R: Winding my first toroid on my K2 kit
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Hi,
In order to check the accuracy of my bridge, I measured the colour based inductors, and the measured values closely matched the expected ones, when measured on my HP 4260A. In the meantime, I winded up RFC11, 20 turns. Instead of the published 100uH, I measured a value of 270, with a Q of 5. There is a note on the manual cautioning NOT to match the published inductance, but to stick to the published number of turns. I wonder what it means... Then I made another consideration... RFC11 has 20 turns, and the published value is 100uH. Then RFC14 has 10 turns and it is published at 18 UH. There is no proportion between those published values, on my humble opinion... While the two measured values (I rechecked them to the utmost accuracy available with my ancient instrument) were 270 uH and 130uH; half the turns, half the inductance. And that makes sense... While the accuracy of my HP 4260A seems confirmed by the solenoidal "green body" inductors. There is something missing there.... Cheers, IK4YNG Paolo -----Messaggio originale----- Da: Arie Lukkassen [mailto:[hidden email]] Inviato: lunedì 25 settembre 2006 14.11 A: paolo gramigna Oggetto: Re: [Elecraft] Winding my first toroid on my K2 kit Some are used as rf chokes and the value has a big tolerance. the toroid material might be the culprit b because the wiring supplied does not vary much in parameters. Why do not measure some of the colour banded inductors as a reference and the special supplier inductor for the PLL. This is one is very important. Rgds Arie --- paolo gramigna <[hidden email]> wrote: > Hi all, > > I'm arrived at page 53 of the manual, and I'm making my first toroid. > I followed the instructions, and then out of curiosity I tried to > measure the inductance, using my old HP 4260A. I know that I'm not > supposed to match the indicated inductance, and that I should stick to > the published turns count; in fact I was just willing to give a try to > the HP 4260A, the least used instrument in my lab. > > Well, it ended up indicating a value of 160 uH, not > 18 uH as supposed. So I > tried to measure the value on another bridge I had there by chance, > and ended up with a very similar value. > > So I tried the HP 4260A on the solenoidal RFC (the green bodied) and I > found values very similar to what I expected. > > I know that i'm doing something wrong, but I cannot understand what's > my mistake.... > > Cheers, > > IK4YNG Paolo > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: R: Winding my first toroid on my K2 kit
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Paolo:
Inductance is proportional to number of turns squared, so two inductors, otherwise equal. If one has 10 turns and one with 20 turns, the inductor with 20 turns will have (20/10)^2 = 4 times the inductance of the 10 turn one. This assumes all the flux links all the turns, which is usually a decent assumption for toroid with high permeability. Jack paolo gramigna wrote: > Hi, > In order to check the accuracy of my bridge, I measured the colour based > inductors, and the measured values closely matched the expected ones, when > measured on my HP 4260A. > > In the meantime, I winded up RFC11, 20 turns. Instead of the published > 100uH, I measured a value of 270, with a Q of 5. > > There is a note on the manual cautioning NOT to match the published > inductance, but to stick to the published number of turns. I wonder what it > means... > > Then I made another consideration... RFC11 has 20 turns, and the published > value is 100uH. Then RFC14 has 10 turns and it is published at 18 UH. There > is no proportion between those published values, on my humble opinion... > While the two measured values (I rechecked them to the utmost accuracy > available with my ancient instrument) were 270 uH and 130uH; half the turns, > half the inductance. And that makes sense... While the accuracy of my HP > 4260A seems confirmed by the solenoidal "green body" inductors. There is > something missing there.... > > Cheers, > IK4YNG Paolo > > > > -----Messaggio originale----- > Da: Arie Lukkassen [mailto:[hidden email]] > Inviato: lunedì 25 settembre 2006 14.11 > A: paolo gramigna > Oggetto: Re: [Elecraft] Winding my first toroid on my K2 kit > > Some are used as rf chokes and the value has a big tolerance. the toroid > material might be the culprit b because the wiring supplied does not vary > much in parameters. > > > > > Why do not measure some of the colour banded inductors as a reference and > the special supplier inductor for the PLL. This is one is very important. > > Rgds > Arie > > --- paolo gramigna <[hidden email]> > wrote: > > >> Hi all, >> >> I'm arrived at page 53 of the manual, and I'm making my first toroid. >> I followed the instructions, and then out of curiosity I tried to >> measure the inductance, using my old HP 4260A. I know that I'm not >> supposed to match the indicated inductance, and that I should stick to >> the published turns count; in fact I was just willing to give a try to >> the HP 4260A, the least used instrument in my lab. >> >> Well, it ended up indicating a value of 160 uH, not >> 18 uH as supposed. So I >> tried to measure the value on another bridge I had there by chance, >> and ended up with a very similar value. >> >> So I tried the HP 4260A on the solenoidal RFC (the green bodied) and I >> found values very similar to what I expected. >> >> I know that i'm doing something wrong, but I cannot understand what's >> my mistake.... >> >> Cheers, >> >> IK4YNG Paolo >> >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com >> >> > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by IK4YNG
Paolo:
Continuing our discussion on measuring RF inductors, I tested an inductor I wound on a powdered iron core this morning. 29 turns of #22 wire on a T50-2 (red) core. Nominal value is 4.2 uH if I recall correctly. HP4342A Q-meter, measured at 7.9 MHz: Lp = 4.30uH, Q=212 HP4320A RLC Bridge @ 1 KHz: Auto: 1.5uH Q: N/A Ls (manual) L=2.0uH, Q=0.98 Lp (manual) cannot be measured as Lp requires Q > 8 General Radio GR1650A RLC Bridge @ 1 KHz: Lp=10uH, Q=0.98 Ls=5uH, Q=5uH Leader LCR740 RLC Bridge L=4.50 uH Q=0.98 The Q-meter values are the ones I regard as "correct." I also measured the DC resistance of the inductor, using an HP3468A multi-meter in 4-wire ohms mode: 28 milliohms. We can compute the approximate Q of this inductor at 1 KHz, assuming its true inductance is 4.3 uH (powdered iron has a very flat relative permeability versus frequency relationship, so we should expect the true inductance to be 4.3 uH at 1 KHz.) Xl = 2*pi*L = 27 mOhms. In series model, Q = Xl/Rs = 27/28 = 0.96 Note that both the GR1650A and LCR740 match this Q value almost exactly. (We can safely neglect the core loss and other losses in this approximation, as the inductor's loss is dominated by the DC resistance of the windings.) If you read the instruction manuals on the RLC bridges (GR1650A manual is much better in this regard than HP's 4260A manual in my view) you will see that low Q inductors are difficult to accurately measure. You will also see how to convert the series model to parallel and vice versa. What about that 10uH Lp value from the GR1650A? To compare it with the same instrument's Ls reading, we must convert to consistent models. In this case, we'll use the series model and compute Ls from the Lp measurement: GR1650A Lp=10uH Ls = LpQ^2/(1+Q^2) => Ls = 10uH*0.98^2/(1+0.98^2) = 4.99 uH. Thus, we see that the series model inductance is 5uH, whether measured with the bridge in Ls or Lp mode. The GR1650's accuracy rating is +/- 1uH when on the lowest inductance range (100 uH full scale) at the bottom of the dial, which is where this inductor reads. Hence the measured value of the inductor at 1 KHz is 5 uH +/- 1uH, so we see that the "true" value of 4.3 uH is within the measurement accuracy of the GR1650A bridge. The measurement accuracy at 1 KHz can be improved by calibrating out the residual inductance and some other tricks that are mentioned in the manuals. The GR1650A bridge, by the way, is the same model I used in Electrical Engineering labs when I studied EE in the mid 1960's. Still a good bridge and I find it preferable to the HP4620A. Jack K8ZOA www.cliftonlaboratories.com - home of the Z90/91 digital panadapter. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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