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I want to build an LO

Started by M. Hamed June 8, 2013
Hello the most knowledgeable electronics group on earth!

I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start!

I have a few RF books and the treatment of oscillator can be one of the following:

1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model.
2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this).
3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using.
4- Cookbooks that have the same problem as (2).

Why is it so hard to build an oscillator at an arbitrary frequency?

"M. Hamed"  wrote in message 
news:de1921c5-936a-420a-9eda-66b7346f2d19@googlegroups.com...

>Hello the most knowledgeable electronics group on earth! > >I am trying to build a few LC oscillators for experimenting with mixers. I >do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz >and 100 MHz. I don't know where to start! > >I have a few RF books and the treatment of oscillator can be one of the >following: > >1- Too much theory on the analysis of oscillator circuits, phase noise, >IMD, etc. No circuits to build. Just demo circuits for illustration, >sometimes only the small signal model. >2- Circuits to build but designed at very specific frequencies with very >specific components. Very little on how to generalize things into different >frequencies. (The ARRL handbook 2010 and Experimental Methods fall under >this). >3- Books that give me a design procedure with S parameters but I can't find >any S parameter files for the devices I'm interested in using. >4- Cookbooks that have the same problem as (2). > >Why is it so hard to build an oscillator at an arbitrary frequency?
Idea 1: find a DIP meter schematic. They typically cover a fairly wide range using plug-in coils i.e. you just need to change the inductor. And it's often a single FET circuit. Idea 2: You could cover quite a wide range using an unbuffered CMOS inverter (4069UB) with: cap from input to ground; cap from output to ground; inductor from input to output; maybe a resistor in series with the output. You should get a sinusoid at the inverter input. It'll need buffering to drive your mixer. In both cases you should be able to cover quite a wide frequency range with suitable choices of L and C. You can lash it up on a breadboard. But the upper frequency limit for the above circuits will be well below 100 MHz. You will need a different circuit for VHF.
On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed"
<mhdpublic@gmail.com> wrote:

>Hello the most knowledgeable electronics group on earth! > >I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start! > >I have a few RF books and the treatment of oscillator can be one of the following: > >1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model. >2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this). >3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using. >4- Cookbooks that have the same problem as (2). > >Why is it so hard to build an oscillator at an arbitrary frequency?
It's not. A little Colpitts oscillator is easy. Use a bipolar transistor, a jfet, or a gaasfet at higher frequencies. A rough ballpark for the L and C is to set their reactances to maybe 50 or 100 ohms each at the operating frequency. Use a surface-mount inductor or wind your own. You don't really need s-params. Just make sure you have plenty of gain-bandwidth in the active device. Subtleties like TC and low phase noise are a little more work. Wes Hayward and Randy Rhea have good books. LT Spice should be useful, too. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
On Sat, 08 Jun 2013 13:50:45 -0700, M. Hamed wrote:

> Hello the most knowledgeable electronics group on earth! > > I am trying to build a few LC oscillators for experimenting with mixers. > I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say > 2 MHz and 100 MHz. I don't know where to start! > > I have a few RF books and the treatment of oscillator can be one of the > following: > > 1- Too much theory on the analysis of oscillator circuits, phase noise, > IMD, etc. No circuits to build. Just demo circuits for illustration, > sometimes only the small signal model. > 2- Circuits to build but designed > at very specific frequencies with very specific components. Very little > on how to generalize things into different frequencies. (The ARRL > handbook 2010 and Experimental Methods fall under this). > 3- Books that > give me a design procedure with S parameters but I can't find any S > parameter files for the devices I'm interested in using. > 4- Cookbooks > that have the same problem as (2). > > Why is it so hard to build an oscillator at an arbitrary frequency?
Because oscillator design isn't easy, if you're going to go about it from an engineering perspective, then you need lots of theory. If you're going to go about it from a technician's perspective, then you need a lot of working examples to start with, and a lot of patience. If you really want to wrap your head around the theory, then grab some books from (2) and (4), and apply what the books from (1) and (3) teach you to analyze the circuits. I found that "Oscillator Design and Computer Simulation" by Rhea was very helpful. When you get right down to the nitty-gritty, Rhea's book shows you how to break the loop in an oscillator circuit, put it into a simulator (such as LTSpice), and do a sweep on it to analyze its characteristics. I've also found that whatever magic LTSpice does to be efficient at analyzing switching power supplies must work for oscillators, because it's been very fast and accurate and simulating oscillator start-up. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Sat, 08 Jun 2013 14:37:01 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed" ><mhdpublic@gmail.com> wrote: > >>Hello the most knowledgeable electronics group on earth! >> >>I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start! >> >>I have a few RF books and the treatment of oscillator can be one of the following: >> >>1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model. >>2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this). >>3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using. >>4- Cookbooks that have the same problem as (2). >> >>Why is it so hard to build an oscillator at an arbitrary frequency? > >It's not. A little Colpitts oscillator is easy. Use a bipolar >transistor, a jfet, or a gaasfet at higher frequencies. > >A rough ballpark for the L and C is to set their reactances to maybe >50 or 100 ohms each at the operating frequency. Use a surface-mount >inductor or wind your own. > >You don't really need s-params. Just make sure you have plenty of >gain-bandwidth in the active device. Subtleties like TC and low phase >noise are a little more work. > >Wes Hayward and Randy Rhea have good books. > >LT Spice should be useful, too.
--- I think Hamed is asking for a VFO schematic to get him started, not for show-off grandstanding. Can you help him, or not? -- JF
On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed"
<mhdpublic@gmail.com> wrote:

>Hello the most knowledgeable electronics group on earth! > >I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start! > >I have a few RF books and the treatment of oscillator can be one of the following: > >1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model. >2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this). >3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using. >4- Cookbooks that have the same problem as (2). > >Why is it so hard to build an oscillator at an arbitrary frequency?
With current components, it is no big deal to make a free running oscillator in the 10-100 GHz range. However, in order to be usable in communication systems, some frequency accuracy is needed. At MF at 1 MHz a frequency accuracy of 1 % would correspond to 10 kHz (2x5 kHz audio passband). The same accuracy at 10 GHz TV satellite band would correspond to 2-4 channels. The real question is that it is no problem making a scanner receiver handling the 0-5 GHz frequency range, however making a good receiver or that frequency range is nearly impossible.
On Sat, 08 Jun 2013 17:22:46 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Sat, 08 Jun 2013 14:37:01 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > >>On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed" >><mhdpublic@gmail.com> wrote: >> >>>Hello the most knowledgeable electronics group on earth! >>> >>>I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start! >>> >>>I have a few RF books and the treatment of oscillator can be one of the following: >>> >>>1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model. >>>2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this). >>>3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using. >>>4- Cookbooks that have the same problem as (2). >>> >>>Why is it so hard to build an oscillator at an arbitrary frequency? >> >>It's not. A little Colpitts oscillator is easy. Use a bipolar >>transistor, a jfet, or a gaasfet at higher frequencies. >> >>A rough ballpark for the L and C is to set their reactances to maybe >>50 or 100 ohms each at the operating frequency. Use a surface-mount >>inductor or wind your own. >> >>You don't really need s-params. Just make sure you have plenty of >>gain-bandwidth in the active device. Subtleties like TC and low phase >>noise are a little more work. >> >>Wes Hayward and Randy Rhea have good books. >> >>LT Spice should be useful, too. > >--- >I think Hamed is asking for a VFO schematic to get him started,
Where did he ask for a schematic? You think he's asking for a schematic because that's what you would need. WITH all parts values worked out. not
>for show-off grandstanding.
Where was any grandstanding? I told him what circuit and parts work, how to scale the LC, and added a couple of references. If he wants to discuss it in more detail, I'll be glad to help.
> >Can you help him, or not? >
Books (like the ones I mentioned) and the web are full of Colpitts schematics. They mostly just work. How much help have you contributed so far? Whining is all you can do. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
"John Larkin" <jlarkin@highlandtechnology.com> wrote in message 
news:og87r8d1ntsncj9j1mivfojvnshv4jpn36@4ax.com...
> On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed" > <mhdpublic@gmail.com> wrote: > >>Hello the most knowledgeable electronics group on earth! >> >>I am trying to build a few LC oscillators for experimenting with mixers. I >>do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 >>MHz and 100 MHz. I don't know where to start! >> >>I have a few RF books and the treatment of oscillator can be one of the >>following: >> >>1- Too much theory on the analysis of oscillator circuits, phase noise, >>IMD, etc. No circuits to build. Just demo circuits for illustration, >>sometimes only the small signal model. >>2- Circuits to build but designed at very specific frequencies with very >>specific components. Very little on how to generalize things into >>different frequencies. (The ARRL handbook 2010 and Experimental Methods >>fall under this). >>3- Books that give me a design procedure with S parameters but I can't >>find any S parameter files for the devices I'm interested in using. >>4- Cookbooks that have the same problem as (2). >> >>Why is it so hard to build an oscillator at an arbitrary frequency? > > It's not. A little Colpitts oscillator is easy. Use a bipolar > transistor, a jfet, or a gaasfet at higher frequencies. > > A rough ballpark for the L and C is to set their reactances to maybe > 50 or 100 ohms each at the operating frequency. Use a surface-mount > inductor or wind your own. > > You don't really need s-params. Just make sure you have plenty of > gain-bandwidth in the active device. Subtleties like TC and low phase > noise are a little more work. > > Wes Hayward and Randy Rhea have good books. > > LT Spice should be useful, too. > > > -- >
Just try to build an amplifier and most times you will get an oscillator. tm
On Sat, 08 Jun 2013 13:50:45 -0700, M. Hamed wrote:

> Why is it so hard to build an oscillator at an arbitrary frequency?
Building an oscillator is easy. Keeping it from drifting around is a different story, but if all you need is something that emits radio frequency most schematics will work if you recalculate the tuning part according to the needed frequency. I'm a big fan of the negative resistance oscillator made using two jfets, one N and one P channel, or a N jfet and a PNP BJT, called "lambda diode oscillator". It will work from audio frequency to the UHF just by changing the LC circuit. I made my first GDM using that circuit. Look for "lambda diode" in google images.
On Sat, 8 Jun 2013 13:50:45 -0700 (PDT), "M. Hamed"
<mhdpublic@gmail.com> wrote:

>Hello the most knowledgeable electronics group on earth! > >I am trying to build a few LC oscillators for experimenting with mixers. I do not want to use Crystals, Frequency Synthesis, DDS, etc. Let's say 2 MHz and 100 MHz. I don't know where to start! > >I have a few RF books and the treatment of oscillator can be one of the following: > >1- Too much theory on the analysis of oscillator circuits, phase noise, IMD, etc. No circuits to build. Just demo circuits for illustration, sometimes only the small signal model. >2- Circuits to build but designed at very specific frequencies with very specific components. Very little on how to generalize things into different frequencies. (The ARRL handbook 2010 and Experimental Methods fall under this). >3- Books that give me a design procedure with S parameters but I can't find any S parameter files for the devices I'm interested in using. >4- Cookbooks that have the same problem as (2). > >Why is it so hard to build an oscillator at an arbitrary frequency?
I've done a few... Sinusoidal: http://www.analog-innovations.com/SED/MC1648-DataSheet.pdf Multivibrator: http://www.analog-innovations.com/SED/MC1658-DataSheet.pdf http://www.analog-innovations.com/SED/MC4024_MC4324.pdf Phase/Frequency Detectors: http://www.analog-innovations.com/SED/MC12040-DataSheet.pdf http://www.analog-innovations.com/SED/MC4044_MC4344.pdf Patents: http://www.analog-innovations.com/SED/Pat-3644835.pdf http://www.analog-innovations.com/SED/Pat-3649929.pdf http://www.analog-innovations.com/SED/Pat-3665343.pdf The 1648 can easily be built with discrete components (as it was breadboarded BC... before CAD and Spice ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85140 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.