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

Re: Best wire for medium wave loop

Expand Messages
  • airchecklover
    The absolute best wire would be Litz wire. Lowest resistance (skin effect) and lowest inter-winding capacitance. Will give you tightest bandwidth. Probably a
    Message 1 of 18 , Jun 20, 2009
      The absolute best wire would be Litz wire. Lowest resistance (skin effect) and lowest inter-winding capacitance. Will give you tightest bandwidth. Probably a little more gain too. The serious crystal set builders use only Litz wire for these reasons.

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

      --- In loopantennas@yahoogroups.com, "canondslr71" <canondslr71@...> wrote:
      >
      > I'm looking to build a 36 inch or so magnetic loop antenna for listing to medium wave (BCB). Would like to know what the absolute best wire is for this. I currently have 3 different types of enameled copper wire on hand (the type to wind motors), #17, #24, and #30. Are any of these suitable, or do you recommand something else?
      >
    • gmcjetpilot
      USE SOLID COPPER WIRE FOR CHEAP AND EASY. The problem with wire is the SKIN AFFECT , so keep the gauge down to about 18 or 16 so with a single wire. DO NOT
      Message 2 of 18 , Jun 20, 2009
        USE SOLID COPPER WIRE FOR CHEAP AND EASY.

        The problem with wire is the "SKIN AFFECT", so keep the gauge down to about 18 or 16 so with a single wire.

        DO NOT USE BRAID or TWIST MULTI (BARE) WIRE TOGETHER (MY OPINION FLAME AWAY)

        The reason is again the skin affect (google it).

        The BEST WIRE (and hardest to get in a small quantity but some times you get lucky on ebay) is LITZ wire.

        That is both a name brand and a type of wire. Originally I think its German invention. These are braided wires in very specific weaves, but each wire has an individual ceramic coating. You get the big wire affect, but with each wire separate the skin affect is low.

        You could use the wire you have and twist up your own poor man LITZ wire. Not sure the effort is worth it. That could work. LITZ is not really expensive only that it comes in very long lengths and it tends to be special order. SO you have to scrounge around for left overs or some existing stock they have laying around. May be some one on the list has a 1000' roll of some good right sized LITZ WIRE?

        However the easy cheap is big old Hardware home center solid copper wire, just don't get too large of a wire gage, 18 or 16 will do*. You don't get credit for more copper since all the signal is on the outside of the wire, the skin.

        You have #17 enameled that would be fine. If you are running it in a PVC conduit you could twist a few #30's together to make an effectively larger Gage wire, say 14 gage with less skin affect than the one #17. It does have a positive affect, but how great I don't know. I doubt you would notice it with out test gear.

        *I assume you are RX only? If transmitting that is a different story. I assume than you will need some min copper for the power you are TX'ing with. No comment. If TX I would use copper pipe. In fact I am making a Magnetic RX only antenna now with electronic remote tune (Kind of like the Welbrook).

        Cheers George

        PS LITZ WIRE ALSO HAS A BIG DRAW BACK. The only way to really connect it and make all the connections is if you have a solder pot with tight controlled temp. This will burn off the ceramic coating and make electrical connections. LITZ is MANY very small small gage wires. Heat too much you anneal it and it becomes too fragile. Not enough heat the coating does not allow good electrical contact.



        --- In loopantennas@yahoogroups.com, "canondslr71" <canondslr71@...> wrote:
        >
        > I'm looking to build a 36 inch or so magnetic loop antenna for listing to medium wave (BCB). Would like to know what the absolute best wire is for this. I currently have 3 different types of enameled copper wire on hand (the type to wind motors), #17, #24, and #30. Are any of these suitable, or do you recommand something else?
        >
      • Chris Harris
        I don t know about the ceramic coating on Litz wire, I have a few rolls here. The individual wires appear to be enamelled, with silk on the bundle. I don t
        Message 3 of 18 , Jun 21, 2009
          I don't know about the ceramic coating on Litz wire, I have a few rolls
          here. The individual wires appear to be enamelled, with silk on the
          bundle. I don't know if this is typical.
          I just use a hot soldering iron to burn off the insulation. The stuff
          has a life of it's own and gets tangle very quickly.
          For MW receive the Q doesn't need to be so high. I've had success with
          any wire I've tried, though it may be a different story for a crystal
          set where you don't have any extra gain.

          Regards, Chris



          -----Original Message-----
          From: loopantennas@yahoogroups.com [mailto:loopantennas@yahoogroups.com]
          On Behalf Of gmcjetpilot
          Sent: Sunday, 21 June 2009 6:58 p.m.
          To: loopantennas@yahoogroups.com
          Subject: [loopantennas] Re: Best wire for medium wave loop





          USE SOLID COPPER WIRE FOR CHEAP AND EASY.

          The problem with wire is the "SKIN AFFECT", so keep the gauge down to
          about 18 or 16 so with a single wire.

          DO NOT USE BRAID or TWIST MULTI (BARE) WIRE TOGETHER (MY OPINION FLAME
          AWAY)

          The reason is again the skin affect (google it).

          The BEST WIRE (and hardest to get in a small quantity but some times you
          get lucky on ebay) is LITZ wire.

          That is both a name brand and a type of wire. Originally I think its
          German invention. These are braided wires in very specific weaves, but
          each wire has an individual ceramic coating. You get the big wire
          affect, but with each wire separate the skin affect is low.

          You could use the wire you have and twist up your own poor man LITZ
          wire. Not sure the effort is worth it. That could work. LITZ is not
          really expensive only that it comes in very long lengths and it tends to
          be special order. SO you have to scrounge around for left overs or some
          existing stock they have laying around. May be some one on the list has
          a 1000' roll of some good right sized LITZ WIRE?

          However the easy cheap is big old Hardware home center solid copper
          wire, just don't get too large of a wire gage, 18 or 16 will do*. You
          don't get credit for more copper since all the signal is on the outside
          of the wire, the skin.

          You have #17 enameled that would be fine. If you are running it in a PVC
          conduit you could twist a few #30's together to make an effectively
          larger Gage wire, say 14 gage with less skin affect than the one #17. It
          does have a positive affect, but how great I don't know. I doubt you
          would notice it with out test gear.

          *I assume you are RX only? If transmitting that is a different story. I
          assume than you will need some min copper for the power you are TX'ing
          with. No comment. If TX I would use copper pipe. In fact I am making a
          Magnetic RX only antenna now with electronic remote tune (Kind of like
          the Welbrook).

          Cheers George

          PS LITZ WIRE ALSO HAS A BIG DRAW BACK. The only way to really connect it
          and make all the connections is if you have a solder pot with tight
          controlled temp. This will burn off the ceramic coating and make
          electrical connections. LITZ is MANY very small small gage wires. Heat
          too much you anneal it and it becomes too fragile. Not enough heat the
          coating does not allow good electrical contact.


          --- In loopantennas@ <mailto:loopantennas%40yahoogroups.com>
          yahoogroups.com, "canondslr71" <canondslr71@...> wrote:
          >
          > I'm looking to build a 36 inch or so magnetic loop antenna for listing
          to medium wave (BCB). Would like to know what the absolute best wire is
          for this. I currently have 3 different types of enameled copper wire on
          hand (the type to wind motors), #17, #24, and #30. Are any of these
          suitable, or do you recommand something else?
          >







          [Non-text portions of this message have been removed]
        • toddroberts2001@aol.com
          In a message dated 6/21/2009 6:51:21 A.M. Eastern Daylight Time, chris.harris@actrix.gen.nz writes: I don t know about the ceramic coating on Litz wire, I have
          Message 4 of 18 , Jun 21, 2009
            In a message dated 6/21/2009 6:51:21 A.M. Eastern Daylight Time,
            chris.harris@... writes:

            I don't know about the ceramic coating on Litz wire, I have a few rolls
            here. The individual wires appear to be enamelled, with silk on the
            bundle. I don't know if this is typical.
            I just use a hot soldering iron to burn off the insulation. The stuff
            has a life of it's own and gets tangle very quickly.
            For MW receive the Q doesn't need to be so high. I've had success with
            any wire I've tried, though it may be a different story for a crystal
            set where you don't have any extra gain.

            Regards, Chris



            Hi,
            There are two types of Litz wire insulation. Most of the older Litz wire
            has a standard tough enamel coating on the individual strands that will not
            melt with ordinary soldering techniques. I have found the best way to
            prepare these strands for soldering is to dip the wire ends into a small cup or a
            bottlecap filled with a little paint remover. Allow the strands to soak
            for about 1/2 hour or so, then wipe with a rag. The dissolved enamel will
            wipe right off without hurting the strands, leaving the copper clean and shiny
            and ready to solder. Excessive heat can damage the fine strands of Litz
            wire.

            The newer manufactured Litz wire has a coating on the strands called
            Soldereze. This coating will melt off the individual strands when they are hot
            enough to solder. Makes soldering to this kind of wire easy and simple.
            Almost all newer manufactured Litz wire has this kind of coating.

            That being said using Litz wire is usually overkill for a broadcast band
            receiving loop as the Q will be too high. This will make the tuning too
            sharp and hard to tune and will even hurt the fidelity of the stations you are
            listening to by being so sharp it will cut off the high audio frequencies
            making the signal sound bassy and mushy. Even some loops made with regular
            solid enamel wire include a "Q-Killer" which is a high-value variable pot or
            resistor connected across the loop, perhaps a 500K - 1.0 Megohm pot. This
            allows the user to adjust the Q or sharpness of the loop if the tuning is
            too sharp for listening conditions.

            Usually only crystal radio set builders are interested in building extra
            hi-Q coils or loops for the broadcast band where every last ounce of signal
            level is needed. The crystal detector again lowers the Q so the tuning
            usually ends up not being too sharp.

            Solid enamel wire size #16-#17-#18 is probably just about right for a
            medium wave receiving loop. Some people have had good luck using silver/Teflon
            stranded wire of about #16-#18 size also.

            73 Todd WD4NGG



            **************Download the AOL Classifieds Toolbar for local deals at your
            fingertips.
            (http://toolbar.aol.com/aolclassifieds/download.html?ncid=emlcntusdown00000004)
          • jrtow3rd@bellsouth.net
            ... I am one of those folks who have used #16 stranded & insulated, thanks to a hamfest eons ago, for a 1 meter square MW loop. It has ten turns spaced .5 on
            Message 5 of 18 , Jun 21, 2009
              --- In
              >
              > Solid enamel wire size #16-#17-#18 is probably just about right for a
              > medium wave receiving loop. Some people have had good luck using silver/Teflon
              > stranded wire of about #16-#18 size also.
              >
              > 73 Todd WD4NGG
              >
              I am one of those folks who have used #16 stranded & insulated, thanks to a hamfest eons ago, for a 1 meter square MW loop. It has ten turns spaced .5" on centers with a single turn about 4" in for coupling. The tuning of the entire BCB requires a dual gang cap - an old fashioned mixer/LO type works well - but a dual 365-409 pF works better. Running #18 zipcord to the pickup loop - then to a balanced input, either my HF/PR-150 combo or a homebrew BALUN and my R8, etc, yields decent reception with a good enough Q you need a large knob on the cap to tweek it.

              I've also killed the Q by hooking it directly to 50 Ohms, as well as removed said coupling loop and fed the bitter ends to a diecast box enclosed balanced jFET amp/remotely tuned (varactors) amp fed via a pair of RG-6 leads to the homebrew head (TenTec box - mini box enclosed amp - very well shielded. It also had penlights to add to the 12V lead acid battery used for receiver power as the varactors needed 16-18 Vr for minimum capacitance.). I had a speck of daytime IMD from a local daytime 50kW-er with it in the attic. Just the loop now has to be in the yard to avoid AC powerline hash & QRM.

              Back in the 60's, I think even Belden wire displays had small spools of Litz wire. I know Lafayette and Allied both carried it - and even had 7" ferrite rods... I played more back then. A local ham store carried Amidon - even .33 & .5" x 7" rods - back 'in the day'. I wonder how long it's been since they carried even a 'Philmore' 365 pF air variable? I think they were $7.95 the last time I saw one! I remember picking them up at EDI in Chicago - in '69 - $.19/each! I was studying the Collins R-390A in USN ET school at the time.

              Palstar has a new MW/LW ferrite loop antenna ( ...for receive, obviously!) check their site.

              John
            • Jim Dunstan
              ... Hi, I believe the question was in relation to the construction of a magnetic loop for reception in the MW broadcast band. By definition a magnetic loop is
              Message 6 of 18 , Jun 21, 2009
                At 10:22 PM 6/20/2009 -0500, you wrote:


                >i think that everyone is getting too touchy about the resonance and
                >stuff...at that frequency it isn't that critical...try thinking about
                >stuff like 10 meters and up....i have made loops with electric blanket
                >wire!...just for a demonstration...and was directional!


                Hi,

                I believe the question was in relation to the construction of a magnetic
                loop for reception in the MW broadcast band. By definition a magnetic loop
                is small (in relation to a wavelength) and has a very low radiation
                resistance (low efficiency). As a result the loop (whether it is tuned or
                not) should be constructed with 'low loss techniques'. In addition, unless
                special steps are taken to increase receiver gain with additional low noise
                amplification, the loop should be 'tuned' to resonance which provides great
                receiving advantage .... as well as a few disadvantages. The increased 'Q'
                of a well constructed tuned loop greatly increases signal strength to the
                receiver, narrows the bandwidth reducing general received noise as well as
                inter mod. noise, and in my experience it seems to make the dip in the
                radiation pattern narrower and deeper.

                The mag loop is also inherently less susceptible to local noise due to its
                lower response to the electrical portion of local noise radiation. After
                going to the trouble of constructing a 3' loop frame I wouldn't recommend
                going to the electric blanket for appropriate wire hi hi. I also assume
                that going to the length of construction a 3' loop would indicate weak
                signal reception. Again, low loss construction would be in order.

                However, if the desire is to provide a minimal antenna for casual listening
                to local MW broadcast stations .... and one is using a receiver without a
                built in antenna such as a communications receiver or up-scale Hi-Fi
                receiver then a small loop 8 to 10 inches in diameter is all you need ...
                or, just clip it to the electric blanket hi. All other MW receivers
                already have built in (and tuned to resonance) antennas.

                So, if one is interested in constructing a loop to provide low level signal
                reception for receivers without an antenna or provide a 'boost' to the
                performance of portable receivers with a built-in antenna I recommend using
                low loss construction techniques .... and unless additional steps are taken
                to provide additional amplification ... make the loop tuneable .... eg that
                resonance stuff hi hi.

                As an example, there are no more MW broadcast stations in the small
                community in which I live. The nearest stations are about 200 miles away
                in the Duluth/Iron Range area. Sitting out on the deck in the morning I
                enjoy listening to local broadcasting in Northern Minn. and Wisc. Without
                the addition of a tuned loop sitting on the coffee table (giving my
                receiver a signal boost) I wouldn't be able to copy a single station ....
                and I am certain wire from an old electric blanket wouldn't do the trick
                either hi hi.

                Earlier I mentioned that a 3' loop was pretty large. The loop on my coffee
                table is a little more than 1 ft square .... I just shuffle the loop and
                radio around a little for best reception (minimum noise and best coupling)
                and then the stations 'pop' out of the background and drop back into the
                background as I tune the loop through their transmit frequency. Even after
                using the technique for years I am still amazed how the small wood frame,
                wire, and capacitor can be so dramatically effective. When a friend drops
                over for coffee (non radio type) they always think there is more to it and
                can't believe its coming directly from Duluth hi hi.

                Each to his own ... in my case if I want to hear anything with my portable
                MW receiver I need a tuneable loop .... and demonstrates that tuning is
                critical.

                P.S. I can also hear the stations pretty well on my communications
                receiver down in my Ham station (which is connected to a dipole 60 ft in
                the air) ... but not a whole lot better than my portable on the coffee
                table out on the deck.

                Jim







                > Original Message -----
                >From: Jim Dunstan
                >To: <mailto:loopantennas%40yahoogroups.com>loopantennas@yahoogroups.com
                >Sent: Saturday, June 20, 2009 2:43 PM
                >Subject: Re: [loopantennas] Best wire for medium wave loop
                >
                >At 11:49 AM 6/20/2009 -0400, you wrote:
                >
                > >canondslr71 wrote:
                > > > I'm looking to build a 36 inch or so magnetic loop
                > > > antenna for listing to medium wave (BCB). Would like to
                > > > know what the absolute best wire is for this. I
                > > > currently have 3 different types of enameled copper wire
                > > > on hand (the type to wind motors), #17, #24, and #30.
                > > > Are any of these suitable, or do you recommand something
                > > > else?
                > >
                > >Any could work. But I would probably use the #17, just for
                > >simple ruggedness and low resistance. However, at this
                > >frequency, the skin effect will waste quite a bit of the
                > >copper in this sized wire. If you were really concerned
                > >with wasting copper, you could parallel some strands of #30
                > >and get the same or lower AC resistance with less total
                > >weight of metal. But the result would be a lot more fragile.
                > >
                > >--
                > >Regards,
                > >
                > >John Popelish
                >
                >Hi,
                >
                >This is an interesting suggestion. I have created my own 'twisted pair' of
                >insulated wire (for other purposes) by putting the pair in a drill chuck
                >and giving them a twist the length of the run. It might be interesting to
                >put a number of parallel strands of #30 enameled wire in a drill and
                >twisting them to create a cable. Calculate the approx. total length you
                >might need 12' x 8 turns for example parallel 3 to 5 stands, clamp one
                >end in a vise and the other end in the chuck of a drill. Pull taught and
                >apply the drill creating a single strand that certainly would be
                >strong. As John suggests, the purpose is to create the maximum amount of
                >wire surface in order to reduce the RF resistance while creating cable
                >strength hi hi. I would be interested in how this works out if you go this
                >route.
                >
                >Jim
                >
                > >
                >
                >----------
                >
                >[Non-text portions of this message have been removed]
                >
                >[Non-text portions of this message have been removed]
                >
                >

                ----------



                [Non-text portions of this message have been removed]
              • cank13cat
                My MW BCB loop is made from old TV coaxial cable. It s just 25 -30 of cable wrapped twice around a closet door as a frame, so the dimensions are... whatever
                Message 7 of 18 , Jun 21, 2009
                  My MW BCB loop is made from old TV coaxial cable. It's just 25'-30' of cable wrapped twice around a closet door as a frame, so the dimensions are... whatever the size of the closet door is.

                  The basic design was taken from Joe Carr's "Receiving Antenna Handbook", and I've seen similar designs elsewhere on the web. Nothing fancy but it works. Just check around for any of the diagrams featuring a shielded loop with a small break in the shield.

                  It deviates from most MW loops in one way - no tuning capacitor. I tried it first without a tuning capacitor (which I already had handy, cannibalized from an old radio), just as a test. It worked well enough that I left it as-is.

                  Covers the MW frequency range and HF up to 10 MHz, with significant attenuation beyond approximately 7000 kHz. So while it's useful as an all purpose antenna, this passive loop is pretty much limited to fairly strong shortwave stations, not for DXing. But it's much quieter than most indoor antennas I've tried for shortwave.

                  Using a closet door as a frame helps make it somewhat directional. Just open or close the door. It works well enough to separate XEEP in Mexico on 1060 from WLNO in Louisiana (I'm in Texas). On shortwave it's not directional in terms of receiving signals, but adjusting the door can help minimize the effects of locally generated noise. I'm in an extremely noisy semi-urban area so this is important. Between flickering streetlights, neighbors with appliances, bad powerlines, etc., other antennas pick up too much noise and are painful to listen through, even on MW.

                  Below approximately 1000 kHz, my portables with internal ferrite antennas beat the loop. Above that, the loop, connected to a Palstar R30C, beats either of the portables (Magnavox D2935, Sony 2010). Helps a lot when trying to separate KXTR in Kansas City from the crowd of same-same-sports cluttering 1660.

                  --- In loopantennas@yahoogroups.com, "canondslr71" <canondslr71@...> wrote:
                  >
                  > I'm looking to build a 36 inch or so magnetic loop antenna for listing to medium wave (BCB)...
                • Bruce Carter
                  ... Here are some ideas --- my former employer was throwing away spools of 24 guage solid hookup wire. I used some for a couple of loops and found - to my
                  Message 8 of 18 , Jun 23, 2009
                    > I'm looking to build a 36 inch or so magnetic loop antenna

                    Here are some ideas --- my former employer was throwing away spools of 24 guage solid hookup wire. I used some for a couple of loops and found - to my surprise I might add - that the resulting loops were very selective! I've gone to no spacing between wires, it seems to boost the Q of the loop tremendously.

                    Radio Shack used to sell an outdoor shortwave antenna kit that had about 70 or 80 feet of Litz wire. I got one in the late 90's and used it in my backyard. Unfortunately, the Florida climate soon corroded the wire out. But - this could make a readily available source of Litz wire.

                    I do not recommend doorbell wire, because I haven't had much luck making high Q loops out of it, but they have all been spaced out between turns. Perhaps put tightly spaced, the Q might go up. Doorbell wire comes as a twisted pair, it is a fair amount of effort to separate over 100 feet, but when you do you have enough for two loops.

                    I've heard of some people using outdoor landscaping light wire for speaker wire and for loops. Pretty smart, because you can get large guage 16 or so relatively inexpensively.

                    Some people have even used monster speaker wire, but they find they have to put resistance in parallel because the Q is too high!
                  • canondslr71
                    Thanks all for the replies. Now, how would something like the CC Crane or Quantum ferrite loop compare to a 36 inch magnetic loop in terms of pulling in those
                    Message 9 of 18 , Jun 24, 2009
                      Thanks all for the replies. Now, how would something like the CC Crane or Quantum ferrite loop compare to a 36 inch magnetic loop in terms of pulling in those distant stations?
                    • Jim Dunstan
                      ... Sensitivity of a tuned loop ..... or how well it manages to transfer signals to the receiver .... either through mutual induction or via a link coil ...
                      Message 10 of 18 , Jun 24, 2009
                        At 01:39 PM 6/24/2009 +0000, you wrote:


                        >Thanks all for the replies. Now, how would something like the CC Crane or
                        >Quantum ferrite loop compare to a 36 inch magnetic loop in terms of
                        >pulling in those distant stations?

                        Sensitivity of a tuned loop ..... or how well it manages to transfer
                        signals to the receiver .... either through mutual induction or via a link
                        coil ... depends first on construction .... that is how high the circuit
                        'Q' .... and second the size .... the capture area. A well constructed
                        High Q tuned loop 1' square with adjustable coupling could outperform a
                        poor quality, low 'Q' loop 3' square even though it, the 3' loop, has
                        almost 10 times the capture area.

                        However, a 3' tuned loop constructed with reasonable care will run circles
                        around the smaller commercial loops on weak signals. If the signals are
                        relatively strong ... e.g. you can hear the stations without the loop ...
                        then the difference between loops will not be noticeable as the receiver
                        AGC will make up the difference. A 3' loop is a bit awkward to use and
                        works best on signals that you can't hear at all on the receiver without
                        the external antenna.

                        For example. If I use a receiver of average sensitivity with a 1' loop I
                        can bring 4 daytime distant stations in at a comfortable level. If I use a
                        more sensitive receiver (SRIII) with the same loop I can pickup 2
                        additional distant stations (the first 4 stations aren't improved very
                        much). However if I use the SRIII receiver and a 3' loop I can add 6 or
                        more additional stations ... not all at a comfortable level but
                        identifiable. However physically the 3' loop is difficult to use. The
                        result is large loop only comes out for special occasions hi hi.

                        Jim
                      • airchecklover
                        I built a 3.5 ft.8-sided loop from PVC. It was big and awkward and was not leaps and bounds better than a 2 ft. square MTM Scientic loop - except as Jim points
                        Message 11 of 18 , Jun 24, 2009
                          I built a 3.5 ft.8-sided loop from PVC. It was big and awkward and was not leaps and bounds better than a 2 ft. square MTM Scientic loop - except as Jim points out on the incredibly weak signals. So I scrapped it and the wire is now outdoors as an end-fed sloper. The 2ft loop about equals the CCrane T-F (I also have) but doesn't require batteries and has no cables. The Quantum probably will not be beat from what i've heard and read but it is not cheap. Magnetically coupling the loop to the T-F head and the T-F direct to a good radio gives almost double the gain of either antenna alone (with good S/N) and playing the loop against the T-F head, cardoid nulls are achievable. I can get 100% quieting on either of two stations on 570 daytime. They are about 30 degrees apart.

                          Mark

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

                          --- In loopantennas@yahoogroups.com, "canondslr71" <canondslr71@...> wrote:
                          >
                          > Thanks all for the replies. Now, how would something like the CC Crane or Quantum ferrite loop compare to a 36 inch magnetic loop in terms of pulling in those distant stations?
                          >
                        Your message has been successfully submitted and would be delivered to recipients shortly.