Jeroen Belleman wrote:> On 2022-02-01 16:59, Phil Hobbs wrote: >> piglet wrote: >>> On 01/02/2022 3:27 pm, jlarkin@highlandsniptechnology.com wrote: >>>> Not actually a Hartley, bacause the Ls are not coupled. >>>> >>>> Version 4 > [Deleted ... ] >>> >> With no coupling, it's a species of Colpitts--it's only the tank Q that >> does the impedance transformation, with no help from the transformer >> action of the mutual inductance.> > To me, a Colpitts has two C's and one L in its tank. This one doesn't. > A capacitive divider is also an impedance transformer.Not without the resonance, it isn't. The input is at the tap and the output is at the top of the tank, so it isn't a voltage divider. The math of a real Hartley is different from the Colpitts case, but with uncoupled inductors it's the same except for the sign of the reactance. 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
strange oscillator
Started by ●February 1, 2022
Reply by ●February 1, 20222022-02-01
Reply by ●February 1, 20222022-02-01
On 2022-02-01 19:44, Phil Hobbs wrote:> Jeroen Belleman wrote: >> On 2022-02-01 16:59, Phil Hobbs wrote: >>> piglet wrote: >>>> On 01/02/2022 3:27 pm, jlarkin@highlandsniptechnology.com >>>> wrote: >>>>> Not actually a Hartley, bacause the Ls are not coupled. >>>>> >>>>> Version 4 >> [Deleted ... ] >>>> >>> With no coupling, it's a species of Colpitts--it's only the tank >>> Q that does the impedance transformation, with no help from the >>> transformer action of the mutual inductance. > >> >> To me, a Colpitts has two C's and one L in its tank. This one >> doesn't. A capacitive divider is also an impedance transformer. > > Not without the resonance, it isn't. The input is at the tap and the > output is at the top of the tank, so it isn't a voltage divider. > > The math of a real Hartley is different from the Colpitts case, but > with uncoupled inductors it's the same except for the sign of the > reactance. > > Cheers > > Phil Hobbs >The concepts of input and output are somewhat slippery in oscillators. One could choose any or none of the three terminals of a transconductance gain element as common, and inputs and outputs move about as a result. My point is that two of the three reactances that make up the tank are of the same sign, and one is opposite, and the low-Z node of the gain block connects to the node where the two equal-sign reactances connect. It's easier to draw than to describe. The signs of the reactances are to me what makes the difference between Colpitts and Hartley oscillators. Jeroen Belleman (Whose oscillators oscillate and whose amplifiers amplify. Usually, anyway. :-) )
Reply by ●February 1, 20222022-02-01
On Tue, 01 Feb 2022 09:00:07 -0800, jlarkin@highlandsniptechnology.com wrote:>On Tue, 1 Feb 2022 16:17:15 +0000, piglet <erichpwagner@hotmail.com> >wrote: >>> >>> Yes, decades ago I built something similar using an NPN BJT at kHz >>> frequencies. I used two molded chokes and had initially them loose >>> coupled but was amazed that I could separate them or re-orient so there >>> was no mutual couplling and still got oscillation. >>> >>> I think Irving Gottlieb described three types of Hartley in his >>> Oscillator Handbook and this is one of his "type 2" Hartleys, there is >>> no mutual coupling and the action is negative resistance. >>> >>> piglet >>> >>> >>> >> >>Found the book online, p145-146 were what I was thinking of ... >> >><https://www.qsl.net/pa2efr/manuals/Doc/Practical%20Oscillator%20Handbook%201997-Irving%20M%20Gottlieb.pdf> >> >>piglet > >Nice. It's from 1997 but includes oldies like thyratrons, spark gaps, >tunnel diodes.Gottlieb's 'Understanding Oscillators' was in its 3rd Ed in 1971. RL
Reply by ●February 1, 20222022-02-01
On Tue, 01 Feb 2022 09:00:07 -0800, jlarkin@highlandsniptechnology.com wrote:>On Tue, 1 Feb 2022 16:17:15 +0000, piglet <erichpwagner@hotmail.com> >wrote: >>> >>> Yes, decades ago I built something similar using an NPN BJT at kHz >>> frequencies. I used two molded chokes and had initially them loose >>> coupled but was amazed that I could separate them or re-orient so there >>> was no mutual couplling and still got oscillation. >>> >>> I think Irving Gottlieb described three types of Hartley in his >>> Oscillator Handbook and this is one of his "type 2" Hartleys, there is >>> no mutual coupling and the action is negative resistance. >>> >>> piglet >>> >>> >>> >> >>Found the book online, p145-146 were what I was thinking of ... >> >><https://www.qsl.net/pa2efr/manuals/Doc/Practical%20Oscillator%20Handbook%201997-Irving%20M%20Gottlieb.pdf> >> >>piglet > >Nice. It's from 1997 but includes oldies like thyratrons, spark gaps, >tunnel diodes.First published 1970. 4th Ed ? RL
Reply by ●February 1, 20222022-02-01
On Tuesday, February 1, 2022 at 8:08:02 AM UTC-8, jla...@highlandsniptechnology.com wrote:> I was just fooling around. What I really want is a 1.5 GHz oscillator > with two antiphase outputs. A MMIC might be a good gain element.Why bother? An IMPATT diode will do the oscillation (negative resistance) just fine, and antiphase is pretty easy; at 1.5 GHz, a few inches of transmission line is a hundred eighty phase shift. Tunnel diode type items are the bomb for this kind of thing.
Reply by ●February 1, 20222022-02-01
On Tue, 1 Feb 2022 13:53:21 -0800 (PST), whit3rd <whit3rd@gmail.com> wrote:>On Tuesday, February 1, 2022 at 8:08:02 AM UTC-8, jla...@highlandsniptechnology.com wrote: > >> I was just fooling around. What I really want is a 1.5 GHz oscillator >> with two antiphase outputs. A MMIC might be a good gain element. > >Why bother? An IMPATT diode will do the oscillation (negative resistance) >just fine, and antiphase is pretty easy; at 1.5 GHz, a few inches of transmission >line is a hundred eighty phase shift. Tunnel diode type items are the bomb for >this kind of thing.Have you built an impatt oscillator in this frequency range? Impatts are usually pulsed, high power at higher frequencies. Does anybody still sell TDs? -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●February 1, 20222022-02-01
jlarkin@highlandsniptechnology.com wrote:> Not actually a Hartley, bacause the Ls are not coupled.[...] Without doubt, the worst oscillator I have ever seen anyone design. You are right. You are not an analog guy.
Reply by ●February 1, 20222022-02-01
On Wed, 2 Feb 2022 01:55:39 -0000 (UTC), Arnie Dwyer <spamme@not.com> wrote:>jlarkin@highlandsniptechnology.com wrote: > >> Not actually a Hartley, bacause the Ls are not coupled. > >[...] > >Without doubt, the worst oscillator I have ever seen anyone design. You are >right. You are not an analog guy.What's wrong with it? It worked first try. We have surface-mount inductors in stock, many values, but no tapped inductors in that range. -- I yam what I yam - Popeye
Reply by ●February 2, 20222022-02-02
jlarkin@highlandsniptechnology.com wrote:> On Wed, 2 Feb 2022 01:55:39 -0000 (UTC), Arnie Dwyer <spamme@not.com> > wrote: > >>jlarkin@highlandsniptechnology.com wrote: >> >>> Not actually a Hartley, bacause the Ls are not coupled. >> >>[...] >> >>Without doubt, the worst oscillator I have ever seen anyone design. You >>are right. You are not an analog guy. > > What's wrong with it? It worked first try. > > We have surface-mount inductors in stock, many values, but no tapped > inductors in that range.You don't need tapped inductors. You make the feedback with tapped capacitors. That means capacitors in series. The problems are obvious. You tried to make a colpitts with a hartley configuration. You ended up with parasitic oscillations and very poor control over the oscillator amplitude. This gives unwanted sidebands in the output and very poor phase noise. Just for you, I looked up my old xtalosc.zip file. Start with the readme.txt file. It is intended for colpitts oscillators but will work with any lc oscillator. Just start with an inductor impedance of 50 ohms at your target frequency and use a fast enough transistor or logic device. https://tinyurl.com/2p9yrxmy
Reply by ●February 2, 20222022-02-02
On Wed, 2 Feb 2022 07:23:10 -0000 (UTC), Arnie Dwyer <spamme@not.com> wrote:>jlarkin@highlandsniptechnology.com wrote: > >> On Wed, 2 Feb 2022 01:55:39 -0000 (UTC), Arnie Dwyer <spamme@not.com> >> wrote: >> >>>jlarkin@highlandsniptechnology.com wrote: >>> >>>> Not actually a Hartley, bacause the Ls are not coupled. >>> >>>[...] >>> >>>Without doubt, the worst oscillator I have ever seen anyone design. You >>>are right. You are not an analog guy. >> >> What's wrong with it? It worked first try. >> >> We have surface-mount inductors in stock, many values, but no tapped >> inductors in that range. > >You don't need tapped inductors. You make the feedback with tapped >capacitors. That means capacitors in series.Sure. Colpitts has been around for about a century. This is a design group. Instant hostility to ideas is easy. -- I yam what I yam - Popeye
