Post by: Hayseed on 28/10/2019 18:47:03
Two function generators. Three resonant dipole antennas. One scope. And an amp for scope, if needed.
Attach antennas to generators and scope. Separate generator antennas from scope antenna with appropriate distance. Try to eliminate near field effects. The frequency you select is a trade off, between antenna area and space needed(ROOM) and speed of measuring equipment needed(COST). One might need a ham friend at a distance.
Feed a sine(360 degrees) repetitively, into one dipole and measure on scope at distance. One should see a sine at scope from the antenna.
Now, with the other generator, feed a half sine(180 degrees) repetitively, and measure scope. The same polarities are constantly fed into antenna.
Will I see anything at scope? Will I see the same thing at scope?
Full function generators(30MHz) with 10 volt over 50 ohms can be had for about $70 now.
Working with GHz is easier in a lab, but the the generators and scope will cost you. But one might use a sdr dongle for detector. But generating a half sine in GHz is difficult.
What do you think this will show?
Edit: Most of these function generators are 2 channel now. So, only one generator is needed.
Post by: hamdani yusuf on 29/10/2019 08:21:00
You can simulate it using spreadsheet such as Excel file following the formula for HPF and LPF.
https://en.wikipedia.org/wiki/High-pass_filter#Algorithmic_implementation
Quote
y := α * (y[i-1] + x - x[i-1])https://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filter
Quote
y := y[i-1] + α * (x - y[i-1])here is step by step procedure to make the simulation:
Open the spreadsheet.
type following formulas into the corresponding cells.
B1 : =PI()/40
this cell determine the period
C1 : 0.5
this cell determine the value of α for HPF
D1 : 0.1
this cell determine the value of α for LPF
A2 : i
B2 : input
C2 : HPF
D2 : LPF
E2 : HLPF
F2 : LHPF
A3 to F3 : 0
A4 to A 243 : integer from 1 to 240
B4 : =ABS(SIN(A4*$B$1))
this is the formula to generate half sinewave signal
C4: =$C$1*(C3-B3+B4)
this is the formula to produce HPF of the input signal
D4: =D3+$D$1*(B4-D3)
this is the formula to produce LPF of the input signal
E4 : =E3+$D$1*(C4-E3)
this is the formula to show the result if the input signal is fed to HPF first, and then LPF
F4 : =$C$1*(F3-D3+D4)
this is the formula to show the result if the input signal is fed to LPF first, and then HPF
Copy the cells B4 to F4, then paste into cells B5 to B243
You'll find that the results in column E equal those in column F. This shows that those functions are commutative.
To get visual representation, just select the cells A2 to F243. From command menu select insert>scatter(X,Y) chart
You can see how the variables in cells B1 to D1 change the shape of the curves. They represents simplified linear combination of the antennas and electronic circuitries of your transmitter and receiver.
Post by: Hayseed on 29/10/2019 20:09:25
Post by: Bored chemist on 29/10/2019 21:00:07
Do you mean something like this?
half sine.JPG (17.71 kB . 370x212 - viewed 3301 times)Post by: Bored chemist on 29/10/2019 21:00:53
Your system is basically a band pass filter,Not really.
Post by: Hayseed on 29/10/2019 21:21:09
Post by: Bored chemist on 29/10/2019 21:40:58
A repetitive half sine would be like the output of a full wave rectifier. Sorry for the lack of clarity.So, do you mean just a single "hump" rather than the 2 I drew?
It hardly matters.
If the voltage at the top end of the antenna goes up and then down it must be because the voltage at the bottom end went up and then (compared to the voltage at the top) it went down. So it is still alternating polarity.
Exactly what you get at the receiving antenna is complicated.
What do you know about Fourier analysis?
Post by: Hayseed on 29/10/2019 22:45:42
Feed-line at receiver doesn't matter. A receiving antenna is always resonant. An antenna is a field to wave and wave to field transducer. One mode resonant and one mode not resonant.
We transmit half sines but receive full sines. And receiving a full sine makes people think a full sine was transmitted and moved thru space. I believe this to be wrong.
Also that RF is intermittent. It's discreet. In half sine lengths with half sine durations. The emission is instant, but the wave passing by or thru has that length duration.
This means.....that half the time and half of space occupancy is not used. This means that we could fill that time and space with the same amount of data.......without increasing the bandwidth.
Can you follow what I am trying to say?
Another way to verify(the original experiment), would be to send repetitive humps, and still get full sines at receiver. This would be easier, and perhaps cause the necessary curiosity to investigate further.
Edit: Think of it as sending out DC and receiving AC.
Post by: hamdani yusuf on 30/10/2019 02:58:28
I believe that you have mis-understood the experiment. This has nothing to do with filters. I am trying to show you a whole new way to look at radio.Have you tried the simulation I posted? You only need to copy-paste the formulas into corresponding cells.
The transmitter and receiver are not intended as filter per se, but they are effectively have some sort of filtering function. Below some low frequency threshold, your receiver has low response to the transmitter signal.
Above some high frequency threshold, your receiver also has low response to the transmitter signal.
Post by: Hayseed on 30/10/2019 03:28:52
The payoff......is the increase in information density. Imagine all rf channels carrying twice the data without an increase in bandwidth.
During the duration that is applied the the element......a field is grown and extends out to 1/2 wavelength from element. This field is growing and moving at c. After that 180 degrees duration.......that moving c field is cut......... when it is cut.......it changes from a rotational field......to a linear wave. It's just a change in direction at c speed. It takes an instant and science calls it emission. It's a snap, not a continuous event. That snap sends that 1/2 wavelength of electrical disturbance out into space. The snap happens every 1/2 wavelength, or 1 pi, or one half sine, or 180 degrees. However you wish to look at it.
Are you following anything at all of what I a saying?
Post by: Bored chemist on 30/10/2019 10:41:26
So, the antenna will act as a resonator for all the other frequencies.
You will get a mess.
Much of the transmitted power will be at frequencies that you don't want.
Post by: Hayseed on 30/10/2019 16:48:51
Post by: Bored chemist on 30/10/2019 16:55:31
The "hump" is 180 degrees of one frequency.No it is not.
What would you expect to get if I put a half wave rectified sine wave into a spectrum analyser?
Post by: Hayseed on 30/10/2019 18:33:00
If you believe the experiment has no merit, then don't do the experiment. The whole point of the experiment is too disprove simulations. A simulation will not agree with this experiment.
You may predict and argue all you want, but only the experimental results, matter.
The point of the experiment is to show you something new.
But you may only see it with experiment, for an experiment is the only thing that will convince you.
There are a thousand reasons not to do the experiment.(old knowledge) But there is only one reason to do the experiment.(new knowledge)
Post by: Colin2B on 31/10/2019 16:15:39
I have performed the experiment you suggest during a series of demonstrations of antenna response to different waveforms. The fullwave rectifier is useful as it demonstrates something some people fail to realise.
Your main misunderstanding is assuming that what goes into the antenna will be transmitted unchanged, but the antenna is a network of L, C and R and does not respond in the same way to different frequencies and in particular DC.
A steady state DC voltage applied to an antenna does not accelerate any charges and hence does not radiate any emr. If you look at the rectified waveform you will see that it has an average dc component (offset voltage) around which the waveform oscillates, so the antenna only sees +ve going humps and the -ve going almost triangular excursions. It is these humps and triangles which accelerate to electrons back and forth and produce the emr. Note that dc offset voltages are common in electronic circuits and transmission lines and have no effect on the ac component, so what we are describing here is standard cct practice.
The next thing to recognise is that your idea that an antenna is anti resonant is completely wrong. The whole point about antenna is that they are resonators, that’s why their length is in multiple of wavelengths. This resonance will also modify the waveforms partly because it will limit the number of harmonics that can be transmitted. If you look at the fullwave waveform it is wholly even harmonics but a dipole antenna resonates at odd harmonics - not a good match.
The main point here is that you will not be transmitting +ve going humps with nothing in the -ve side.
Overall, many of you responses to topics in the physics section are incorrect or misleading. Please read https://www.thenakedscientists.com/forum/index.php?topic=66954.0 and confine your speculations to New Theories.
Post by: Bored chemist on 31/10/2019 19:43:34
Hayseed,The "hump" is 180 degrees of one frequency.No it is not.
What would you expect to get if I put a half wave rectified sine wave into a spectrum analyser?
Feel free to actually answer the question.
You might, in researching that answer, gain some new knowledge.
Sometimes the experiment is not the thing that matters- not least, because you can look to see what answer the last experiment gave, and thus save the trouble of repeating it.
Post by: hamdani yusuf on 01/11/2019 03:29:11
The "hump" is 180 degrees of one frequency.Please read this
https://en.wikipedia.org/wiki/Fourier_series#Table_of_common_Fourier_series
(https://wikimedia.org/api/rest_v1/media/math/render/svg/e63f9c426b486ba298d872a96241b0662eeebf72)(https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/PlotRectifiedSineSignal.svg/250px-PlotRectifiedSineSignal.svg.png)(https://wikimedia.org/api/rest_v1/media/math/render/svg/5e06009fc45c46493649b92d252452b1350d01ed)
(https://wikimedia.org/api/rest_v1/media/math/render/svg/5c4f9766b13d913ed8f35f06c7d1facd81121ab4)
Post by: hamdani yusuf on 11/11/2019 10:49:42
Your system is basically a band pass filter, which is a combination of high pass filter and low pass filter.To save you time and effort, I uploaded the Excel file in my Google drive.
You can simulate it using spreadsheet such as Excel file following the formula for HPF and LPF.
https://en.wikipedia.org/wiki/High-pass_filter#Algorithmic_implementationQuotey := α * (y[i-1] + x - x[i-1])https://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filterQuotey := y[i-1] + α * (x - y[i-1])here is step by step procedure to make the simulation:
Open the spreadsheet.
type following formulas into the corresponding cells.
B1 : =PI()/40
this cell determine the period
C1 : 0.5
this cell determine the value of α for HPF
D1 : 0.1
this cell determine the value of α for LPF
A2 : i
B2 : input
C2 : HPF
D2 : LPF
E2 : HLPF
F2 : LHPF
A3 to F3 : 0
A4 to A 243 : integer from 1 to 240
B4 : =ABS(SIN(A4*$B$1))
this is the formula to generate half sinewave signal
C4: =$C$1*(C3-B3+B4)
this is the formula to produce HPF of the input signal
D4: =D3+$D$1*(B4-D3)
this is the formula to produce LPF of the input signal
E4 : =E3+$D$1*(C4-E3)
this is the formula to show the result if the input signal is fed to HPF first, and then LPF
F4 : =$C$1*(F3-D3+D4)
this is the formula to show the result if the input signal is fed to LPF first, and then HPF
Copy the cells B4 to F4, then paste into cells B5 to B243
You'll find that the results in column E equal those in column F. This shows that those functions are commutative.
To get visual representation, just select the cells A2 to F243. From command menu select insert>scatter(X,Y) chart
You can see how the variables in cells B1 to D1 change the shape of the curves. They represents simplified linear combination of the antennas and electronic circuitries of your transmitter and receiver.
https://drive.google.com/file/d/1G_1NfYTFZeM6hUchfAp17gxJnLtVdkRx/view
Post by: teragram on 02/12/2019 20:52:58
Post by: Bored chemist on 02/12/2019 22:04:56
Excuse me interrupting (as a non-expert) but is this topic related to Single Sideband Transmission? As invented by radio hams decades ago?Only tangentially.