Loading ...
Sorry, an error occurred while loading the content.
 

Re: [loopantennas] loops and nearby objects

Expand Messages
  • richard
    On Thu, 07 Jan 2010 20:16:05 -0800 Richard (Rick) Karlquist wrote: Sorry Rick I managed to delete your last message , so cant quote
    Message 1 of 13 , Jan 8 10:15 AM
      On Thu, 07 Jan 2010 20:16:05 -0800
      "Richard (Rick) Karlquist" <richard@...> wrote:
      Sorry Rick I managed to delete your last message , so cant quote from it.

      Shunt loading the tower~ maybe, but there are a lot of expensive electronics up there, there are
      microwave transverters for 13 cms and 6 cms as well as masthead pre-amps for 23 cms, 70 cms & 2mtrs.
      The base of the tower is well earthed so finding the fed point could be difficult, but if you have
      info of an idiot proof way of loading the tower , I'd be very interested.
      I'm not so sure that loops are for Rx only, any thing that can be made to resonate is fair game for
      putting RF in to it.

      AS for the high Q and high voltages, in the UK the most used part of top band has a limit of 30W,
      with a Q of 1100 , that a peak voltage across the cap of 2KV with a bandwidth of 1.5 KHz, but If
      you listen on top band in the UK you find most QSO s are centered around 1.933 MHz only offset by a
      K or so.
      At the full limit on topband there is a section which allows 400W , but thats still only 7.5 KV,
      easily handled by some of the vacuum caps available.



      --
      Best wishes

      Richard Bown

      ###################################################################################
      Registered Linux User 36561
      OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
      Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
      ###################################################################################
    • Rick Karlquist
      ... I don t think shunt feeding the tower on 80 or 160 meters would bother VHF equipment. I don t know that there is an idiot proof way of shunt feeding a
      Message 2 of 13 , Jan 8 10:37 AM
        richard wrote:
        > On Thu, 07 Jan 2010 20:16:05 -0800
        > "Richard (Rick) Karlquist" <richard@...> wrote:
        > Sorry Rick I managed to delete your last message , so cant quote from it.
        >
        > Shunt loading the tower~ maybe, but there are a lot of expensive
        > electronics up there, there are
        > microwave transverters for 13 cms and 6 cms as well as masthead pre-amps
        > for 23 cms, 70 cms & 2mtrs.
        > The base of the tower is well earthed so finding the fed point could be
        > difficult, but if you have
        > info of an idiot proof way of loading the tower , I'd be very interested.
        > I'm not so sure that loops are for Rx only, any thing that can be made to
        > resonate is fair game for
        > putting RF in to it.

        I don't think shunt feeding the tower on 80 or 160 meters would
        bother VHF equipment. I don't know that there is an idiot proof
        way of shunt feeding a tower. However, you can model the tower
        with EZNEC and do your experimenting on the computer. Then you
        should be able to build the actual feed and have a good chance
        of it working.



        >
        > AS for the high Q and high voltages, in the UK the most used part of top
        > band has a limit of 30W,
        > with a Q of 1100 , that a peak voltage across the cap of 2KV with a
        > bandwidth of 1.5 KHz, but If
        > you listen on top band in the UK you find most QSO s are centered around
        > 1.933 MHz only offset by a
        > K or so.
        > At the full limit on topband there is a section which allows 400W , but
        > thats still only 7.5 KV,
        > easily handled by some of the vacuum caps available.
        >
        > Richard Bown

        Very interesting. I had no idea how it worked in the UK. In
        the US, we can run 1500W from 1.8 to 2, but I rarely go above 1.9.
        I recently worked G3MMT around 1830 kHz and he was over S9 here on
        the west coast. I guess a loop could work OK for your purposes.

        Rick N6RK
      • richard
        On Fri, 08 Jan 2010 17:20:41 -0000 ... Hi Andrew I ve had a look at Ben s site and I maybe able to get 128 in but I cant get the height shame -- Best wishes
        Message 3 of 13 , Jan 8 11:53 AM
          On Fri, 08 Jan 2010 17:20:41 -0000
          "capntripps2000" <capntripps2000@...> wrote:

          > There are alternatives. If maximum transmitting efficiency is the goal then a 1/4w circumference
          > loop made of wire would work very well if you feed the antenna next to the tuning capacitor where
          > the impedance is much higher and the resistive losses are minimized.
          >
          > See Ben G0CWT's web site: http://g0cwt.co.uk/magloops/
          > Review all the above thoroughly.
          >
          > I built an 80M wire magnetic loop using Ben's feed method and use it with great success on both
          > 80M and 160M. Mind you stealth is what I had in mind and this fit the bill.
          >
          > Andrew
          > N3LCW
          >
          >
          > --- In loopantennas@yahoogroups.com, "Richard (Rick) Karlquist" <richard@...> wrote:
          >
          > > If I made one out of 4 inch plastic pipe covered with foil, the
          > > Q would easily be over 1000. That gives a bandwidth of only a few
          > > kHz on 160 meters. The voltage across the tuning capacitor at
          > > any significant power would be astronomical.
          > >
          > > And that's why loops are only for receiving IMHO.
          > >
          > > Rick N6RK
          > >
          >
          >
          Hi Andrew
          I've had a look at Ben's site and I maybe able to get 128' in but I cant get the height

          shame

          --
          Best wishes

          Richard Bown

          ###################################################################################
          Registered Linux User 36561
          OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
          Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
          ###################################################################################
        • capntripps2000
          Richard, Don t worry about the height, make it fit however you can. Unless you can get the bottom of the 160M loop high above the ground the pattern will have
          Message 4 of 13 , Jan 9 9:27 AM
            Richard,

            Don't worry about the height, make it fit however you can. Unless you can get the bottom of the 160M loop high above the ground the pattern will have a large NVIS component and will be quite broad also, more oval shape. It will work very well. I've had reports from other's who've tried a short squat 160M wire magnetic loop with excellent results.

            Andrew


            --- In loopantennas@yahoogroups.com, richard <richard.bown@...> wrote:
            >
            > On Fri, 08 Jan 2010 17:20:41 -0000
            > "capntripps2000" <capntripps2000@...> wrote:
            >
            > > There are alternatives. If maximum transmitting efficiency is the goal then a 1/4w circumference
            > > loop made of wire would work very well if you feed the antenna next to the tuning capacitor where
            > > the impedance is much higher and the resistive losses are minimized.
            > >
            > > See Ben G0CWT's web site: http://g0cwt.co.uk/magloops/
            > > Review all the above thoroughly.
            > >
            > > I built an 80M wire magnetic loop using Ben's feed method and use it with great success on both
            > > 80M and 160M. Mind you stealth is what I had in mind and this fit the bill.
            > >
            > > Andrew
            > > N3LCW
            > >
            > >
            > > --- In loopantennas@yahoogroups.com, "Richard (Rick) Karlquist" <richard@> wrote:
            > >
            > > > If I made one out of 4 inch plastic pipe covered with foil, the
            > > > Q would easily be over 1000. That gives a bandwidth of only a few
            > > > kHz on 160 meters. The voltage across the tuning capacitor at
            > > > any significant power would be astronomical.
            > > >
            > > > And that's why loops are only for receiving IMHO.
            > > >
            > > > Rick N6RK
            > > >
            > >
            > >
            > Hi Andrew
            > I've had a look at Ben's site and I maybe able to get 128' in but I cant get the height
            >
            > shame
            >
            > --
            > Best wishes
            >
            > Richard Bown
            >
            >
          • Pronto. (Military)
            I ve built some Magnetic loops and in particular The DCTL Loop for 40 Meters . The loop is only 48 inches square and when tuned is oblivious to surrounding
            Message 5 of 13 , Jan 14 5:49 AM
              I've built some Magnetic loops and in particular The DCTL Loop for 40 Meters . The loop is only 48 inches square and when tuned is oblivious to surrounding nearby structures. It is actually a rendition of the DDRR military loop (Direct Discontinuity Ring Radiator.) I have operated this antenna within my house and it outperformed an external dipole.
              I have design ideas for a broadband version of this square loop as well.
              I have posted pictures under VE3DDY.
              Jim VE3DDY

              --- In loopantennas@yahoogroups.com, "Richard (Rick) Karlquist" <richard@...> wrote:
              >
              > I have done a lot of experimenting with a 160 meter loop (20 ft
              > perimeter) and found that nearby objects are quite detrimental
              > if you want to get a sharp null. Certainly, 4 ft from a tower
              > is a non starter. BTW, I have found that 12 ft diameter is
              > too large to get a good null even on 160 meters, let alone
              > higher bands.
              >
              > Rick N6RK
              >
              > richard wrote:
              > >
              > >
              > > Hi all
              > >
              > > Now I've got this 12' dia loop nearly constructed, how critical are loop
              > > to nearby objects ?
              > > ie could I mount it on the side of the tower with say a 4' standoff
              > > between the tower and the
              > > loop ?.
              > >
              > > Or could I mount it on a 2" dia Aluminium pole fixed at the top and
              > > bottom with just 1" separation
              > > between the loop and pole ?
              > > TIA
              > > --
              > > Best wishes
              > >
              > > Richard Bown
              > >
              > > ###################################################################################
              > > Registered Linux User 36561
              > > OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
              > > Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz &
              > > 5.7GHz & 10 GHz
              > > ###################################################################################
              > >
              > >
              >
            • g3squ
              Hi Jim Had a look at the pics and am very interested in this antenna. Is there a technical description anywhere? A Google of DCTL reveals that it is a
              Message 6 of 13 , Jan 15 10:03 AM
                Hi Jim

                Had a look at the pics and am very interested in this antenna. Is there a technical description anywhere? A Google of "DCTL" reveals that it is a much-used acronym: what does yours stand for?

                Chris
                G3SQU

                --- In loopantennas@yahoogroups.com, "Pronto. (Military)" <portdoverbells@...> wrote:
                >
                > I've built some Magnetic loops and in particular The DCTL Loop for 40 Meters . The loop is only 48 inches square and when tuned is oblivious to surrounding nearby structures. It is actually a rendition of the DDRR military loop (Direct Discontinuity Ring Radiator.) I have operated this antenna within my house and it outperformed an external dipole.
                > I have design ideas for a broadband version of this square loop as well.
                > I have posted pictures under VE3DDY.
                > Jim VE3DDY
                >
                > --- In loopantennas@yahoogroups.com, "Richard (Rick) Karlquist" <richard@> wrote:
                > >
                > > I have done a lot of experimenting with a 160 meter loop (20 ft
                > > perimeter) and found that nearby objects are quite detrimental
                > > if you want to get a sharp null. Certainly, 4 ft from a tower
                > > is a non starter. BTW, I have found that 12 ft diameter is
                > > too large to get a good null even on 160 meters, let alone
                > > higher bands.
                > >
                > > Rick N6RK
                > >
                > > richard wrote:
                > > >
                > > >
                > > > Hi all
                > > >
                > > > Now I've got this 12' dia loop nearly constructed, how critical are loop
                > > > to nearby objects ?
                > > > ie could I mount it on the side of the tower with say a 4' standoff
                > > > between the tower and the
                > > > loop ?.
                > > >
                > > > Or could I mount it on a 2" dia Aluminium pole fixed at the top and
                > > > bottom with just 1" separation
                > > > between the loop and pole ?
                > > > TIA
                > > > --
                > > > Best wishes
                > > >
                > > > Richard Bown
                > > >
                > > > ###################################################################################
                > > > Registered Linux User 36561
                > > > OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
                > > > Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz &
                > > > 5.7GHz & 10 GHz
                > > > ###################################################################################
                > > >
                > > >
                > >
                >
              • shibukiau
                Hi Richard -- I just read your request for info!! Due to antenna restrictions, I use a homebuilt 6 ft dia loop on 80/40m inside my aluminum clad garage
                Message 7 of 13 , Mar 1, 2010
                  Hi Richard -- I just read your request for info!!

                  Due to antenna restrictions, I use a homebuilt 6 ft dia loop on 80/40m inside my aluminum clad garage alongside my car and still able to work out almost as well as others with average dipoles! The car will shift the tune point a bit and probably doesn't help much but it does work! The Q will be affected more by the loop material and resistance of the loop/cap assembly than anything else!

                  If you have to mount the loop on a mast I'd go for the aluminum mast, I use one myself and it doesn't appear to affect it!

                  BTW -- a good cost effective loop can be made out of 7/8 inch Heliax, which is what I used. This stuff can be found used at most fleamarkets for next to nothing as many of the cell towers are removing it due to new equipment configurations! My loop uses about 19 ft of Heliax and a dual gang air variable cap turned by a DC motor feed over the coax from a MFJ loop control box! Very simple but effective!
                  I also use the MFJ loops, the 20-10m one is a good performer and easy to use!!

                  If you would like more info on how to make one for 160m Google "vk4amz" as he has a nice web site describing his 160m loop. I've seen his and have heard him on the air. He does extremely well compared to other stations using full size antennae!

                  Main thing is don't be discouraged, just go ahead and try it as I guarantee you will be impressed by the performance of a well built loop!

                  Cheers!
                  VK4ERQ/VE3ERQ

                  --- In loopantennas@yahoogroups.com, richard <richard.bown@...> wrote:
                  >
                  > Hi all
                  >
                  > Now I've got this 12' dia loop nearly constructed, how critical are loop to nearby objects ?
                  > ie could I mount it on the side of the tower with say a 4' standoff between the tower and the
                  > loop ?.
                  >
                  > Or could I mount it on a 2" dia Aluminium pole fixed at the top and bottom with just 1" separation
                  > between the loop and pole ?
                  > TIA
                  > --
                  > Best wishes
                  >
                  > Richard Bown
                  >
                  > ###################################################################################
                  > Registered Linux User 36561
                  > OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
                  > Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
                  > ###################################################################################
                  >
                • richard
                  On Mon, 01 Mar 2010 12:12:59 -0000 ... Well my loop is up in the garden now, and works surprisingly well. Its just under 4 mtrs dia, made from LDF4-50, which
                  Message 8 of 13 , Mar 1, 2010
                    On Mon, 01 Mar 2010 12:12:59 -0000
                    "shibukiau" <kubisl@...> wrote:

                    > Hi Richard -- I just read your request for info!!
                    >
                    > Due to antenna restrictions, I use a homebuilt 6 ft dia loop on 80/40m inside my aluminum clad
                    > garage alongside my car and still able to work out almost as well as others with average dipoles!
                    > The car will shift the tune point a bit and probably doesn't help much but it does work! The Q
                    > will be affected more by the loop material and resistance of the loop/cap assembly than anything
                    > else!
                    >
                    > If you have to mount the loop on a mast I'd go for the aluminum mast, I use one myself and it
                    > doesn't appear to affect it!
                    >
                    > BTW -- a good cost effective loop can be made out of 7/8 inch Heliax, which is what I used. This
                    > stuff can be found used at most fleamarkets for next to nothing as many of the cell towers are
                    > removing it due to new equipment configurations! My loop uses about 19 ft of Heliax and a dual
                    > gang air variable cap turned by a DC motor feed over the coax from a MFJ loop control box! Very
                    > simple but effective! I also use the MFJ loops, the 20-10m one is a good performer and easy to
                    > use!!
                    >
                    > If you would like more info on how to make one for 160m Google "vk4amz" as he has a nice web site
                    > describing his 160m loop. I've seen his and have heard him on the air. He does extremely well
                    > compared to other stations using full size antennae!
                    >
                    > Main thing is don't be discouraged, just go ahead and try it as I guarantee you will be impressed
                    > by the performance of a well built loop!
                    >
                    > Cheers!
                    > VK4ERQ/VE3ERQ
                    >
                    >Hiya
                    Well my loop is up in the garden now, and works surprisingly well.
                    Its just under 4 mtrs dia, made from LDF4-50, which interfaces with 15mm Cu water pipe for the
                    end terminations ect.At the moment I'm using a single 100 pF doorknob cab, which centers it on
                    3.755 MHz.I now have the motor to drive a 100pF vacuum variable cap which is rated at 10Kv ,
                    that'll allow 400W to be used.
                    Still trying to sort out the cap mounting which has to be rock solid, or the belt drive to the motor
                    will slip, and getting a position indicator back in the shack.
                    --
                    Best wishes

                    Richard Bown

                    ###################################################################################
                    Registered Linux User 36561
                    OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
                    Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
                    ###################################################################################
                  Your message has been successfully submitted and would be delivered to recipients shortly.