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

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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

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http://users.fulladsl.be/spb13810/bwnl.htm
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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 . com,
"RHF" wrote:

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.

Nice reasoning, but:

When coil A - ant has 5 turns, and coil B - radio has 5 turns, the
voltage (or so) is the same.

When we now double A / or B, the voltage should vary for the same
amount, I learned.... so you can make the sig higher ???

In my physics book (Halliday/Resnick Fundamentals of Physics), p 445 -
transformers it says:
N1 / V1 = N2 / V2


would it be possible to double the number of turns on B (which is
sometimes easier ... space requirements) ??? That would lead to double
V2 and higher sig ... ???

Of course, problem remains ... resonance. You can't add tunrs to A, or
you loose resonance ... Adding turns to A means .. making it smaller
.... to have the same resonance properties ...

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Switcher,

For most applications using "Receive Only" Matching
Transformers (MT) the Idea is to step down the Voltage.
If the Antenna-Side of the MT has a Voltage difference
of 0.9uv (Weak Signal) to 180uv (Strong Signal) and the
Receiver-Side of the MT would have a Voltage difference
of 0.3uv to 60uv which most Receivers could better
handle.

It is my simple understanding the two things that we
wish to accomplish with the Receiver-Side of the
Matching Transformer is to Match the Impedance
of the Receiver's Antenna Input for the Range of
Frequencies we hope to hear and to adjust the RF
Signal 'differential' to better match the Limits of the
Dynamic Range of the Receiver's Circuitry.


someone correct me if i am wrong - iane ~ RHF