Litz wire for AM ferrite Rod Antenna?
in [Basics]
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From: amdx on 25 Mar 2007 06:44 "Bill Bowden" <wrongaddress(a)att.net> wrote in message news:1174787636.562038.124710(a)e65g2000hsc.googlegroups.com... On Mar 24, 8:22 am, John Popelish <jpopel...(a)rica.net> wrote: > Bill Bowden wrote: > > How much improvement can I expect using Litz wire to wind a AM ferrite > > Rod antenna as opposed to using solid copper wire? > > > Is it worth the trouble to obtain Litz wire, or can I expect almost > > the same response at say 1 MHz using regular solid enamaled copper > > wire? > > If you would like to see some comparative experimental data, > Ben Tongue has performed some experiments and posted the > data to his web site.http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html >Thanks John, >Yes, it looks like Litz wire has a significant advantage. If I read >the results right, the unloaded Q factor at 943Khz is 141 using solid >copper wire verses a Q factor of 1030 using Litz wire. >That's quite a significant difference. Am I reading the results right? That's the way I read it. Quite a large difference. And according to Table 7 using a smaller wire diameter, even with the higher DC resistance gives better Q. I found that interesting, I new I could get higher Q's when I spaced turns about one wire diameter, but it seem there's a little more to it. Oh, and that contrawound thing is neat to. I wonder if there is any advantage to three or four contrawound windings. Great article. Thanks, Mike Quote from website: Table 7: Simulation of inductor BB in FEMM at 1 MHz, with various conductor diameters (type 61 core material) Wire dia. in inches Inductance in uH Resistive losses in ohms Hysteresis losses in ohms Total losses in ohms DC resistance Q 0.02530 258.5 11.16 1.32 12.48 0.16 130.1 0.02320 259.6 8.04 1.33 9.36 0.18 174.2 0.02127 260.5 6.26 1.33 7.59 0.22 215.7 0.01951 261.1 5.13 1.34 6.47 0.28 253.7 0.01789 261.6 4.37 1.34 5.71 0.36 288.0 0.01265 263.4 2.91 1.35 4.26 0.64 388.1 0.008995 264.0 2.48 1.36 3.84 1.25 431.9 0.006300 264.4 3.02 1.36 4.38 2.62 379.7 0.008995* 264.5 2.57 1.40 3.97 1.00 418.6 Table 7 shows the benefits of space winding when using solid wire. All the inductors in Table 7 use centered have solenoids of 58 turns and a length of 1.624". The only variable is the diameter of the conductor, which controls the spacing of the turns (the winding pitch is held constant). The lesson here is that, when using solid copper wire, there can be a great Q benefit by space winding the solenoid, using an optimum size wire, in this case a Q of 431.9 vs 130.1 at 1 MHz.
From: MassiveProng on 25 Mar 2007 12:46 On 24 Mar 2007 18:53:56 -0700, "Bill Bowden" <wrongaddress(a)att.net> Gave us: > The proximity >effect, but not the skin effect loss may be much reduced if the wires >are space-wound. Use insulated wire, and another good sub for litz is SPC (silver plated copper), as you get a slightly better skin, and the insulation gives the space winding. A twisted group of smaller SPC wires can give a slight Litz effect as well, like 7 32 ga SPC wires in teflon, or other sheathing twisted together evenly. Not true litz, but better than a single conductor. Particularly if the space winding effect are the main desire.
From: amdx on 25 Mar 2007 18:42 "MassiveProng" <MassiveProng(a)thebarattheendoftheuniverse.org> wrote in message news:il9d03tohd4u68ili8u6oa7on5q69i6lhu(a)4ax.com... > On 24 Mar 2007 18:53:56 -0700, "Bill Bowden" <wrongaddress(a)att.net> > Gave us: > >> The proximity >>effect, but not the skin effect loss may be much reduced if the wires >>are space-wound. > > Use insulated wire, and another good sub for litz is SPC (silver > plated copper), as you get a slightly better skin, and the insulation > gives the space winding. > >A twisted group of smaller SPC wires can > give a slight Litz effect as well, like 7 32 ga SPC wires in teflon, > or other sheathing twisted together evenly. Not true litz, but better > than a single conductor. Particularly if the space winding effect are > the main desire. I'd be interested in seeing the results of that experiment. Ben's best Q is 431 using a single #31 wire. The results shown in Table 7 suggest that, getting the wires close to each other reduces Q. Twisting 7-#32 wires (with teflon) together and winding with that bundle would probably end up with no space between turns. Mike Let the name calling begin, but try to use something new.
From: John Larkin on 25 Mar 2007 21:35 On 24 Mar 2007 18:53:56 -0700, "Bill Bowden" <wrongaddress(a)att.net> wrote: >On Mar 24, 8:22 am, John Popelish <jpopel...(a)rica.net> wrote: >> Bill Bowden wrote: >> > How much improvement can I expect using Litz wire to wind a AM ferrite >> > Rod antenna as opposed to using solid copper wire? >> >> > Is it worth the trouble to obtain Litz wire, or can I expect almost >> > the same response at say 1 MHz using regular solid enamaled copper >> > wire? >> >> If you would like to see some comparative experimental data, >> Ben Tongue has performed some experiments and posted the >> data to his web site.http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html > >Thanks John, > >Yes, it looks like Litz wire has a significant advantage. If I read >the results right, the unloaded Q factor at 943Khz is 141 using solid >copper wire verses a Q factor of 1030 using Litz wire. >That's quite a significant difference. Am I reading the results right? In a superhet, high Q will make it that much harder to track the LO, so you may well lose signal with a q=1000 rod. Why do you want a high antenna Q? In the AM band, gain is cheap and s/n is dominated by ambient noise, so it won't matter much. John
From: John Popelish on 25 Mar 2007 22:27
John Larkin wrote: > In a superhet, high Q will make it that much harder to track the LO, > so you may well lose signal with a q=1000 rod. Why do you want a high > antenna Q? In the AM band, gain is cheap and s/n is dominated by > ambient noise, so it won't matter much. I think the main point to keep in mind is that it is easy to throw Q away, but hard to make it if the L and C don't have it, to start with. You might want to calculate the ideal Q, and then use an antenna coil construction technique that is pretty sure to exceed that requirement. |