best antenna

[lutorm]

It is Voltage wave which is reflected: VSWR "Voltage Standing Wave Ratio", not "Power Standing Wave Ratio".
What about DC, where there is no wave, no reflected wave, no standing wave, and still full power does not flow from source to load until impedance matching is done i.e. source resistance is equal to load resistance (in DC circuits impedance = resistance)

Because the voltage wave drives a current in the cable, and P=U*I, there is a power wave going along with it. If there wasn't, how would a transmitter work? The transmitter outputs some power as an RF wave, and this power goes to the antenna (hopefully... and is radiated away.

The DC case is fundamentally different because, as you say, there is no wave. The impedance of the "feedline" doesn't matter at all, either, ideally you'd have a 0ohm wire to take your DC power from source to load. And no antenna will radiate any power at DC, either. None of this is really relevant for a discussion about RF. Electrodynamics are very different from Electrostatics.

[abcd567]

From reaction of forum members, I realize that the term "Mismatch Loss" is misguiding to most. It gives impression of loss of power, like power wasted in a resistor in the form of heat. What it actually implies is "restriction in flow of power caused by mismatch", like water flow in pipe is restricted by turning the valve/tap half way.

Another confusion is about an item expressed in decibels (dB). Generally dB is taken as synonymous to power level.
Actually dB is a way to express a ratio, any ratio, not just power.
A ratio of two quantities can be expressed in various ways.
For example if age of A is 30 years and B is 25 years, the ratio of their ages is expressed as 30:25, or 6:5, or 30/25, or 6/5, or 1.2, or 120%. These can be called "plain ratios".
There is another way to express the ratio, the Logarithmic ratio, which is equal to 10 times the log of the plain ratio. The unit is called deciBell or dB. Hence in the above example, the Logarithmic ratio of ages of A & B is 10 x log (30/25) = 0.7918 dB. We can then say "A is 0.7918 dB older than B"

[SpaxmoidJAm]

Right this aerial.
WP_20140422_001a.jpg
performed like this
dipoel2.jpg
Easily upto 50nm but struggling to get to 100nm.

compared to
wire1.jpgWP_20140404_001a.jpg
Easily up to 50nm with a maximum up to 150nm

it safe to ignore the large range spike on the first as they must be decode errors.

I'm giving the j-pole another go, as i misread the ratio's so it wasn't a fair test. Lets just say i needed to trim it considerably.

[abcd567]

Because the voltage wave drives a current in the cable, and P=U*I, there is a power wave going along with it. If there wasn't, how would a transmitter work? The transmitter outputs some power as an RF wave, and this power goes to the antenna (hopefully... and is radiated away.

The DC case is fundamentally different because, as you say, there is no wave. The impedance of the "feedline" doesn't matter at all, either, ideally you'd have a 0ohm wire to take your DC power from source to load. And no antenna will radiate any power at DC, either. None of this is really relevant for a discussion about RF. Electrodynamics are very different from Electrostatics.

CASE (1): I have a credit card with $1000 limit. I spend $450 at a store. My credit card company pays the store $450 and I pay the credit card company $450. Accounts are balanced.

CASE (2): I have a credit card with $1000 limit. I pay the credit card company $1000. My credit card company pays the store $1000. I spend $450 at a store. The store keeps $450 out of $1000 & returns balance $550 to credit card company. The credit company returns me $550. Accounts are balaced.

In reality case (1) takes place. Case (2) is a hypothetical case, but gives perfect account balance, and at best is an accounting technique.

"RF Power Reflection" is similar to credit card case (2). It is hypothetical and does not occur in reality. It is a calculation technique and gives perfect results.

This does not happen in reality:
"A 1000 Watt transmitter sends 1000 watts to antenna which absorbs 450 watts, and reflects 550 wats back to transmitter."

This is what happens in reality:
"A 1000 Watt transmitter sends to antenna only the power which can be absorbed by antenna (450 watts in this example). The antenna absorbs all 450 watts, and reflects nothing back to transmitter."

[trigger]

[ATTACH=CONFIG]3941[/ATTACH]

8 segment coco.JPG
Interesting to note that the shape of your range plot is similar to mine. Not much North of Watford but way down into Brittany. I thought it was my location but it must be the flight paths.

[F-EGLF1]

[ATTACH=CONFIG]3943[/ATTACH]
Interesting to note that the shape of your range plot is similar to mine. Not much North of Watford but way down into Brittany. I thought it was my location but it must be the flight paths.

Just for comparison this is what I am getting with the official FR24 kit, taken over about 2 hours. (I cannot plot for longer as ADSBscope bombs every few minutes, I think the framerate is too high, it reaches 145,000 or more and I have to disconnect and re-connect the raw data feed)
image.jpg

(If anyone knows how to get ADSBscope running for longer I would love to know)

[lutorm]

This is what happens in reality:
"A 1000 Watt transmitter sends to antenna only the power which can be absorbed by antenna (450 watts in this example). The antenna absorbs all 450 watts, and reflects nothing back to transmitter."

Please read the articles I linked, specifically the first, by ARRL, "Understanding SWR by example".

Table 1 lists how much voltage and power is reflected for various SWR values.

and

The SWR for this setup is calculated as 100/50, or 2:1. Now the energy wave hits the antenna and part of it is radiated by the antenna, but part of it is reflected back down the line toward the transmitter. That is, the antenna is not matched to the line, so there is a reflection.

I don't know how much clearer it gets. RF circuits carry traveling waves, they do not work like a DC circuit.

[abcd567]

Please read the articles I linked, specifically the first, by ARRL, "Understanding SWR by example".


and


I don't know how much clearer it gets. RF circuits carry traveling waves, they do not work like a DC circuit.

Thanks for the links. I will read these. I am always open to listen to views of other side. It is possible that what I believe is not right. Let me read further on the subject to discover the truth.

[abcd567]

Please read the articles I linked......

Here is one which may be of interest to you:
"Forward & Reflected Powers: What do they Mean?"

http://www.advanced-energy.com/upload/File/White_Papers/SL-WHITE7-270-01.pdf

[abcd567]

@lutorm:
My present understanding is that reflected power, reflected & standing waves are mathematical concepts, not a physical entity. These concepts provide very powerful tools for RF calculations and consequently are in widespread & prolonged used. Their widespread and prolonged use has caused people to believe these are real physical entities, like kidz watching a cartoon series every evening start believing the characters are real.

[Birdie]

@lutorm:
My present understanding is that reflected power, reflected & standing waves are mathematical concepts, not a physical entity. These concepts provide very powerful tools for RF calculations and consequently are in widespread & prolonged used. Their widespread and prolonged use has caused people to believe these are real physical entities, like kidz watching a cartoon series every evening start believing the characters are real.

Forward & Reflected standing waves are important if you are using the antenna for transmitting.

The Reflected power indicates the degree of MIS-TUNING of the antenna at that Operating Frequency.

If the Reflected Power = Zero (0) = The Antenna is TUNED to the Operating Frequency. All the transmitted power from the Transmitter is transferred to the Antenna for radiation out.

No power is reflected BACK ( via the transmission line ) into the Transmitter.

For receiving Antenna, Forward & Reflected SWR is not important BUT an indication of the degree of Antenna TUNED to the Operating Frequency.

If the Antenna is tuned to the Operating Frequency, its reception is better ( theory of resonant frequency ).

http://en.wikipedia.org/wiki/Resonance

[abcd567]

Forward & Reflected standing waves are important if you are using the antenna for transmitting.

The Reflected power indicates the degree of MIS-TUNING of the antenna at that Operating Frequency.

If the Reflected Power = Zero (0) = The Antenna is TUNED to the Operating Frequency. All the transmitted power from the Transmitter is transferred to the Antenna for radiation out.

No power is reflected BACK ( via the transmission line ) into the Transmitter.

For receiving Antenna, Forward & Reflected SWR is not important BUT an indication of the degree of Antenna TUNED to the Operating Frequency.

If the Antenna is tuned to the Operating Frequency, its reception is better ( theory of resonant frequency ).

http://en.wikipedia.org/wiki/Resonance

I agree what you have said about importance of reflected wave. My dispute is about their real nature:are these physical entities or mathematical concepts? I do not dispute their importance & usefulness for calculating & improving the performance. What I say is that these are not real physical entities, only mathematical concepts & tools.

[Birdie]

You are partially correct. They are both physical & mathematical.

It tells the Physical ( receiving or radiating element ) size of the antenna in relation to its operating frequency.

Try to keep the Reflected SWR to the minimum. Simple rule to follow:

Low Reflected = Antenna Tuned to Operating Frequency

High Reflected = Antenna NOT tuned to Operating Frequency.


If you have time, try to decode what the " Smith Chart " on Antenna is showing. Hahahaha - getting into more theories. LOL

http://en.wikipedia.org/wiki/Smith_chart

If you have spare USD 26 in your pocket, purchase this book and read. It explained all. LOL

http://www.arrl.org/shop/Understanding-Your-Antenna-Analyzer

[abcd567]

You are partially correct. They are both physical & mathematical.

It tells the Physical ( receiving or radiating element ) size of the antenna in relation to its operating frequency.

Try to keep the Reflected SWR to the minimum. Simple rule to follow:

Low Reflected = Antenna Tuned to Operating Frequency

High Reflected = Antenna NOT tuned to Operating Frequency.


If you have time, try to decode what the " Smith Chart " on Antenna is showing. Hahahaha - getting into more theories. LOL

http://en.wikipedia.org/wiki/Smith_chart

If you have spare USD 26 in your pocket, purchase this book and read. It explained all. LOL

http://www.arrl.org/shop/Understandi...tenna-Analyzer

Thanks for the links. As I have said in my earlier post, I am going to study further litrature to find out what i believe is right or wrong. I will come back with my findings after my study is completed.

Here is one which may be of interest to you:
"Forward & Reflected Powers: What do they Mean?"

http://www.advanced-energy.com/upload/File/White_Papers/SL-WHITE7-270-01.pdf

[trigger]

Just for comparison this is what I am getting with the official FR24 kit, taken over about 2 hours. (I cannot plot for longer as ADSBscope bombs every few minutes, I think the framerate is too high, it reaches 145,000 or more and I have to disconnect and re-connect the raw data feed)
[ATTACH=CONFIG]3944[/ATTACH]

(If anyone knows how to get ADSBscope running for longer I would love to know)

My framerate runs about 10 - 15,000 fpm with about 80 - 110 aircraft during the day. I have no idea why your adsbScope bombs but you may be right about the high framerate.

You appear to be getting perfect coverage which I suppose is to be expected with proper kit. Do you have a good view of the horizon in all directions?