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SWL Loop

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  • blacklabpupp
    Hi Since I joined the group I have poured over the Files page and gathered quite a bit of info. My goal is for a loop antenna for SWLing from 3-30 meg.
    Message 1 of 13 , Feb 4, 2009
      Hi
      Since I joined the group I have poured over the Files page and gathered
      quite a bit of info. My goal is for a loop antenna for SWLing from 3-30
      meg. Everything I have built has not come up to the promised results. I
      am in the process of constructing another loop, but I want something
      that is not so lousy on higher bands. Does anyone have any ideas what I
      should do? All the best Curtis
    • kevin asato
      What type of receiver are you using? How are you coupling to the radio? What type of signals are you expecting to receive? What higher bands? Indoor loop?
      Message 2 of 13 , Feb 5, 2009
        What type of receiver are you using? How are you coupling to the radio?
        What type of signals are you expecting to receive?
        What higher bands?
        Indoor loop? Outdoor loop?

        Just trying to find out why "it does not work" means. I'm not the expert but this is how I go about trying to resolve problems during my day job.

        73,
        kevin
        kc6pob

        --- On Wed, 2/4/09, blacklabpupp <blacklabpupp@...> wrote:
        From: blacklabpupp <blacklabpupp@...>
        Subject: [loopantennas] SWL Loop
        To: loopantennas@yahoogroups.com
        Date: Wednesday, February 4, 2009, 9:38 PM












        Hi

        Since I joined the group I have poured over the Files page and gathered

        quite a bit of info. My goal is for a loop antenna for SWLing from 3-30

        meg. Everything I have built has not come up to the promised results. I

        am in the process of constructing another loop, but I want something

        that is not so lousy on higher bands. Does anyone have any ideas what I

        should do? All the best Curtis


































        [Non-text portions of this message have been removed]
      • blacklabpupp
        I am using a Palstar 30A. There is nothing wrong with the radio as far as I can tell. I also have and older Yaesu FRG 7 recently checked out and claimed it was
        Message 3 of 13 , Feb 5, 2009
          I am using a Palstar 30A. There is nothing wrong with the radio as far
          as I can tell. I also have and older Yaesu FRG 7 recently checked out
          and claimed it was in fine shape. I made a small 24" loop and was not
          impressed by the performance. I dont know if I am in a poor area for
          reception, but things were alot better before I moved. I have tried a
          longwire and the noise was to much. I placed a tuner in line, placed a
          balun in line, changed to a dipole. My former neighbor used a loop on
          20 daily. He talked me into trying a loop. I am in the process of
          setting up a loop for contact on 20 as well. But some how I am not so
          sure this is going to work with such poor success of the receiving
          loop. I reall enjoy following SWL broadcast and CW on 20 but with the
          situation now I am not sure it can be over come. Curtis
        • jr_dakota
          It will probably take two tuned loops to cover that range .... You can gain some low end range on a loop that will tune to 30Mhz by placing an equal or
          Message 4 of 13 , Feb 5, 2009
            It will probably take two tuned loops to cover that range .... You can
            gain some low end range on a loop that will tune to 30Mhz by placing
            an equal or slightly smaller value cap in parallel with the existing
            tuning cap (A larger value cap could be used to go lower but your
            ranges won't overlap) Or you can put two variables in parallel which
            is slightly better because it doesn't spoil the Q as much

            Another option would be to make a multi turn loop (maybe 2 or 3 turns)
            and switch turns in and out.. For example 2 turns for the low band and
            one turn for the upper ... again you have the same p[oblem with lower
            Q as the number of turns rise but it doesn't seem to be as bad as with
            the parallel cap option .... Extra turns and/or capacitance also
            affect the nulls but a loop's null isn't all that great at above 30 or
            40 meters anyway

            JR


            --- In loopantennas@yahoogroups.com, "blacklabpupp" <blacklabpupp@...>
            wrote:
            >
            > Hi
            > Since I joined the group I have poured over the Files page and gathered
            > quite a bit of info. My goal is for a loop antenna for SWLing from 3-30
            > meg. Everything I have built has not come up to the promised results. I
            > am in the process of constructing another loop, but I want something
            > that is not so lousy on higher bands. Does anyone have any ideas what I
            > should do? All the best Curtis
            >
          • tmartin831@aol.com
            Have you tried a Ray Moore tunable loop? They are tough to find now...I think Ray has long since passed on. In a message dated 2/5/2009 12:52:31 A.M. Eastern
            Message 5 of 13 , Feb 5, 2009
              Have you tried a Ray Moore tunable loop? They are tough to find now...I
              think Ray has long since passed on.


              In a message dated 2/5/2009 12:52:31 A.M. Eastern Standard Time,
              blacklabpupp@... writes:

              Since I joined the group I have poured over the Files page and gathered
              quite a bit of info. My goal is for a loop antenna for SWLing from 3-30
              meg. Everything I have built has not come up to the promised results. I
              am in the process of constructing another loop, but I want something
              that is not so lousy on higher bands. Does anyone have any ideas what I
              should do?

              **************Stay up to date on the latest news - from sports scores to
              stocks and so much more. (http://aol.com?ncid=emlcntaolcom00000022)


              [Non-text portions of this message have been removed]
            • John Hoopes
              May I suggest in your case to give up the loop idea and put up an active E-probe or active whip antenna as high and in the clear as you can get it, preferably
              Message 6 of 13 , Feb 5, 2009
                May I suggest in your case to give up the loop idea and put up an active E-probe or active whip antenna as high and in the clear as you can get it, preferably on the roof above all the surrounding noise. If you can lay a chicken wire ground screen around it (10X10 square) and tie it to the shield of the coax, it would help in preventing near field noise from entering the probe from below.

                Active whips are very broad banded. Usually from 100 kHz to 30 MHz and should satisfy your need.

                John

                --- On Thu, 2/5/09, blacklabpupp <blacklabpupp@...> wrote:
                From: blacklabpupp <blacklabpupp@...>
                Subject: [loopantennas] Re: SWL Loop
                To: loopantennas@yahoogroups.com
                Date: Thursday, February 5, 2009, 4:02 AM












                I am using a Palstar 30A. There is nothing wrong with the radio as far

                as I can tell. I also have and older Yaesu FRG 7 recently checked out

                and claimed it was in fine shape. I made a small 24" loop and was not

                impressed by the performance. I dont know if I am in a poor area for

                reception, but things were alot better before I moved. I have tried a

                longwire and the noise was to much. I placed a tuner in line, placed a

                balun in line, changed to a dipole. My former neighbor used a loop on

                20 daily. He talked me into trying a loop. I am in the process of

                setting up a loop for contact on 20 as well. But some how I am not so

                sure this is going to work with such poor success of the receiving

                loop. I reall enjoy following SWL broadcast and CW on 20 but with the

                situation now I am not sure it can be over come. Curtis


































                [Non-text portions of this message have been removed]
              • Jim Dunstan
                ... Hi Curtis, When I was in the big city for several years in an apartment situation I used such a loop for SWL. I tried a number of different arrangements.
                Message 7 of 13 , Feb 5, 2009
                  At 05:38 AM 2/5/2009 +0000, you wrote:

                  >Hi
                  >Since I joined the group I have poured over the Files page and gathered
                  >quite a bit of info. My goal is for a loop antenna for SWLing from 3-30
                  >meg. Everything I have built has not come up to the promised results. I
                  >am in the process of constructing another loop, but I want something
                  >that is not so lousy on higher bands. Does anyone have any ideas what I
                  >should do? All the best Curtis

                  Hi Curtis,

                  When I was in the big city for several years in an apartment situation I
                  used such a loop for SWL. I tried a number of different arrangements.

                  The criteria I required:

                  must be tuned to provide maximum Q and thus selectivity and noise reduction.
                  must be directional ... e.g. have a sharp null to reduce local noise.
                  must be able to be tuned from a small distance as I wanted to locate the
                  antenna out on the balcony.

                  Here's how it works:

                  I formed a loop with light copper tubing .. perhaps 1/4 in. The diameter
                  of the loop was approx. 2.5 to 3 ft. (not critical)
                  I supported the loop on wood sticks everything held together with
                  electrical tie wraps (great invention)
                  I fed the loop with balanced feed line (TV twin lead)

                  I used if from about 4 mhz tropical band up to 15mhz ... you should be able
                  to tune higher if you keep the feed line length short.

                  Jim
                • Jim Dunstan
                  ... addendum hi I terminated the 300 ohm TV twin lead in a balanced antenna tuner at the listening position. Jim
                  Message 8 of 13 , Feb 5, 2009
                    At 10:48 AM 2/5/2009 -0500, you wrote:

                    >Hi Curtis,
                    >
                    >When I was in the big city for several years in an apartment situation I
                    >used such a loop for SWL. I tried a number of different arrangements.
                    >
                    >The criteria I required:
                    >
                    >must be tuned to provide maximum Q and thus selectivity and noise reduction.
                    >must be directional ... e.g. have a sharp null to reduce local noise.
                    >must be able to be tuned from a small distance as I wanted to locate the
                    >antenna out on the balcony.
                    >
                    >Here's how it works:
                    >
                    >I formed a loop with light copper tubing .. perhaps 1/4 in. The diameter
                    >of the loop was approx. 2.5 to 3 ft. (not critical)
                    >I supported the loop on wood sticks everything held together with
                    >electrical tie wraps (great invention)
                    >I fed the loop with balanced feed line (TV twin lead)
                    >
                    >I used if from about 4 mhz tropical band up to 15mhz ... you should be able
                    >to tune higher if you keep the feed line length short.
                    >
                    >Jim

                    addendum hi

                    I terminated the 300 ohm TV twin lead in a balanced antenna tuner at the
                    listening position.

                    Jim
                  • brian russell
                    Curtis, I myself used a 138ft perimeter diamond shape horizontal wire loop at 25ft for over 25 years as an SWL, covering all bands 40m - 10m, it worked
                    Message 9 of 13 , Feb 5, 2009
                      Curtis,
                      I myself used a 138ft perimeter diamond shape horizontal wire loop at 25ft
                      for over 25 years as an SWL, covering all bands 40m - 10m, it worked
                      exceptionally well.
                      Since 1985 I have used it on transmit with equal success.
                      Below 40m I just disconnect one side of the twin feeder and use it as a long wire.
                      Look on the Internet for ' Skywires ' or NVIS antennas.
                      72, Brian, G0NSL-QRP.
                      ----- Original Message -----
                      From: blacklabpupp
                      To: loopantennas@yahoogroups.com
                      Sent: Thursday, February 05, 2009 5:38 AM
                      Subject: [loopantennas] SWL Loop


                      [Non-text portions of this message have been removed]
                    • blacklabpupp
                      Thanks for all the response. I have been busy this morning checking out all the work I had done. Thinking I had created a nice piece of work. It was little
                      Message 10 of 13 , Feb 5, 2009
                        Thanks for all the response. I have been busy this morning checking
                        out all the work I had done. Thinking I had created a nice piece of
                        work. It was little more than junk. Last week I ordered a Autek
                        Analyst. It came this morning and quickly it showed that the cap I
                        was using was bad. It was a new piece but not working. I took it
                        apart and discovered that the insulation used to hold the shaft was
                        bad. I cannot explain why. It looks fine, but when you remove it the
                        Autek says it is ok. If you reinsert it, it fails the test. Shorted.
                        I have worked with many caps and bought used ones at ham fests but I
                        have never seen anything like this. So in the trash it goes. No way I
                        could put all back together and make it work. I wrapped a piece of
                        cardboard around the shaft and it worked and tested fine. It would
                        have been a waste of time to make it work. I purchased another with a
                        lower capacitance. It seems to not matter, because the radio now
                        jumps to life on the AM BCB. I am surprised. I guess you don't need
                        all the extra capacitance. I will replace it with a larger size. I am
                        still not happy with the performance on the SW bands. I guess I am
                        going to use some of the ideas you guy have given to see if I can get
                        a better signal on SW. I plan on making a butterfly cap this weekend
                        for a 20 meter loop. Two other questions Does the diameter of the
                        tubing make a difference in bandwidth? If you use wire, is it
                        neccessary to use mutiple turns say for 20 meters. If anyone has
                        ideas on where not to make a
                        mistake please let me know. Also thanks for the friendly responses
                        from all, as well for the advice. All the best Curtis
                      • Hiram
                        Yes, The diameter does make a difference. Some folks have made HF loops out of 2 diameter copper pipe(!), for transmitting, it does make a difference. For
                        Message 11 of 13 , Feb 6, 2009
                          Yes,
                          The diameter does make a difference. Some folks have made HF loops out
                          of 2" diameter copper pipe(!), for transmitting, it does make a
                          difference. For receiving, not so much.

                          Here's a page with a lot of info:
                          http://www.qsl.net/mnqrp/Loop/Mag_Loops.htm

                          Here's a page with a lot of loop links:
                          http://www.mindspring.com/~loop_antenna/
                          And another:
                          http://www.dxzone.com/catalog/Antennas/Loop/

                          Good luck,
                          Pappy Hiram



                          --- In loopantennas@yahoogroups.com, "blacklabpupp" <blacklabpupp@...>
                          wrote:
                          .....Does the diameter of the
                          tubing make a difference in bandwidth? If you use wire, is it
                          neccessary to use mutiple turns say for 20 meters......
                        • blacklabpupp
                          Thanks Pappy The links are very helpful. I should have done an internet scan but I have been so busy searching books at the library. The eneginnering books I
                          Message 12 of 13 , Feb 6, 2009
                            Thanks Pappy

                            The links are very helpful. I should have done an internet scan but I
                            have been so busy searching books at the library. The eneginnering
                            books I have read through are poor on hf loops, but heavy on loops
                            designed for satelite data used in the 60's. How much of it relates I
                            dont know. When I moved I gave away most of the books I used never
                            thinking I would need them again. Thanks for the links.


                            --- In loopantennas@yahoogroups.com, "Hiram" <daveleb55@...> wrote:
                            >
                            > Yes,
                            > The diameter does make a difference. Some folks have made HF loops
                            out
                            > of 2" diameter copper pipe(!), for transmitting, it does make a
                            > difference. For receiving, not so much.
                            >
                            > Here's a page with a lot of info:
                            > http://www.qsl.net/mnqrp/Loop/Mag_Loops.htm
                            >
                            > Here's a page with a lot of loop links:
                            > http://www.mindspring.com/~loop_antenna/
                            > And another:
                            > http://www.dxzone.com/catalog/Antennas/Loop/
                            >
                            > Good luck,
                            > Pappy Hiram
                            >
                            >
                            >
                            > --- In loopantennas@yahoogroups.com, "blacklabpupp" <blacklabpupp@>
                            > wrote:
                            > .....Does the diameter of the
                            > tubing make a difference in bandwidth? If you use wire, is it
                            > neccessary to use mutiple turns say for 20 meters......
                            >
                          • cank13cat
                            I ve been getting good results with a homebrewed passive magnetic loop for my Palstar R30C. Assuming the new R30A is pretty similar (I think it has internal
                            Message 13 of 13 , Feb 7, 2009
                              I've been getting good results with a homebrewed passive magnetic loop
                              for my Palstar R30C. Assuming the new R30A is pretty similar (I think
                              it has internal 9:1 impedance transformers inline with both antenna
                              inputs), you might give it a try.

                              It's based on the design written up by Joe Carr in his Receiving
                              Antenna Handbook and repeated in several places online with minor
                              variations. Coaxial cable with an opening in the shield at one point.
                              In my case I looped the coax around a handy closet door! Opening and
                              closing the door makes it somewhat directional.

                              Most designs call for a tuning capacitor. I was in a hurry to try
                              mine and omitted the air core tuning cap I'd cannibalized from an old
                              radio. Turns out it works fine without the tuning cap from MW through
                              approx. 10 MHz. Could be improved with a tuning cap, but I'm content
                              since it works on the bands I listen to most (1000-1700 kHz on MW at
                              night for skywave; 5000-7000 kHz shortwave). Very quiet, rejects most
                              indoor noise generated by my own appliances and neighbors.

                              Perfect for my apartment since I can't put up a permanent outdoor
                              antenna. Random wire up a tree gets stronger signals on HF, but with
                              a lot more noise. The loop is quiet enough that I can leave the
                              receiver on all day and not go nuts from the static. Signals that
                              would be S9+10 or +20 on a random wire are S7-S9 on the loop, but with
                              very low noise, so intelligibility is comparable.
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