FM Oscillator

[camediaman]

Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what
kind of oscillator is it, where is the input/output/feedback, what
are these thick lines - is it waveguide technology, what is the
equivalent component, is it a transformer?

 

[John Larkin]

On Tue, 6 Apr 2004 15:08:53 +0100, "camediaman"
<camediaman@freenet.com> wrote:

Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what
kind of oscillator is it, where is the input/output/feedback, what
are these thick lines - is it waveguide technology, what is the
equivalent component, is it a transformer?

Some people draw inductors that way. If so, it's a Hartley.

John

 

[Dbowey]

camediaman posted:

<< Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what kind of
oscillator is it, where is the input/output/feedback, what are these thick
lines - is it waveguide technology, what is the equivalent component, is it a
transformer?

---

NOT in order of the questions:

• The type of oscillator is Hartley.

• The thick lines are strip-line inductors
cut into one side of a 2-sided board.

The longer one is equivalent to a multi-turn
coil, tapped at about 25% from the bottom.

The smaller, is equivalent to a 1 turn coil
(a "link") adjacent to the top end of the larger
inductor.

• Output is from the small inductor (the link)
at the point designated "ANT"(enna).

• Feedback is from the inductor's tap, to T1's source.

• Is it waveguide technology? hmmm! tough question...
Waveguides and other technologies cross each other
at many junctures, and stripline was probably first
in microwave circuits, some of which have striplines
within waveguides, but I don't think I would consider
striplines to be waveguide technology. It is too
broadly used elsewhere.

• The "input" is audio. I'd say the input is where R2
connects to D1.

• Equivalent component: Use coil inductors as described
above. I estimate the larger inductor should be about
0.25 uH end-to-end. All the other parts and values
are fine.

Don

 

[camediaman]

. Feedback is from the inductor's tap, to T1's source.

It seems as though T1 is not biased, can you see any
DC current flowing? Vgs=0 should imply Id=0

. Is it waveguide technology? hmmm! tough question...
Waveguides and other technologies cross each other
at many junctures, and stripline was probably first
in microwave circuits, some of which have striplines
within waveguides, but I don't think I would consider
striplines to be waveguide technology. It is too
broadly used elsewhere.

Sorry, I meant to say micro strip technology, but I think they
are related to waveguide aren't they, they probably borrowed
the technique to create the Hartley coils.

Any ideas what are C6/D2 for ?

 

[Rich Grise]

"Dbowey" <dbowey@aol.com> wrote in message
news:20040406135757.09444.00000637@mb-m24.aol.com...

camediaman posted:

Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what kind of
oscillator is it, where is the input/output/feedback, what are these thick
lines - is it waveguide technology, what is the equivalent component, is
it a
transformer?

---

NOT in order of the questions:

. The type of oscillator is Hartley.

. The thick lines are strip-line inductors
cut into one side of a 2-sided board.

This is very misleading; I'm not trying to be a strip-line expert, since I'm
not, but just by the seat of my pants, the conductor from the source of
T1 to the tap would have more inductance than the whole tuned circuit!

I'd be willing to bet real money that that's just the way that particular
designer draws (bulk, ordinary, wound) inductors, judging from the styles
of the other parts.

Of course, there's just as much of a chance that the schematic doesn't
really represent the mechanical layout, but if that's the case, then why
provide a more pictorial version of just the one component?

Cheers!
Rich

 

[Dbowey]

Camidiaman posted, in part:
<< Any ideas what are C6/D2 for ? >>

---

C6 brings the drain closer to ground for RF.

D2: I think it's main purpose is to prevent the RF voltage from becoming high
enough to damage T1. I haven't checked the spec on D2.... It could also be a
polarity guard, but that is not an ideal location for that function.

So.... when are you going to build it?

For my first experience with stripline I built oscillators generating signals
in the UHF TV band so I could find the signal with a frequency calibrated UHF
TV tuner. This helped me determine the dialectric constant of the board
materials I used. A Moto Tool makes rough cuts, but it got the job done.

Don

 

[Dbowey]

Rich posted:

<< "Dbowey" <dbowey@aol.com> wrote in message
news:20040406135757.09444.00000637@mb-m24.aol.com...

camediaman posted:

Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what kind of
oscillator is it, where is the input/output/feedback, what are these thick
lines - is it waveguide technology, what is the equivalent component, is
it a
transformer?

---

NOT in order of the questions:

. The type of oscillator is Hartley.

. The thick lines are strip-line inductors
cut into one side of a 2-sided board.

This is very misleading; I'm not trying to be a strip-line expert, since I'm
not, but just by the seat of my pants, the conductor from the source of
T1 to the tap would have more inductance than the whole tuned circuit!
<<

It is definitely stripline - That is how they are shown schematicaly.
Schematics rarely show the critical nature of layout. The source of T1 would
have a very short lead-length to the "tap" point.

I'd be willing to bet real money that that's just the way that particular
designer draws (bulk, ordinary, wound) inductors, judging from the styles

of the other parts.

Of course, there's just as much of a chance that the schematic doesn't
really represent the mechanical layout, but if that's the case, then why
provide a more pictorial version of just the one component?
Because it isn't a coil. All other components have their representative icon;
so does stripline.

Don

 

[camediaman]

Thanks everyone, one more question, is the dc bias point
saturated, seems like Vgs=0 which should result in Id=Idss
and R3 is not going to offer any high current protection,
this is strange, the transistor could burn ?

 

[Watson A.Name \"Watt Sun]

Dbowey wrote:

camediaman posted:

Can someone explain to me the following fm oscillator

http://www.geocities.com/myelectronicsrevision/fmosc.jpg

No need to explain the audio section, just the oscillator, what kind of
oscillator is it, where is the input/output/feedback, what are these thick
lines - is it waveguide technology, what is the equivalent component, is it a
transformer?

---

NOT in order of the questions:

• The type of oscillator is Hartley.

• The thick lines are strip-line inductors
cut into one side of a 2-sided board.

The longer one is equivalent to a multi-turn
coil, tapped at about 25% from the bottom.

The smaller, is equivalent to a 1 turn coil
(a "link") adjacent to the top end of the larger
inductor.

• Output is from the small inductor (the link)
at the point designated "ANT"(enna).

• Feedback is from the inductor's tap, to T1's source.

• Is it waveguide technology? hmmm! tough question...
Waveguides and other technologies cross each other
at many junctures, and stripline was probably first
in microwave circuits, some of which have striplines
within waveguides, but I don't think I would consider
striplines to be waveguide technology. It is too
broadly used elsewhere.

• The "input" is audio. I'd say the input is where R2
connects to D1.

• Equivalent component: Use coil inductors as described
above. I estimate the larger inductor should be about
0.25 uH end-to-end. All the other parts and values
are fine.

Except the audio section is a huge waste of parts. They went to all the
trouble to step the impedance down to drive a 1k pot, then feed that
into a 220k resistor! Stoopid! Could've been done with a single
transistor or FET, and a lot less parts.

> Don

 

[Watson A.Name \"Watt Sun]

Rich Grise wrote:

[snip]

I'd be willing to bet real money that that's just the way that particular
designer draws (bulk, ordinary, wound) inductors, judging from the styles
of the other parts.

Of course, there's just as much of a chance that the schematic doesn't
really represent the mechanical layout, but if that's the case, then why
provide a more pictorial version of just the one component?

I agree with Rich. Those are regular coil wound inductors.

Cheers!
Rich

 

[Dbowey]

Watson posted:

<< Rich Grise wrote:

[snip]

I'd be willing to bet real money that that's just the way that particular
designer draws (bulk, ordinary, wound) inductors, judging from the styles
of the other parts.

Of course, there's just as much of a chance that the schematic doesn't
really represent the mechanical layout, but if that's the case, then why
provide a more pictorial version of just the one component?

I agree with Rich. Those are regular coil wound inductors.
Now that we have heard from someone who has the actual board, I agree the board
does not contain a stripline inductor. The schematic, however, does denote
stripline.

Don

 

[Rich Grise]

Thanks - I guess I didn't really know what "stripline" is.
But, I'm pretty sure that I've seen coil-wound inductors
shown as a black bar like that, usually either in old or
foreign schems.

Or have I been hallucinating? ;-)

"Robert C Monsen" <rcsurname@comcast.net> wrote in message news:d54dc.96043

"Dbowey" <dbowey@aol.com> wrote in message
Watson posted:
Rich Grise wrote:
stripline.

Don

Sorry, I must have been confusing in my post. It IS a stripline inductor,
the trace is wound around like this:

-------------------------|
| --------------------| |
| | ###------------- | |
| | ###2 | | |
| | | | |
| | ###1 | | |
| | ###------------- | |
| | ###--------------- |
| |---------------------|
| |
| |
| |
| |
| | 1 is the junction for a diode and variable cap
| |
| |
| | 2 is jumpered over to another pad where the
| | antenna is connected.
| |
| | The traces are 1mm, the distance between is 1mm
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


The scale is off, but this is the way the traces are layed out.

Regards,
Bob Monsen

 

[Michael Black]

"Robert C Monsen" (rcsurname@comcast.net) writes:

"Dbowey" <dbowey@aol.com> wrote in message
news:20040407192810.09410.00000669@mb-m24.aol.com...
Watson posted:

Rich Grise wrote:

[snip]

I'd be willing to bet real money that that's just the way that
particular
designer draws (bulk, ordinary, wound) inductors, judging from the
styles
of the other parts.

Of course, there's just as much of a chance that the schematic doesn't
really represent the mechanical layout, but if that's the case, then why
provide a more pictorial version of just the one component?

I agree with Rich. Those are regular coil wound inductors.


Now that we have heard from someone who has the actual board, I agree the
board
does not contain a stripline inductor. The schematic, however, does
denote
stripline.

Don

Sorry, I must have been confusing in my post. It IS a stripline inductor,
the trace is wound around like this:

-------------------------|
| --------------------| |
| | ###------------- | |
| | ###2 | | |
| | | | |
| | ###1 | | |
| | ###------------- | |
| | ###--------------- |
| |---------------------|
| |
| |
| |
| |
| | 1 is the junction for a diode and variable cap
| |
| |
| | 2 is jumpered over to another pad where the
| | antenna is connected.
| |
| | The traces are 1mm, the distance between is 1mm
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


The scale is off, but this is the way the traces are layed out.

Regards,
Bob Monsen


But what makes that stripline?

Is it double sided board, with the other side simply grounded?

If not then it's not stripline.

It's as you described it before, an inductor that etched right
on the circuit board. It's no different than if one used wire
to make up that coil. It likely is more mechanically stable
etched right on the board, but if the board varies with some condition,
such as temperature, that might affect the inductor.

Such inductors are rarely seen, but they aren't new. They aren't
practical unless the inductor value is small enough, and for that matter
there is limited application where you need a small inductor and can
live with it being out in the open.

And having once seem a brief article in a hobby magazine about
how to "wind" one of those inductors, details are either rare or
hidden in professional material. And unlike winding a coil with
wire, if you don't get it right you have to scrap the board and
start again. Not so great when experimenting.

Michael

 

[Robert Monsen]

et472@FreeNet.Carleton.CA (Michael Black) wrote in message news:<c53tm9$4pm$1@freenet9.carleton.ca>...

"Robert C Monsen" (rcsurname@comcast.net) writes:
"Dbowey" <dbowey@aol.com> wrote in message
news:20040407192810.09410.00000669@mb-m24.aol.com...
Watson posted:

Rich Grise wrote:
But what makes that stripline?

Is it double sided board, with the other side simply grounded?

If not then it's not stripline.

It's as you described it before, an inductor that etched right
on the circuit board. It's no different than if one used wire
to make up that coil. It likely is more mechanically stable
etched right on the board, but if the board varies with some condition,
such as temperature, that might affect the inductor.

Such inductors are rarely seen, but they aren't new. They aren't
practical unless the inductor value is small enough, and for that matter
there is limited application where you need a small inductor and can
live with it being out in the open.

And having once seem a brief article in a hobby magazine about
how to "wind" one of those inductors, details are either rare or
hidden in professional material. And unlike winding a coil with
wire, if you don't get it right you have to scrap the board and
start again. Not so great when experimenting.

Michael

Its a single sided board. The components are on the other side, but
there is no grounding layer. I can see through the board, so there
isn't an internal grounding layer either.

So, what is the definition of 'stripline'? I thought it meant a trace
which acts like a circuit element (which is what these traces do.)

Regards,
Bob Monsen

 

[John Larkin]

On 8 Apr 2004 21:43:13 -0700, rcmonsen@comcast.net (Robert Monsen)
wrote:

et472@FreeNet.Carleton.CA (Michael Black) wrote in message news:<c53tm9$4pm$1@freenet9.carleton.ca>...
"Robert C Monsen" (rcsurname@comcast.net) writes:
"Dbowey" <dbowey@aol.com> wrote in message
news:20040407192810.09410.00000669@mb-m24.aol.com...
Watson posted:

Rich Grise wrote:
But what makes that stripline?

Is it double sided board, with the other side simply grounded?

If not then it's not stripline.

It's as you described it before, an inductor that etched right
on the circuit board. It's no different than if one used wire
to make up that coil. It likely is more mechanically stable
etched right on the board, but if the board varies with some condition,
such as temperature, that might affect the inductor.

Such inductors are rarely seen, but they aren't new. They aren't
practical unless the inductor value is small enough, and for that matter
there is limited application where you need a small inductor and can
live with it being out in the open.

And having once seem a brief article in a hobby magazine about
how to "wind" one of those inductors, details are either rare or
hidden in professional material. And unlike winding a coil with
wire, if you don't get it right you have to scrap the board and
start again. Not so great when experimenting.

Michael


Its a single sided board. The components are on the other side, but
there is no grounding layer. I can see through the board, so there
isn't an internal grounding layer either.

So, what is the definition of 'stripline'? I thought it meant a trace
which acts like a circuit element (which is what these traces do.)

Regards,
Bob Monsen

Stripline is an inner-layer trace on a multilayer board, where
adjacent layers are ground planes.

Microstrip is a surface layer, where the opposite side (or an inner
layer) is a ground plane.

(Sometimes striplines and microstrips are used without ground planes,
but that's not common.)

It seems the OP's circuit is neither.

Download Agilent's Appcad, select "passive circuits", and play around.

John

 

[camediaman]

I think (as someone pointed out) the circuit of this velleman kit
(www.velleman.be) is a one side pcb, where these coils which
are denoted as thick lines are in effect coils which are drawn
on the track side of the pcb in a form of a sipral.

I have another question about this circuit. It is about T1 and its
dc bias configuration. It seems that there is no dc voltage source.
My electronics book says that when Vgs=0 the transistor will
be saturated (because it is a fet). Is this the correct analysis ?