AM Radio Design Log

[Fred Abse]

Now I'm going crazy. My multimeter connected to the tank shows 100mV in
the AC setting when my scope is showing 9V p-p. I thought the Ac setting
measures RMS!!

What frequency. What multimeter? You're lucky if you have a meter that
covers more than a few kHz.

My (expensive) Fluke 87V only goes to 20kHz on *some* ranges. On others
it's 5kHz.

My even more expensive HP bench multimeters likewise.

 

[M. Hamed]

What frequency. What multimeter? You're lucky if you have a meter that

covers more than a few kHz.



My (expensive) Fluke 87V only goes to 20kHz on *some* ranges. On others

it's 5kHz.



My even more expensive HP bench multimeters likewise.



--

"For a successful technology, reality must take precedence

over public relations, for nature cannot be fooled."

(Richard Feynman)

Yes. It was a dumb thing to expect What was I thinking?!!

 

[Fred Abse]

Is it really American to give every freaking circuit a name? I do not even
remember those names.

Americans, Brits, and (I believe) Australians, Germans, and Frenchmen
honor designers by naming their designs after them. Even your idols, the
Soviets did.

I'm sure I could name some Nederlanders, too, given time.

 

[M. Hamed]

Zero, as I explained before.

Ok, now it's starting to sink in! Thanks.

 

[Fred Abse]

Do you see those 2 round white ceramic disks? That is what I happen to be
playing with these days.

Yes, I see them. Tell me more.

 

[John S]

Americans, Brits, and (I believe) Australians, Germans, and Frenchmen
honor designers by naming their designs after them. Even your idols, the
Soviets did.

I'm sure I could name some Nederlanders, too, given time.

It is frequently convenient to refer to standard circuits by name to
assist communication between discussers ;-)

 

[John S]

On Saturday, July 20, 2013 9:32:25 AM UTC-7, Jan Panteltje wrote:

<Snip>

So you're essentially suggesting to convert to a Colpitts. I have
built Colpitts oscillators before and they seem easier to understand.
I thought I'd take a shot at this strange Hartley and the use of
tapped inductors.

The Hartley can be constructed using two inductors rather than one that
is tapped. In my opinion, that makes it sort of a Colpitts anyway. I
don't like tapped inductors because it is harder to change for
experiments. YMMV.

While I'm thinking about it, I had some problems getting a Colpitts to
start and run properly. I learned that my ceramic caps had high (for
ceramic) dissipation factors (low Q). Replacing them with NP0 cured the
problem. You may not run in to this problem, but it might be worthwhile
to remember.

You're doing great. Keep up the good work.

Cheers,
JohnS

 

[John S]

The Hartley can be constructed using two inductors rather than one that
is tapped. In my opinion, that makes it sort of a Colpitts anyway. I
don't like tapped inductors because it is harder to change for
experiments. YMMV.

Yow! I just looked at your LTSpice thing. Your simulation is actually
using 4 inductors, not 2. The reason is that you do not provide coupling
between the tapped parts.

Just FYI.

JohnS

 

[Glenn]

On a sunny day (Sat, 20 Jul 2013 20:53:24 +0300) it happened Tauno Voipio


Is it really American to give every freaking circuit a name?
I do not even remember those names.

....

Jan - then you do not know the Vacker oscillator either ;-)

E.g. Why do engines have names V8, Stirling Engine, Jet Engine and so on.

-

My presumption is that all variable LC oscillators ought to be using
Vacker design to correctly maintain oscillation combined with low
feedback and amplitude - over a small - or especially wide frequency
variation.

With all the electronic made in the last 30 years, why has no one found
this design (again)? Why has no one been educated about this oscillator?


The Vackar VFO oscillator:
http://www.qsl.net/va3diw/vackar.html
Quote: "...
Jiri Vackar [Jiří Vackář] invented his VFO oscillator during late 40s.
It is probably the most stable VFO oscillator known. Thanks George!
....
The frequency tuning range is above 2.5, not observable in any other
type of oscillator. The Coupling ratio is fixed; typical range is 1:4 up
to 1:9.
[]
The tuning is provided independently of coupling. Transistor's
parametric variables are isolated from the resonator. The transistor
input is not overloaded as Clapp or other circuits.
....
The stability is close to XO.
....
Ordinary oscillator has poor tuning range, the output voltage swing is
unstable, and the frequency stability is poor as well. The industry
tries hard to make its sale pitch, to replace single oscillator with 50
ICs, digital dividers, approximation registers, thermostats, and other
junk. Now what?
....
The best regulator of all times is maybe the LM723. [really ]
....
The VFO is better solution than the AD9850,AD9891 DDS - direct digital
synthesizer chip.
....
Do you want to spend time calling around and dealing with ten weeks lead
time? An old cap from an old TV tuner can help to solve your problem.
The treasures are around you.
...."

Scanning of original paper:
http://web.archive.org/web/20120219062848/n1ekv.org/Oscillators/Vackar_wholepaper.pdf
http://n1ekv.org/Oscillators/Vackar_wholepaper.pdf

http://n1ekv.org/Oscillators/2003 MUD resources.htm

-

A regenerative receiver ought to be easier to tune with Vacker design.
Why has anyone not thought of that - assuming no one did - please
correct me if I am wrong.

Glenn

 

[Glenn]

On 20/07/13 22.10, Jan Panteltje wrote:
....

Here are 2 other oscillators that may make your head spin:
http://panteltje.com/pub/5_dollar_LNB_PCB_IMG_3582.GIF

Do you see those 2 round white ceramic disks?
That is what I happen to be playing with these days.

White Hockey puck oscillators...

 

[[email protected]]

White Hockey puck oscillators...

Named after their inventor Dr White-Hockey?

 

[Glenn]

On a sunny day (Sat, 20 Jul 2013 20:53:24 +0300) it happened Tauno Voipio


Is it really American to give every freaking circuit a name?
I do not even remember those names.

....

Jan - then you do not know the Vacker oscillator either ;-)

E.g. Why do engines have names V8, Stirling Engine, Jet Engine and so on.

-

My presumption is that all variable LC oscillators ought to be using
Vacker design to correctly maintain oscillation combined with low
feedback and amplitude - over a small - or especially wide frequency
variation.

With all the electronic made in the last 30 years, why has no one found
this design (again)? Why has no one been educated about this oscillator?


The Vackar VFO oscillator:
http://www.qsl.net/va3diw/vackar.html
Quote: "...
Jiri Vackar [Jiří Vackář] invented his VFO oscillator during late 40s.
It is probably the most stable VFO oscillator known. Thanks George!
....
The frequency tuning range is above 2.5, not observable in any other
type of oscillator. The Coupling ratio is fixed; typical range is 1:4 up
to 1:9.
[]
The tuning is provided independently of coupling. Transistor's
parametric variables are isolated from the resonator. The transistor
input is not overloaded as Clapp or other circuits.
....
The stability is close to XO.
....
Ordinary oscillator has poor tuning range, the output voltage swing is
unstable, and the frequency stability is poor as well. The industry
tries hard to make its sale pitch, to replace single oscillator with 50
ICs, digital dividers, approximation registers, thermostats, and other
junk. Now what?
....
The best regulator of all times is maybe the LM723. [really ]
....
The VFO is better solution than the AD9850,AD9891 DDS - direct digital
synthesizer chip.
....
Do you want to spend time calling around and dealing with ten weeks lead
time? An old cap from an old TV tuner can help to solve your problem.
The treasures are around you.
...."

Scanning of original paper:
http://web.archive.org/web/20120219062848/n1ekv.org/Oscillators/Vackar_wholepaper.pdf

http://n1ekv.org/Oscillators/Vackar_wholepaper.pdf

http://n1ekv.org/Oscillators/2003 MUD resources.htm

-

A regenerative receiver ought to be easier to tune with Vacker design.
Why has anyone not thought of that - assuming no one did - please
correct me if I am wrong.

Glenn

http://en.wikipedia.org/wiki/Vackář_oscillator
Quote: "...
Specifically, Vackář found that forward transconductance varied as ω3
for the Clapp oscillator, as 1/ω for the Seiler oscillator, and as ω/Q
for his design, where the Q factor of the coil (L1) increases with ω.
...."

/Glenn

 

[Glenn]

Right, the fun is the 'pucks'(been a while since I played hockey)
are not really mechanicaly or electrically ? connected to anything.
They are EM coupled however to 2 nearby mircro strips,
and one oscillates at 9.75 GHz (the big one), and the other at 10.6 GHz.
http://en.wikipedia.org/wiki/Dielectric_resonator

These YIG-stones is also smart - great oscillator and filter balls - but
not named after any human? They are also EM coupled:
http://en.wikipedia.org/wiki/Yttrium_iron_garnet
http://en.wikipedia.org/wiki/YIG_sphere

Used in elder quality spectrum analyzers.

 

[josephkk]

Right, I had that problem several times, perhaps ceramic caps dissipate
away energy by mechanical vibration.

I often write 'poly' next to tuning caps, in one of those voltage
converters the ceramic caps actually got hot. Was way below their
specified operating voltage.

Wouldn't surprise me. Most of the High K ceramic dielectrics are
piezoelectric in nature. They also make physically resonant filters with
the same materials.

?-)

 

[Glenn]

On 21/07/13 10.39, Jan Panteltje wrote:
....

in one of those voltage converters the ceramic caps actually got hot.
Was way below their specified operating voltage.

The reason is high ESR. Even ce-capacitors are divided in "normal"-ESR
and low-ESR.

http://en.wikipedia.org/wiki/Equivalent_series_resistance

In window "Applications" you can choose SMPS filtering:
http://www.digikey.com/product-search/en/capacitors/ceramic-capacitors/131083

Capacitor Values:
Don’t Believe the Label:
http://powerelectronics.com/site-fi...ackaging_interconnects/packaging/705PET21.pdf

Therefore some ceramic types can be used for measuring voltage or
temperature, because the capacitance vary.

 

[Fred Abse]

Jan - then you do not know the Vacker oscillator either ;-)

Shouldn't that be "Vackar"?

 

[M. Hamed]

The Hartley can be constructed using two inductors rather than one that
is tapped. In my opinion, that makes it sort of a Colpitts anyway.

Yes. That was done on purpose. I remembered reading somewhere that coupling is not needed (I think it was in Hayward's Introduction to RF Design).

I don't like tapped inductors because it is harder to change for
experiments. YMMV.

It was something I wanted to try and it saves me an extra toroid. Wounding both inductors on the same toroid would have been essentially the same.

You're doing great. Keep up the good work.

Thanks John. I appreciate the encouragement.

 

[M. Hamed]

While I'm thinking about it, I had some problems getting a Colpitts to
start and run properly. I learned that my ceramic caps had high (for
ceramic) dissipation factors (low Q). Replacing them with NP0 cured the
problem. You may not run in to this problem, but it might be worthwhile
to remember.

From my readings, capacitor low Q is usually not an issue up to high frequencies. Before that the inductor Q is more important. I am compelled to ask at which frequencies was this a problem to you?

 

[M. Hamed]

The discussion about capacitors reminded me of a good article I read a few weeks back on EDN:

http://bit.ly/12cukvF

It has mention of piezoelectric effects and also variations with voltage which are often not specified.

 

[Glenn]

Thanks, nice table.

PS, as mentioned on that site, there is also an other issue with at least some ceramic caps:
they are not perfect insulators, and cause noise by themselves.
In this project:
http://panteltje.com/panteltje/pic/mag_pic/
at one point I thought I was seeing the magnetic variations in the earth core...
(Those exists at very low level), but in this case it turned out
to be fluctuating DC current changes (say varying leakage) in those
brown 470nF caps...
Bummer...

OK those were cheap caps...

Some pesky ceramics are superconductors:
https://en.wikipedia.org/wiki/YBCO