[Moved from Analog Design]: Flat antenna design

cybertron · Feb 3, 2015

Found this antenna on yahoo sometime ago can't find the site again.

I need to know how to make this antenna.

I need to make a 400 micro Henry antenna like the one attached.

Using 26g stranded wire or 20g magnetic wire.Which one would be better.

How many turns with it take to get with either type of wire at 400uH.

Each antenna can not be more the 1.8'' wide.

Can someone help me to calculate. And who know's about these types of flat pancake antenna.

Also? Do the two end wires get connected as one.Or do they need to be connected in a circuit separately in circuit.I don't know how to connect it in circuit.

cybertron · Feb 3, 2015

Can anyone Help who knows about there antenna's. T hey moved it here the thread. Don't why. I got a reply from a poster.But its gone. When it was moved Here.

Help?

volker@muehlhaus · Feb 4, 2015

This "antenna" is simply an inductor. Low frequency RFID etc use magnetic coupling.

Inductor calculation is described here:
http://www.pulsedpower.eu/toolbox/toolbox_inductances.html#inductances

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cybertron said:
Do the two end wires get connected as one.Or do they need to be connected in a circuit separately in circuit.

You want to drive current through the coil. It is typically used with capacitors to form some resonance at the operating frequency.

chuckey · Feb 4, 2015

It looks like a metal detector search coil. For these sort of coils you should use "Litz" wire. https://en.wikipedia.org/wiki/Litz_wire
Frank

cybertron · Feb 13, 2015

1.In post #1 I need to make this antenna.I still don't know how many turns it take to make a 400uH
pancake flat coil. How long would the wire be for the number of turns I would need,

2. How do I get a variable frequency of 1KHz to 12KHz with the antenna coil in Post#1.What capacitor
value would I need to get this variable FQ. And do i need a resistor for damping.

3. This coil antenna will need to be use for sending and receiving on the same antenna.

I need to use less math.And how to do this. Or at lease a very simple explanation.
Example? How to calculate this. Any help?

volker@muehlhaus · Feb 13, 2015

cybertron said:
1.In post #1 I need to make this antenna.I still don't know how many turns it take to make a 400uH
pancake flat coil. How long would the wire be for the number of turns I would need,

See the link in my post #3 and look for "single layer short solenoid" on that calculator page.

FvM · Feb 13, 2015

From the coil types offered by the calculation tool, spiral (flat coil) fits the intended design better than the short solenoid, I believe.

From an RF engineering viewpoint, an inductive coupler wouldn't be considered as antenna, it can be analyzed as a pure AC magnetic device. Respectively it has neglibible radiation resistance, only inductance, loss resistance and possibly windings capacitance.

For 12 kHz maximum operation frequency, skin depth is large enough to make the coil with solid magnet wire up to AWG 18 (1.0 mm).

Some questions in your latest post can be only answered if we know the intended transmission bandwidth respectively acceptable resonance Q.

cybertron · Feb 14, 2015

volker@muehlhaus said:
See the link in my post #3 and look for "single layer short solenoid" on that calculator page.

I don't get the answer for a flat coil of 400uH with this calculation tool.
Maybe the spiral flat coil might be a better choice.I don't know?
There's no calculation tool to enter specs for a spiral flat coil.

This is the calculation I get with the Single layer short Solenoid.
R=45
l=0 flat
N=30
L= infinity uH

These are the specs I used. As you can see. It doesn't calculate to 400uH

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FvM said:
From the coil types offered by the calculation tool, spiral (flat coil) fits the intended design better than the short solenoid, I believe.

From an RF engineering viewpoint, an inductive coupler wouldn't be considered as antenna, it can be analyzed as a pure AC magnetic device. Respectively it has neglibible radiation resistance, only inductance, loss resistance and possibly windings capacitance.

For 12 kHz maximum operation frequency, skin depth is large enough to make the coil with solid magnet wire up to AWG 18 (1.0 mm).

Some questions in your latest post can be only answered if we know the intended transmission bandwidth respectively acceptable resonance Q.

For 12 kHz maximum operation frequency, skin depth is large enough to make the coil with solid magnet wire up to AWG 18 (1.0 mm).

OK? What do you mean by skin depth is large enough to make the coil.

Also the frequency could be at 50Khz max. would the same 18 AWG WORK for 50K.

I was thinking using just 26 AWG magnetic wire or strandard wire. would that work.

Some questions in your latest post can be only answered if we know the intended transmission bandwidth respectively acceptable resonance

1K to 12Khz and 12K to 50kHz for transmitting and for receiving. There will be a switch like a spdt on-on or dpdt on-on-on.To switch back to selected frequencies on same coil. If i didn't understand your latest question please explain.

FvM · Feb 14, 2015

Obviously the short solenoid tool doesn't work for l=0, that's "less" than short.

You are right, there's no tool for the spiral coil, but a formula. I get e.g. N=85 for R=2.4 cm, w=2cm.

I'm unable to read a bandwidth specification from your description.

cybertron · Feb 15, 2015

You are right, there's no tool for the spiral coil, but a formula. I get e.g. N=85 for R=2.4 cm, w=2cm.

I don't know how that formula works. So I don't know how to calculate for the flat coil.

How did you get N=85 R=2.4cm and W=2cm. How did you arrive at these values with the formula.
I may not understand it.

I'm unable to read a bandwidth specification from your description

Digital:min. pulse width > 0.01 msec. Analog: all significant frequency components < 1K 12k 50 KHz
Bandwidth is not critical for transmitting and receiving. 2400 9600. If I'm understanding you.Correctly?

cybertron · Feb 17, 2015

You are right, there's no tool for the spiral coil, but a formula. I get e.g. N=85 for R=2.4 cm, w=2cm.

I don't know how that formula works. So I don't know how to calculate for the flat coil.

How did you get N=85 R=2.4cm and W=2cm. How did you arrive at these values with the formula.
I may not understand it.:???:

I'm unable to read a bandwidth specification from your description

Digital:min. pulse width > 0.01 msec. Analog: all significant frequency components < 1K 12k 50 KHz
Bandwidth is not critical for transmitting and receiving. 2400 9600. If I'm understanding you.Correctly?

I still also need help on the questions i posted in post #5

Aussie Susan · Feb 17, 2015

I can see where you say (repeatedly) that you need to make this antenna, but I cannot see what you intend to do with it.
It seems to me that this is a good example of the "XY Problem" (https://xyproblem.info/).
There may well be better solutions to your real problem if only we knew what that was.
Susan

FvM · Feb 17, 2015

How did you get N=85 R=2.4cm and W=2cm. How did you arrive at these values with the formula.

I estimated R=2.4 cm and W=2cm from your drawing and get N=85 for L=400 µH using Wheelers formula. The meaning of R and W is given in the paper, what's unclear with it?

You can also use the "imperial" version from this link **broken link removed**

Flat "pancake" coil
L (uH) = r^2 * n^2 / (8 * r + 11 * w)

where

r = radius to center of windings in inches
w = width of windings (in inches)
n = number of turns

Length of wire can be calculated from coil dimensions and number of turns using secondary schools math. (N*mean diameter*pi)

The answer to the other questions is identical with designing the transceiver. Surely no resonant circuit covers a frequency range of 1:10 or more.

cybertron · Feb 28, 2015

FvM

The answer to the other questions is identical with designing the transceiver. Surely no resonant circuit covers a frequency range of 1:10 or more.

What did you mean by this. That no resonant circuit covers a frequency range of 1:10 or more.

frequency range of 1:10 or more. Explain this please.

FvM · Feb 28, 2015

Making a resonant circuit with the coil is your idea, not mine. But changing the LC resonance frequency over a range of 1:12 with fixed L means a C variation by a factor of 144. For this reason practical tuner with wide frequency range, e.g. in SW transmitters involve switching L and C.

Referring to Aussie Susan, I think it's time to explain problem X and search a solution for it.

cybertron · Mar 1, 2015

FvM said:
Making a resonant circuit with the coil is your idea, not mine. But changing the LC resonance frequency over a range of 1:12 with fixed L means a C variation by a factor of 144. For this reason practical tuner with wide frequency range, e.g. in SW transmitters involve switching L and C.

I can't change (L) in the LC resonance FQ of the Coil, that needs to be Fixed. Only the (C) I would be-able to change. for 1:12 range. But you stated that is not possible.

OK explaining X.
I want to make a magnetic field recorder. That could pick-up electromagnetic radiation emitting from electronic devices and there control signals. and play it back on an oscilloscope. Think of it as an (audio recorder) But? Record's electromagnetic noise emission. Very low Frequencies and Low Frequency signals. And the recorder can be a simple chipcorder like they use in greeting cards.

So the recorder would need to record for a maximum of up to 5-8 mins then plays back the signals..

The LC resonance frequency circuit is the big problem to interface with the recorder. it will need a amp to pick up
the low signals and maybe a low pass filter for DC filtering
before its send to the recorder. The same pickup coil is use for receiving and play back the signal. So there's an output and input that controls receiving/transmitting.

Using the flat pancake coil as the pick-up antenna.

Understand it now. Or not.

BradtheRad · Mar 1, 2015

cybertron said:
Very low Frequencies and Low Frequency signals.

I've heard of this. The signals are unusual. Atmospheric phenomena, 'whistlers', etc.

With the very long wavelength, the antenna needs to be as large as possible. The project I read about specified that several loops of wire should be wrapped all around a room, and attached to its walls.

These are not everyday rf frequencies. A small pancake antenna will not do the job.

FvM · Mar 1, 2015

I don't see why the receiver circuit must be necessarily tuned. Instead of switching a resonance frequency, the circuit could be designed nonresonant to cover the 1 -12 kHz range without switching.

You are also talking about "playback", but it's not clear what it means related to the coil.

cybertron · Mar 2, 2015

BradtheRad said:
I've heard of this. The signals are unusual. Atmospheric phenomena, 'whistlers', etc.

With the very long wavelength, the antenna needs to be as large as possible. The project I read about specified that several loops of wire should be wrapped all around a room, and attached to its walls.

These are not everyday rf frequencies. A small pancake antenna will not do the job.

Thanks for your input.But? What you are talking about isn't any thing you stated is what I'm trying to do.Every body has a comment.But just don't understand what I want or need. In this thread.

I just don't know how to explain it where a non electronic's engineer who could understand it.
And by the way. A small pancake coil would work.

And I'm not an engineer.But? I do know what I need.

I just need the right electronic's engineer who does understand me And what I need. On this site.

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FvM said:
I don't see why the receiver circuit must be necessarily tuned. Instead of switching a resonance frequency, the circuit could be designed nonresonant to cover the 1 -12 kHz range without switching.

You are also talking about "playback", but it's not clear what it means related to the coil.

I would like to tuned in on the frequencies that I mentioned post #10 and post #11 for more actuate monitoring of those signals. CAN IT be both resonance for those frequencies for actuate detection and nonresonant for to cover 1K-50K FQ range. it could be switched back and fourth. Assuming.

The playback on the recorder circuit. You have record when you are receiving.
then you switch to Play. So the same coil is used for receiving and transmitting ''playback''. Got it.

BradtheRad · Mar 2, 2015

I might have spoken too soon. There are 'whistler' (VLF wideband) receivers that have a short antenna. Perhaps it makes a difference which you want to detect: photons, or magnetic fields.

It appears you can get by with a short wire antenna. It does not need to be resonant. See projects at links:

**broken link removed**

http://www.stormwise.com/project5.htm

http://www.techlib.com/electronics/VLFwhistle.htm

[Moved from Analog Design]: Flat antenna design

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