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  • Originally posted by trigger View Post
    As promised
    [ATTACH=CONFIG]3932[/ATTACH][ATTACH=CONFIG]3933[/ATTACH]
    At last you succeeded in making a CoCo with 150NM range, comparable to your Franklin..Congratulations.
    Last edited by abcd567; 2014-04-22, 13:36.

    Comment


    • Originally posted by abcd567 View Post
      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.
      Patrik J. / KB1VGP / FR24 T-PHTO1

      Comment


      • 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"

        Comment


        • 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.
          Last edited by SpaxmoidJAm; 2014-04-22, 19:29.
          T-EGLF8

          Comment


          • Originally posted by lutorm View Post
            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."
            Last edited by abcd567; 2014-04-22, 21:05.

            Comment


            • Originally posted by SpaxmoidJAm View Post
              [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.
              T-EGUB1

              Comment


              • Originally posted by trigger View Post
                [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)
                Last edited by F-EGLF1; 2014-04-22, 21:56. Reason: Req for ADSBscope help
                FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

                Comment


                • Originally posted by abcd567 View Post
                  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.
                  Patrik J. / KB1VGP / FR24 T-PHTO1

                  Comment


                  • Originally posted by lutorm View Post
                    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.

                    Comment


                    • Originally posted by lutorm View Post
                      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/uploa...TE7-270-01.pdf

                      Comment


                      • @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.

                        Comment


                        • Originally posted by abcd567 View Post
                          @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
                          F-WSSS1 - Cats refused to Pee & Pooh on RadarBox - Running a FR24 Receiver & DVB-T Dongle 24/7 to piss off The Chief Thief.

                          Comment


                          • Originally posted by Birdie View Post
                            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.

                            Comment


                            • 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
                              Last edited by Birdie; 2014-04-23, 04:02.
                              F-WSSS1 - Cats refused to Pee & Pooh on RadarBox - Running a FR24 Receiver & DVB-T Dongle 24/7 to piss off The Chief Thief.

                              Comment


                              • Originally posted by Birdie View Post
                                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/uploa...TE7-270-01.pdf

                                Comment

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