Tunable RF coils question

[colin55]

You CANNOT use 2N3866.

Do not give advice if you don't know what you are taking about.

A 2N3866 is a POWER TRANSISTOR. You will NEVER be able to drive it.

You have obviously NEVER made an RF circuit.

 

[Ziddik]

still you did not say what is possible replacement for 2N3563, i googled it but no luck, moreover the 2N3563 is an RF powertransistor!

 

[Ziddik]

try to use 2N3866 locally available . but biasing would change. please check pinout while mounting

thanx, but i might need some slight modifications in the circuit and a driver transistor if i am going to use 2N3866,

 

[audioguru]

Don't you think the range of the simple transmitter depends on the quality and sensitivity of the radio that receives it??

A cheap radio is severely overloaded when the transmitter is nearby so the signal is across the entire dial and you cannot find the correct tuning point so the range is very low. My Sony Walkman FM stereo radio becomes severely overloaded even when its local-distant switch attenuates the signal. My home stereo and car radio do not become overloaded.

My FM transmitter has a range of more than 2km (across a large river valley with nothing in between) to my home stereo and car radio, 400m to my Sony Walkman radio when it is not attenuated and a range of across the street to a cheap clock radio and to a "radio" from The Dollar Store.

The transmitter and receiver antennas must be parallel for the most range.

 

[Ziddik]

I got an FM radio in my cellphone (Nokia N70) And i use it to recieve the signals,also it has auto search function that detects the signals automatically

 

[mvs sarma]

as i suggested in my pm, i openly advise you to use the AG's Mod4 version of FM TX and it works. i had even made a small pcb for it.
we can enclose it is a small metal can. AG has tested it for almost few Km. If the terrain is open unlike concrete jungle of cities, it covers a longer distance even. It is a question of optimising antenna impedance to get a good VSWR

regarding 2N3866, such high power might land you into troubles from government. so, better don't use unless say for a short time like few minutes of testing.

@ Audioguru,
yes. A good receiver is always preferable.

 

[transistor495]

In you circuit, you may not use a 2n3866 in place of 3563 because it may need at least 1/2watts or more RF power to drive efficiently to output couple of watts.

 

[Ziddik]

This design also works(see post #17) and its stability is perfect, but the only problem i am having is its range is only a few Meters, (16M max), i don't want to use a high power transmitter due to it's illegal so i just want to build one and test it and show it to my friends as they'r challenging me that "You can't build such a high power RF transmitter!" its a bet infact!, a 1KM version would be enough for me as i just want to prove them that it is possible by me!

Btw, can anyone post AG's MOD4 transmitter for me?

 

[mvs sarma]

This design also works(see post #17) and its stability is perfect, but the only problem i am having is its range is only a few Meters, (16M max), i don't want to use a high power transmitter due to it's illegal so i just want to build one and test it and show it to my friends as they'r challenging me that "You can't build such a high power RF transmitter!" its a bet infact!, a 1KM version would be enough for me as i just want to prove them that it is possible by me!

Btw, can anyone post AG's MOD4 transmitter for me?

here it is

 

[Ziddik]

it's a horrible circuit!!
Why are there lots of components in that circuit? And hey i found another circuit from EFY! Please check it out if it is better than AG's i will go with it or i will build Ag's as it looks like a standard one

 

[mvs sarma]

Perhaps a personal feeling.
i dont know how you came to that conclusion.
dont be biased against.
even if you count, the additional components are not many. if you love to make different circuits that may trouble you like what you already enjoyed( a low coverage), Fine. best of luck.

 

[transistor495]

it's a horrible circuit!!
Why are there lots of components in that circuit? And hey i found another circuit from EFY! Please check it out if it is better than AG's i will go with it or i will build Ag's as it looks like a standard one

Long range satisfaction guaranteed if you can successfully implement this circuit and is way too complicated than AG's one.

Let me know if you can grab the transistors/components exactly specified in the circuit. RF assembling is an art that you need careful 'layouting' to get maximum out of it.

 

[audioguru]

The new circuit you found uses very old parts that are not made anymore. It has a high output power that will probably cause interference to radios, TVs, aircraft communications, police and fire department communications and will get you into trouble.

 

[Ziddik]

Long range satisfaction guaranteed if you can successfully implement this circuit and is way too complicated than AG's one.

Let me know if you can grab the transistors/components exactly specified in the circuit. RF assembling is an art that you need careful 'layouting' to get maximum out of it.

Your profile says that you are interested in RF, So have you ever made an FM transmitter?

 

[Ziddik]

The electronic shops here can't supply 2n3866 and 2n2219a! So i tried to buy components for AG's, same crap! They can't supply the LM2931!!

 

[mvs sarma]

Ziddik, i don't feel that you need that much power by one 2N2219 and finally by 2N3866. I fear, this experiment at that power might risk you legally. Better confine with lower output power, and derive efficiency by optimizing the antenna.

Advantage of LM2931is that, until the supply comes to 5.6V or so, you get 5v output. LM2931 should not be difficult to get. otherwise you might also get smd like LM1117-5. Request some friend to get one from Kochi where you are sure to get it. if you are sure that the input supply is 9v OR ATLEAST 7.5v ABOVE, YOU CAN USE 7805.

As far possible don't use adopter for this experiment as you can't control the power hum.

there is a sequence of optimization of final transistor tank circuit.
if the tank circuit is tuned properly and the antenna is coupled through a small cap like 10pF or some such as indicated in AG's circuit, the RF won't be transferred efficiently. This is the very reason you are not getting the range.

it needs methodical approach. you need to have patience and skill to optimize the antenna matching and tank circuit optimizing.
please try to understand and dont risk yourself with too high powers

 

[audioguru]

I used the LM2931 low-dropout 5V regulator because it still regulates when the 9V drops to 5.6V. You can use a 78L05 ordinary little 5V regulator but it stops regulating (it drops out) when the battery is still fairly new at 7.5V.
There tens of thousands of this low-dropout regulator stocked at the two largest electronic parts distributors in North America.
There are many other low-dropout 5V regulators made by most semiconductor manufacturers.

My antenna is a quarter wavelength at 80cm long. It hanged vertically so it was parallel to the whip antenna on my home stereo and on my car. Colin's antenna is double the length which is not correct for a single piece of wire. Rabbit ear antennas are double the length of mine because they have two ears and are directional.

 

[Ziddik]

Thanx sarma and AG, Maybe i can find them online, but i don't know how to buy online! Do i need a bank account for this purpose or can i pay when it gets to my house (cash on delivery)or are there any other options? I think you guys already know it bcz i can see a "forum supporter" icon, please explain, n might come to cochin next month if it's not possible to find them online

 

[Ziddik]

Hey sarma, can i find some PCB creating tools there in cochin? These local crap shops can't supply anything that are neccessary for me! Thus i had to avoid many projects, i think that "transistor495" dude is from cochin

 

[transistor495]

Your profile says that you are interested in RF, So have you ever made an FM transmitter?

This statement has pretty insulted me I feel ;-)

Regarding components availability, nowadays it is difficult to find such parts even in kochi too. However you can try it out, make a list of them and come here and search please I hardly get time for these activities actually.

If you really need help then send me a list, I'll search for you when I get some time.