Tunable RF coils question

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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.
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Isn't it AMAZING. I get a much better range with 175cm than 80cm. That's because the antenna length is ALL WRONG!!!!!
 
colin55 said:
Isn't it AMAZING. I get a much better range with 175cm than 80cm. That's because the antenna length is ALL WRONG!!!!!
Click to expand...
I can't be bothered to copy and paste from Wikipedia where it says a whip antenna is 1/4 wavelength which is resonant (75cm for the FM broadcast band) and has 3dB more gain than a half wave dipole.
 
finally, i got a miraculous solution for the fm transmitter! I did't add a power amplifier in last stage (but removed it.) and removed the 2n3904 from oscillator stage and just added a transistor stamped "c1959"on it and got more than 1Km range even only with a 10 cm antenna!! I still can't believe it how did this phenomenon happend!! I did't add even a preamp but a 2n3904 to amplify mic. The transmitter is very stable, its frequencey does not change even when i carry it with me or touching the antenna! I don't know, i got the c1959 from my junkbox!!
 
Your 2SC1959 has almost the same spec's as a 2N3904 transistor except the pins are different.
Maybe you had the pins backwards before.
Please post the new schematic.
 
audioguru said:
Your 2SC1959 has almost the same spec's as a 2N3904 transistor except the pins are different.
Maybe you had the pins backwards before.
Please post the new schematic.
Click to expand...

no way guru, if i did so it would not work!
And the schematic is same as i posted in #17! I don't know what happend! Maybe as i added 2 feedback caps? One 5pf and another 8pf

@sarma

i got another datasheet, it says it's Npn
https://google.co.in/m/url?channel=...jAFOAo&usg=AFQjCNEkU5zROVipyDaWwl0C7bJAz6l0dw
 
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You made a simple single transistor FM transmitter. There are hundreds of circuits like that on the internet with a range of 100m to a very sensitive FM radio.
The antenna connects to the tuned LC circuit so of course anything that moves toward or away from the antenna changes the Tuning Capacitance so changes the frequency. Maybe your radio has AFC (automatic frequency control) which follows the change of frequency.
 
I never had much luck with 2N3094's in these, I can remember replacing it with a 2N2222 and it worked.
 
@Guru, i replaced the variable cap with a fixed 15 pf cap, and still i can touch its antenna without any problems! The frequency changes only when i touch the coil
 
i think the c1959 is such a great transistor. alas! I had only one left and i used it in this circuit, i don't get another one from the shops.. I think
 
hi sarma, i don't know, it's stamped c1959 and T Y on it, and it's an NPN transistor, i tested it with my multimeter
 
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it is a high power transistor power almost 500mw at Ic of 500mA
see the datasheet at c1959-y anyway be careful that you are safe from the hands of police who monitor these frequencies.
perhaps these are used in TV sets and imported Audio systems etc
 
Ziddik said:
@Guru, i replaced the variable cap with a fixed 15 pf cap, and still i can touch its antenna without any problems! The frequency changes only when i touch the coil
Click to expand...
Don't you understand what I said about AFC in your radio?
 
mvs sarma said:
it is a high power transistor power almost 500mw at Ic of 500mA
Click to expand...
But in this circuit it has only a 3.7V supply and it has a 100 ohm emitter resistor.
The average emitter current is only 10mA so any little low current transistor will work.

It does not work in a simulation unless its antenna is more than 680 ohms (a short little antanna producing short range). A quarter-wave antenna is about 75 ohms for max power and far range.
 
All said, we expect a latest sch of what exactly Ziddik did. the new device used by him has ECB pin order. hope he would have bent pins and swapped properly.

@ziddik,
please edit the new diagram in any way you know and provide. Are you sure that pins are properly placed as the order is different. Don't feel that we are questioning your ability !!
 
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I simulated the circuit made by S!dd!k.
I increased the value of the tuning capacitor by 5pf to 20pf due to stray capacitance and to reduce the frequency away from the aircraft band to the FM broadcast band.
I used a powerful 2N4401 transistor.
The oscillator stops when a load on its collector is less than 680 ohms so its output power is very low.

I added an RF amplifier transistor to isolate the antenna from the oscillator. The oscillator stops when the RF amplifier is cap-coupled to its collector but works fine when cap-coupled to its emitter. The RF amplifier drives the 75 ohm 1/4 wave antenna. The output power is low but useable.
The output has strong even harmonics which will cause interference to communications.
 

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well, another interesting thing that i found today is the wing shing S8050 works and delivers R waves in a distance of abt 2Kms! And has alot better stability than c1959!, i didn't download its datasheet but a site says it has 1W power!, i wonder how come these transistors in an ordinary TO-92 packages while the same watt rated transistor (like.2n2219a,2n3866) come in metal cases? New technology? But to achive 2Km range,i had to power the transmitter with a 9V supply and a two meters long antenna, another important thing that i found today is i could power it using a mains transformer with lm317 regulator and abt 7 of those green 'sack like' caps to avoid hum completely!, anyway guys, i think we should design a circuit as mvs_sarma said, but i might need your help.
 
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