FM Transmitter

[chui]

can anybody Please recommand me on some FM Transmitter/s?
a good one..
thnks

 

[TheOne]

Message is unavailable.

 

[zachtheterrible]

wut r u looking for? high power? bug (cuz i got a really good bug)?

 

[Dr.EM]

I want to hear about this bug, if nobody else! Show us!

 

[zachtheterrible]

this is the coolest transmitter mainly because it has such good performance off of only 3v. Since its 3v, two AA's can be used, giving it MUCH more battery life than your regular ol' 9v transmitter. @ a range of about 50 feet, this transmitter lasted for FIVE days! of course it would last longer if you keep getting closer and closer. oh yeah, and the transmitter was overpowering a very strong local radio station for those 5 days.

i plan to find a receiver that i can modify to go above the regular 88-108 MHZ and then im sure that i can get even more range out of the transmitter.

 

[pike]

I'm trying to do what your doing atm. But i'm trying to to it digitally. The output signal is a digital wave. Theoretically you can make an extremely powerful transmitter. possibly stronger than the licensed stations aswell. It would have to be crystal locked with a PLL. This would also be very very accurate and have virtually zero frequency drift.

were still looking for a pll of high enough frequency range (30mhz+)

*Note however this is for extremist in this field who want power :twisted:

 

[zachtheterrible]

i dont get wut ur saying pike. r u saying that ur trying to build a low voltage transmitter that is extemely powerful?

 

[Nigel Goodwin]

I'm trying to do what your doing atm. But i'm trying to to it digitally. The output signal is a digital wave. Theoretically you can make an extremely powerful transmitter. possibly stronger than the licensed stations aswell. It would have to be crystal locked with a PLL. This would also be very very accurate and have virtually zero frequency drift.

were still looking for a pll of high enough frequency range (30mhz+)

*Note however this is for extremist in this field who want power :twisted:

It's common in VHF radio to use a far lower frequency and multiply it to the frequency you require, the 2M amateur band (144MHz) usually uses 12MHz oscillators and multiplies it 12 times. This also has the desirable effect of increasing your deviation. However, with a crystal you're not likely to get the high deviation required for a broadcast receiver.

If you search on these forums, there was a link (not long ago) to just such a PLL transmitter, which applied the modulation in the phase lock circuit, giving broadcast style deviation and accurate frequeny settings.

I presume unlicenced broadcasting in Australia is severely illegal?, as in the UK - and certainly if you're looking at higher powers than commercial stations you are going to be VERY easy to catch.

It's also going to be expensive to build high power transmitters, and complicated as well - with a need for expertise and specialised test equipment.

Assuming the laws are similar to the UK?, if (when?) caught EVERYTHING connected with it will be confiscated - transmitter, audio equipment, CD's, computer - the LOT. Plus a potentially very large fine, and possible jail sentence.

If caught, I would advise grovelling in court - I used to know a guy who got caught three times! (only with low power), the first time he was fined, the second time a bigger fine, the third time he grovelled embarrasingly in court and escaped with a warning :lol:

In all three cases all his gear was confiscated and destroyed, including his complete record collection (it predated DC's).

 

[pike]

ok maybe not powerful enough to take over other stations, but certainly powerful enough for 400m radius (1200ft??)

Most of those kits that say they transmitt 1km, is bogus. In the end they only transmitt 30m.

If I cant find a pll suitable i'll get the low power digital kit, and amp it up with lots and lots of 2n2222's. Or even a mosfet!!

Yes I know laws are put in place. but as long as i'm not transmitting over emergency service signals (if they failed, someone could die as a result)

the signals however would be transmitted very rarely.

zach: I'm pretty sure that the power transmitted doesn't solely rely on voltage, but also the amount of current being converted to electromagnetic radiation.

 

[Nigel Goodwin]

ok maybe not powerful enough to take over other stations, but certainly powerful enough for 400m radius (1200ft??)

Bit of a turn round? :lol:

Suddenly dropped from multi-kilowatts to milliwatts!.

Most of those kits that say they transmitt 1km, is bogus. In the end they only transmitt 30m.

The little single transistor 'bug' types will do a couple of hundred feet, those that quote a 1km range usually have an output amplifier stage, and should easily do a kilometer - obviously depending on the aerials employed, and the local conditions (outside in clear space is obviously best).

If I cant find a pll suitable i'll get the low power digital kit, and amp it up with lots and lots of 2n2222's. Or even a mosfet!!

It doesn't sound like you have the faintest idea how to build an RF power amplifier!, they aren't trivial devices, both in the design and the construction. Using multiple devices is certainly possible, but makes both design and construction MUCH more difficult - it's usual to use one or two correctly rated devices, rather than multiple under-rated ones. Obvious exceptions are very high power transmitters, where the only way to get the power (using semiconductors!) is by multiple devices.

Yes I know laws are put in place. but as long as i'm not transmitting over emergency service signals (if they failed, someone could die as a result)

the signals however would be transmitted very rarely.

Again, it depends on the power! - you were talking previously of using higher power than commercial stations (multi-kilowatt), obviously dropping down to milliwatts instead is a lot less likely to cause problems.

zach: I'm pretty sure that the power transmitted doesn't solely rely on voltage, but also the amount of current being converted to electromagnetic radiation.

In theory the supply voltage is irrelevent, but in practice too low a voltage will limit your output power - simply due to the problems with extremely low impedance taps on coils, and losses in low voltage conductors due to the high currents.

 

[TheOne]

It's also going to be expensive to build high power transmitters, and complicated as well - with a need for expertise and specialised test equipment.

100% so, even to just build a low power high performance PLL unit you need special equipment like spectrum analyzer (to make sure your harmonics is low), distortion meter (to ensure good quality audio will be received), modulation analyzer (make sure you are not over deviating your carrier) etc.

 

[zachtheterrible]

zach: I'm pretty sure that the power transmitted doesn't solely rely on voltage, but also the amount of current being converted to electromagnetic radiation.

yup, im quite aware of this, but as nigel sed, it is pretty hard to get a high pwr transmitter of 2 AA batteries :lol:

 

[chui]

Hey,
The PDF link dosent work!!
Im looking for a good FMTransmitter Chip, which will be able to handle deviation and harling.. I heard something with crystal will be good,

Its for a cartoy.

thnks

 

[zachtheterrible]

thats strange :?

try this: https://www.electro-tech-online.com/custompdfs/2004/12/DIY-k7-2.pdf

 

[pike]

Ive just found an alternative. I'll utilise the space in the amatuers band which has much less restsrictions. This also means i'm changing over to AM which is fine by me. I'll build a crystal locked version set at 20mhz by a crystal. Then amp it up.

Now for the recieving end...

Yes, you are right nigel. I haven't got the faintest idea on how to build a transmitter, but i'm extremely will powered on this!!! On the other hand i'm more proficient on the digital side of things.

I think the saying goes: 'where there's a will, there a way'something like that. Much Like zach, with his persistent questions on these boards!! 8)

 

[zachtheterrible]

I think the saying goes: 'where there's a will, there a way'something like that. Much Like zach, with his persistent questions on these boards!!

haa haa, quite right :lol: this forum is the best thing to every happen to me in the area of electronics. i was just about to give it up and then i found out about this forum, phew! now i tinker around with electronics instead of playing mindless video games. i have nothing against playin em once in a wile tho, like halo, the best multiplayer game ever as far as im concerned :lol:

hopefuly the questions will be lessening in a wile because im getting some more books on electronics to increase my knowledge a TON (of course there will be questions about the books)