Reduce the L to reduce the resistive loss - the essence of L
is the energy stored in its current carrying, and it is the current that
causes I^2 R losses. The energy stored in the C is static. (Yes, there
are some losses in polarising the dielectrics but these are small enough
to be ignored)

"Paul Burridge" wrote in message
...
ISTR that one can improve Q in resonant tanks by having a low L-C
ratio. Or was it high L-C ratio. I can't remember but need to know.

Airy,
What you said would be relevant only if you were trying to determine circuit
losses due to "unloaded" Q of the components. I believe Paul is trying to
determine the 'loaded" Q in order to obtain best selectivity (narrowest
bandwidth). Is this true Paul?

In order to obtain maximum selectivity, the loaded Q needs to be as high as
possible. In the case of a resonant 'tank', the tank reactances are loaded
by the external environment. The circuit Q (or 'loaded' Q) in this case is
Q=R/X. In order to maximize loaded Q, the X term (reactance) needs to be
minimized. This means low L and high C.

In any case, the actual circuit losses will be a function of the ratio of
unloaded Q (Q of the components) to loaded Q. The higher the unloaded Q of
the components, the lower the losses in the circuit.

Joe
W3JDR


"Airy R. Bean" wrote in message
...
Reduce the L to reduce the resistive loss - the essence of L
is the energy stored in its current carrying, and it is the current that
causes I^2 R losses. The energy stored in the C is static. (Yes, there
are some losses in polarising the dielectrics but these are small enough
to be ignored)

"Paul Burridge" wrote in message
...
ISTR that one can improve Q in resonant tanks by having a low L-C
ratio. Or was it high L-C ratio. I can't remember but need to know.

On Sun, 21 Mar 2004 16:02:18 GMT, "W3JDR" wrote:

Airy,
What you said would be relevant only if you were trying to determine circuit
losses due to "unloaded" Q of the components. I believe Paul is trying to
determine the 'loaded" Q in order to obtain best selectivity (narrowest
bandwidth). Is this true Paul?

Some clarification is necessary!
The application is the tank in a frequency multiplier.
I am seeking to select for the 5th harmonic. Therefore, the tank needs
to have as little loss as possible given the fact that the 5th will be
way down dB-wise on the fundamental. I can't afford to attenuate it
too much as it's already weak to begin with. Ergo, I need the lowest
loss components and the best selectivity for the desired 5th harmonic.
Thanks,

p.
--

The BBC: Licensed at public expense to spread lies.

Paul, in approaching the problem from your viewpoint havn't you set yourself
the task of winding an inductor to have a particular value of Q ?

If you intend to use a solenoid then Q can be increased only by increasing
its physical size without changing its proportions too much.

Utimately you will need to know what is the Q of a particular size coil,
number of turns, wire gauge, etc. It will be reduced by its proximity to
other components and circuit board by some indeterminate amount. I think
you should stop and check whether you have room for the coil in the
equipment space available. ;o)

Program SOLNOID2 may be of assistance in this onerous task.

Download in a few seconds from website below and run immediately.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

On Sun, 21 Mar 2004 18:54:19 +0000 (UTC), "Reg Edwards"
wrote:

Paul, in approaching the problem from your viewpoint havn't you set yourself
the task of winding an inductor to have a particular value of Q ?

If you intend to use a solenoid then Q can be increased only by increasing
its physical size without changing its proportions too much.

Utimately you will need to know what is the Q of a particular size coil,
number of turns, wire gauge, etc. It will be reduced by its proximity to
other components and circuit board by some indeterminate amount. I think
you should stop and check whether you have room for the coil in the
equipment space available. ;o)

Program SOLNOID2 may be of assistance in this onerous task.

Download in a few seconds from website below and run immediately.

Reg, SOLNOID2 has been withdrawn from your site IIRC. I *had* been
using it to great effect, but you presumably made some improvements,
implemented them, and renamed it SOLNOID3 which is what I now use.
Great program!
I'm still none the wiser as to whether it's better to have big-L ||
small C or vice versa, though. :-/
BTW, Reg - can you write a program to work out how I'm going to afford
my Council Tax this year? Thanks! :-)
--

The BBC: Licensed at public expense to spread lies.

Paul,

I updated program SOLNOID2 to 3 because somebody had difficulty with
defining the length of a coil as related to the number of turns when there
are only a very few turns on it. Its a more complicated little problem than
you might think. But the length of a coil, 1, the number of turns, 1, 2, 3
etc., and the winding pitch are all insisted on by the program.

So to clarify the point I rewrote the operating instructions. The program
itself remained unchanged.
---
====================================

You have been led up the garden path by the old wives. The L/C ratio has
very little to do with the Q of a resonant circuit. Q is controlled
independently by the losses in L and C. Since the loss in L predominates Q
= omega*L/R.

The ratio L/C, everything else remaining unchanged, affects only the
parallel impedance of the circuit. A high L/C ratio gives a high parallel
impedance. You get a higher voltage gain in an amplifier with a high L/C
ratio when the load is a parallel tuned circuit.

The parallel impedance is given by L/C/R = Q*Omega*L = Q/Omega/C.

Very often L and C are chosen from what you have in the bottom of the junk
box.
----
Reg, G4FGQ


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

"Paul Burridge" wrote in message
...
On Sun, 21 Mar 2004 18:54:19 +0000 (UTC), "Reg Edwards"
wrote:

Paul, in approaching the problem from your viewpoint havn't you set
yourself
the task of winding an inductor to have a particular value of Q ?

If you intend to use a solenoid then Q can be increased only by
increasing
its physical size without changing its proportions too much.

Utimately you will need to know what is the Q of a particular size coil,
number of turns, wire gauge, etc. It will be reduced by its proximity to
other components and circuit board by some indeterminate amount. I think
you should stop and check whether you have room for the coil in the
equipment space available. ;o)

Program SOLNOID2 may be of assistance in this onerous task.

Download in a few seconds from website below and run immediately.

Reg, SOLNOID2 has been withdrawn from your site IIRC. I *had* been
using it to great effect, but you presumably made some improvements,
implemented them, and renamed it SOLNOID3 which is what I now use.
Great program!
I'm still none the wiser as to whether it's better to have big-L ||
small C or vice versa, though. :-/
BTW, Reg - can you write a program to work out how I'm going to afford
my Council Tax this year? Thanks! :-)
--

The BBC: Licensed at public expense to spread lies.

Paul,

I updated program SOLNOID2 to 3 because somebody had difficulty with
defining the length of a coil as related to the number of turns when there
are only a very few turns on it. Its a more complicated little problem than
you might think. But the length of a coil, 1, the number of turns, 1, 2, 3
etc., and the winding pitch are all insisted on by the program.

So to clarify the point I rewrote the operating instructions. The program
itself remained unchanged.
---
====================================

You have been led up the garden path by the old wives. The L/C ratio has
very little to do with the Q of a resonant circuit. Q is controlled
independently by the losses in L and C. Since the loss in L predominates Q
= omega*L/R.

The ratio L/C, everything else remaining unchanged, affects only the
parallel impedance of the circuit. A high L/C ratio gives a high parallel
impedance. You get a higher voltage gain in an amplifier with a high L/C
ratio when the load is a parallel tuned circuit.

The parallel impedance is given by L/C/R = Q*Omega*L = Q/Omega/C.

Very often L and C are chosen from what you have in the bottom of the junk
box.
----
Reg, G4FGQ


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

"Paul Burridge" wrote in message
...
On Sun, 21 Mar 2004 18:54:19 +0000 (UTC), "Reg Edwards"
wrote:

Paul, in approaching the problem from your viewpoint havn't you set
yourself
the task of winding an inductor to have a particular value of Q ?

If you intend to use a solenoid then Q can be increased only by
increasing
its physical size without changing its proportions too much.

Utimately you will need to know what is the Q of a particular size coil,
number of turns, wire gauge, etc. It will be reduced by its proximity to
other components and circuit board by some indeterminate amount. I think
you should stop and check whether you have room for the coil in the
equipment space available. ;o)

Program SOLNOID2 may be of assistance in this onerous task.

Download in a few seconds from website below and run immediately.

Reg, SOLNOID2 has been withdrawn from your site IIRC. I *had* been
using it to great effect, but you presumably made some improvements,
implemented them, and renamed it SOLNOID3 which is what I now use.
Great program!
I'm still none the wiser as to whether it's better to have big-L ||
small C or vice versa, though. :-/
BTW, Reg - can you write a program to work out how I'm going to afford
my Council Tax this year? Thanks! :-)
--

The BBC: Licensed at public expense to spread lies.

Let me clarify. Because Q is largely out of your control, the logical way
of circuit design is FIRST OF ALL to allocate a practical, reasonably
attainable value of Q to the inductor, taking the SPACE AVAILABLE into
account.

Then design the remainder of the circuit around it to meet the required
objectives. You really have no alternative.

Choosing a starting value for Q without knowing the inductance depends
entirely on experience and visual imagination. But you will find program
SOLNOID2 very useful in getting you in the right ballpark - only after you
decide on the space and clearance available for a coil.

I'm still toying with the idea of using an oscillator locked to the 5th
harmonic. Q and size of the coil don't matter two hoots. And you have all
the output you could possibly want.

On second thoughts I would probably have gone about the whole job in an
entirely different manner. ;o)
----
Reg, G4FGQ

On Sun, 21 Mar 2004 18:54:19 +0000 (UTC), "Reg Edwards"
wrote:

Paul, in approaching the problem from your viewpoint havn't you set yourself
the task of winding an inductor to have a particular value of Q ?

If you intend to use a solenoid then Q can be increased only by increasing
its physical size without changing its proportions too much.

Utimately you will need to know what is the Q of a particular size coil,
number of turns, wire gauge, etc. It will be reduced by its proximity to
other components and circuit board by some indeterminate amount. I think
you should stop and check whether you have room for the coil in the
equipment space available. ;o)

Program SOLNOID2 may be of assistance in this onerous task.

Download in a few seconds from website below and run immediately.

Reg, SOLNOID2 has been withdrawn from your site IIRC. I *had* been
using it to great effect, but you presumably made some improvements,
implemented them, and renamed it SOLNOID3 which is what I now use.
Great program!
I'm still none the wiser as to whether it's better to have big-L ||
small C or vice versa, though. :-/
BTW, Reg - can you write a program to work out how I'm going to afford
my Council Tax this year? Thanks! :-)
--

The BBC: Licensed at public expense to spread lies.

Let me clarify. Because Q is largely out of your control, the logical way
of circuit design is FIRST OF ALL to allocate a practical, reasonably
attainable value of Q to the inductor, taking the SPACE AVAILABLE into
account.

Then design the remainder of the circuit around it to meet the required
objectives. You really have no alternative.

Choosing a starting value for Q without knowing the inductance depends
entirely on experience and visual imagination. But you will find program
SOLNOID2 very useful in getting you in the right ballpark - only after you
decide on the space and clearance available for a coil.

I'm still toying with the idea of using an oscillator locked to the 5th
harmonic. Q and size of the coil don't matter two hoots. And you have all
the output you could possibly want.

On second thoughts I would probably have gone about the whole job in an
entirely different manner. ;o)
----
Reg, G4FGQ