I have a 4G modem whether it is using antenna or no antenna it seems there is no significant difference in the signal reception...that leads to my question is the antenna really necessary in most RF electronic device? especially like mobile phone?

Another reason for this question is that when i take a 4G antenna and put it outside the house and measure the frequency reception...there is nothing...what more to say if it is inside a room where i put my 4G modem. So why does RF electronic devices really need an antenna when there is nothing coming from it?

 

Yes, an antenna is necessary in the same way you need legs to walk upright. You might not need much of a antenna or need to use a external antenna if the RF communications link is short and the signal to noise ratio is high.

 

antenna
You may not want play with antenna some transmitters will burn out without one.

 

antenna
You may not want play with antenna some transmitters will burn out without one.

My apology not putting the detail actually i am talking about receiver not transmitter

 

My apology not putting the detail actually i am talking about receiver not transmitter

What is and is not an antenna has a sensitive dependence on frequency, signal strength at the receiver, distance from the transmitter, and propagation pathways. I suspect that for short range VHF and UHF signals the the traces on the circuit board can function as a rudimentary antenna. Specific circumstances are everything in this context and it is dangerous to generalize. Test, measurement, and analysis are the only way to avoid the road to perdition.

 

I have a 4G modem whether it is using antenna or no antenna it seems there is no significant difference in the signal reception...that leads to my question is the antenna really necessary in most RF electronic device? especially like mobile phone?

Another reason for this question is that when i take a 4G antenna and put it outside the house and measure the frequency reception...there is nothing...what more to say if it is inside a room where i put my 4G modem. So why does RF electronic devices really need an antenna when there is nothing coming from it?

The main role of any receiving antenna is to covert electromagnetic fields propagating in space as a combination of E- and H-fields into an electric current (flow of electrons) and voltage (force moving electrons). As soon as the antenna is connected to an active or passive circuit this current and voltage is amplified and processed. Finally, you might measure the signal, hear it, or detect any other way.

An antenna connected to transmitter works transforming current and voltage generated by generator of signal into electromagnetic waves that are capable to carry energy through the space to the receiving antenna. See above.

Therefore, NO antenna means NO communication.

There is always some kind of small antenna inside any modem invisible from outside. That is why you can receive signal from it. The outside antenna is required if a modem and your mobile phone or any other device is relatively far away.

 

The main role of any receiving antenna is to covert electromagnetic fields propagating in space as a combination of E- and H-fields into an electric current (flow of electrons) and voltage (force moving electrons). As soon as the antenna is connected to an active or passive circuit this current and voltage is amplified and processed. Finally, you might measure the signal, hear it, or detect any other way.

An antenna connected to transmitter works transforming current and voltage generated by generator of signal into electromagnetic waves that are capable to carry energy through the space to the receiving antenna. See above.

Therefore, NO antenna means NO communication.

There is always some kind of small antenna inside any modem invisible from outside. That is why you can receive signal from it. The outside antenna is required if a modem and your mobile phone or any other device is relatively far away.

Simple to the point answer i liked. Thanks for the info...understood all the points

 

I have a 4G modem whether it is using antenna or no antenna it seems there is no significant difference in the signal reception...that leads to my question is the antenna really necessary in most RF electronic device? especially like mobile phone?

Another reason for this question is that when i take a 4G antenna and put it outside the house and measure the frequency reception...there is nothing...what more to say if it is inside a room where i put my 4G modem. So why does RF electronic devices really need an antenna when there is nothing coming from it?

You are welcome. Send more questions please. I'm an expert in antennas and all issues connected to EM waves and systems.

 

You are welcome. Send more questions please. I'm an expert in antennas and all issues connected to EM waves and systems.

Nice i like your attitude and your points are the best of all...i have another questions...

I saw some TV antennas as well as satellite require a balun so my questions are

1. What is the function of balun after antenna received the signal?
2. Does it apply to UHF frequencies like 2.6 Ghz?
3. How many turns is common balun have for each side (primary and secondary)?
4. How does it help to amplify greater reception of signal?
5. What is an active antenna?

 

Nice i like your attitude and your points are the best of all...i have another questions...

I saw some TV antennas as well as satellite require a balun so my questions are

1. What is the function of balun after antenna received the signal?
2. Does it apply to UHF frequencies like 2.6 Ghz?
3. How many turns is common balun have for each side (primary and secondary)?
4. How does it help to amplify greater reception of signal?
5. What is an active antenna?

1. What is the function of balun after antenna received the signal?


Balun is a simple device with a coaxial output (an unbalanced line like a battery in your car where one pole is grounded and has zero potential) and two wires balance input (similar to a battery where one pole is + and second one is -) connected to two identical conductive elements of the symmetrical dipole. If the coax cable is connected to dipole directly the part of received by dipole current flows down the outer side of the coax outer conductor and is completely lost through reradiation mainly. Indeed, that so-called antenna effect reduces the power of the received signal.

As soon as the outer side of the coax outer conductor becomes able to radiate, it might work as a receiving antenna too delivering the additional signal back to the coaxial line. Therefore, now two signals of different magnitude and phase propagate simultaneously in the same coax, interfere, and could actually cancel each other, and the signal is completely lost.

Additionally, balun often works like a transformer matching the antenna and coax impedance.

Check for more details http://www.antenna-theory.com/definitions/balun.php


2. Does it apply to UHF frequencies like 2.6 GHz? Sure.


3. How many turns is common balun have for each side (primary and secondary)? It depends on the impedance of antenna coax (50 or 75 Ohms).


4. How does it help to amplify greater reception of signal? See answer to the question 1.


5. What is an active antenna? That is an antenna integrated with the amplifier. Sometimes this amplifier includes a circuit processing or canceling multipath signals.

 

1. What is the function of balun after antenna received the signal?


Balun is a simple device with a coaxial output (an unbalanced line like a battery in your car where one pole is grounded and has zero potential) and two wires balance input (similar to a battery where one pole is + and second one is -) connected to two identical conductive elements of the symmetrical dipole. If the coax cable is connected to dipole directly the part of received by dipole current flows down the outer side of the coax outer conductor and is completely lost through reradiation mainly. Indeed, that so-called antenna effect reduces the power of the received signal.

As soon as the outer side of the coax outer conductor becomes able to radiate, it might work as a receiving antenna too delivering the additional signal back to the coaxial line. Therefore, now two signals of different magnitude and phase propagate simultaneously in the same coax, interfere, and could actually cancel each other, and the signal is completely lost.

Additionally, balun often works like a transformer matching the antenna and coax impedance.

Check for more details http://www.antenna-theory.com/definitions/balun.php


2. Does it apply to UHF frequencies like 2.6 GHz? Sure.


3. How many turns is common balun have for each side (primary and secondary)? It depends on the impedance of antenna coax (50 or 75 Ohms).


4. How does it help to amplify greater reception of signal? See answer to the question 1.


5. What is an active antenna? That is an antenna integrated with the amplifier. Sometimes this amplifier includes a circuit processing or canceling multipath signals.

Love all your answers -- never get bored of reading good facts and knowledge.

By the way in this balun picture which one connect to the antenna and which side going to the output (tv, satellite, modem etc)?