Chip with simple program for Toy

[Phil Allison]

<emailaddress@insightbb.com>


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.





...... Phil

 

[starfire]

<sodaant@gmail.com> wrote in message
news:93b9943c-d66b-48b0-b3b9-65c42caf5dab@8g2000hse.googlegroups.com...

I need a new soldering station to replace one I lost during a move.
This is for hobby use in microcontrollers and general analog/digital
work.

Is a Metcal MX-500 a reasonable choice for these applications? I know
it's more expensive than other stations, but I've heard good things
about it.

Anything else I should consider?

I think someone already mentioned going to E-Bay to look for a used Metcal.
Great idea! I did that and am very happy with the rsults. I got an MX-100
with a lot of extras (extra tips, solder, and tools) for a very reasonable
price. You can't beat the flexibility of the Metcal stations, especially if
you need to (eventually) do fine-pitch surface mount work. All that being
said, I still use an old Weller WES051 station for quick solder jobs, also.
Its been a work-horse for a lot of years!

Dave

 

[Phil Allison]

<emailaddress@insightbb.com>


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.




...... Phil

 

[john jardine]

"Bill Bowden" <wrongaddress@att.net> wrote in message
news:f0885697-6c81-4c90-835e-5817c55e30ff@d77g2000hsb.googlegroups.com...

What is the best way to measure unloaded Q of a tuned LC circuit (AM
loop Antenna) without a Q meter?

I tried a scope and generator and loosly coupled the generator to the
loop, using a single turn of wire and 50 ohm resistor, and monitored
amplitude against frequency, but I get different results depending on
the setup. The scope probe is 10X. The frequency of interest is 500KHz
to 2 MHz.

How can I accurately measure the Q of the circuit without a Q meter?

-Bill

Yep, each measurement can turn out different. The pleasing upside is
acknowledging that the most accurate test setup was the one that returned
the highest Q value!.
http://www.crystal-radio.eu/enqmeting.htm describes in great detail what
Mike has already noted. Also look at the series of "LC experiments".

 

[Paul E. Schoen]

<emailaddress@insightbb.com> wrote in message
news:da3d3fd0-1853-4851-adaa-d062241579be@x41g2000hsb.googlegroups.com...
On Jul 11, 2:34 pm, ehsjr
<e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:

I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear. There is no single formula for you. Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved. You insist on ignoring them. So, we can't
help you, no matter how hard we try. Sorry.

"A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation."

"There is an equation that could be made. How accurate the answer from
it would depend on how complete it was. I came here looking to make
as complete an equation as possible but it seems everyone else is
apathetic about the idea and only wants to tell me I don't "need" to
know or that it can't be done."

"It's not magic. A caveman looking at a bic lighter would think that
is magic but is it? Your great great grandfather, if he were alive
today, might think a computer is magic, but is it? Just because
someone doesn't know something it doesn't become magic. It would just
require someone bothering to do so, which I was attempting but it
seems I'm going it alone because others think it's too hard or they're
too lazy or whatever the reason. That's fine, nobody is compelled to
do anything but if they had no assistance (some replying did!) then as
always they should've just moved on to the next thread."

=========================================================================

I find it curious that you reply only to those who either disagree with you
or do not give you a formula that automagically takes into account every
design parameter and spits out the answers you demand. And who is the lazy
one? You are asking for free advice, and you are getting a lot of bang for
your buck. Contract a design engineer at $100/hour and they will not be
"lazy".

The factors involved in your design are numerous:

Input voltage range
Frequency range
Physical size constraints
Efficiency
Costs (NRE, materials, labor)
Environmental conditions (temp, humidity, altitude, etc.)
Safety (UL, NEMA, Medical, etc.)
Isolation/insulation/leakage current
Surge withstand
EMI/RFI
Load variations
Duty cycle
Overcurrent and short circuit protection
Reverse connection protection
Charging current/voltage/time/temperature profile
Acceptable MTBF

You have constrained the parameters by saying that the charger circuit has
been designed and you are not willing or able to change that. So you are
only looking for a cheap and dirty AC to DC power supply that will meet
your needs. Your charger circuit must have specifications for what it can
accept as raw DC input, and what sort of current it will draw under all
conditions. IOW, you need to model this circuit with a "formula" or SPICE
model. Then you must decide if you want to use an off-the-shelf transformer
or design one specifically to meet your needs. An OTS solution will be
initially cheaper, but you will sacrifice something, like efficiency or
physical size that will not be optimized. You will need to choose one that
meets (but probably exceeds) your specifications.

There are many simplified formulas that have been given to you, that will
give results close enough to choose from several OTS transformers that
should meet your specs. You can also model the transformer pretty well in
SPICE. But you will, sooner or later, need to build a prototype and test
the hell out of it. After a few hours of testing, you can pretty well
characterize the transformer, and then fine tune your selection. Or you can
use the results to design a custom transformer that exactly meets your
needs. But tranny design gets rather complex when you are pushing the
limits of efficiency, cost, size, regulation, and other factors.

You have all the information you need to design, build, and simulate your
DC front-end circuit. We do not have all the information we need to model
your charger load, and even if we did, it is up to you to actually design
the thing. As I said before, SPICE is essentially a mathematical formula
that you can modify with all the parameters you want, and run step and
sweep analyses to make sure your initial design is OK. Then you can tweak
it ad nauseum to get it as close to perfect as it will ever be.

Paul

 

[Paul E. Schoen]

<mrdarrett@gmail.com> wrote in message
news:0631a23f-0a93-4a34-a703-b3bd4e22ba06@j22g2000hsf.googlegroups.com...

On Jul 12, 7:40 am, emailaddr...@insightbb.com wrote:
..snip..

However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.


Universal equation. Here you go.

http://en.wikipedia.org/wiki/Heat_equation
http://en.wikipedia.org/wiki/Newton%27s_law_of_cooling#Newton.27s_law_of_cooling

Also check out "Introduction to Heat Transfer" by Incropera and
DeWitt.

The game is to keep the transformer wires at only a moderate
temperature higher than ambient, or you will melt the wiring
insulation.

Knock yourself out.

Michael

These equations are only part of the overall solution. Transformers are
complex physical entities with many materials having different thermal
characteristics, and the temperature of any spot in the transformer depends
on the amount of power being applied, time, and the way in which heat is
radiated, conducted, or convected away from the source of the heat. The
winding insulation is rated at a certain temperature according to the
insulation class, and may vary from about 105 C (Class A) to 180 C (Class
H).

http://www.engineeringtoolbox.com/nema-insulation-classes-d_734.html

That is for motors (and I think it applies also to transformers), but here
is information more specific to trannies, and allows for hot spots:
http://www.jeffersonelectric.com/cgi-bin/site.pl?3208&dwContent_contentID=12

This shows a wider range of classes up to "S", which is 250 C. Now, that's
hot!
http://www.pleo.com/ulsystem/eis_apply.htm

This is a detailed document with more formulas for the OP to use when he
designs his transformer:
http://www.superioressex.com/uploadedFiles/News/White_Papers/emcwa-nema_magnet-thermal-class-ratings.pdf

Paul

 

[Jim Yanik]

Cleveland Tech <ClevelandTech@Hotmail.com> wrote in
news:Xns9AD9B94BE7F09clevelandTechhotmail@207.115.33.102:

John Fields <jfields@austininstruments.com> wrote in
newsnnf745jmrbsbpv7d4e28pka5f5866tdeq@4ax.com:

On Fri, 11 Jul 2008 21:39:59 GMT, Cleveland Tech
ClevelandTech@Hotmail.com> wrote:

I've looked over the newsgroup for a few weeks, and haven't seen
anything pop up, so thought I'd ask.

Has anyone seen any schematics floating around to make an electronic
model rocket launcher? If so, have they / could they be posted here?

---
They're posted, but rarely.

Tell us what you want to do and someone might be able to help you.

I've crossposted this to a few more groups, so you might get some
responses from them as well.

Also, you might want to try:

http://www.google.com/search?sourceid=navclient&ie=UTF-8
&rls=GFRC,GFRC:
2006-50,GFRC:en&q=electronic+model+rocket+launcher

JF


Thanks for the reply! I will also check the other newsgroups.

My idea was to build something that can handle multiple rockets either
simultaneously (up to 4 or 5) or in succession, for a father son group.

how are you planning to track all those rockets? you could lose some of
them that way.It's not a fireworks show.

I have a couple of Estes branded launchers, and they're only for A to D
sized engines. Part of the plan is to build a little bit more to also
handle E sized engines as well.

have you tried rec.model.rockets NG ?

to fire several rocket igniters,you will need a high current source like a
lead-acid battery like a small car battery,heavy gauge leads,perhaps a
relay type system to keep the battery close to the launchers while keeping
the controller a fair distance away.I'd avoid semiconductors,as they can
fail from surges/shorts,be static-damaged;they are a safety issue.

--
Jim Yanik
jyanik
at
kua.net

 

[Phil Allison]

"Jamie" = Maynard A. Philbrook = radio ham KA1LPA

WARNING: Ignore everything this total moron posts.

For example, lets assume you have 120 volt service into a wallwart, the
unit outputs 12 volts, this would be a 10:1 ratio. So if we were to
measure lets say 200 ohms on the primary side, we would thus scale that
down by 10 = 20 ohms. The DC resistance on the secondary side is simply
added to this to give you a sum R..

** WRONG !!!!!!!!

Primary resistance appears at the secondary divided by the SQUARE of the
transformer's actual turns ratio.

The turns ratio is always less than the nominal voltage ratio, to allow for
voltage drop under load, so - for the above case, ( very small
transformer) the turns ratio is about 8 and reflected resistance is
therefore 200 /64 = 3.13 ohms.



....... Phil

 

[Phil Allison]

"John Fields"

I've seen it a few times also, and I think it's a way of trying to
save face by not admitting that the gift that was given incurred
emotional indebtedness.

That is, if you give me a gift of knowledge and I dis it, I'll still
have the gift but in my mind I won't owe you anything for it.

Make sense?

** If you imagine some little a brat throwing a toy that is not the one he
wanted back at Santa.



...... Phil

 

[Paul E. Schoen]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:6dt714F47182U1@mid.individual.net...

"Jamie" = Maynard A. Philbrook = radio ham KA1LPA

WARNING: Ignore everything this total moron posts.



For example, lets assume you have 120 volt service into a wallwart,
the unit outputs 12 volts, this would be a 10:1 ratio. So if we were to
measure lets say 200 ohms on the primary side, we would thus scale that
down by 10 = 20 ohms. The DC resistance on the secondary side is simply
added to this to give you a sum R..


** WRONG !!!!!!!!

Primary resistance appears at the secondary divided by the SQUARE of the
transformer's actual turns ratio.

The turns ratio is always less than the nominal voltage ratio, to allow
for voltage drop under load, so - for the above case, ( very small
transformer) the turns ratio is about 8 and reflected resistance is
therefore 200 /64 = 3.13 ohms.

You're right. I just tried a SPICE model with a tranny that has 400 mH
primary and 25 mH secondary, which is a 4:1 transformer with an impedance
ratio of 16:1. Adding 16 ohms to the primary series resistance, or 1 ohm to
the secondary, gives the same result into a load. It makes sense, because
you have four times the current and 1/4 the voltage in the secondary, so
the effective resistance (or impedance) ratio is a square function.

If you try the simulation, you will need to keep at least about 1 uOhm of
series R in the primary.

Paul

==================================================================

Version 4
SHEET 1 880 680
WIRE 128 128 16 128
WIRE 336 128 224 128
WIRE 128 208 16 208
WIRE 336 208 224 208
WIRE 16 224 16 208
WIRE 336 224 336 208
FLAG 16 224 0
FLAG 336 224 0
SYMBOL ind2 112 112 R0
WINDOW 0 4 -10 Left 0
WINDOW 3 -12 124 Left 0
SYMATTR InstName L1
SYMATTR Value 400m
SYMATTR Type ind
SYMATTR SpiceLine Rser=16
SYMBOL ind2 240 224 R180
WINDOW 0 2 122 Left 0
WINDOW 3 -8 -11 Left 0
SYMATTR InstName L2
SYMATTR Value 25m
SYMATTR Type ind
SYMATTR SpiceLine Rser=0
SYMBOL voltage 16 112 R0
WINDOW 0 -12 -2 Left 0
WINDOW 3 -34 192 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 2.828 60 0 0 0 100)
SYMBOL res 320 112 R0
SYMATTR InstName R1
SYMATTR Value 1
TEXT 112 272 Left 0 !K1 L1 L2 1
TEXT -20 268 Left 0 !.tran 1

 

[Phil Allison]

"Paul E. Schoen"

Primary resistance appears at the secondary divided by the SQUARE of the
transformer's actual turns ratio.

The turns ratio is always less than the nominal voltage ratio, to allow
for voltage drop under load, so - for the above case, ( very small
transformer) the turns ratio is about 8 and reflected resistance is
therefore 200 /64 = 3.13 ohms.

You're right. I just tried a SPICE model with a tranny that has 400 mH
primary and 25 mH secondary, which is a 4:1 transformer with an impedance
ratio of 16:1. Adding 16 ohms to the primary series resistance, or 1 ohm
to
the secondary, gives the same result into a load. It makes sense, because
you have four times the current and 1/4 the voltage in the secondary, so
the effective resistance (or impedance) ratio is a square function.

** Errr - so YOU were blissfully unaware that all transformers convert
primary side impedances to secondary side ones by the inverse square of the
turns ratio ??

Transformer Basics 101 - pal.




...... Phil

 

[amdx]

"Bill Bowden" <wrongaddress@att.net> wrote in message
news:0cc848c7-5b33-4790-951c-8cff1365720b@59g2000hsb.googlegroups.com...

On Jul 12, 8:13 am, "john jardine" <john.jard...@idnet.co.uk> wrote:
"Bill Bowden" <wrongaddr...@att.net> wrote in message

news:f0885697-6c81-4c90-835e-5817c55e30ff@d77g2000hsb.googlegroups.com...

What is the best way to measure unloaded Q of a tuned LC circuit (AM
loop Antenna) without a Q meter?

I tried a scope and generator and loosly coupled the generator to the
loop, using a single turn of wire and 50 ohm resistor, and monitored
amplitude against frequency, but I get different results depending on
the setup. The scope probe is 10X. The frequency of interest is 500KHz
to 2 MHz.

How can I accurately measure the Q of the circuit without a Q meter?

-Bill

Yep, each measurement can turn out different. The pleasing upside is
acknowledging that the most accurate test setup was the one that returned
the highest Q value!.http://www.crystal-radio.eu/enqmeting.htm describes
in great detail what
Mike has already noted. Also look at the series of "LC experiments".

Yes, I'm getting a Q of around 100 at 1 MHz, but I think it's higher.
I used a 1 meg resistor in series with the scope probe and the half
power points are around 9KHz apart. Using a 100K resistor gives a much
lower Q, so it looks like a 100k load effects the circuit
significantly.

Thanks for the link.

-Bill
Just a check, you are using half power point and not half voltage point,

right?
.707 vs. .5
Mike

 

[ZACK.]

this looks like scam

<moemobb00@yahoo.com> wrote in message
news:5934fc6b-1d8d-4461-bab1-3887fd8036df@34g2000hsh.googlegroups.com...
SAFER THAN MAIL $$ THIS SYSTEM TRULY WORKS $$

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WORKS!!! BUT YOU HAVE TO FOLLOW IT TO THE LETTER FOR IT TO WORK!!!! $$
$
A little while back, I was browsing through newsgroup, just like you
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#2) brittany124@excite.com
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Dear ************

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on the internet this year.

Thank you for using PayPal! Sincerely, PayPal Community Support

GOOD LUCK AND GOD BLESS
We Can Achieve Anything With Each Others Help

 

[starfire]

<jalbers@bsu.edu> wrote in message
news:0623d550-c8c3-4bef-a8da-5ead2095a659@l42g2000hsc.googlegroups.com...

I am trying to do a simple experiment involving an ocilliscope and a
function generator in the same circuit. My plane is to have the
function generator set to produce a 10V (no load) sine wave an vary
the freq from 100-2700 Hz.

A .1 uf capactictor and a 1K resistor are connected in series across
the output leads of the function generator. I want to connect the
ocilliscope leads across the resistor to measure the voltage drop
across the resistor. I calculate that the voltage drops should range
between .6V and 8.6V using the above frequencies.


Scope: Tektronix D10 5103
Function Generator: MCP SG1639A

The problem that I am having is that I think that the scope and
function generator share a common ground because as soon as I connect
the positive leads of the scope and function generator together
(without connecting the ground leads together) I get a wavefrom on the
scope that represent the 10V sine wave. If I connect both leads of
the scope probe across the resistor I get the same 10V sine wave
signal not the .6V AC signal. Why are the gound test leads of the
scope anf freq generator common. I can't see any switch on the
function generator to control this.

Is my assumption about the common ground correct? Do I need to
connect the scope or function generator to an isolation transformer?

Also, is it safe to short the output leads of the function generator
together.

Any help would be greatly appreciated. Thanks

We just ran across a similar problem when trying to use a function generator
and a scope to measure low-amplitude waveforms. Both devices were
AC-powered. The grounds on some scopes and function generators are tied to
the common chassis ground and are common through the AC-lines. Oddly
enough, we tried using an isolation transformer trying to solve the problem
and it did not help. We traced it down to the isolation transformer itself.
The ground (third wire) was common between input and output on the isolation
transformer. I'm not sure if this is always the case but it was true of two
different models we checked.

Our ultimate solution was to go to either a totally isolated
(battery-operated) scope or function generator. We bought battery-operated
scopes and the problems went away. I'm putting together a battery-operated
function generator as a solution when the scope has to be plugged in, also.

Good luck.

Dave

 

[Tom Biasi]

<jalbers@bsu.edu> wrote in message
news:0623d550-c8c3-4bef-a8da-5ead2095a659@l42g2000hsc.googlegroups.com...

I am trying to do a simple experiment involving an ocilliscope and a
function generator in the same circuit. My plane is to have the
function generator set to produce a 10V (no load) sine wave an vary
the freq from 100-2700 Hz.

A .1 uf capactictor and a 1K resistor are connected in series across
the output leads of the function generator. I want to connect the
ocilliscope leads across the resistor to measure the voltage drop
across the resistor. I calculate that the voltage drops should range
between .6V and 8.6V using the above frequencies.


Scope: Tektronix D10 5103
Function Generator: MCP SG1639A

The problem that I am having is that I think that the scope and
function generator share a common ground because as soon as I connect
the positive leads of the scope and function generator together
(without connecting the ground leads together) I get a wavefrom on the
scope that represent the 10V sine wave. If I connect both leads of
the scope probe across the resistor I get the same 10V sine wave
signal not the .6V AC signal. Why are the gound test leads of the
scope anf freq generator common. I can't see any switch on the
function generator to control this.

Is my assumption about the common ground correct? Do I need to
connect the scope or function generator to an isolation transformer?

Also, is it safe to short the output leads of the function generator
together.

Any help would be greatly appreciated. Thanks

If your devices are sharing common ground (quite common) then you could
isolate one of them, or you could connect the resistor to the grounded side
of the generator and just use your probe on the other side.

Tom

 

[Dan Coby]

"Tom Biasi" <tombiasi***@optonline.net> wrote in message
news:vJ6dnZwn0_T8K-bVnZ2dnUVZ_jydnZ2d@giganews.com...

jalbers@bsu.edu> wrote in message
news:0623d550-c8c3-4bef-a8da-5ead2095a659@l42g2000hsc.googlegroups.com...
I am trying to do a simple experiment involving an ocilliscope and a
function generator in the same circuit. My plane is to have the
function generator set to produce a 10V (no load) sine wave an vary
the freq from 100-2700 Hz.

A .1 uf capactictor and a 1K resistor are connected in series across
the output leads of the function generator. I want to connect the
ocilliscope leads across the resistor to measure the voltage drop
across the resistor. I calculate that the voltage drops should range
between .6V and 8.6V using the above frequencies.


Scope: Tektronix D10 5103
Function Generator: MCP SG1639A

The problem that I am having is that I think that the scope and
function generator share a common ground because as soon as I connect
the positive leads of the scope and function generator together
(without connecting the ground leads together) I get a wavefrom on the
scope that represent the 10V sine wave. If I connect both leads of
the scope probe across the resistor I get the same 10V sine wave
signal not the .6V AC signal. Why are the gound test leads of the
scope anf freq generator common. I can't see any switch on the
function generator to control this.

Is my assumption about the common ground correct? Do I need to
connect the scope or function generator to an isolation transformer?

Also, is it safe to short the output leads of the function generator
together.

Any help would be greatly appreciated. Thanks

If your devices are sharing common ground (quite common) then you could isolate one of them, or
you could connect the resistor to the grounded side of the generator and just use your probe on
the other side.

If you cannot connect the resistor to ground, then most oscilloscopes have
a 'subtract' mode. Connect a pair of leads (one to each side of the resistor)
and then subtract channel B from channel A to get the voltage across the
resistor.

 

[christofire]

"John Fields" <jfields@austininstruments.com> wrote in message
news:ugjn7454bj03ii1m975o9eni73ubdpvele@4ax.com...

On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett@gmail.com wrote:

http://en.wikibooks.org/wiki/Practical_Electronics/Resistors

So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
Atlantic)

---
I think it needs a zero in front of it, like 0R2

JF

.... and not everyone 'east of the Atlantic' uses a comma for a decimal
point. How crass!

C

 

[Paul E. Schoen]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:kq6o74ts5gcvig0fhinsi9nfd9oe4ut8fn@4ax.com...

On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett@gmail.com wrote:

http://en.wikibooks.org/wiki/Practical_Electronics/Resistors

So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
Atlantic)

Michael

Horrible circuit, horrible nomenclature.

The right way to write 0.2 ohms is "0.2" or "0.2R", if you can't make
the omega symbol.

The problem is that the decimal point can become faint and disappear when
photographic copies are made, or when the schematic is converted to a
graphics format. With just the leading zero above, it is fairly obvious
even if the decimal were not there, but what about 2.2 ohms? I have become
used to the newer convention. You can also use 200 mOhms (milliohms) to
avoid confusion.

Paul

 

[Richard Crowley]

"Rich Grise" wrote ...

Mr.T wrote:
"Joerg" wrote
Some large Polynesian mussel shells supposedly do that. When you hold
them to your ear you hear the sounds of the sea.

Or the sound of your blood flow being acoustically amplified and
reflected back to your ear, at least.

I'm sure the ambient noise swamps the sound of your blood by a few orders
of magnitude. ;-)

The sound of your heartbeat can seem deafening if you spend
much time in a good anechoic chamber. I tried it in ElectroVoice's
chamber in Buchannan many years ago.

 

[john jardine]

"Bill Bowden" <wrongaddress@att.net> wrote in message
news:cacfb357-b9f2-4235-a803-31f797ce8fd9@l42g2000hsc.googlegroups.com...

On Jul 13, 11:36 am, "amdx" <a...@knology.net> wrote:
"Bill Bowden" <wrongaddr...@att.net> wrote in message

news:0cc848c7-5b33-4790-951c-8cff1365720b@59g2000hsb.googlegroups.com...

On Jul 12, 8:13 am, "john jardine" <john.jard...@idnet.co.uk> wrote:
"Bill Bowden" <wrongaddr...@att.net> wrote in message


news:f0885697-6c81-4c90-835e-5817c55e30ff@d77g2000hsb.googlegroups.com...

What is the best way to measure unloaded Q of a tuned LC circuit
(AM
loop Antenna) without a Q meter?

I tried a scope and generator and loosly coupled the generator to
the
loop, using a single turn of wire and 50 ohm resistor, and
monitored
amplitude against frequency, but I get different results depending
on
the setup. The scope probe is 10X. The frequency of interest is
500KHz
to 2 MHz.

How can I accurately measure the Q of the circuit without a Q
meter?

-Bill

Yep, each measurement can turn out different. The pleasing upside is
acknowledging that the most accurate test setup was the one that
returned
the highest Q
value!.http://www.crystal-radio.eu/enqmeting.htmdescribes
in great detail what
Mike has already noted. Also look at the series of "LC experiments".

Yes, I'm getting a Q of around 100 at 1 MHz, but I think it's higher.
I used a 1 meg resistor in series with the scope probe and the half
power points are around 9KHz apart. Using a 100K resistor gives a much
lower Q, so it looks like a 100k load effects the circuit
significantly.

Thanks for the link.

-Bill

Just a check, you are using half power point and not half voltage
point,
right?
.707 vs. .5
Mike

Yes, half power points, 0.707 voltage points. 0.707 squared is 0.5.

-Bill

Loathe to do any paying work today, I spent a diverting hour measuring some
aerial coils kicking about.
A data-point ...
http://img140.imageshack.us/img140/2631/ferriterodcoilqba6.jpg
Would seem Q's of a couple of hundred are not unreasonable using Litz wire.
(Q's were measured using an 'Advance C.M.1' Q meter)