boylesg
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Forget that project - it is absolute nonsense. The IC is incapable of running at the right frequency, the construction will never work reliably and the 'pop can' antenna suggests the writer is doing this as a joke.
Start with a design that uses an LC tuned circuit that resonates on the frequency you want, not a digital timer operating outside it's specification.
Brian.
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The dial on my radio says x10kHz and the range is 530 1600 to 1600, so that's about 5.3MHz to 1.6GHz.
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You might have misread the scale on dial. The MW Band dial should be x khz and not x10 khz . The MW AM Band is from 530 Khz to 1600Khz.
555 timer based am transmitter relies on harmonics for the MWband.
you can try the circuit in :
http://www.techlib.com/electronics/amxmit.htm
(may be the phono oscillator in that page).
Any self respecting HAM would know to avoid a circuit like that (I hope!).Could it be the author of the 555 based circuit did bot intend the signal to be picked up on a conventional AM/FM radio? But in a HAM radio instead?
Any self respecting HAM would know to avoid a circuit like that (I hope!).
It worked by producing square waves, the transistor at the output served no purpose whatsoever as it never passes any current. Square wave signals comprise many harmonics and it's one of those they picked up on their radio. Bear in mind that the frequency stability would be EXTREMELY bad (think of drifting 10's of KHz as the battery voltage or temperature changed) and the effect that has on harmonics is multiplied.
The first 'techlib' schematic is good, it properly modulates only the amplitude of the signal but has the drawback of not being tunable, you have to start with a quartz crystal at the frequency you want to transmit on. You might be able to change the crystal for an LC circuit but you would have to screen it from magnetic coupling with the output coils.
Avoid any schematic that modulates the oscillator stage, they always suffer from frequency deviation as well as AM. The schematic in post #5 will work but probably produces more FM than AM output. I would also be wary of any design that has no output tuned circuit, especially one that uses 1KV rated capacitors in a design that runs from a 9V battery and has both ends of the tuning control 'live'. It makes it almost impossible to adjust without the frequency shifting as you touch the tuning control.
Incidentally, the range is 530KHz to 1600KHz (0.53MHz to 1.6MHz) not GHz!
Brian.
Just for a bit of amusement I want to transmit and an annoying piercing tone over his radio that he has tuned into AM 1224 (SBS) and going 24/7.
The 50mW transmitter is AM. The oscillator frequency is decided by L1 and the capacitors around it. Note that no audio is fed to the oscillator itself. The modulation comes from changing the supply to the amplifier stage Q3 by varying the current through Q5.
Brian.
The calculation formula is:
f = 1/((2 * pi) * sqrt( L * C ))
where
f is in Hz
L is in Henries
C is in Farads
The units are very big for radio use so remember that 'pF' means 10E-12 Farads and 'uH' means 10E-6 Henries.
For example 150pf and 120uH resonate at 1/(6.28 * sqrt(150E-12 * 120E-6)) = 1186872Hz or 1.186872MHz. I approximated 2 * pi as 6.28 to keep it simple.
In the oscillator you have to take into account the total capacitance in the circuit, including the feedback capacitors. If you assume the tuning capacitor goes from rated value at maximum and about 10% at minimum (they never go down to zero) you can work out the anticipated tuning range. In general, if you want a wider tuning range you have to make the variable component larger compared to the fixed ones so it plays a bigger part in the calculation. In the schematic, the tuning capacitance plays a relatively small part, if it is 40pF maximum and lets say 4pF minimum and it has two 100pF capacitors across it, the combined capacitance is 204pf to 240pF. To get full tuning range, I would design it for 1.6Mhz and note the capacitance needed then work out the capacitance needed at 530KHz. The difference is the amount you have to add in the tuning control.
Incidentally, 47uH with 204pF resonates at 1.625MHz and with 240pF it resonates at 1.499MHz so the existing range is quite small. If you want to cover the whole band I would suggest making the inductor 150uH, the parallel capacitor 33pF and the tuning capacitor 470pF, that gives a resonance range of about 1.6MHz to about 580KHz. The exact range will depend upon other factors in the circuit, for example wiring length and capacitance between and inside other components.
Brian.
If you are successful, remember I didn't help you !
Personally, I would go with camera blinding option but using IR LEDs instead of a laser. Don't forget that transmitting a jamming signal is illegal and also that it may interfere over a greater range than just your neighbor.
Brian.
If you can find a low frequency speaker that can play infrasound frequencies (most cannot) then do not play a squarewave because it is full of harmonics that the speaker can produce and that people can clearly hear. Only a low distortion sinewave has no harmonics but most low frequency speakers generate distortion that can be heard.
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