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New Loop

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  • Michael Stevenson
    This past weekend saw my new loop antenna mounted on a short metal mast firmly cemented into the ground in the middle of my backyard, on top of this mast is a
    Message 1 of 18 , Aug 9, 2004
      This past weekend saw my new loop antenna mounted on a short metal mast firmly cemented into the ground in the middle of my backyard, on top of this mast is a rotator then the PVC mast that the loop is mounted to. The loop has remote tuning using a geared motor on old fashioned dual gang tuning capacitor with a relay for remote switching of the extra capacitance to enable the loop to cover the lower tropical bands of 90 and 120 metres. It also has a preamp. I have run the 5 cables under ground through 19 mm plastic tubing. I have yet to finish the control box to be able to do final testing of the loop in it's new position (it worked most impressively inside my DX shack running through the 23 metres of cable) and I have to mount plastic clothes line guy wires just above the rotator just to stabilise it during periods of high winds.
      I will post results and photos into this group once it is all fully finished.
      Best regards!
       
      Michael Stevenson,
      Australia.
    • dean_0_way
      After messing around with a mini Bog wire antenna for a few day s i started to think of my next project; I have a crawl space in the upper part of the house
      Message 2 of 18 , Aug 11, 2009
        After messing around with a mini Bog wire antenna for a few day's i started to think of my next project;

        I have a crawl space in the upper part of the house that would be a nice place for a Bigger Loop,so in preperation for that ,today i built a 3 foot loop with 4 inch wood ,added 8 turns of 18 ga. insulated wire ,and an old 2 stage tuning cap.

        I went outside with it for the first test,in the middle of the afternoon it will clearly bring in stations of the 5000w range from 300-400 miles away,also had one from 200 miles away that is a 500w.

        But as you might suspect my old nemesis is back ,besides the home freg. I now have several harmonics above and below 1350 ,so what i'm wondering is if there is a way to block that 1350khz signal,and if that's possible will it also kill the harmonics?

        Iv'e been looking around for a fix but have'nt come up with a great fix so far .

        Tonight I will test it again after my local powers down but i'm sure the results will be about the same,and i want to see how far i can push this loop. :)

        If i can get some magic bullet for this problem i'm going to build a second loop and try to phase them both in the crawl space,as soon as i figure a way to adjust the tuning cap from 10 feet away ? lol :\

        Any help appreciated Thanks

        Dean_0
      • Jim Dunstan
        ... Hi, Not sure what you mean about harmonics and how they relate to 1350 khz. .... e.g. your nemesis . Is it a strong station on 1350 that appears on your
        Message 3 of 18 , Aug 11, 2009
          At 11:29 PM 8/11/2009 +0000, you wrote:


          >But as you might suspect my old nemesis is back ,besides the home freg. I
          >now have several harmonics above and below 1350 ,so what i'm wondering is
          >if there is a way to block that 1350khz signal,and if that's possible will
          >it also kill the harmonics?
          >
          >Iv'e been looking around for a fix but have'nt come up with a great fix so
          >far .

          Hi,

          Not sure what you mean about harmonics and how they relate to 1350
          khz. .... e.g. 'your nemesis'. Is it a strong station on 1350 that
          appears on your receiver at other points on the dial ??? . Either the
          station is overloading your receiver front end and/or the image is coming
          through. What you describe sounds like a receiver problem. 1350 khz can't
          be a harmonic since the fundamental would have to be 675 and stations are
          assigned at 10khz intervals ... e.g. either 670 khz or 680 khz. If the
          station is on 1350 then the harmonic would be 2700 khz ... way out of the
          MW broadcast band.

          Describe what you are hearing. Forgive me if you have already done so.

          Jim
        • dean_0_way
          ... The station is at 1350 khz and a block and a half from my house ,the harmonics i refered to was i get that station on 1280 and several places above 1350,so
          Message 4 of 18 , Aug 11, 2009
            > Hi,
            >
            > Not sure what you mean about harmonics and how they relate to 1350
            > khz. .... e.g. 'your nemesis'. Is it a strong station on 1350 that
            > appears on your receiver at other points on the dial ??? . Either the
            > station is overloading your receiver front end and/or the image is coming
            > through. >
            > Describe what you are hearing. Forgive me if you have already done so.
            >
            > Jim
            >
            The station is at 1350 khz and a block and a half from my house ,the harmonics i refered to was i get that station on 1280 and several places above 1350,so i think your right about overload,as you might have guessed i'm putting big antennas on smaller radio's to get distant DX ,just to compare i have a 2100 kaito with a 16 inch tuned loop on it and sometimes it does the same thing although not as bad,

            Beside this station my nearset other AM station is 70 miles away so you can see i have a pretty tuff time getting enough gain to recieve far away, with this flame thrower in my back yard, he heh.


            But i thought with a little black magic i might figure it out ?
            Besides i don't have enything else interesting to do :\

            thanks ,
            Dean_0
          • Notareal
            Hi ! Have you thought about using band-stop filter or band-rejection filter for that frequency ? BR ...
            Message 5 of 18 , Aug 12, 2009
              Hi !

              Have you thought about using band-stop filter or band-rejection filter for that frequency ?

              BR



              > To: loopantennas@yahoogroups.com
              > From: dean_0_way@...
              > Date: Wed, 12 Aug 2009 05:22:32 +0000
              > Subject: [loopantennas] Re: New Loop
              >
              > > Hi,
              > >
              > > Not sure what you mean about harmonics and how they relate to 1350
              > > khz. .... e.g. 'your nemesis'. Is it a strong station on 1350 that
              > > appears on your receiver at other points on the dial ??? . Either the
              > > station is overloading your receiver front end and/or the image is coming
              > > through. >
              > > Describe what you are hearing. Forgive me if you have already done so.
              > >
              > > Jim
              > >
              > The station is at 1350 khz and a block and a half from my house ,the harmonics i refered to was i get that station on 1280 and several places above 1350,so i think your right about overload,as you might have guessed i'm putting big antennas on smaller radio's to get distant DX ,just to compare i have a 2100 kaito with a 16 inch tuned loop on it and sometimes it does the same thing although not as bad,
              >
              > Beside this station my nearset other AM station is 70 miles away so you can see i have a pretty tuff time getting enough gain to recieve far away, with this flame thrower in my back yard, he heh.
              >
              >
              > But i thought with a little black magic i might figure it out ?
              > Besides i don't have enything else interesting to do :\
              >
              > thanks ,
              > Dean_0
              >
              >
              >
              > ------------------------------------
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              _________________________________________________________________
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              [Non-text portions of this message have been removed]
            • Ya`akov N. Miles
              ... [--CUT--] ... Sorry, I don t see why a big loop is required for RECEIVING. I have a six transistor AM-only Radio (500-2000 KiloCycles/sec) that picks up
              Message 6 of 18 , Aug 12, 2009
                --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@...> wrote:
                >
                > After messing around with a mini Bog wire antenna for a few day's
                > started to think of my next project;
                >
                > I have a crawl space in the upper part of the house that would be
                > a nice place for a Bigger Loop,so in preperation for that ,today I
                > built a 3 foot loop with 4 inch wood ,added 8 turns of 18 ga.
                > insulated wire ,and an old 2 stage tuning cap.
                >
                [--CUT--]
                > Dean_0
                >

                Sorry, I don't see why a big loop is required for RECEIVING.
                I have a six transistor AM-only Radio (500-2000 KiloCycles/sec)
                that picks up stations from all over North America when I use
                it here in my ground floor suite in this multi-story wood frame
                apartment building. The loop antenna is a small multi-turn
                loop wound on a Ferrite (Ferrite is Magnetic) 1/2 inch diameter
                rod. Please note the difference between CAPTURE AREA
                (i.e. how much signal an antenna "brings in") as opposed to
                the SIGNAL/NOISE ratio. A deficit in CAPTURE AREA can usually
                be made up with a high gain low noise solid-state preamplifier.
                In my case of my portable "PLAY-MATE" six transistor AM-only
                radio, the loop is HIGH-Q (very low loss) and is tuned in
                tandem with the oscillator by the two-gang capacitor in the
                radio. (One gang for Loop, one gang for Heterodyne Oscillator)

                Receiving loops do NOT have to be efficient. Transmitting loops
                do, so they are usually bigger. For info on Transmitting loops

                http://members.shaw.ca/yehudi2/loop.html

                73 de Yakov, VE7ALQ - Same Callsign since 1969, Fists #11117

                - Where radios are DC, not AC/DC or AC

                http://members.shaw.ca/yehudi2/tim.jpg << When I was little.

                http://www.yaakov.ca << When I grew up. Scared of me, U.S.A.?
              • gmcjetpilot
                ... What kind of super radio is that Playmate ? The only one I found that was close with the name playmate. http://www.richardsradios.co.uk/playmate.html ...
                Message 7 of 18 , Aug 12, 2009
                  > "I have a six transistor AM-only Radio (500-2000 KiloCycles/sec)
                  > that picks up stations from all over North America when I use
                  > it here in my ground floor suite in this multi-story wood frame
                  > apartment building."

                  >"PLAY-MATE" six transistor AM-only radio"

                  What kind of super radio is that "Playmate"?
                  The only one I found that was close with the name playmate.

                  http://www.richardsradios.co.uk/playmate.html

                  >"500-2000 KiloCycles/sec" That is an Odd range I have never heard in AM radios. Is that a European thing? How old is this thing?

                  Please tell us more, where do you live and what stations have you logged. I am impressed if its all over North America. I'm going to get one of those playmates. Also could you give the design specs for that super loop you have. I'd like to replicate it.

                  I have a tiny pocked Realistic AM/FM radio (late 1990's) with digital tune. With my Terk AM Advantage 9" loop I can tune in some impressive MW DX stations. The internal loop stick is 2.5" long (may be even closer to 2").

                  What do you have against large loop antennas? The larger loop also serves in other aspects, such as LF reception. Many people DX with crystal radios or one tube radios. If the conditions are right you can do amazing things with basic receivers and antennas.

                  Cheers George

                  PS that is a serious home page you have.




                  --- In loopantennas@yahoogroups.com, "Ya`akov N. Miles" <ve7alq@...> wrote:
                  >
                  > Sorry, I don't see why a big loop is required for RECEIVING.
                  > I have a six transistor AM-only Radio (500-2000 KiloCycles/sec)
                  > that picks up stations from all over North America when I use
                  > it here in my ground floor suite in this multi-story wood frame
                  > apartment building. The loop antenna is a small multi-turn
                  > loop wound on a Ferrite (Ferrite is Magnetic) 1/2 inch diameter
                  > rod. Please note the difference between CAPTURE AREA
                  > (i.e. how much signal an antenna "brings in") as opposed to
                  > the SIGNAL/NOISE ratio. A deficit in CAPTURE AREA can usually
                  > be made up with a high gain low noise solid-state preamplifier.
                  > In my case of my portable "PLAY-MATE" six transistor AM-only
                  > radio, the loop is HIGH-Q (very low loss) and is tuned in
                  > tandem with the oscillator by the two-gang capacitor in the
                  > radio. (One gang for Loop, one gang for Heterodyne Oscillator)
                  >
                  > Receiving loops do NOT have to be efficient. Transmitting loops
                  > do, so they are usually bigger. For info on Transmitting loops
                  >
                  > http://members.shaw.ca/yehudi2/loop.html
                  >
                  > 73 de Yakov, VE7ALQ - Same Callsign since 1969, Fists #11117
                  >
                  > - Where radios are DC, not AC/DC or AC
                  >
                  > http://members.shaw.ca/yehudi2/tim.jpg << When I was little.
                  >
                  > http://www.yaakov.ca << When I grew up. Scared of me, U.S.A.?
                  >
                • Jim Dunstan
                  ... Hi Dean_O I understand your problem and empathize with you. At my location ... I have no local MW broadcast stations within a couple of hundred miles!!
                  Message 8 of 18 , Aug 12, 2009
                    At 05:22 AM 8/12/2009 +0000, you wrote:



                    > > khz. .... e.g. 'your nemesis'. Is it a strong station on 1350 that
                    > > appears on your receiver at other points on the dial ??? . Either the
                    > > station is overloading your receiver front end and/or the image is coming
                    > > through. >
                    > > Describe what you are hearing. Forgive me if you have already done so.
                    > >
                    > > Jim
                    > >
                    >The station is at 1350 khz and a block and a half from my house ,the
                    >harmonics i refered to was i get that station on 1280 and several places
                    >above 1350,so i think your right about overload,as you might have guessed
                    >i'm putting big antennas on smaller radio's to get distant DX ,just to
                    >compare i have a 2100 kaito with a 16 inch tuned loop on it and sometimes
                    >it does the same thing although not as bad,
                    >
                    >Beside this station my nearset other AM station is 70 miles away so you
                    >can see i have a pretty tuff time getting enough gain to recieve far away,
                    >with this flame thrower in my back yard, he heh.
                    >
                    >But i thought with a little black magic i might figure it out ?
                    >Besides i don't have enything else interesting to do :\
                    >
                    >thanks ,
                    >Dean_O


                    Hi Dean_O

                    I understand your problem and empathize with you. At my location ... I
                    have no local MW broadcast stations within a couple of hundred miles!! MW
                    DXing is a pleasure. back to your problem. If you want to work DX on MW
                    with a strong local station the ideal receiving combination would be as
                    follows:

                    1. A receiver WITHOUT a built-in ferrite loop antenna .... or at least
                    disconnects the ferrite loop antenna when you plug in an external antenna.
                    2. Construct or purchase a HI-Q band pass filter (pre-selector) which can
                    be placed between your external antenna and your receiver antenna input.
                    3. Construct your external loop (not too big ... and located where you can
                    adjust both orientation and coupling to the receiver)
                    4. You could make 2 similar loops .... The first loop that tunes the
                    desired station must be oriented for maximum null on the 1350
                    station. Jiggle orientation and tuning for best reception of DX
                    station. The second loop can then be oriented in relation to the first
                    loop and tuned to the 1350 station. Jiggle orientation and tuning to
                    minimize 1350 reception. In other words, the second loop is simply brought
                    into the vicinity of the first loop and will 'suck out 1350 signals. This
                    is an old trick used by crystal set radio aficionados.

                    When you 'jiggle' the tuning in the second loop you are adjusting the phase
                    of the 1350 signal such that one loop field cancels the other loop
                    field. There is commercial gear available that will accomplish this ...
                    and they are advertised as noise cancelling devices. MFJ makes such a device.

                    Between nulling and phasing your 2 small loops the DX station is maximized
                    and the interfering station is maximized. Ideally the first loop would be
                    coupled to the radio via the preselector. However if your radio has a
                    ferrite loop then it will be inductively coupled to the loops and will have
                    to 'jiggled' as well.

                    Jim
                  • dean_0_way
                    ... There yaa go! now we are on the right track . Thanks Dean_0
                    Message 9 of 18 , Aug 12, 2009
                      --- In loopantennas@yahoogroups.com, Notareal <not_a_real@...> wrote:
                      >
                      >
                      > Hi !
                      >
                      > Have you thought about using band-stop filter or band-rejection filter for that frequency ?
                      >
                      > BR
                      >
                      There yaa go! now we are on the right track .

                      Thanks

                      Dean_0
                    • dean_0_way
                      ... OK now along with my other problem........ I m jealous -Hahah ... 2. Construct or purchase a HI-Q band pass filter (pre-selector) which can be placed
                      Message 10 of 18 , Aug 12, 2009
                        --- In loopantennas@yahoogroups.com, Jim Dunstan <jimdunstan@...> wrote:
                        > I understand your problem and empathize with you. At my location ... I
                        > have no local MW broadcast stations within a couple of hundred miles!! MW
                        > DXing is a pleasure.
                        -------------
                        OK now along with my other problem........ I'm jealous -Hahah
                        -------------
                        2. Construct or purchase a HI-Q band pass filter (pre-selector) which can
                        be placed between your external antenna and your receiver antenna input.
                        ------------
                        Thanks ..this is the direction i'm going with this idea,i was hoping to avoid buying a bunch of stuff ,but a phaser and a few other things are on my wish list ;\

                        thanks all

                        Dean-0
                      • dean_0_way
                        ... I did some more research and it looks like what i might need is a notch filter ? Dean-0
                        Message 11 of 18 , Aug 12, 2009
                          --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@...> wrote:
                          >
                          > --- In loopantennas@yahoogroups.com, Notareal <not_a_real@> wrote:
                          > >
                          > >
                          > > Hi !
                          > >
                          > > Have you thought about using band-stop filter or band-rejection filter for that frequency ?
                          > >
                          > > BR
                          > >
                          > There yaa go! now we are on the right track .
                          >
                          > Thanks
                          >
                          > Dean_0
                          >
                          I did some more research and it looks like what i might need is a notch filter ?
                          Dean-0
                        • Hiram
                          Dean-o, I think a simple filter can be made with a coil and variable cap in series with the antenna (that is, between the antenna and radio, coil and cap in
                          Message 12 of 18 , Aug 12, 2009
                            Dean-o,
                            I think a simple filter can be made with a coil and variable cap in series with the antenna (that is, between the antenna and radio, coil and cap in series with each other) and tuning the variable to null out the offending station. I read this somewhere, but my computer is in the shop and all my links, etc. are on it. Capacitor should be standard 365Pf variable, coil can be anything that will resonate on the BC band, a small ferrite from an old radio would probably work. However, if it's overloading the front end of your radio and getting into the IF stage, then this probably won't work!
                            Then I would try to shield the whole radio; if it's small enough, you could put it in a cookie tin or similar, if it's big, you could foil the inside, just make sure the foil doesn't short out to anything, and make sure it's grounded.

                            Some things to try, anyway. Good luck and keep us informed,

                            Pappy Hiram






                            --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@...> wrote:
                            >
                            > --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@> wrote:
                            > >
                            > > --- In loopantennas@yahoogroups.com, Notareal <not_a_real@> wrote:
                            > > >
                            > > >
                            > > > Hi !
                            > > >
                            > > > Have you thought about using band-stop filter or band-rejection filter for that frequency ?
                            > > >
                            > > > BR
                            > > >
                            > > There yaa go! now we are on the right track .
                            > >
                            > > Thanks
                            > >
                            > > Dean_0
                            > >
                            > I did some more research and it looks like what i might need is a notch filter ?
                            > Dean-0
                            >
                          • gmcjetpilot
                            The first person to mentioned band pass filters, rightly so, gold star for them. You can build a band-pass or band-stop/notch, low, high for that freq.
                            Message 13 of 18 , Aug 13, 2009
                              The first person to mentioned band pass filters, rightly so, gold star for them. You can build a band-pass or band-stop/notch, low, high for that freq.

                              http://en.wikipedia.org/wiki/Band-pass_filter

                              Lots of info on the web. There are plans to make a filter box with selectable freq. This goes on the front end.

                              Try making some filters, they are easy to make.
                              http://www.arrl.org/tis/info/rf-filter.html
                              http://focus.ti.com/lit/an/sloa093/sloa093.pdf

                              There could be some local RFI on that freq. Have you tried to hunt it down, Direction find or is it omnipresent? Have you tried different radios?

                              I have two strong MW stations near my home at 850KHz 3 miles (10KW Day 5 KW Night) ... AND ... 680 KHz 6.6 mile due East (50KW Clear channel, Omni day, N-S Night). Thankfully at night they go directional (I'm to the side of pattern) or drop power in half. Surprisingly they don't cause much problem; except I forget DX'ing any stations on those exact two freq, especially to the West or S-West and N-West, which is too bad. A loop is great, but if I point it West, it is pointing East as well. When I point my Loop more or less N-S the two strong stations to the East almost disappeared. YEA for LOOPS!


                              May be I can get a omni directional antenna, but my loops have classic bi-directional semi omni patterns. If I point them West they are pointing right at these stations East. There are stations on these two freq to the West in TX, MO, IA, GA, NM, MT, CA, WA I just can't get. When the stations are North or South no problem with the loop and good radio.

                              These stations don't cause to much problems for me with a loop antenna an a digital PPL Dual conversion radio with a dozen internal RF microprocessor controlled filters and selectable band width, I don't have problems.

                              However with my old 1940's and 50's tube radios (just Zenith AM/FM, no super SW boat-anchors), there are intermodulation issues and may be image rejection issues. Superhet radios have good qualities but some draw backs. You may know all about superheterodyne radio design. I am no expert but Image response or image response rejection ratio (IMRR) can cause problems. If you have an issue with 1350Khz the problem may be 455Khz lower, say at 890Khz or 900Khz. Is this a problem on all your radios? What kind of radios do you have? Do you have a strong station nearby (radio-locator.com).

                              Also Graveyard channels, where lots of low powered stations operate, typically 1220-1500khz, 1230, 1240, 1340, 1400, 1450, and 1490khz, makes a mess at night anyway. 1350Khz is in that ball park.

                              Cheers


                              --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@...> wrote:
                              >
                              > After messing around with a mini Bog wire antenna for a few day's i started to think of my next project;
                              >
                              > I have a crawl space in the upper part of the house that would be a nice place for a Bigger Loop,so in preperation for that ,today i built a 3 foot loop with 4 inch wood ,added 8 turns of 18 ga. insulated wire ,and an old 2 stage tuning cap.
                              >
                              > I went outside with it for the first test,in the middle of the afternoon it will clearly bring in stations of the 5000w range from 300-400 miles away,also had one from 200 miles away that is a 500w.
                              >
                              > But as you might suspect my old nemesis is back ,besides the home freg. I now have several harmonics above and below 1350 ,so what i'm wondering is if there is a way to block that 1350khz signal,and if that's possible will it also kill the harmonics?
                              >
                              > Iv'e been looking around for a fix but have'nt come up with a great fix so far .
                              >
                              > Tonight I will test it again after my local powers down but i'm sure the results will be about the same,and i want to see how far i can push this loop. :)
                              >
                              > If i can get some magic bullet for this problem i'm going to build a second loop and try to phase them both in the crawl space,as soon as i figure a way to adjust the tuning cap from 10 feet away ? lol :\
                              >
                              > Any help appreciated Thanks
                              >
                              > Dean_0
                              >
                            • airchecklover
                              Like Jim suggests, I use a 2ft multi-turn loop and a CCrane Twin-Ferrite. The T-F direct connects to the radio, the head of the T-F is placed very close to
                              Message 14 of 18 , Aug 13, 2009
                                Like Jim suggests, I use a 2ft multi-turn loop and a CCrane Twin-Ferrite. The T-F direct connects to the radio, the head of the T-F is placed very close to the loop. I play one pickup pattern atgainst the other and can null two stations which are physically only 30 degrees apart. That's impressive. Yes, it takes some "jiggling" but not only do I get super-tight nulls, the gain from the two antennas is literally 1+1 (doubling gain of either single antenna) and since both loops are tuned circuits, I get no overloading or image problems.


                                -Mark

                                ================================

                                > Hi Dean_O
                                >
                                > I understand your problem and empathize with you. At my location ... I
                                > have no local MW broadcast stations within a couple of hundred miles!! MW
                                > DXing is a pleasure. back to your problem. If you want to work DX on MW
                                > with a strong local station the ideal receiving combination would be as
                                > follows:
                                >
                                > 1. A receiver WITHOUT a built-in ferrite loop antenna .... or at least
                                > disconnects the ferrite loop antenna when you plug in an external antenna.
                                > 2. Construct or purchase a HI-Q band pass filter (pre-selector) which can
                                > be placed between your external antenna and your receiver antenna input.
                                > 3. Construct your external loop (not too big ... and located where you can
                                > adjust both orientation and coupling to the receiver)
                                > 4. You could make 2 similar loops .... The first loop that tunes the
                                > desired station must be oriented for maximum null on the 1350
                                > station. Jiggle orientation and tuning for best reception of DX
                                > station. The second loop can then be oriented in relation to the first
                                > loop and tuned to the 1350 station. Jiggle orientation and tuning to
                                > minimize 1350 reception. In other words, the second loop is simply brought
                                > into the vicinity of the first loop and will 'suck out 1350 signals. This
                                > is an old trick used by crystal set radio aficionados.
                                >
                                > When you 'jiggle' the tuning in the second loop you are adjusting the phase
                                > of the 1350 signal such that one loop field cancels the other loop
                                > field. There is commercial gear available that will accomplish this ...
                                > and they are advertised as noise cancelling devices. MFJ makes such a device.
                                >
                                > Between nulling and phasing your 2 small loops the DX station is maximized
                                > and the interfering station is maximized. Ideally the first loop would be
                                > coupled to the radio via the preselector. However if your radio has a
                                > ferrite loop then it will be inductively coupled to the loops and will have
                                > to 'jiggled' as well.
                                >
                                > Jim
                                >
                              • dean_0_way
                                ... Ok great maybe when you get your machine back if you have a link you can post it for me? Thanks for all the info guy s i found many of the same links that
                                Message 15 of 18 , Aug 13, 2009
                                  --- In loopantennas@yahoogroups.com, "Hiram" <daveleb55@...> wrote:
                                  >
                                  > Dean-o,
                                  > I think a simple filter can be made with a coil and variable cap in series with the antenna
                                  >
                                  > Pappy Hiram
                                  >
                                  Ok great maybe when you get your machine back if you have a link you can post it for me?

                                  Thanks for all the info guy's i found many of the same links that were posted ,the only problem is that i am schematically challenged , or was that schematic A-D-D? ;0

                                  Dean_0
                                • jr_dakota
                                  That s pretty much how I built mine, I bought a 3 dollar radio at a dollar store and took out the loopstick and tuning cap since it s already set up to tune
                                  Message 16 of 18 , Aug 16, 2009
                                    That's pretty much how I built mine, I bought a 3 dollar radio at a dollar store and took out the loopstick and tuning cap since it's already set up to tune the AM band and placed them in series between the antenna feedpoint and ground

                                    I would recommend putting it in a shielded box and place it right at the feedpoint of the antenna ... It'll be outdoors but you only need to tune it once so that's not a big deal

                                    The notch will be kinda broad so you'll lose a station or two just below and just above the target station .... If you need a narrower notch then you need a higher Q inductor/coil like an aircore wound on a piece of 1 1/2" PVC

                                    But for most people the ferrite loopstick will do just fine

                                    JR

                                    --- In loopantennas@yahoogroups.com, "Hiram" <daveleb55@...> wrote:
                                    >
                                    > Dean-o,
                                    > I think a simple filter can be made with a coil and variable cap in series with the antenna (that is, between the antenna and radio, coil and cap in series with each other) and tuning the variable to null out the offending station. I read this somewhere, but my computer is in the shop and all my links, etc. are on it. Capacitor should be standard 365Pf variable, coil can be anything that will resonate on the BC band, a small ferrite from an old radio would probably work. However, if it's overloading the front end of your radio and getting into the IF stage, then this probably won't work!
                                    > Then I would try to shield the whole radio; if it's small enough, you could put it in a cookie tin or similar, if it's big, you could foil the inside, just make sure the foil doesn't short out to anything, and make sure it's grounded.
                                    >
                                    > Some things to try, anyway. Good luck and keep us informed,
                                    >
                                    > Pappy Hiram
                                    >
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@> wrote:
                                    > >
                                    > > --- In loopantennas@yahoogroups.com, "dean_0_way" <dean_0_way@> wrote:
                                    > > >
                                    > > > --- In loopantennas@yahoogroups.com, Notareal <not_a_real@> wrote:
                                    > > > >
                                    > > > >
                                    > > > > Hi !
                                    > > > >
                                    > > > > Have you thought about using band-stop filter or band-rejection filter for that frequency ?
                                    > > > >
                                    > > > > BR
                                    > > > >
                                    > > > There yaa go! now we are on the right track .
                                    > > >
                                    > > > Thanks
                                    > > >
                                    > > > Dean_0
                                    > > >
                                    > > I did some more research and it looks like what i might need is a notch filter ?
                                    > > Dean-0
                                    > >
                                    >
                                  • Joe
                                    Hi All, After much time spent thinking about loop antennas I finally got to build one. The loop I built is a 36 inch diameter loop of 3/8 inch soft copper
                                    Message 17 of 18 , May 23, 2010
                                      Hi All,

                                      After much time spent thinking about loop antennas I finally got to build one.

                                      The loop I built is a 36 inch diameter loop of 3/8 inch soft copper tubing. I
                                      am feeding it with a wire loop. (not a faraday shield).
                                      I also built a stand which holds the bottom of the loop about 4 feet off the
                                      floor. The cap I used is a two gang cap with the gangs connected in series so I
                                      do not go thru any wiper connections.

                                      I placed the feed loop at the top so I could get to the cap better for tuning.

                                      The results of this loop and the cap I used are:

                                      Tunes from 20 meters to 10 meters with a SWR on 20 meters of 1.1:1 and it goes
                                      up until I get to 10 meters where it is 1.5:1. I have not been able to get the
                                      SWR flat across this frequency spread.

                                      So far I have not made any contacts with it. On receive it seems to be about 1
                                      S unit below my attic antennas. (I live in a restricted area and cannot have
                                      outside antennas.)

                                      With the cap I am using I cannot use output power over 20 watts. I guess this
                                      will be my QRP antenna to use with my FT-817. I hope to use it portable in
                                      local parks. The stand I built is of Schedule 40 PVC pipe. I built it so I can
                                      take it apart in a few sections to make it easy for transporting.

                                      I would be interested in hearing any comments from other users of this type of
                                      antenna.

                                      73 ... Joe/K2ZFD
                                    • Richard Harrison
                                      Joe: Pls keep me/us informed of your progress with the ft-817 and loop. I plan on also using a ft-817 and building the same size loop for use during Field
                                      Message 18 of 18 , May 24, 2010
                                        Joe: Pls keep me/us informed of your progress with the ft-817 and loop. I plan on also using a ft-817 and building the same size loop for use during Field Day.

                                        de Rich/N2JR

                                        With the cap I am using I cannot use output power over 20 watts. I guess this
                                        will be my QRP antenna to use with my FT-817. I hope to use it portable in
                                        local parks. The stand I built is of Schedule 40 PVC pipe. I built it so I can
                                        take it apart in a few sections to make it easy for transporting.

                                        I would be interested in hearing any comments from other users of this type of
                                        antenna.

                                        73 ... Joe/K2ZFD

                                        From my iPad...R. Harrison



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