Litz wire for AM ferrite Rod Antenna?
in [Basics]
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From: Bill Bowden on 24 Mar 2007 00:50 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? -Bill
From: MassiveProng on 24 Mar 2007 01:00 On 23 Mar 2007 21:50:54 -0700, "Bill Bowden" <wrongaddress(a)att.net> Gave us: >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? You are only talking microvolts/femtowatts here. Loop antennas are what most stereo receivers use these days. Ferrite rod versions are for handheld portables. The increase is enough that those portable radio makers use it. Hell, just buy a cheap one or grab on at a yard sale and disassemble it. Better, just go to a military surplus store or industrial liquidator in your town.
From: John Popelish on 24 Mar 2007 12:22 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
From: Bill Bowden on 24 Mar 2007 21:53 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? Quote from website: " Solid wire instead of litz?: Keep in mind that the work described here used close-wound 125/46 litz wire. If one duplicates 'Coil and Former B' in Table 2, except using 22 ga. solid copper wire (having the same diameter) as 125/46 litz, the Q values drop to about 1/6 of the values achieved with the litz wire. The cause is the large proximity effect resistive losses in the solid wire. The proximity effect, but not the skin effect loss may be much reduced if the wires are space-wound. New trade-offs now must be considered: Same wire diameter, and therefore a longer solenoid, or a smaller wire diameter and the same overall length? If one wishes to use solid wire, it should probably be wound directly on the ferrite, not on a former. The overall Q will still be much less than when using litz, but the loss from the high (tan δ) dielectric of the ferrite will be pretty well swamped out because of the now higher losses from the skin and proximity effect losses. The Q values, using a close-wound solenoid of 22 ga. solid copper wire on a polyethylene former, as in 'Coil and Former' B in Table 2 are: 520 kHz: 130, 943 kHz: 141 and 1710 kHz: 150 when using the "best core". The Q drops only 3, 3, and 5 points respectively if the "worst core" is used. " -Bill
From: John Popelish on 24 Mar 2007 22:16
Bill Bowden 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? I think you are interpreting this correctly. Keep in mind that this is the Q of the coil, unloaded by any receiver circuit. If the circuit adds a significant load, the Q differences for a tuned antenna would be a smaller ratio different. 22 AWG is also pretty heavy wire for a typical antenna coil. With smaller wire, the Qs would be smaller but closer. > Quote from website: > > " Solid wire instead of litz?: Keep in mind that the work described > here used close-wound 125/46 litz wire. If one duplicates 'Coil and > Former B' in Table 2, except using 22 ga. solid copper wire (having > the same diameter) as 125/46 litz, the Q values drop to about 1/6 of > the values achieved with the litz wire. The cause is the large > proximity effect resistive losses in the solid wire. The proximity > effect, but not the skin effect loss may be much reduced if the wires > are space-wound. New trade-offs now must be considered: Same wire > diameter, and therefore a longer solenoid, or a smaller wire diameter > and the same overall length? If one wishes to use solid wire, it > should probably be wound directly on the ferrite, not on a former. > The overall Q will still be much less than when using litz, but the > loss from the high (tan δ) dielectric of the ferrite will be pretty > well swamped out because of the now higher losses from the skin and > proximity effect losses. The Q values, using a close-wound solenoid > of 22 ga. solid copper wire on a polyethylene former, as in 'Coil and > Former' B in Table 2 are: 520 kHz: 130, 943 kHz: 141 and 1710 kHz: 150 > when using the "best core". The Q drops only 3, 3, and 5 points > respectively if the "worst core" is used. " > > -Bill > |