Some More Simple FM Transmitters

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Re: Question about "fmtransmitter3.gif"

dfhrace said:
yes i have a question about the circuit "fmtransmitter3.gif", i wanted to know could i put a headphone jack input in place of the mic? because i was going to use this for my ipod inplace of buying an itrip so any help would be good thanks

dan
Click to expand...
The headphones output level of an ipod is about 200 times higher than the level from a microphone. The entire preamp transistor stage of the transmitter must be removed.

The simple transmitter circuit is a lousy child's toy that would sound horrible:
1) Its RF frequency drifts all over the place if something gets near it or its antenna, and if its battery voltage drops.
2) It is mono, not stereo.
3) It doesn't have pre-emphasis (treble boost) like FM radio stations have, so it would sound muffled like an AM radio.
 
VHF POWER METER

can anyone please suggest a simple circuit for RF POWER METER for testing the oscillator output. i foun one in the site
https://electronics-diy.com/tx500.php.
i bulid the schematic below but it doesnt work.
for the 2pF i use 1pF conected parallel. in the image of the project in the
site he uses 1.8 conected in series and he 270 resistor for the emmiter insted of 1k that he has the shematic. any suggestions;
The scematic below is from the site https://electronics-diy.com/tx200.php
thanks in advance
 

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The power meter's circuit has the LED backwards.
Also the transistor is not biased correctly but it might work.

I don't know which 1.8, 270, 1k and emitter you are talking about.
 
You are talking about the 2watt one? Anyway it is not even 1 watt.

The coil could have 5 to 6 turns on a 6 mm diameter with a 0.6 to 1 mm wire.
C1 is better to be a variable one with values up to 60 pf and C2 can be a 12 or 15 pf capacitor. The coil does not need to be a variable one but an aircore.

Regards
P.
 
sorry if i'm asking a stupid question. but...
would this work if i connected a headphone jack to the transmitter and put that in my ipod instead of the microphone?
 
Yes but you need an attenuator (this is no problem a couple of resistors will do) and simple transmitter circuits like this give crap mono AM radio sound quality.
 
hello

audioguru said:
Mine has a power amp stage and goes very far:
Click to expand...
its that really working and what bout the range of that fm transmitter? an you explain the circuit to me.. so that i can understand thanks
 
My FM transmitter has an RF amplifier on its output.
With a new 9V alkaline battery its range is more than 2km across a large river valley to my very sensitive home FM tuner and to my very sensitive car radio.
The range is about 300m to my Sony Walkman radio.

Hills, buildings and trees block the signal.
 
I think I heard your broadcast of Gordon Lightfoot's song, The Edmund Fitzgerald. The transmission must have rode in on one of those Great Lakes gales that begin this time of year!!
BTW, sometime I want to discuss these Alberta Clippers that you folks send our way. That stuff has got to stop or we start sending you illegal Mexicans .... (and we have enough of them to cripple your economy!
 
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Canada gets its share of illegal foreigners. They do the "dirty" work that local people don't want to do. Boatloads arrive from China each year.
 
Does anyone have a circuit of a simple low power FM transmitter that uses crystal 1MHz and has a 105Mhz output? dont know how that is done but if anyone can help??
 
FM transmitter

You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff.

Thanks
 
TinaiKevin said:
You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff.
Click to expand...

No, from a 1MHz crystal you have to use a PLL system, you couldn't even use multipliers - which would be complicated anyway.
 
If you can use 15MHz crystal as oscillator and derive the 7th harmonic, perhps you may end up getting the required 105MHz. Mostly a single 74HCU04 and few pf caps and an inductor are all that are needed. It could work off 5Vsupply. A sample diagram is attached , thanks to G Baars the designer of SW radio capture.
 
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