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Re: [loopantennas] Two turn transmitting loop

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  • Bill
    Brian, SGC TUNERS has something like that in one of their online PDF documents. I think its in the STEALTH BOOK . I have it somewhere, if you cant find it.
    Message 1 of 28 , Apr 22, 2013
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      Brian,
      SGC TUNERS has something like that in one of their online PDF documents.
      I think its in the "STEALTH BOOK".
      I have it somewhere, if you cant find it.
      It is on a PVC frame, four turns, I think.
      With a SGC tuner they claim can tune up most hf bands.
      I guess you could cut it exactly for 40. And no tuner.
      I plan on building one for my attic, wishful thinking is 75 meters...:)
      Vertical mounted, delta shape about 10x10x10. Multiple turns. Possibly on a rotor. R&D stage.
      But then I can dream right;)
      Bill
      N2VIL

      burnsguitar <brian@...> wrote:

       

      Hello All,

      Has anyone had any experience with reducing a transmitting loop size by half by going to two turns? That seems to be a size that falls in between the usual definitions of a "small" narrow bandwidth loop, and the full wave, or "skywire" loop. I've not been able to find any info on the size, but it could make a rotatable loop for 40 meters at least within reason, at 15 or so feet square.

      Cheers,

      Brian Burns

    • la2pj
      SGC has a description here: http://sgcworld.com/Publications/Manuals/stealthman.pdf Good Luck! Egil - LA2PJ
      Message 2 of 28 , Apr 23, 2013
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        SGC has a description here: http://sgcworld.com/Publications/Manuals/stealthman.pdf

        Good Luck!

        Egil - LA2PJ
      • ik1wvq
        Hi, take a look at http://www.nonstopsystems.com/radio/frank_radio_antenna_SM0VPO.htm I tried the 40 meters versions: My antenna and capacitor:
        Message 3 of 28 , Apr 23, 2013
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          Hi,

          take a look at http://www.nonstopsystems.com/radio/frank_radio_antenna_SM0VPO.htm

          I tried the 40 meters versions:

          My antenna and capacitor:
          http://www.stmb.it/grabber/foto/loop_40_1.jpg
          http://www.stmb.it/grabber/foto/loop_40_2.jpg
          http://www.stmb.it/grabber/foto/loop_40_3.jpg

          and here the results of 24 hours of WSPR with PRC320 military radio (15W measured)and this antenna placed inside in attic .. show only stations what RECEIVED my signals !

          http://www.stmb.it/grabber/foto/40_loop_WSPR.jpg

          enjoy ..

          Mauro IK1WVQ
          (enthusiastic of small SERIOUS antenna systems....)


          --- In loopantennas@yahoogroups.com, "burnsguitar" <brian@...> wrote:
          >
          > Hello All,
          >
          > Has anyone had any experience with reducing a transmitting loop size by half by going to two turns? That seems to be a size that falls in between the usual definitions of a "small" narrow bandwidth loop, and the full wave, or "skywire" loop. I've not been able to find any info on the size, but it could make a rotatable loop for 40 meters at least within reason, at 15 or so feet square.
          >
          > Cheers,
          >
          > Brian Burns
          >
        • Brian Burns
          Hello Mauro, Great references! Thanks very much! Do you notice much directional effect when you rotate the antennas? 73 Brian From:
          Message 4 of 28 , Apr 23, 2013
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            Hello Mauro,

             

            Great references! Thanks very much! Do you notice much directional effect when you rotate the antennas?

             

            73

             

            Brian

             

            From: loopantennas@yahoogroups.com [mailto:loopantennas@yahoogroups.com] On Behalf Of ik1wvq
            Sent: Tuesday, April 23, 2013 6:57 AM
            To: loopantennas@yahoogroups.com
            Subject: [loopantennas] Re: Two turn transmitting loop

             

             


            Hi,

            take a look at http://www.nonstopsystems.com/radio/frank_radio_antenna_SM0VPO.htm

            I tried the 40 meters versions:

            My antenna and capacitor:
            http://www.stmb.it/grabber/foto/loop_40_1.jpg
            http://www.stmb.it/grabber/foto/loop_40_2.jpg
            http://www.stmb.it/grabber/foto/loop_40_3.jpg

            and here the results of 24 hours of WSPR with PRC320 military radio (15W measured)and this antenna placed inside in attic .. show only stations what RECEIVED my signals !

            http://www.stmb.it/grabber/foto/40_loop_WSPR.jpg

            enjoy ..

            Mauro IK1WVQ
            (enthusiastic of small SERIOUS antenna systems....)

            --- In loopantennas@yahoogroups.com, "burnsguitar" <brian@...> wrote:
            >
            > Hello All,
            >
            > Has anyone had any experience with reducing a transmitting loop size by half by going to two turns? That seems to be a size that falls in between the usual definitions of a "small" narrow bandwidth loop, and the full wave, or "skywire" loop. I've not been able to find any info on the size, but it could make a rotatable loop for 40 meters at least within reason, at 15 or so feet square.
            >
            > Cheers,
            >
            > Brian Burns
            >

          • Brian Burns
            Hello again Mauro, I had a look at the references that you sent, and it looks like these loops are definitely in the “small loop” category. I do like your
            Message 5 of 28 , Apr 23, 2013
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              Hello again Mauro,

               

              I had a look at the references that you sent, and it looks like these loops are definitely in the “small loop” category.

               

              I do like your home-made high voltage capacitor, and those are an impressive number of contacts for a compact antenna, and low power!

               

              The antenna that I have in mind is in a kind of “no man’s land” between the full wave, square loop with ¼ wavelength sides, and the narrow-band small loop.

               

              I am fortunate to be able to put an antenna outside of my radio shack, but a square 40 meter full wave loop with 10 meter sides would be impractical. I’m just wondering if there would be much sacrifice in performance by going to a two turn loop with 1/8th wavelength (5 meter) sides, that resonates without a tuning capacitor, and has somewhat better bandwidth.

               

              Thanks again for all the references! I love to see hams making their own gear out of materials from the hardware store!

               

              Cheers,

               

              Brian

               

               

              See my website:  www.lessonsinlutherie.com

               

               

            • Rick Karlquist
              ... Using more than 1 turn does nothing to increase the radiation efficiency of the loop, and may decrease it due to additional copper losses. For a given size
              Message 6 of 28 , Apr 23, 2013
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                Brian Burns wrote:

                > just wondering if there would be much sacrifice in performance by going to
                > a
                > two turn loop with 1/8th wavelength (5 meter) sides, that resonates
                > without
                > a tuning capacitor, and has somewhat better bandwidth.

                Using more than 1 turn does nothing to increase the radiation
                efficiency of the loop, and may decrease it due to additional copper
                losses.

                For a given size loop, the product of bandwidth and efficiency
                is bounded. Often, changes in loop design that increase that
                bandwidth decrease the efficiency. Using multiple turns does nothing
                to affect this inevitable tradeoff. For additional information,
                Google on "Wheeler Chu small antennas".

                Rick N6RK
              • Brian Burns
                Hello Rick, Thanks for the reply, and the link! ~ Using more than 1 turn does nothing to increase the radiation efficiency of the loop, and may decrease it due
                Message 7 of 28 , Apr 23, 2013
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                  Hello Rick,

                  Thanks for the reply, and the link!

                  ~ Using more than 1 turn does nothing to increase the radiation
                  efficiency of the loop, and may decrease it due to additional copper losses.

                  I’m expecting a decrease in radiation efficiency by going to a smaller size. I’m trying to avoid the very narrow bandwidth of the “small” loop, and the resultant need for a motor driven capacitor.

                  I can come up with a method of erecting a 5 meter (or so) square loop, and rotating it. If that size can be made to resonate on 40 meters by using two turns, without the need for additional capacitance, and can provide modest bandwidth and a bit of directional gain, then I’m happy.

                  The next fantasy is to turn that concept into a practical size of 40 meter cubical quad.

                  Cheers,

                   

                  Brian__,,___

                • Andy
                  I don t know if this helps, but there is another Yahoogroup called Skywires (http://groups.yahoo.com/group/SkyWires/) which is more along the lines of
                  Message 8 of 28 , Apr 25, 2013
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                    I don't know if this helps, but there is another Yahoogroup called
                    "Skywires" (http://groups.yahoo.com/group/SkyWires/) which is more
                    along the lines of full-size loops as opposed to small loops. I think
                    what you're doing is closer to a full size loop ... just cutting the
                    area in half but with about the same amount of wire. Thus, the
                    observations about trying to increase the efficiency don't really
                    apply. Small loops assume that the current is uniform around the
                    circumference of the loop, which would not be true of your antenna.

                    I recall reading a question (in one of my many email lists over the
                    last several years), by someone also considering a 2-turn loop. I
                    don't recall now whether he was trying to make the loop area smaller
                    (like you), or doubling the wire by wrapping it twice around the same
                    footprint. In any event, my impression was that there was not a lot
                    of work done in that area already and you, and he, might be on your
                    own.

                    I have seen elsewhere that the "full size" loop supposedly can be used
                    as low as where the loop is only a half wavelength long. Most
                    references to full size loops say that the lowest frequency is 1
                    wavelength circumference; but apparently it can work at half that.
                    (And I don't mean like the old QST Skywire article where they use an
                    80m loop on 160 by turning it into a top-loaded vertical!)

                    Andy
                  • kevin asato
                    Here s something different in transmitting loop antennas that I found in an old ARRL Antenna Book with original reference cited in Electronics, January, 1963 -
                    Message 9 of 28 , Apr 25, 2013
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                      Here's something different in transmitting loop antennas that I found in an old ARRL Antenna Book with original reference cited in Electronics, January, 1963 - the DDRR (directional discontinuity ring radiator). It's basically a 1/4 wave radiator in a loop in close proximity to a ground plane/screen. It's main propagation mode is magnetic (loop is mounted horizontally, radiation is in the vertical plane ala NVIS). Feed to antenna is gamma type and loop is at ground potential. Diameter of tubing that comprises the loop varies according to frequency/band to minimize losses. A search using DDRR will turn up numerous references.

                      73,
                      kevin
                      kc6pob

                      From: Andy <ai.egrps@...>
                      To: loopantennas@yahoogroups.com
                      Sent: Thursday, April 25, 2013 10:54 AM
                      Subject: Re: [loopantennas] Two turn transmitting loop

                       
                      I don't know if this helps, but there is another Yahoogroup called
                      "Skywires" (http://groups.yahoo.com/group/SkyWires/) which is more
                      along the lines of full-size loops as opposed to small loops. I think
                      what you're doing is closer to a full size loop ... just cutting the
                      area in half but with about the same amount of wire. Thus, the
                      observations about trying to increase the efficiency don't really
                      apply. Small loops assume that the current is uniform around the
                      circumference of the loop, which would not be true of your antenna.

                      I recall reading a question (in one of my many email lists over the
                      last several years), by someone also considering a 2-turn loop. I
                      don't recall now whether he was trying to make the loop area smaller
                      (like you), or doubling the wire by wrapping it twice around the same
                      footprint. In any event, my impression was that there was not a lot
                      of work done in that area already and you, and he, might be on your
                      own.

                      I have seen elsewhere that the "full size" loop supposedly can be used
                      as low as where the loop is only a half wavelength long. Most
                      references to full size loops say that the lowest frequency is 1
                      wavelength circumference; but apparently it can work at half that.
                      (And I don't mean like the old QST Skywire article where they use an
                      80m loop on 160 by turning it into a top-loaded vertical!)

                      Andy


                    • Rick Karlquist
                      ... This thing has been pretty thoroughly debunked. I wouldn t bother with it. Rick N6RK
                      Message 10 of 28 , Apr 25, 2013
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                        kevin asato wrote:
                        > Here's something different in transmitting loop antennas that I found in
                        > an old ARRL Antenna Book with original reference cited in Electronics,
                        > January, 1963 - the DDRR (directional discontinuity ring radiator). It's

                        This thing has been pretty thoroughly debunked. I wouldn't bother with it.

                        Rick N6RK
                      • Brian Burns
                        Hello Andy, Thanks for the suggestions. I subscribed to loop skywires for quite a while, and may even have asked my two turn question there some time ago.
                        Message 11 of 28 , Apr 25, 2013
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                          Hello Andy,

                           

                          Thanks for the suggestions. I subscribed to “loop skywires” for quite a while, and may even have asked my two turn question there some time ago. You’re right that there doesn’t seem to have been much work on the idea, though Ike’s suggestion looks promising. I really should shell out the cash to subscribe to AtennaX—I’ll look into that.

                           

                          Cheers,

                           

                          Brian Burns

                          .

                          Image removed by sender.

                        • qrpbear
                          Rick, What s to debunk about the DDRR? They work quite well when properly installed over a ground plane that extends to 2X the DDRR diameter. I installed a lot
                          Message 12 of 28 , Apr 25, 2013
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                            Rick,

                            What's to debunk about the DDRR? They work quite well when properly installed over a ground plane that extends to 2X the DDRR diameter. I installed a lot of them back in the '80s for use on VHF Lo-Band (30-50MHz) business radio systems. Nice fat, low angle pattern with a low profile and stable SWR when compared to a loaded whip. On VHF Hi-Band I used to install them as stealth antennas on the underside of unmarked police vehicles.

                            Don't knock it if you ain't tried it.

                            73,

                            'Bear' NH7SR

                            --- In loopantennas@yahoogroups.com, "Rick Karlquist" <richard@...> wrote:
                            >
                            > kevin asato wrote:
                            > > Here's something different in transmitting loop antennas that I found in
                            > > an old ARRL Antenna Book with original reference cited in Electronics,
                            > > January, 1963 - the DDRR (directional discontinuity ring radiator). It's
                            >
                            > This thing has been pretty thoroughly debunked. I wouldn't bother with it.
                            >
                            > Rick N6RK
                            >
                          • Richard (Rick) Karlquist
                            ... Because the originator s theory of operation ( directional discontinuity ) is bunk. It s just an inverted L with the horizontal wire bent into an arc.
                            Message 13 of 28 , Apr 25, 2013
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                              On 4/25/2013 5:54 PM, qrpbear wrote:
                              > Rick,
                              >
                              > What's to debunk about the DDRR? They work quite well when properly

                              Because the originator's theory of operation ("directional
                              discontinuity") is bunk.
                              It's just an inverted L with the horizontal wire bent into an arc.
                              Nothing new about bending the top of an inverted L, even in 1963.
                              With a very short vertical section (that's the only part that
                              radiates). It doesn't make sense to limit yourself to such
                              a short vertical unless you are under some sort of height
                              limit. As far as working well is concerned, if high efficiency
                              is somehow achieved in a DDRR, it is sure to have very limited
                              bandwidth due to the small size. No way to get around that.

                              Rick N6RK
                            • Brian Burns
                              Hello All, My shack lends itself nicely to transmitting north and south with a dipole or vertical skywire loop, but the lot is way too narrow for stringing up
                              Message 14 of 28 , May 13, 2013
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                                Hello All,

                                 

                                My shack lends itself nicely to transmitting north and south with a dipole or vertical skywire loop, but the lot is way too narrow for stringing up such an antenna for east west work. It occurred to me that a simple full wave loop for 17 meters could be supported by a Dacron line at 43 feet that is already in place. Since a simple loop is bi-directional, there would only be the need to rotate it 90° to cover all directions, and it would have a db or two gain over a dipole.

                                 

                                So I looked up the full wave loop in the 1997 ARRL antenna handbook--downloaded for free from the AMforever forum, an excellent source for free downloads of back issues of magazines and handbooks. According to that handbook the nominal feed impedance of a full wave loop at resonance is 100 ohms.

                                 

                                That value sounded familiar, so I checked, and CAT-5 twisted pair cable has that impedance. I have a fond remembrance of the availability of 72 ohm balanced line, back in the day, and was wondering if anyone has tried feeding any sort of antenna with CAT-5 cable, or any other twisted pair configuration. Twisted pair supposedly picks up less noise and other signals, so it could well be a good receiving antenna transmission line.

                                 

                                CAT-5 may not have good weatherability for outdoor use, but that brings up the possibility of DIY twisted pair transmission line, and that really tickles my frugal Scottish whiskers!

                                 

                                Any thoughts or experiences on the subject would be appreciated (:->)…

                                 

                                Cheers,

                                 

                                Brian Burns

                                 

                                 

                                 

                              • Phil
                                Hi, I use a CAT6 cable to connect my Active longwave loop to the controller in the house. For my purposes it is ideal as I use one pair to feed power to the
                                Message 15 of 28 , May 13, 2013
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                                  Hi,
                                  I use a CAT6 cable to connect my "Active" longwave loop to the
                                  controller in the house. For my purposes it is ideal as I use one pair
                                  to feed power to the loop-amp, another pair to feed a variable Voltage
                                  from the "Tune" potentiometer in the controller to the Varactor tuning
                                  diodes, and finally, a pair to bring the signal back down into the
                                  house. In my case I use a BalUn at each end of the feedline to keep the
                                  line balanced, and RF chokes in each of the DC lines so that the loop is
                                  totally isolated from ground and noise on the DC lines.

                                  It works very well for me, but of course, the highest frequency of the
                                  loop is 530KCs. Not sure how it would work on higher frequencies.

                                  NOTE: There are different grades of CAT5 cable, some optimized for
                                  higher frequencies, (that's what I had). Without doing research (again)
                                  better stuff is called CAT6. . .

                                  And yes, you CAN get UV resistant CAT cable, that's what I have, and
                                  it's grey colored. If in doubt, you can always spray paint it with a
                                  non-lead paint.

                                  --
                                  73 de Phil, KO6BB
                                  http://www.qsl.net/ko6bb/ (Web Page)

                                  RADIOS:
                                  Grundigs: S-350 (2006) & G6 (2011).
                                  Icom: R-75 Receiver with 250Hz CW Filter.
                                  Icom: IC-735 Transceiver w 250 HZ CW filter (circa ~1990).
                                  Radio Shack: DX-380 digital portable (circa 1990).
                                  Zenith: Royal-7000 Transoceanic (circa 1969).

                                  Decoder Software: Gray-matter between two Mark 1 earholes.

                                  ACCESSORIES: Homebrew LF-MF Pre-Amp, MFJ-949E HF Tuner
                                  Homebrew 6 Hz Audio Filter.

                                  ANTENNAS: 88' Long Ladder-line fed dipole at 35 feet AGL.
                                  Active Whip at 36 Feet AGL for LF/MW.
                                  4 Foot/side Tuned Rotatable Loop at 15 Feet AGL for LF

                                  Merced, Central California, 37, 18, 37N 120, 30, 6W CM97rh

                                  On 5/13/2013 5:42 PM, Brian Burns wrote:
                                  >
                                  >
                                  > Hello All,
                                  >
                                  > My shack lends itself nicely to transmitting north and south with a
                                  > dipole or vertical skywire loop, but the lot is way too narrow for
                                  > stringing up such an antenna for east west work. It occurred to me
                                  > that a simple full wave loop for 17 meters could be supported by a
                                  > Dacron line at 43 feet that is already in place. Since a simple loop
                                  > is bi-directional, there would only be the need to rotate it 90° to
                                  > cover all directions, and it would have a db or two gain over a dipole.
                                  >
                                  > So I looked up the full wave loop in the 1997 ARRL antenna
                                  > handbook--downloaded for free from the AMforever forum, an excellent
                                  > source for free downloads of back issues of magazines and handbooks.
                                  > According to that handbook the nominal feed impedance of a full wave
                                  > loop at resonance is 100 ohms.
                                  >
                                  > That value sounded familiar, so I checked, and CAT-5 twisted pair
                                  > cable has that impedance. I have a fond remembrance of the
                                  > availability of 72 ohm balanced line, back in the day, and was
                                  > wondering if anyone has tried feeding any sort of antenna with CAT-5
                                  > cable, or any other twisted pair configuration. Twisted pair
                                  > supposedly picks up less noise and other signals, so it could well be
                                  > a good receiving antenna transmission line.
                                  >
                                  > CAT-5 may not have good weatherability for outdoor use, but that
                                  > brings up the possibility of DIY twisted pair transmission line, and
                                  > that really tickles my frugal Scottish whiskers!
                                  >
                                  > Any thoughts or experiences on the subject would be appreciated (:->)…
                                  >
                                  > Cheers,
                                  >
                                  > Brian Burns
                                  >
                                  >
                                • brian nsl
                                  Brian, I have used loop antennas both vertical and horizontal since starting my SWL days in 1970. Normally these have a been a full wave on 40m ( 138.5 ft )
                                  Message 16 of 28 , May 13, 2013
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                                    Brian,
                                             I have used loop antennas both vertical and horizontal since
                                    starting my SWL days in 1970.
                                    Normally these have a been a full wave on 40m ( 138.5 ft ) since the garden
                                    can only take around 200ft perimeter and that is in  ' no mans land '
                                    coverage wise, the height has never exceeded 35ft.
                                    All the loops have had the same feed system, an electrical 1/4 wave of 120 ohm
                                    feeder ( appx 23.5ft ) which is no more than 15 amp rated black / red DC lead.
                                    All fed from a Kenwood TS-130V with 5 watts SSB.. and to date 245 DXCC
                                    entities worked / confirmed using 40 - 10m bands.
                                    They do work despite the nickname of ' skywire ' hi!
                                    A point to remember is that loops attract static and I have suffered a few ' belts '
                                    over the years !!!!
                                                                                    Regards,
                                                                                         72, Brian, GØNSL.
                                    ----- Original Message -----
                                    Sent: Monday, May 13, 2013 6:42 PM
                                    Subject: RE: [loopantennas] CAT-5 cable?
                                  • Jerry Flanders
                                    When I needed to make up a set of long component cables for my HDTV in the bedroom (to reach from the DISH rx in the den), I looked up the specs on CAT5
                                    Message 17 of 28 , May 13, 2013
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                                      When I needed to make up a set of long
                                      "component" cables for my HDTV in the bedroom (to
                                      reach from the DISH rx in the den), I looked up
                                      the specs on CAT5 cable and found it to be a good
                                      choice. I just put 3 rca plugs at each end and
                                      marked them color-wise and plugged it all up.
                                      Made an extra run for the stereo audio. Works
                                      fine - no crosstalk, good freq response, etc. This was an 80 ft run.

                                      The specs show extremely low crosstalk, and that
                                      also means low/no pickup from external sources.

                                      IIRC, the impedance for a single pair was 200
                                      ohms, so two pairs paralleled would give 100 ohms
                                      and all 4 pairs paralleled would give 50. I think
                                      it would be an excellent feed line for up to maybe 100 watts RF.

                                      Jerry W4UK

                                      At 01:42 PM 5/13/2013, you wrote:


                                      >Hello All,
                                      >
                                      >My shack lends itself nicely to transmitting
                                      >north and south with a dipole or vertical
                                      >skywire loop, but the lot is way too narrow for
                                      >stringing up such an antenna for east west work.
                                      >It occurred to me that a simple full wave loop
                                      >for 17 meters could be supported by a Dacron
                                      >line at 43 feet that is already in place. Since
                                      >a simple loop is bi-directional, there would
                                      >only be the need to rotate it 90° to cover all
                                      >directions, and it would have a db or two gain over a dipole.
                                      >
                                      >So I looked up the full wave loop in the 1997
                                      >ARRL antenna handbook--downloaded for free from
                                      >the AMforever forum, an excellent source for
                                      >free downloads of back issues of magazines and
                                      >handbooks. According to that handbook the
                                      >nominal feed impedance of a full wave loop at resonance is 100 ohms.
                                      >
                                      >That value sounded familiar, so I checked, and
                                      >CAT-5 twisted pair cable has that impedance. I
                                      >have a fond remembrance of the availability of
                                      >72 ohm balanced line, back in the day, and was
                                      >wondering if anyone has tried feeding any sort
                                      >of antenna with CAT-5 cable, or any other
                                      >twisted pair configuration. Twisted pair
                                      >supposedly picks up less noise and other
                                      >signals, so it could well be a good receiving antenna transmission line.
                                      >
                                      >CAT-5 may not have good weatherability for
                                      >outdoor use, but that brings up the possibility
                                      >of DIY twisted pair transmission line, and that
                                      >really tickles my frugal Scottish whiskers!
                                      >
                                      >Any thoughts or experiences on the subject would be appreciated (:->)…
                                      >
                                      >Cheers,
                                      >
                                      >Brian Burns
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                    • John
                                      Another commonly available balanced line in the 70-100 Ohm range is standard #18/#20 Zip cord - once known as lamp cord, but today known as speaker wire!
                                      Message 18 of 28 , May 13, 2013
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                                        Another commonly available balanced line in the 70-100 Ohm range is standard #18/#20 Zip cord - once known as lamp cord, but today known as speaker wire! Seriously - the vf was ~.66 back then - modern dielectrics may have changed that. Certainly there must be UV-tolerant variants now. Once upon a time, there was a company - maybe B&W - that made SWL receive-only trap dipoles that came either with the balanced Zip cord or a coax connector. For a receive feedline, it'll work well - if the dielectric is weatherproof. A lot of speaker cable is no longer pure copper - it's 'CCA' - Copper Clad Aluminum wire. Probably wouldn't do well flapping in the breeze - for long (Plastic failure of the Al core.).

                                        I used it, years ago, to feed a homebrew Tilted Terminated Folded Dipole with, including a 2:1 (n ratio - Z ratio: 4:1) Z transformer (400 Ohm to ~100 Ohm) at the feedpoint insulator. It left the TTFD with no DC path to ground, so I went to 450 Ohm ladder line to a homebrew balanced tuner with a CT ground to drain off the static charge. Received signal strengths from common/stable SW stations, like CFRX, CHU, Radio Australia, WRNO, were similar in strength averaged over a few days. The TTFD is a great low noise antenna that pretty much loses the FD/Dipole bi-directional nature and seems more sensitive than it's signal dissipating resistor would imply. A 'loop' of sorts!

                                        John
                                      • Jack Smith
                                        A few years ago, I measured the loss of typical zip cord, using lab grade equipment, taking due care to treat the line as balanced. Results: The second column,
                                        Message 19 of 28 , May 13, 2013
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                                          A few years ago, I measured the loss of typical zip cord, using lab grade equipment, taking due care to treat the line as balanced. Results:

                                          The second column, "measured loss" is for a 17.4 ft length and the loss / 100 ft is extrapolated from that measured length. This is with matched loads - i.e., 109 ohms source and termination impedance (measured Zo for this piece of zip cord as 109 ohms). Operating it into a mis-matched load will, of course, increase the loss.

                                          Frequency MHzMeasured Loss (dB)Loss (dB)/100 ft
                                          50.42.3
                                          100.63.5
                                          150.84.6
                                          200.955.5
                                          251.26.9
                                          301.48.1

                                          It's not the worst possible transmission line, I suppose, although it has greater loss than RG-174 (3.3 dB / 100 ft @ 10 MHz versus 3.5 dB/100 ft measured for the twin lead), it has the virtue of being available in an emergency from a hardware store. And, not all zip cord is equal. However, cables constructed to carry signals use rather different dielectric material than those constructed to carry 50/60 Hz power and that difference translates into significant loss.

                                          At 10 MHz, CAT-5 ethernet cable has a loss of about 2 dB/100 ft, despite using significantly smaller diameter wire than for the measured zip cord.

                                          So, will zip cord work as a  transmission line? Yes. Does it work well? No, at least if one views the term "well" as including the concept of low loss.

                                          Jack K8ZOA


                                          On 5/13/2013 3:25 PM, John wrote:
                                           

                                          Another commonly available balanced line in the 70-100 Ohm range is standard #18/#20 Zip cord - once known as lamp cord, but today known as speaker wire! Seriously - the vf was ~.66 back then - modern dielectrics may have changed that. Certainly there must be UV-tolerant variants now. Once upon a time, there was a company - maybe B&W - that made SWL receive-only trap dipoles that came either with the balanced Zip cord or a coax connector. For a receive feedline, it'll work well - if the dielectric is weatherproof. A lot of speaker cable is no longer pure copper - it's 'CCA' - Copper Clad Aluminum wire. Probably wouldn't do well flapping in the breeze - for long (Plastic failure of the Al core.).

                                          I used it, years ago, to feed a homebrew Tilted Terminated Folded Dipole with, including a 2:1 (n ratio - Z ratio: 4:1) Z transformer (400 Ohm to ~100 Ohm) at the feedpoint insulator. It left the TTFD with no DC path to ground, so I went to 450 Ohm ladder line to a homebrew balanced tuner with a CT ground to drain off the static charge. Received signal strengths from common/stable SW stations, like CFRX, CHU, Radio Australia, WRNO, were similar in strength averaged over a few days. The TTFD is a great low noise antenna that pretty much loses the FD/Dipole bi-directional nature and seems more sensitive than it's signal dissipating resistor would imply. A 'loop' of sorts!

                                          John


                                        • Brian Burns
                                          Hello again All, Thanks very much for all the responses on CAT-5! A week ago a guitar making student of mine, who happens to be an EE, dumped a carload of
                                          Message 20 of 28 , May 13, 2013
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                                            Hello again All,

                                             

                                            Thanks very much for all the responses on CAT-5!

                                             

                                            A week ago a guitar making student of mine, who happens to be an EE, dumped a carload of “gems and junque” in my shop. Among the gems was a working ‘scope, so I was happy to take on the disposal of the rest. Amongst what I thought of as junque was a 300 foot spool of standard RJ-11 telephone hook-up wire (several lifetime’s supply). It’s the 4 conductor standard stuff.

                                             

                                            Until Jerry mentioned that CAT-5 would probably be useable up to 100 watts of RF, the possibility of using the RJ-11 wire as transmission line hadn’t entered my head. There is a powerful incentive for using what you’ve got, if you have taken the vows of poverty, as I have.

                                             

                                            I googled around for quite a while, but couldn’t find any data on the characteristic impedance of the stuff, and was wondering if anyone happens to know anything about it. I would probably just parallel pairs of conductors to make a two conductor parallel line out of it.

                                             

                                            Cheers,

                                             

                                            Brian

                                             

                                             

                                          • Jack Smith
                                            I assume you mean the 4 conductor indoor (local premises) wiring cable - red, black, yellow and green. My Bell System friends called this JK cable if I
                                            Message 21 of 28 , May 13, 2013
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                                              I assume you mean the 4 conductor indoor (local premises) wiring cable - red, black, yellow and green. My Bell System friends called this JK cable if I remember correctly, but don't hold me to that.

                                              It's also known, subsequently, as Cat-1 cable, and the normal recommendation is not to use it above a few hundred KHz.

                                              On the other hand, there are umpteen miles of that wire still in use, and some of it is used with DSL which operates in the few MHz range at the upper end, so it will pass RF. The question is how well it will pass the RF as in a normal residential installation, the local premises wire will be only a few dozen feet in length and the overall circuit response is dominated by the distribution plant wiring, not the local premises wire. (Lots of equalization is used in the DSL modems to offset the high loss in telephone distribution plant once you up above audio range.)

                                              The wire I'm thinking of is solid conductor, and probably would rapidly fail from metal fatigue if flexed by the wind.  Also don't know if the jacket is UV stabilized of waterproof, as it's strictly an indoor use only cable.

                                              As for impedance, I can't recall any specs on it, but I suspect from the dimensions it's in the 100 ohm range. Given the normal wire and insulation dimensions, it's difficult to make a cable the size of indoor telephone wire much outside the 100 ohm figure.

                                              So, yes it can be made to work--wouldn't be my first choice but if that's the only way to transport RF, give it a try.

                                              Jack K8ZOA


                                              On 5/13/2013 6:46 PM, Brian Burns wrote:
                                               

                                              Hello again All,

                                               

                                              Thanks very much for all the responses on CAT-5!

                                               

                                              A week ago a guitar making student of mine, who happens to be an EE, dumped a carload of “gems and junque” in my shop. Among the gems was a working ‘scope, so I was happy to take on the disposal of the rest. Amongst what I thought of as junque was a 300 foot spool of standard RJ-11 telephone hook-up wire (several lifetime’s supply). It’s the 4 conductor standard stuff.

                                               

                                              Until Jerry mentioned that CAT-5 would probably be useable up to 100 watts of RF, the possibility of using the RJ-11 wire as transmission line hadn’t entered my head. There is a powerful incentive for using what you’ve got, if you have taken the vows of poverty, as I have.

                                               

                                              I googled around for quite a while, but couldn’t find any data on the characteristic impedance of the stuff, and was wondering if anyone happens to know anything about it. I would probably just parallel pairs of conductors to make a two conductor parallel line out of it.

                                               

                                              Cheers,

                                               

                                              Brian

                                               

                                               


                                            • Brian Burns
                                              Hello Jack, Thanks for the info! ~ I assume you mean the 4 conductor indoor (local premises) wiring cable - red, black, yellow and green. Yep, that s it all
                                              Message 22 of 28 , May 13, 2013
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                                                Hello Jack,

                                                 

                                                Thanks for the info!

                                                 

                                                ~ I assume you mean the 4 conductor indoor (local premises) wiring cable - red, black, yellow and green.

                                                 

                                                Yep, that’s it all right, but it happens to be stranded. Each conductor is made up of 7 strands of .006” diameter copper wire—I had to put on my 10X Optivisor to see the stuff!


                                                ~ On the other hand, there are umpteen miles of that wire still in use, and some of it is used with DSL which operates in the few MHz range at the upper end, so it will pass RF. The question is how well it will pass the RF

                                                 

                                                ~ Also don't know if the jacket is UV stabilized of waterproof, as it's strictly an indoor use only cable.

                                                ~ As for impedance, I can't recall any specs on it, but I suspect from the dimensions it's in the 100 ohm range. Given the normal wire and insulation dimensions, it's difficult to make a cable the size of indoor telephone wire much outside the 100 ohm figure.

                                                 

                                                The antenna will be located right outside my shack wall, and will be a PVC pipe that goes up vertically to support a couple of cross members that in turn support the loop. The phone cable could run up the interior of the PVC, and exit at the lower center of the loop so that it wouldn’t be exposed to UV. The total length of the run would be about 30 feet.

                                                 

                                                I have a Harvey Wells antenna tuner that has a balanced output for open wire line, so it can match the transmitter to the phone line nicely. If the 100 ohm impedance of the line matches the 100 ohm impedance of the antenna, then “Bob’s my uncle”, right? I do love the idea of matching the impedances everywhere, even if it really doesn’t matter very much (;->)…


                                                ~ So, yes it can be made to work--wouldn't be my first choice but if that's the only way to transport RF, give it a try.

                                                 

                                                I could probably sell the spool of phone cable for enough to buy the “first choice”, but there is something appealing about the idea of using the phone cable. BTW what would be your first choice?

                                                 

                                                Cheers,

                                                 

                                                Brian




                                                 

                                                .

                                                Image removed by sender.

                                              • Jack Smith
                                                First choice depends whether your design requires balanced or unbalanced feed line and the required impedance. If high Z balanced, then 450 ohm ladder line,
                                                Message 23 of 28 , May 13, 2013
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                                                  First choice depends whether your design requires balanced or unbalanced feed line and the required impedance.

                                                  If high Z balanced, then 450 ohm ladder line, window type is reasonably low loss, mechanically decent and not terribly expensive. If you need low Z balanced line, there is a 72 or 75 ohm paired balanced line available, made with insulation designed for RF use. Some of these are available with copperweld conductors - that's fine if you need mechanical strength, but your description suggests a standard copper conductor version will be mechanically satisfactory. (Copperweld is miserable stuff to work with so I try to avoid it unless absolutely necessary.)

                                                  If unbalanced then there is a wealth of coaxial cables to consider. For a 30 ft run, it probably doesn't matter much, but  RG-58 for small diameter coax or RG-213 for larger diameter would be it for me. Look for high quality cable, stay away from aluminum braid types unless you know exactly what you are doing. I would not buy cheap import coax cable unless you have the knowledge and experience to separate good from bad because a lot of it is really trash.

                                                  I've written a bit about coax cable:
                                                  http://www.cliftonlaboratories.com/the_curious_case_of.htm
                                                  http://www.cliftonlaboratories.com/Aug_2011.htm skip the first couple entries.

                                                  Jack K8ZOA

                                                  On 5/13/2013 7:42 PM, Brian Burns wrote:
                                                   

                                                  Hello Jack,

                                                   

                                                  Thanks for the info!

                                                   

                                                  ~ I assume you mean the 4 conductor indoor (local premises) wiring cable - red, black, yellow and green.

                                                   

                                                  Yep, that’s it all right, but it happens to be stranded. Each conductor is made up of 7 strands of .006” diameter copper wire—I had to put on my 10X Optivisor to see the stuff!


                                                  ~ On the other hand, there are umpteen miles of that wire still in use, and some of it is used with DSL which operates in the few MHz range at the upper end, so it will pass RF. The question is how well it will pass the RF

                                                   

                                                  ~ Also don't know if the jacket is UV stabilized of waterproof, as it's strictly an indoor use only cable.

                                                  ~ As for impedance, I can't recall any specs on it, but I suspect from the dimensions it's in the 100 ohm range. Given the normal wire and insulation dimensions, it's difficult to make a cable the size of indoor telephone wire much outside the 100 ohm figure.

                                                   

                                                  The antenna will be located right outside my shack wall, and will be a PVC pipe that goes up vertically to support a couple of cross members that in turn support the loop. The phone cable could run up the interior of the PVC, and exit at the lower center of the loop so that it wouldn’t be exposed to UV. The total length of the run would be about 30 feet.

                                                   

                                                  I have a Harvey Wells antenna tuner that has a balanced output for open wire line, so it can match the transmitter to the phone line nicely. If the 100 ohm impedance of the line matches the 100 ohm impedance of the antenna, then “Bob’s my uncle”, right? I do love the idea of matching the impedances everywhere, even if it really doesn’t matter very much (;->)…


                                                  ~ So, yes it can be made to work--wouldn't be my first choice but if that's the only way to transport RF, give it a try.

                                                   

                                                  I could probably sell the spool of phone cable for enough to buy the “first choice”, but there is something appealing about the idea of using the phone cable. BTW what would be your first choice?

                                                   

                                                  Cheers,

                                                   

                                                  Brian




                                                   

                                                  .

                                                  Image
removed by sender.


                                                • Andy
                                                  The JK (or JKT?) indoor phone wire I have seen, is four wires with a gentle twist of the whole bunch. Taking a cross section, the four wires are in a square.
                                                  Message 24 of 28 , May 15, 2013
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                                                    The JK (or JKT?) indoor phone wire I have seen, is four wires with a gentle twist of the whole bunch.  Taking a cross section, the four wires are in a square.  The "pairs", if you will, are opposite corners of the square.  Thus, if the signals on both pairs are differential, crosstalk is minimized because even though each pair is fully immersed within the field of the other pair, it is in such a way that the differential components cancel.

                                                    The use of opposite corners to form a pair, raises the characteristic impedance from what it would be if they had twisted the pairs.

                                                    Since this stuff was intended for voice use only, they might have never characterized its impedance Zo.  At audio frequencies, twisted pair copper wires do not have a constant characteristic impedance.  It typically increases by more than an order of magnitude at audio frequencies, compared to higher frequencies where it finally levels off.

                                                    There is some mythology that telco uses Zo = 600 ohms for all its wire pairs.  I have seen references that argue why this is not true.  In the very very old days telco used open wire lines which might have been in that range, or greater.  Twisted wire lines in cable bundles, which make up the majority of telco lines, were closer to 100 ohms Zo, but did not reach that until well above audio frequencies.

                                                    Andy


                                                  • Rick Karlquist
                                                    ... If you wire the cable as the traditional 4-wire line then it turns out that the characteristic impedance is 70.7% of the impedance of an individual side
                                                    Message 25 of 28 , May 16, 2013
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                                                      Andy wrote:

                                                      > The use of opposite corners to form a pair, raises the characteristic
                                                      > impedance from what it would be if they had twisted the pairs.

                                                      If you wire the cable as the traditional "4-wire line" then it turns
                                                      out that the characteristic impedance is 70.7% of the impedance of
                                                      an individual side by side pair. 4 wire line ties together opposite
                                                      wires and then drives the tied pairs against each other. This is
                                                      normally described in the context of open wire line with circular
                                                      disk spacers, but the concept should be extensible to quadrifilar
                                                      twisted line.

                                                      Rick N6RK
                                                    • John Popelish
                                                      ... Have you a reference for this 4 wire transmission line configuration and impedance? I can t find one. All I find is references to star-quad audio cable,
                                                      Message 26 of 28 , May 16, 2013
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                                                        On Thu, May 16, 2013 at 1:00 PM, Rick Karlquist <richard@...> wrote:
                                                        Andy wrote:

                                                        If you wire the cable as the traditional "4-wire line" then it turns
                                                        out that the characteristic impedance is 70.7% of the impedance of
                                                        an individual side by side pair.  4 wire line ties together opposite
                                                        wires and then drives the tied pairs against each other.  This is
                                                        normally described in the context of open wire line with circular
                                                        disk spacers, but the concept should be extensible to quadrifilar
                                                        twisted line.

                                                        Rick N6RK 

                                                        Have you a reference for this 4 wire transmission line configuration and impedance?
                                                        I can't find one.  All I find is references to star-quad audio cable, that is intended to be used this way, for low impedance mics.  And it is shielded.

                                                        --
                                                        Regards,

                                                        John Popelish
                                                      • Richard (Rick) Karlquist
                                                        ... See Edmund Laport s Radio Antenna Engineering now free on the web at: http://www.lulu.com/product/ebook/ra...shelf/center/2 Rick N6RK
                                                        Message 27 of 28 , May 16, 2013
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                                                          On 5/16/2013 10:33 AM, John Popelish wrote:
                                                          >
                                                          >

                                                          >
                                                          >
                                                          > Have you a reference for this 4 wire transmission line configuration and
                                                          > impedance?
                                                          > I can't find one. All I find is references to star-quad audio cable,
                                                          > that is intended to be used this way, for low impedance mics. And it is
                                                          > shielded.


                                                          See Edmund Laport's "Radio Antenna Engineering" now free on the web at:

                                                          http://www.lulu.com/product/ebook/ra...shelf/center/2

                                                          Rick N6RK
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