Resonance

[BobK]

In other words, build an illegal transmitter.

Bob

 

[duke37]

An efficient antenna must be at least a quarter wavelength long.
The wavelength = 300 000 000/freq meters
Work out the antenna size for 0.57Hz
500mhz is very low. Do you mean 500MHz?

 

[BobK]

Oh, I missed that fact that the range of frequences if from .5 to .57 Hz. I guess the power radiated would fall below the legal limits then, so my comment above was wrong

 

[davenn]

Oh, I missed that fact that the range of frequences if from .5 to .57 Hz. I guess the power radiated would fall below the legal limits then, so my comment above was wrong

naaaa he means 500MHz he just isnt using captialisation correctly
its all just adding to the general confusion of this thread.

Electro132

there are signal generators that cover this freq range but they are expensive ~ US$2000 to the sky's the limit in price. Tho most of them will start at 10kHz, as noone is really interested in RF freq's below 10kHz
The one I have in my workshop goes from 10kHz to 8.4 GHz and cost me $2500 second hand (not new)

you are not ready to build something like this at home, its way, way out of your so far displayed skills ability
its going to involve multiple VCO's ...do you know what a VCO is ? .... that you will have to switch between as you go up from lowest to highest freq.

forget about your linear, log or digital pots ..... they are a side issue and they are the least of your problems
Your real problems are in building a whole bunch of oscillators and getting them working

Dave

 

[dietermoreno]

Ok, well this is what i have in mind:

E.g. Starts from 0.57hz and ends at 500 mhz (or more)

May I ask, why?

Are you sure you don't mean 0.57MHZ which = 570KHZ?

I think that RC circuit that car wipers use that is close to 0.5Hz depending on the wiper speed setting is not a good idea for radio transmission because in the long interval of time while no signal of amplitude is in the circuit then you introduce radio interference, so any radio signal transmitted is just dumb luck of repeating received radio interference. That is only if I have this correct, which I tend to not know anything about electronics so I'm probably wrong about this, or at best not quite correct.

 

[BobK]

And there is still the problem that if you are amplifying this to more and about 100mW and putting it on an antenna, you are breaking the law.

Bob

 

[Electro132]

And there is still the problem that if you are amplifying this to more and about 100mW and putting it on an antenna, you are breaking the law.

Bob

Not so. Here are the reasons why:

1) If you must know, anything from 1 - 20 hz is part of neuro-science since it has something to do with our brains. Scientists have been playing with the idea of being able to fuse technology with our brains like for reasons such as helping the handicapped/disabled people use a computer without having to use their disabled arms or the elderly being too slow and old to move anything so using their brain to move a mouse on the computer to do things is relevant.

2) Amplifying it just makes the signal stronger. Therefore the disabled do not need to be too close to the computer or have their wireless commands to the computer fade out as it travels along the way.

Besides anyway, i would like it if you could teach me how does a radio tuner work and whether it would be the same if i applied a Tank circuit to it? Because i remember someone telling me before that a radio tuner CAN tune between a start frequency and an end frequency to pick up FM or AM radio.

Thanks Bob

 

[BobK]

So you really are not talking about 500Mz?

Bob

 

[dietermoreno]

Not so. Here are the reasons why:

1) If you must know, anything from 1 - 20 hz is part of neuro-science since it has something to do with our brains. Scientists have been playing with the idea of being able to fuse technology with our brains like for reasons such as helping the handicapped/disabled people use a computer without having to use their disabled arms or the elderly being too slow and old to move anything so using their brain to move a mouse on the computer to do things is relevant.

2) Amplifying it just makes the signal stronger. Therefore the disabled do not need to be too close to the computer or have their wireless commands to the computer fade out as it travels along the way.

Besides anyway, i would like it if you could teach me how does a radio tuner work and whether it would be the same if i applied a Tank circuit to it? Because i remember someone telling me before that a radio tuner CAN tune between a start frequency and an end frequency to pick up FM or AM radio.

Thanks Bob

A radio tuner that receives medium wave AM and VHF FM doesn't tune to 20Hz.

An efficient antenna must be at least a quarter wavelength long.
The wavelength = 300 000 000/freq meters
Work out the antenna size for 0.57Hz
500mhz is very low. Do you mean 500MHz?

So I think the 300 000 000 meters/second is the speed of light.

Radio waves travel at the speed of light.

So then the equation is: wavelength = c / f , where wavelength is in meters, c is the speed of light 3.0x10^8 meters/second, and f is the frequency in hertz

So then the wavelength for 500KHZ would be (300 000 000 m/s )/ (500 000 (1/s)) = 600 m

So the wavelength for 500MHZ would be (300 000 000 m/s )/ (500 000 000 (1/s)) = 0.6 m = 60 cm

So then the wavelength for 5GHZ would (300 000 000 m/s )/ (5 000 000 000 (1/s)) = 0.06 m = 6 cm

So then the wavelength for 50 KHZ would (300 000 000 m/s )/ (50 000 (1/s)) = 6 000 m = 6 km

So then the wavelength for 5 KHZ would (300 000 000 m/s )/ (5 000 (1/s)) = 60 000 m = 60 km

So then the wavelength for 5 Hz would (300 000 000 m/s )/ (5 (1/s)) = 60 000 000 m =
60 000 km



So then the effective antenna length for 500 KHZ would be 150 meters long. Think antenna mast that has a blinking light on top so airplanes don't hit it. So the antenna mast helps receive signals for you so you don't have to have a 150 meter tall antenna in your backyard to receive 500 KHZ.

So then the effective antenna length for 500 MHZ would be 15 cm long. It can fit in your pocket, so cell phone uses UHF.

So then the effective antenna length for 5 GHZ would be 1.5 cm long. It can fit on a finger nail, so blue tooth, wireless game controllers, wireless printers, and WiFi use it.

So then the effective antenna length for 50 KHZ would be 1500 meters long = 1.5 km. Think antenna is as tall as Smokey Mountains in Northwest Georgia in USA. I think the U.S. Navy uses such low frequencies as ground penetrating and sea penetrating radio for communicating with submarines underwater and it runs antenna wire underground for several km in a rural area (in America we would call it a few miles, but since the moderators of this forum are from Australia, I have used km and using km also makes the math easier; dumb Americans that can't use metric so it makes the math much harder).

So then the effective antenna length for 5 Hz would be 15 000 km long. Think the antenna is the circumference of the Earth, read as its impossible only the Earth can resonate at that frequency.



So it is impossible to build a radio transmitter that transmits radio waves of 0.57 hertz. So having a long interval of time in between oscillations is the least of your problems when you would need to run an antenna wire around the circumference of the Earth.

 

[john monks]

Now that I know what you want to do I can wrap my mind around what you want to do. I and my cooworkers worked on electroencephalography machines years ago. We used connectors that connected with the scalp directly. The voltage from the scalp is typically in the order of a microvolt. This does not radiate very well through the air and what little that does is so far down in the noise level the signal is worthless.

Tuned tank circuits are typically used at much higher frequencies.
AM and FM radio are typically superheterodyne receivers. Some are direct conversion receivers where a computer takes a resultant beat frequency and turns that back into audio. This may be the direction you wish to go for two reasons. First the signal from the brain appears to be scrambled and would take a computer to get intelligence from it. Secondly the signal is of low frequencies, in terms of cycles per second, and does not readily lend itself to tuned circuits.

Bottom line I think you need to attach something directly to the persons head, amplify it, transmit the signal, and use a receiver attached to computer to interpret the signals.

Good luck.

 

[Electro132]

A radio tuner that receives medium wave AM and VHF FM doesn't tune to 20Hz.

So it is impossible to build a radio transmitter that transmits radio waves of 0.57 hertz. So having a long interval of time in between oscillations is the least of your problems when you would need to run an antenna wire around the circumference of the Earth.

Thanks for this. Ok so 0.57 hz might be abit far off. But i found out that it is achievable in an LC circuit through the use of 7 henries and 0.47 F cap. It would only be the antenna that needs to be shorter.

I'm thinking, could it be that the TYPE of antenna used (material used, type of metal used, etc..) be the cause for its restrictions? For example: normal steel used as an antenna could restrict its wavelength abilities and thus having 5 ghz frequency applied would mean it needs to be at least 50 meters tall or having a titanium steel antenna could cause it to be shorter (50cm ) with the same Frequency applied.

Also, with a radio Tuner - What happens if you invert the demodulator to a modulator and send through an amplifier so instead of receiving you are transmitting?

To Bob >>>> Sort of. Was thinking of building a FM first but didn't know the caps, resistors and number of turns used. Would you know?

 

[duke37]

Antennas need to be made from low resistance material, silver is the best, copper comes close and aluminium is the lightest. Look around and you will see aluminium antennas on houses fed with copper cable.
Magnetic materials are bad news, look up skin effect.

What is titanium steel?

I think you should start by making a crystal set and then an audio amplifier to make it louder to learn the fundamentals of circuitry.

 

[dietermoreno]

Also, with a radio Tuner - What happens if you invert the demodulator to a modulator and send through an amplifier so instead of receiving you are transmitting?

To Bob >>>> Sort of. Was thinking of building a FM first but didn't know the caps, resistors and number of turns used. Would you know?

You don't send an RF signal through an audio amplifier. An amplifier demodulates, at least in simple transcievers that don't have an RF gain stage, if my Wikipedia readings are correct. The Wikipedia article on regenerative radio receiver says that the audio amplifier also functions as the detector. Audio amplifers can not handle RF. Audio amplifiers demodulate RF and amplify what was demodulated.

No you are not thinking of building an FM radio. FM radio uses super heterodyne receiver, and you have not mentioned anything about super heterodyne receiver. I think you are thinking of ampliying the audio signal from a crystal receiver (I don't think you need the crystal anymore if you have amplification because transistors and tubes demodulate RF).

 

[Electro132]

Antennas need to be made from low resistance material, silver is the best, copper comes close and aluminium is the lightest. Look around and you will see aluminium antennas on houses fed with copper cable.
Magnetic materials are bad news, look up skin effect.

What is titanium steel?

I think you should start by making a crystal set and then an audio amplifier to make it louder to learn the fundamentals of circuitry.

Your right. I figured a tuning capacitor would be best. I know a 6 - 160 pf tuning capacitor will place me around the FM band 88 - 108 Mhz with an extra 70 khz giving me 88.07 Mhz - 108.07 Mhz. But i'm wondering, what if i changed that tuning capacitor to something less or more for the experiment?

 

[Electro132]

You don't send an RF signal through an audio amplifier. An amplifier demodulates, at least in simple transcievers that don't have an RF gain stage, if my Wikipedia readings are correct. The Wikipedia article on regenerative radio receiver says that the audio amplifier also functions as the detector. Audio amplifers can not handle RF. Audio amplifiers demodulate RF and amplify what was demodulated.

No you are not thinking of building an FM radio. FM radio uses super heterodyne receiver, and you have not mentioned anything about super heterodyne receiver. I think you are thinking of ampliying the audio signal from a crystal receiver (I don't think you need the crystal anymore if you have amplification because transistors and tubes demodulate RF).

Ok so this is what i know:

When using the FM band it turns into sound on the circuit, this sound then gets amplified with a log pot and then further gets amplified some more with a darlington pair. The sound itself can be attuned depending on the frequency chosen with the tuning capacitor and thus changes the sine wave form to be bigger in size or smaller. E.G. from vvvvvvv to VVVVVVVVVVVVVVV.

Could this be achievable then?

 

[davenn]

Ok so this is what i know:

When using the FM band it turns into sound on the circuit,

The Rf section of the receiver is tuned to the frequency of the radio station, in that way its no different to an AM receiver
Its the detection method that is different for a FM or an AM signal

this sound then gets amplified with a log pot

What's this obsession you have with log pots ??

Log pots dont amplify anything !!, a pot, log or linear is a passive device and as such will actually introduce loss into the circuit depending on its setting
There is NO GAIN

and then further gets amplified some more with a darlington pair.

Well it may or may not be a darlington pair .... generally that would be very rare in commercial audio amplifiers ...
normally, depending on the power output required it may be a single driver transistor driving a single power transistor, or several drivers driving a pair of power transistors in a push-pull configuration.
Or it may be an IC amplifier module, they are the most common in modern day electronics... low power - eg the LM386

The sound itself can be attuned depending on the frequency chosen with the tuning capacitor and thus changes the sine wave form to be bigger in size or smaller. E.G. from vvvvvvv to VVVVVVVVVVVVVVV.
Could this be achievable then?

that statement just makes no sense at all, see my first response

here is a block diag of a basic receiver....

you really, really need to do some reading up on how receivers work
The ARRL handbook would be a very good place to start
You need to do this to get rid of all the misunderstandings you have ... then you will be able to ask questions in a way that are understandable and get answers that you will have a chance of understanding

Dave

 

[davenn]

here's a block diag of a super het receiver like dietermoreno mentioned....

it could be for FM or AM reception, the determination of that is all on the type of detector stage


Dave

 

[Electro132]

here's a block diag of a super het receiver like dietermoreno mentioned....

it could be for FM or AM reception, the determination of that is all on the type of detector stage

Dave

I see. I did some reading and understand that a Demodulator is nothing more than a diode.
And since a diode can only go one way then i was wondering what if i inverted it on the receiver what will it become then and will it still work?

 

[BobK]

I don't get it.

Back in post 7, I asked what you were trying to do. Here was your reply:

Ok basically here's what i want to build. I am looking to have an inverter connected to 3V power source which is connected somehow to 3 different oscillators (audio 16hz - 20khz, RF 100 khz - 100 ghz & LFO under 20hz) in resistors and capacitors (or if there are much more better and simple components) using a switch which are then amplified and controlled by a VCO and projected out using one of the waveforms (not sure if it's an antenna or emitter used for best method).

What does an FM receiver have to do with this? Or have you just changed your mind about what you want to build?

Bob

 

[Electro132]

I don't get it.

Back in post 7, I asked what you were trying to do. Here was your reply:

What does an FM receiver have to do with this? Or have you just changed your mind about what you want to build?

Bob

No, no it is still the same thing. I was just trying to break it down for you so you can understand my level of thinking. Basically what it is, is that the tuning dial has caps that work around from 0 - 20 hz or close to. i figured a radio is best since it can tune to many freqs within a given range.

But if the range 0 - 20 hz don't work then i'd go for something closer but between the range of 0 - 3000 Mhz. Anywhere between that range would be good for the experiment.