supply.
Can you scrounge some old tube-type TV sets?
See if you can get access to an 1960's or 1970's "The Radio Amateur's Handbook". It has all the basic circuits, oscillator, FM modulator, RF power amplifier, Power Supplies, and antennas. The older books had a lot of tube circuits which might be easier to duplicate from parts from a TV set compared to newer books with use specialized IC and solid-state parts which you will have a hard time obtaining.
In reality, the range of any radio transmitter isn't so much dependant on modulation type as much as frequency. There are optimal frequency bands between 160 meters and 6 meters which can transmit a great distance given ionospheric conditions and sunspots.
FM is typically not used in lower frequency radio because of the bandwidth requirements and the available "real estate".
In your case, it sounds like you want to use the accepted "commercial" frequencies for FM radio, for which recievers are commonplace. This would typically limit transmissions to Line-of-site and a measure beyond depending on terrain, amplifier power, and antenna height,construction. You would be amazed at how much you can do with very little power. I have QSL cards using CW (morse code) communication from clear around the world using less than 1 watt.
A few suggestions that might "help", assuming you can construct a maximized transmitter...
Antenna height. If you are in a mountainous area, that tiny transmitter might surprise you at elevation. If you are doing this for fun and not a permenant set-up, you may think of a portable radio station on a mountaintop. If you have the ability to weather-proof your equipment and have sufficient battery power, and a secret location, you might have fun doing it that way with an automated transmitter.
ANTENNA. You mention 5-miles *around*, and this would be a typical omnidirectional vertical antenna, but a resonant wire dipole will give you bidirectional coverage...if you aim at population centers you will achieve some gain (which is a misnomer in a way, but in other words you concentrate the transmission and reduce loss)
LOSS...important concept. Transmission lines intoduce loss with standing waves and resistance. The better your transmission line and all of your connections, and the shorter the line, the more use of your transmitting power that will not be wasted as heat.
If you have the inclination, a YAGI style antenna (think outdoor tv antenna) has maximized gain in a single direction. The reflector dipole elements help focus transmitter power. Multi-element yagis further do this. It is the equivelant of mirrors and lenses in an optical system, only with radio waves.
The antenna needs to be a full wavelength above ground, more if you can. Given a 10 meter antenna as an example, it will work optimally at 30+ feet above the ground.
Also, some evidence shows transmitting across saltwater helps with gain, though I doubt this will apply in what you are doing.
Some or none of this info might help you, but perhaps you did learn something new or someone else.
Oh one more thing...polarization. (Most) Any antenna style can be polarized vertically or horizontally, and with short range transmitters (for which even 5 mile radius includes) it is important that the recieving station be polarized the same way, It has been a while since I played with my radios and built antennas, but 10-100 dB of loss occurs with cross-polarization.
It might be educational and fun for you to refer to the radio amateur's antenna handbook and googling "radio antenna", "dipole", "yagi", etc to get construction ideas and formulas for your frequency specifics.
Remember, a resonant antenna is by definition a function of radio frequency. A dipole is 1/2 wavelength, with 1/4 for each element to be efficient. There are off-center and multi-wavelength designs as well that give differing patterns for the transmission, but it is very hard to beat the standard 1/2 wave dipole.
And for transmission line, if you have the ability to match the impedance of your transmitters amplifier properly, parallel ladder line is very good, low loss stuff and you can construct it yourself with copper wire and popcycle sticks.
It is IMPERATIVE though, for the sake of your transmitter amplifer, that the impedance of your antenna is matched to the output impedance of the power transistor. Matching networks can be built, and that is, unfortunatley, where RLC circuits are neccessary.
However, matching can be done with the dimensions of the ladderline as well, along with methods you can employ found all over the internet.
Bad consideration is that many of these projects require at a minimum an SWR meter or an antenna analyzer to tune them to resonance.
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