I need to make some sense on this one...some people build 600 watt, 800 watt or even 1100 watt rf amplifier...but when i check many rf ic only operating around 3 volt to 5 volt which can deliver 6 ghz to 18 ghz of frequency

Now since the ic uses very low voltage why would people prefer to make high outpout rf amplifier...i am confuse....what the significant of high power output does to the signal does it make any better than those common 3 ~ 5 volt rf amp?

My confusion why would someone the difficult of perhaps 1100 watts when there is so much simple way

 

Short answer distance.I was a child of the citizen band era.

 

The power is needed for transmitting the signal through the air.
The more power, the further away the signal can be reliably received (neglecting the curvature of the earth).
High power is not needed for the RF circuits that do the signal processing.

 

There can be several reasons........but the main one is distance.

 

There are industrial processes th use high power Rf, typicall13.5 MHz. They are rare.

 

I need to make some sense on this one...some people build 600 watt, 800 watt or even 1100 watt rf amplifier...but when i check many rf ic only operating around 3 volt to 5 volt which can deliver 6 ghz to 18 ghz of frequency

Now since the ic uses very low voltage why would people prefer to make high outpout rf amplifier...i am confuse....what the significant of high power output does to the signal does it make any better than those common 3 ~ 5 volt rf amp?

My confusion why would someone the difficult of perhaps 1100 watts when there is so much simple way

Think of using a flashing light to transmit information. You could use a flashing LED and this would take less than 100mW. But if you want people miles away to see your flashing light, you might need a 1000W bulb or more. You'd still use the same low-power circuit to generate the flashing, the information, but add a power amplifier as the last stage.

 

It could be for power transfer or heating. Microwaves for heating water......other frequencies for other media.

In theory you could use rf to smelt ore. Make glass......melt or jiggle apart any solid with frequency.

 

I am an amateur radio operator. My standard transceiver has a power output of 100 watts and is powered by a DC supply at 13.8V @25 Amps. I also have a 500 Watt Linear Amplifier with a 70 VDC power supply derived from the 120 VAC mains. I use this amplifier under conditions where a weaker signal cannot be received 8,000-12,000 miles away. Receivers are getting so good that the old rule about: "if you can hear them you can work them" does not apply in some cases. My operations are mostly on the amateur bands from 40M thru 6M.

The amplifier was the last addition to my station. You can do much more with antennas at a much lower cost, than you can with an amplifier.

 

... As the relevant frequency increases, there is a tendency for the propagation to become more like visible light. The Ghz devices which you describe would only work at a distance comparable to a strong flashlight. That is one reason for the numerous cell phone towers. As the working frequency decreases, into the Mhz range and below, the propagation is more wave-like, which, when conditions are good, such as when there is a sunspot cycle peak, reflect off of the ionosphere, traveling thousands of miles. As the frequency decreases even more, the electric field mode propagation becomes less effective, and AM propagation is utilized, with high power being necessary to generate a modulated magnetic field at KHz frequencies. The AM magnetic field propagation does not compare with the electric field distance.

 

I am an amateur radio operator. My standard transceiver has a power output of 100 watts and is powered by a DC supply at 13.8V @25 Amps. I also have a 500 Watt Linear Amplifier with a 70 VDC power supply derived from the 120 VAC mains. I use this amplifier under conditions where a weaker signal cannot be received 8,000-12,000 miles away. Receivers are getting so good that the old rule about: "if you can hear them you can work them" does not apply in some cases. My operations are mostly on the amateur bands from 40M thru 6M.

The amplifier was the last addition to my station. You can do much more with antennas at a much lower cost, than you can with an amplifier.

Thanks for the explanation...and the rest now i know "high power longer distance".

But since you said that antenna will do much cheaper than amplifier...is it possible to use antenna as complementary tools to help the amplifier to achieve greater signal? or they work independent of one another

 

I am an amateur radio operator. My standard transceiver has a power output of 100 watts and is powered by a DC supply at 13.8V @25 Amps. I also have a 500 Watt Linear Amplifier with a 70 VDC power supply derived from the 120 VAC mains. I use this amplifier under conditions where a weaker signal cannot be received 8,000-12,000 miles away. Receivers are getting so good that the old rule about: "if you can hear them you can work them" does not apply in some cases. My operations are mostly on the amateur bands from 40M thru 6M.

Thanks for the explanation...and the rest now i know "high power longer distance".

But since you said that antenna will do much cheaper than amplifier...is it possible to use antenna as complementary tools to help the amplifier to achieve greater signal? or they work independent of one another

They are independent of each other. As an example a good directional yagi antenna might provide 17 dBi of gain for let's say $300. The 500 watt linear amplifier provides 7 dB of gain over the 100 watt barefoot transceiver for $3,500. It does not take a genius to figure out which thing to do first. The combination gives 24 dB for $3800 and you can clearly see that the antenna gives way more bang for the buck.

 

They are independent of each other. As an example a good directional yagi antenna might provide 17 dBi of gain for let's say $300. The 500 watt linear amplifier provides 7 dB of gain over the 100 watt barefoot transceiver for $3,500. It does not take a genius to figure out which thing to do first. The combination gives 24 dB for $3800 and you can clearly see that the antenna gives way more bang for the buck.

This answer give me more understanding...thanks all..

 

They are independent of each other. As an example a good directional yagi antenna might provide 17 dBi of gain for let's say $300. The 500 watt linear amplifier provides 7 dB of gain over the 100 watt barefoot transceiver for $3,500. It does not take a genius to figure out which thing to do first. The combination gives 24 dB for $3800 and you can clearly see that the antenna gives way more bang for the buck.

To add to Papabravo's point, if you want omnidirection operation you are stuck with the amplifier because you can only get antenna gain in one direction at the expense of gain in another. For many operations this is not only acceptable, but desirable. But there are situations in which you want to be as omnidirectional as possible.

 

To add to Papabravo's point, if you want omnidirection operation you are stuck with the amplifier because you can only get antenna gain in one direction at the expense of gain in another. For many operations this is not only acceptable, but desirable. But there are situations in which you want to be as omnidirectional as possible.

Now that leads to another curiosity --- how the antenna actually absorb and emit signal at the same time? How does it look in illustration..does it happen simultaneously or alternately

 

I need to make some sense on this one...some people build 600 watt, 800 watt or even 1100 watt rf amplifier...but when i check many rf ic only operating around 3 volt to 5 volt which can deliver 6 ghz to 18 ghz of frequency

Now since the ic uses very low voltage why would people prefer to make high outpout rf amplifier...i am confuse....what the significant of high power output does to the signal does it make any better than those common 3 ~ 5 volt rf amp?

My confusion why would someone the difficult of perhaps 1100 watts when there is so much simple way

Antennae are difficult thingies and depending on many variables like earth density/moisture/magnetism/hydro and height above the surface and more. Raise the power to overcome this damping is not the best way. (use the antennae as a amplifier using the surrounding as part of the resonance). The electro magnetic wave is also polarized ( horizontal or vertical) and will also effect the distance.
but here is an understandable essay about dipole antennae
http://www.waves.toronto.edu/prof/Balmain/pdffiles/impedshortdipole.pdf

Picbuster

 

Now that leads to another curiosity --- how the antenna actually absorb and emit signal at the same time? How does it look in illustration..does it happen simultaneously or alternately

An antenna is inherently a half duplex device. When the transmitter is off, the receiver picks up incredibly weak signals. When the transmitter is turned on, the receiver is disconnected from the antenna to avoid damage. Although there are still very tiny signals in the antenna they are swamped by the transmitter.

 

Short answer distance.I was a child of the citizen band era.

When I was in college, all of my friends (and their friends) kept asking me to build 1000W amplifiers for their CB rigs.

I always declined because I had a 2nd class FCC license and I could lose it.

 

To add to Papabravo's point, if you want omnidirection operation you are stuck with the amplifier because you can only get antenna gain in one direction at the expense of gain in another. For many operations this is not only acceptable, but desirable. But there are situations in which you want to be as omnidirectional as possible.

The omnidirectional case usually occurs in VHF/UHF line of sight operations. Emergency and disaster related communications are a typical example. In this instance you want to establish a "party line" so everyone in an area can "hear" both sides of the conversation. The antennas in this case are verticals which have an omnidirectional pattern. Some verticals are better than others and exhibit "gain" with respect to "isotropic" radiator.

The other case is that you know the general direction of the station(s) you are trying to contact, so you use a directional, horizontally polarized antenna, mounted on a rotor.

 

"Now that leads to another curiosity --- how the antenna actually absorb and emit signal at the same time? How does it look in illustration..does it happen simultaneously or alternately"

We can do it in two ways........and maybe more. One way is to use different frequencies. The other way is to use different times.

time-division duplexing and frequency-division duplexing

Modern science can only explain these things mathematically. They haven't a clue to the physical movement of charge on an antenna.

I have asked that question for over 40 years.......and have never got a clear explanation.

Current......and the current field around a conductor and the wave emitted from a conductor........
are all described and explained mathematically.........not mechanically.

But the truth is that when using AC circuits.....the transfer of power or information.........the transfer action is thru torque.

 

I wonder if there is any tools that can simulate the propagation of signal to see the patterns how the antenna emit and receive rf signal...