From: "Clemens Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2dbFX3d+jv04M_quU0Nwy=W-g5Jk5vxcN5SP87gg3PmzA@mail.gmail.com> <B507F4F2886F4488A919515FDD664BC3@gnat> <B4BD637350C7488DA8A8BAF58FC09D7D@AGB> <E2FD3CEF9D874A728D06769DF8C30AEA@Clemens0811> <511FF5F0.1080603@iup.uni-heidelberg.de>
In-Reply-To: <511FF5F0.1080603@iup.uni-heidelberg.de>
Date: Sun, 17 Feb 2013 10:30:25 +0100
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Subject: RE: LF: Re: how to increase the Q of my loading coil?
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Stefan,

>So a high Q must be the goal, loaded or unloaded.

Regarding unloaded Q I think there is agreement

Regarding unloaded Q it depends HOW it is increased.
As Jim has pointed out increasing unloaded coil Q also increases =
somewhat
the overall system loaded Q
by reducing circuit total R, this is perhaps what Graham was concerned
about.
But the benefit overweighs this small disadvantage.=20

As a matter of fact with a matching network consisting of two reactive
elements (L,C) or of one coil
and an autotransformer as we have here it is not possible to choose a
desired loaded Q (without the exception above).
You get the lowest possible loaded Q anyhow and it is determined by the
complex impedance of the antenna.
But if you match with three reactive elements like a Pi- or T-Network =
then
you can choose - within certain limits -=20
the loaded Q by choosing the components values but it will be always =
higher
than with two elements.
High XL and XC components will result in a high loaded Q.
In this case time the high loaded Q is detrimental for efficiency,losses =
and
heat go up, so THIS way of increasing=20
loaded Q should be avoided.

The source resistance of a transmitter or a vector network analyzer
decreases the overall loaded system Q =20
which increases bandwidth.
If you would feed the system by a voltage source the 3dB BW-points would
coincide with a VSWR of 5,9.
With a 50 Ohm source you have the 3dB points at a VSWR of 2,6.

My apologizes if this all has been too long and boring. :-)

73
Clemens
DL4RAJ=20






>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org=20
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan =
Sch=E4fer
>Sent: Saturday, February 16, 2013 10:11 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: Re: LF: Re: how to increase the Q of my loading coil?
>
>
>Am 16.02.2013 11:10, schrieb Clemens Paul:
>>   [...]
>> The higher the *loaded circuit* Q the higher are the losses in all=20
>> involved components including the coil due to increasing=20
>circulating currents.
>> Given a certain circuit increasing the Q of its components=20
>always will=20
>> reduce overall losses of that circuit.
>>
>> 73
>> Clemens
>> DL4RAJ
>
>...however if the transmit power is kept constant, then the=20
>radiated power is higher, due to the higher currents through=20
>the radiation resistance. Thus the losses must be lower here.=20
>It is not a constant voltage source, at least Dimitris' class=20
>E PA isn't :-) So a high Q must be the goal, loaded or unloaded.
>
>73, Stefan/DK7FC
>
>
>
>-----
>E-Mail ist virenfrei.
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>Version: 2013.0.2899 / Virendatenbank: 2639/6104 -=20
>Ausgabedatum: 14.02.2013=20
>