From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Sun, 18 Dec 2011 18:01:06 +0100
Thread-Topic: Re: Re: Re: Re: TX system at DK7FC, schematic
Thread-Index: Acy9ohb0zTqmK0YUTf+VnbfqOxH5wgABIqcO
Message-ID: <BF4A524700075746A6467658DFC7102CB0B489A657@ICTS-S-EXC2-CA.luna.kuleuven.be>
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$0401a8c0@xphd97xgq27nyf>
In-Reply-To: <008701ccbda1$cacf4f70$0401a8c0@xphd97xgq27nyf>
Accept-Language: nl-NL, nl-BE
Content-Language: nl-BE
acceptlanguage: nl-NL, nl-BE
MIME-Version: 1.0
Subject: LF: RE: Re: Re: Re: Re: TX system at DK7FC, schematic
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1d404c4eee1d392349
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


There is a difference between the coil Q (unloaded) and the antenna system =
Q.
While the coil Q can indeed be > 1000 the antenna system Q will be much low=
er due to groundloss.
As a fact it is mainly the groundloss that will determine the antenna bandw=
idth.

73, Rik  ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org=
] namens mal hamilton [g3kevmal@talktalk.net]
Verzonden: zondag 18 december 2011 17:26
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: Re: Re: Re: Re: TX system at DK7FC, schematic

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 coi=
l
> 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 th=
e
> > 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
> >
> >
>
>=