a damped LC ???
Does it make sense to introduce a R in the LC circuit and use it as
antenna ??
Does it change eg the Q ??? etc ...

I have tried to put formula's here
(look if they are right !
freq_low=Math.sqrt(1/(inductance*cap_high) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)
freq_high=Math.sqrt(1/(inductance*cap_low) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)

OK ???
)
http://users.fulladsl.be/spb13810/amlooprlc.htm


A high R seems to lower the low freq, that's interesting ...



original formula for LC circuits: (put R = 0 in previous, and you should
get the same ....)

http://users.fulladsl.be/spb13810/amloop.htm

--
een appeltje te schillen met http://applefaulty.be
http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/

The lower Q makes the LC less selective. For a tuned loop, it is not a
good idea to introduce resistance.


switcher wrote:
a damped LC ???
Does it make sense to introduce a R in the LC circuit and use it as
antenna ??
Does it change eg the Q ??? etc ...

I have tried to put formula's here
(look if they are right !
freq_low=Math.sqrt(1/(inductance*cap_high) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)
freq_high=Math.sqrt(1/(inductance*cap_low) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)

OK ???
)
http://users.fulladsl.be/spb13810/amlooprlc.htm


A high R seems to lower the low freq, that's interesting ...



original formula for LC circuits: (put R = 0 in previous, and you should
get the same ....)

http://users.fulladsl.be/spb13810/amloop.htm

--
een appeltje te schillen met http://applefaulty.be
http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/

In article ,
switcher wrote:

a damped LC ??? Does it make sense to introduce a R in the LC circuit
and use it as antenna ?? Does it change eg the Q ??? etc ...

It depends on what you want. Maybe the bandwidth is to narrow or the
tuning action is so sharp it is hard to peak it. You add resistance and
the peak does go down but the bandwidth also widens.

--
Telamon
Ventura, California

On 6 May 2006 13:41:51 -0700, wrote:

The lower Q makes the LC less selective. For a tuned loop, it is not a
good idea to introduce resistance.


switcher wrote:
a damped LC ???
Does it make sense to introduce a R in the LC circuit and use it as
antenna ??
Does it change eg the Q ??? etc ...
It certainly does. One of the ways to calculate Q is
Resistance/Reactance. By definition, increasing resistance will lower
Q.

Q is also the bandwidth/frequency at the point the signal is down to
half peak.

I have tried to put formula's here
(look if they are right !
freq_low=Math.sqrt(1/(inductance*cap_high) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)
freq_high=Math.sqrt(1/(inductance*cap_low) - (resistance * resistance )
/ (4 *inductance *inductance))/(2*Math.PI)

OK ???
)
http://users.fulladsl.be/spb13810/amlooprlc.htm


A high R seems to lower the low freq, that's interesting ...



original formula for LC circuits: (put R = 0 in previous, and you should
get the same ....)

http://users.fulladsl.be/spb13810/amloop.htm

--
een appeltje te schillen met http://applefaulty.be
http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/

In article
,
Telamon wrote:

It depends on what you want. Maybe the bandwidth is to narrow or the
tuning action is so sharp it is hard to peak it. You add resistance and
the peak does go down but the bandwidth also widens.

I was already thinking: if DRM is 12khz wide (am I right ?), then it
might be a tuned loop is too narrow ??

So an R might help ???

--
een appeltje te schillen met http://applefaulty.be
http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/

Switcher,

AM/MW Loop Antenna - Inductive Coupling -vice- Resistor Spoiler
http://groups.yahoo.com/group/Shortw...a/message/9407

To some degree all Circuits are L+C+R
- - - Although anyone of the three may not be significant
enough to factor into the Circuit Design parameters.
- - - Hence an AM/MW Loop Antenna is simply presented
as an L+C Circuit.

"IF" you were to use a Resistor in the Circuit of an
AM/MW Loop Antenna it would be 'because' the Radio
that you were using it with was being OverLoaded by
the Signal from the Loop Antenna.

You could simply achieve the same thing by varying the
AM/MW Loop Antenna 'coupling' with the Radio -by- Moving
the Loop Antenna nearer-to -or- farther-away from the Radio.

AM/MW LOOP ANTENNA COUPLING :
* The Coil of the external AM/MW Loop Antenna
is an Inductor {RF Transformer Coil}
* The Coil of the Radio's internal AM/MW Antenna
is an Inductor {RF Transformer Coil}
* Together the Two Coils form an RF Transformer
Moving the Two Coils and changing their relationship
to each other varies the "Coupling" between them.


THINGS TO READ :

READ - AM/MW DXing = Your Radio + Lazy Susan + Loop Antenna
for better AM/MW Band Reception and DXing with an AM Radio.
http://groups.yahoo.com/group/Shortw...a/message/1787
http://groups.yahoo.com/group/Shortw...a/message/1811

READ - Using the Built-in WHIP Antenna for better AM/MW Band
Reception and DXing with an AM Radio.
http://groups.yahoo.com/group/Shortw...na/message/875

READ - AM/MW Radio Reception : Whip Antenna Up? -or- Down?
for better AM/MW Band Reception and DXing with an AM Radio.
http://groups.yahoo.com/group/Shortw...a/message/1105

READ - AM/MW Random Wire Antenna Tuner using a AM/MW Loop
Antenna for better AM/MW Band Reception and DXing with an AM Radio.
http://groups.yahoo.com/group/Shortw...a/message/1150

READ - "HOW TO USE" a AM/MW Loop Antenna with a 'portable'
AM/FM Shortwave for better AM/MW Band Reception and DXing
with an AM Radio.
http://groups.yahoo.com/group/Shortw...a/message/1865

READ - For Improved AM/MW DXing
- Think Loop Antenna as a Coupler Tuner for better
AM/MW Band Reception and DXing with an AM Radio.
http://groups.yahoo.com/group/Shortw...a/message/2240
http://groups.yahoo.com/group/Shortw...a/message/2272
http://groups.yahoo.com/group/Shortw...a/message/2769

READ - Two 'basic' optional In-Door Antennas for better
AM/MW Band and FM Band using a 'portable' AM/FM Radio.
http://groups.yahoo.com/group/Shortw...a/message/2936

READ - Long "LoopStick" Antenna for AM/MW/BCB DXing
-by- Bill Bowden
http://groups.yahoo.com/group/Shortw...a/message/3075
http://groups.yahoo.com/group/Shortw...a/message/3100
The "L O N G" -Liner- {Skinny} Loop Antenna for better
AM/MW Band Reception and DXing with an AM Radio.


READ - Every Grundig Satellit 800 M Owner's Dream...
a 21" Lazy Susan for better AM/MW Band Reception and
AM/MW DXing )
http://groups.yahoo.com/group/Shortw...a/message/4406

READ - Setting-Up the Sony ICF-SW7600GR with a Loop Antenna
on a Lazy Susan for better AM/MW Band Reception and DXing.
http://groups.yahoo.com/group/Shortw...a/message/5886


RESISTOR AS A SPOILER IN AN AM/MW LOOP ANTENNA CIRCUIT :
-However- If you must use a Resistor in the Circuit of the
AM/MW Loop Antenna - Consider using a Series 1000 Ohm (1K)
Potentiometer (Pot) - So that you could adjust and fine-tune
the Circuit to achieve the Maximum Signal without OverLoading
the Radio. Hook the "Pot" up with the two ends connected
together and the Center Wiper as teh other end of the
Resistance Element of the Circuit. With the Wipper at either
end the Pot is out of the Circuit. As the Wiper is moved
from one of the ends to the Center of the Pot the amount
of Resistance in the Circuit 'increases' and the RF Signal
{EMF Field} of the Loop Antenna is Decreased. Wiring-Up
the Pot this way makes the Resistance Curve non-liner from
"0" to 500 Ohms sort of more like an Audio Taper Pot.


and now you know - iane ~ RHF

In article ,
switcher wrote:

In article

,
Telamon wrote:

It depends on what you want. Maybe the bandwidth is to narrow or
the tuning action is so sharp it is hard to peak it. You add
resistance and the peak does go down but the bandwidth also widens.

I was already thinking: if DRM is 12khz wide (am I right ?), then it
might be a tuned loop is too narrow ??

So an R might help ???

If the tuned loop bandwidth is to narrow then you can deliberately
spoil the Q of the loop by adding resistance and broaden the bandwidth.

I have not calculated it but I expect a LC loop operating in the MHz
range would have a bandwidth greater than 12 KHz so I do not expect you
will have a problem.

--
Telamon
Ventura, California

Telamon wrote:
In article ,
switcher wrote:

In article

,
Telamon wrote:

It depends on what you want. Maybe the bandwidth is to narrow or
the tuning action is so sharp it is hard to peak it. You add
resistance and the peak does go down but the bandwidth also widens.
I was already thinking: if DRM is 12khz wide (am I right ?), then it
might be a tuned loop is too narrow ??

So an R might help ???

If the tuned loop bandwidth is to narrow then you can deliberately
spoil the Q of the loop by adding resistance and broaden the bandwidth.
. . .

A really quick back-of-the envelope look at the problem indicates that
adding a resistance won't make the signal any stronger when the loop is
tuned away from the peak. It'll just make the signal weaker when it is
tuned to the peak. So it's "wider", but no better at any tuning setting
but worse at and near the peak. To check on my calculation, try it:
connect and disconnect the resistor at various tuning settings, on and
off peak. Does it make the signal any stronger at any setting?

The only time there would be any advantage to adding an R to widen the
bandwidth is if it's so narrow that it distorts a modulated signal due
to uneven response across the audio bandwidth. This would mean at least
several dB variation over a couple of kHz for voice SSB or over 10 kHz
for broadcast quality AM.

Roy Lewallen, W7EL

In article ,
Roy Lewallen wrote:

Telamon wrote:
In article ,
switcher wrote:

In article

,
Telamon wrote:

It depends on what you want. Maybe the bandwidth is to narrow or
the tuning action is so sharp it is hard to peak it. You add
resistance and the peak does go down but the bandwidth also widens.
I was already thinking: if DRM is 12khz wide (am I right ?), then it
might be a tuned loop is too narrow ??

So an R might help ???

If the tuned loop bandwidth is to narrow then you can deliberately
spoil the Q of the loop by adding resistance and broaden the bandwidth.
. . .

A really quick back-of-the envelope look at the problem indicates that
adding a resistance won't make the signal any stronger when the loop is
tuned away from the peak. It'll just make the signal weaker when it is
tuned to the peak. So it's "wider", but no better at any tuning setting
but worse at and near the peak. To check on my calculation, try it:
connect and disconnect the resistor at various tuning settings, on and
off peak. Does it make the signal any stronger at any setting?

The only time there would be any advantage to adding an R to widen the
bandwidth is if it's so narrow that it distorts a modulated signal due
to uneven response across the audio bandwidth. This would mean at least
several dB variation over a couple of kHz for voice SSB or over 10 kHz
for broadcast quality AM.

I read his post correctly his concern is a 12 KHz wide DRM signal and
that the tuned loop response will be to sharp and narrow. Firstly he
needs to build the loop and sweep it to see if has a problem to begin
with. Parasitics may cause the loop response to be wide enough that 12
KHz will not be a problem. If it turns out it does he can add
resistance, which will decrease the peak response and broaden it. Adding
resistance will cause the loop to not work as well but that is the price
you pay for greater bandwidth.

--
Telamon
Ventura, California

Telamon wrote:
I read his post correctly his concern is a 12 KHz wide DRM signal and
that the tuned loop response will be to sharp and narrow. Firstly he
needs to build the loop and sweep it to see if has a problem to begin
with. Parasitics may cause the loop response to be wide enough that 12
KHz will not be a problem. If it turns out it does he can add
resistance, which will decrease the peak response and broaden it. Adding
resistance will cause the loop to not work as well but that is the price
you pay for greater bandwidth.


Normally the best thing is to over-couple the loop to the receiver,
rather than loading it with a resistor.

The Q of the loop is not only a function of the loss resistance and L/C
values, it is also a function of the loop loading caused by the
feedline/receiver combination. That introduces resistance to the
system.

Adding a resistor is the last think I'd do. If I had a bandwidth
problem in a resonant loop, I'd simply overcouple to the feedline and
let the feedline/receiver resistance load the antenna.

73 Tom