Message-ID: <008701ccbda1$cacf4f70$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>
Date: Sun, 18 Dec 2011 16:26:27 -0000
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Subject: LF: Re: Re: Re: Re: TX system at DK7FC, schematic
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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
> >
> >
>
>