Message-ID: <009301ccbda4$bea4a850$0401a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <CAA8k23Rn9WpQM3Ukf=cq5-bLmWy+o4SEsH2abf7cAX=BpLWExQ@mail.gmail.com> <op.v6k16ktpyzqh0k@pc-roelof> <033201ccbcab$5c5fe640$1502a8c0@Clemens04> <op.v6mtuugnyzqh0k@pc-roelof> <000901ccbcc4$42768fe0$c763afa0$@com> <4EECC1E8.4000806@iup.uni-heidelberg.de> <002c01ccbd6f$572761c0$0401a8c0@xphd97xgq27nyf> <39D91133A64A480596FBAA4395D85812@JimPC> <007901ccbd9e$69fe2ed0$0401a8c0@xphd97xgq27nyf> <008701ccbda1$cacf4f70$0401a8c0@xphd97xgq27nyf> <4EEE15E7.9080608@freenet.de>
Date: Sun, 18 Dec 2011 16:47:35 -0000
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Subject: Re: LF: Re: Re: Re: Re: TX system at DK7FC, schematic
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Wolf
But surely it is the Loaded Q we are concerned about, what is the point of a
vy high Q unloaded when put into the antenna system it drops dramatically.
Maybe there is a conflict between Theory and Practical application of such
hi Q coils
g3kev


----- Original Message -----
From: "wolf_dl4yhf" <dl4yhf@freenet.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, December 18, 2011 4:33 PM
Subject: Re: LF: Re: Re: Re: Re: TX system at DK7FC, schematic


> Certainly not. What Stefan meant was the coil's *unloaded* Q, which
> cannot be high enough.
>
> The *loaded* Q, in the resonant circuit, will be lower and that's what
> determines the antenna system's bandwidth.
>
> Cheers,
>     Wolf .
>
> Am 18.12.2011 17:26, schrieb mal hamilton:
> > ps
> > With a Q in thousands the bandwidth even on 137 would be too narrow to
be
> > useful
> >
> > ----- Original Message -----
> > From: "mal hamilton"<g3kevmal@talktalk.net>
> > To:<rsgb_lf_group@blacksheep.org>
> > Sent: Sunday, December 18, 2011 4:02 PM
> > Subject: LF: Re: Re: Re: TX system at DK7FC, schematic
> >
> >
> >> Jim es Co
> >> The highest Q coils I have seen are self supporting encased in a helium
> >> container and the Q specified was only in a few hundred. What sort of
coil
> >> construction yields 4000 and above ?
> >> I have yet to encounter such a specimen
> >> mal/g3kev
> >>
> >> ----- Original Message -----
> >> From: "James Moritz"<james.moritz@btopenworld.com>
> >> To:<rsgb_lf_group@blacksheep.org>
> >> Sent: Sunday, December 18, 2011 10:58 AM
> >> Subject: LF: Re: Re: TX system at DK7FC, schematic
> >>
> >>
> >>> Dear Mal, LF Group,
> >>>
> >>>> I can see you resonate your 3mH coild with a motor driven variometer
> > but
> >>>> how
> >>>> do you match this to exactly 50 ohmz for a SWR of 1:1 to the TX
> >>>> I can see your coil and transformer secondary are  in series to earth
> >> but
> >>>> no
> >>>> adjustment for matching.
> >>> Essentially the same arrangement is in use here. The transformer ratio
> > is
> >>> adjusted to match the antenna resistance to 50ohms.
> >>>
> >>> A Q of 1000 is typical for a coil of this size wound using Litz wire.
> > You
> >>> might increase that somewhat by optimising length, diameter, winding
> > pitch
> >>> etc. For something big like the Balboa loading coil in Alex's mail, Q
> > can
> >> be
> >>> considerably higher - Watt's "VLF Engineering" has data on this
> > particular
> >>> antenna system - the coil resistance at 25kHz is about 0.06ohms, and
the
> >>> reactance 225ohms, making the Q about 3800 - it might be higher at
136k,
> >>> since reactance often increases faster than loss resistance as the
> >> frequency
> >>> goes up. Incidentally, I estimate L of the main loading coil about
> > 1.3mH,
> >> so
> >>> GW0EZY would need the variometer in series as well ;-)
> >>>
> >>> Cheers, Jim Moritz
> >>> 73 de M0BMU
> >>>
> >>>
> >>
> >
> >
> >
>
>