On Mon, 06 May 2019 09:03:02 -0500, amdx wrote:> So what type of inductor? Is there a good way to couple to it?Air-core single solenoid - and yes.> Sometimes I just hang a clip lead from the generator near the coil.That might just do the trick... -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Tuned Circuit Selectivity
Started by ●May 5, 2019
Reply by ●May 6, 20192019-05-06
Reply by ●May 6, 20192019-05-06
On Mon, 06 May 2019 14:20:39 +0000, Jan Panteltje wrote:> Yes a bit tricky to use, oh what is large, > in the few MHz range and lower it works.Not IME. But people's perceptions vary and I accept that.> With your raspi as signal generator??? I think you're confusing me with someone else, Jan. I only ever use heavyweight PB equipment for such purposes. God knows I have enough of it! -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Reply by ●May 6, 20192019-05-06
On Mon, 06 May 2019 09:07:40 -0500, John S wrote:> Are you wanting the loaded or unloaded Q of your network?Don't sweat it, John. We've established it's primarily a coupling issue so I can now move on with it. Thanks all the same. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Reply by ●May 6, 20192019-05-06
On Monday, May 6, 2019 at 9:59:24 AM UTC-4, John Larkin wrote:> On Mon, 6 May 2019 13:13:35 -0000 (UTC), Cursitor Doom > <curd@notformail.com> wrote: > > >On Sun, 05 May 2019 16:59:19 -0700, John Larkin wrote: > > > >> How are you coupling the signal gen into the resonant tank? Are you > >> using a 10x probe on the scope? > > > >Yes, 10x/1x switchable. And directly coupled. > > > >> > >> A Q of 50 should be easy at that frequency, and that would make a very > >> sharp peak. > > > >I'd have thought so, yes. > > > >> > >> What are your L and C values? > > > >33uH & 385pF > > > >> > >> Here's my LC program. > > > >I find it's easiest just to use the full features of a programmable > >scientific calculator, TBH. YMMV of course. > > > Xc = Xl = 292 ohms at 1.4 MHz. If you connect a 50 ohm signal > generator across that parallel tank, Q is about 0.16. Not much of a > resonant bump. Couple gently from the generator into the tank, with a > big resistor or a tiny cap, or just proximity.Okay, you're getting close. For parallel resonance, the drive is ideally a current source, and for series resonance it is a voltage source.> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Reply by ●May 6, 20192019-05-06
On Mon, 6 May 2019 08:42:08 -0700 (PDT), bloggs.fredbloggs.fred@gmail.com wrote:>On Monday, May 6, 2019 at 9:59:24 AM UTC-4, John Larkin wrote: >> On Mon, 6 May 2019 13:13:35 -0000 (UTC), Cursitor Doom >> <curd@notformail.com> wrote: >> >> >On Sun, 05 May 2019 16:59:19 -0700, John Larkin wrote: >> > >> >> How are you coupling the signal gen into the resonant tank? Are you >> >> using a 10x probe on the scope? >> > >> >Yes, 10x/1x switchable. And directly coupled. >> > >> >> >> >> A Q of 50 should be easy at that frequency, and that would make a very >> >> sharp peak. >> > >> >I'd have thought so, yes. >> > >> >> >> >> What are your L and C values? >> > >> >33uH & 385pF >> > >> >> >> >> Here's my LC program. >> > >> >I find it's easiest just to use the full features of a programmable >> >scientific calculator, TBH. YMMV of course. >> >> >> Xc = Xl = 292 ohms at 1.4 MHz. If you connect a 50 ohm signal >> generator across that parallel tank, Q is about 0.16. Not much of a >> resonant bump. Couple gently from the generator into the tank, with a >> big resistor or a tiny cap, or just proximity. > >Okay, you're getting close. For parallel resonance, the drive is ideally a current source, and for series resonance it is a voltage source.I got close before you did. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●May 6, 20192019-05-06
On Monday, May 6, 2019 at 11:51:17 AM UTC-4, John Larkin wrote:> On Mon, 6 May 2019 08:42:08 -0700 (PDT), > bloggs.fredbloggs.fred@gmail.com wrote: > > >On Monday, May 6, 2019 at 9:59:24 AM UTC-4, John Larkin wrote: > >> On Mon, 6 May 2019 13:13:35 -0000 (UTC), Cursitor Doom > >> <curd@notformail.com> wrote: > >> > >> >On Sun, 05 May 2019 16:59:19 -0700, John Larkin wrote: > >> > > >> >> How are you coupling the signal gen into the resonant tank? Are you > >> >> using a 10x probe on the scope? > >> > > >> >Yes, 10x/1x switchable. And directly coupled. > >> > > >> >> > >> >> A Q of 50 should be easy at that frequency, and that would make a very > >> >> sharp peak. > >> > > >> >I'd have thought so, yes. > >> > > >> >> > >> >> What are your L and C values? > >> > > >> >33uH & 385pF > >> > > >> >> > >> >> Here's my LC program. > >> > > >> >I find it's easiest just to use the full features of a programmable > >> >scientific calculator, TBH. YMMV of course. > >> > >> > >> Xc = Xl = 292 ohms at 1.4 MHz. If you connect a 50 ohm signal > >> generator across that parallel tank, Q is about 0.16. Not much of a > >> resonant bump. Couple gently from the generator into the tank, with a > >> big resistor or a tiny cap, or just proximity. > > > >Okay, you're getting close. For parallel resonance, the drive is ideally a current source, and for series resonance it is a voltage source. > > I got close before you did.Drives for parallel/series resonant crystal operation are a common application of that principle.> > > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Reply by ●May 6, 20192019-05-06
On a sunny day (Mon, 6 May 2019 15:32:25 -0000 (UTC)) it happened Cursitor Doom <curd@notformail.com> wrote in <qapk29$52e$6@dont-email.me>:>On Mon, 06 May 2019 14:20:39 +0000, Jan Panteltje wrote: > >> Yes a bit tricky to use, oh what is large, >> in the few MHz range and lower it works. > >Not IME. But people's perceptions vary and I accept that. > >> With your raspi as signal generator > >??? I think you're confusing me with someone else, Jan. I only ever use >heavyweight PB equipment for such purposes. God knows I have enough of it!Oh, Ok, though I did see a header raspberry pi as signal generator, I use that sometimes. I also use a shortwave SSB radio to measure some frequencies, works perfectly. The only BIG thing I have is my old Trio analog scope. Oh and the cryo coooler and the TX set and computahs .. but Things are getting more and more nano...
Reply by ●May 6, 20192019-05-06
On 5/6/19 9:18 AM, Cursitor Doom wrote:> On Mon, 06 May 2019 07:28:29 +0000, Jan Panteltje wrote: > >> A grid dip meter was a useful instrument long ago: >> https://en.wikipedia.org/wiki/Grid_dip_oscillator >> Build one once. > > I still have a selection of them and I built one once. NEVER had any luck > with *any* of the damn things for some reason! I suspect they're only > useful if you are testing really physically large combinations of C and L. > > >There are good ones and bad ones. The Heathkits are junk. The Measurements 59 Megacycle Meter is a thing of great beauty--I have three of them (two HF/VHF and one UHF). They give a good-sized dip with very weak coupling, so that the measurements are pretty accurate. I measured the dial calibration accuracy of one of them, and it's still within 2% througout all ranges. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●May 6, 20192019-05-06
On 5/6/2019 10:34 AM, Cursitor Doom wrote:> On Mon, 06 May 2019 09:07:40 -0500, John S wrote: > >> Are you wanting the loaded or unloaded Q of your network? > > Don't sweat it, John. We've established it's primarily a coupling issue > so I can now move on with it. Thanks all the same. >Very well. I suggest you try AMDX (MikeK) component values. And put the capacitor in series with the source. You will see much higher Q and, in fact the voltage across the inductor is a measure of Q. Good luck.
Reply by ●May 6, 20192019-05-06
In article <b6f0delff10il9e92u061jmb7m0g4htvk9@4ax.com>, John Larkin <jjlarkin@highlandtechnology.com> wrote:>Xc = Xl = 292 ohms at 1.4 MHz. If you connect a 50 ohm signal >generator across that parallel tank, Q is about 0.16. Not much of a >resonant bump. Couple gently from the generator into the tank, with a >big resistor or a tiny cap, or just proximity.Proximity, to a grid-dip meter, used as directed (that is, start with fairly close coupling, and move the meter probe away until you just barely get a dip - less pulling that way). Then, without changing the grip-dip meter settings from your best dip point, hold it near a loop antenna connected to a sensitive frequency counter and get a reading.
