> Date: Sun, 15 Dec 2013 17:33:12 +0100
> From: [email protected]
> To: [email protected]; [email protected]
> Subject: Re: LF: A short VLF experiment at DK7FC
>
> Hi Peter, VLF,
>
> Did you see a trace on your grabber? Can you show me a link or a screenshot?
> The signal is well visible on Paul Nicholson's excellent VLF grabber,
> http://abelian.org/vlf/fbins.shtml#p=1387116000&b=110&s=sp but far from
> stable. Is instability is due to my signal of course. Distance to Paul
> is 880 km, http://no.nonsense.ee/qth/map.html?qth=IO83XQ&from=jn49ik00wd
>
> You are right, there are many things to optimise. One thing is the
> housing of the PA. Now it is just mounted on a wooden plate. It is a H
> bridge using 4x IRFP460, switching directly at 230V*1.41, so the output
> of the PA is on mains potential! There is no galvanic decoupling
> transformer on the output (which would allow to use a grounded coax
> then) because such a transformer would have to be a VERY big ferrite
> core with many many turns (> 100). So the PA output is directly
> connected to the primary winding of the loading coil, which couples its
> field into the resonance winding (1200 turns). So the feed line is
> floating on an unknown voltage which depends on the capacitive coupling
> to sourrounding things. In the field experiments 2010/2011 this was no
> problem. But now it is. I guess this is causing EMC problems to the /2
> frequency divider, sometimes. Thus, i will put it into a metallic box
> which is grounded to earth potential.
>
> Another problem is the parallel capacitor which i have to add to come on
> resonance. It's capacity is not high enough and i have to add about 10m
> or wire hanging arround. This additional wire is moving in the wind
> blasts and causes further instability of the signal (kind of AM due to
> modulated resonance peak, i.e. antenna current). Another way would be to
> add more turns to the coil but this antenna system is voltage limited
> and it doesn't matter at all if i have to put 400W or 500W into the system.
>
> BTW this night/day it was 850 mA antenna current and about 400W RF
> power. I will plan to do more QRO, when the new capacitor is ready to use.
>
> Here is an image of the arrangement, taken 30 minutes ago:
> https://dl.dropboxusercontent.com/u/19882028/VLF/20131215_165406.jpg
>
> As soon as the C of "DK7FC" is finished, i will run some OPDS32
> sequences for DF6NM and Paul Nicholson and others :-)
> BTW i have disconnected my VLF grabber antenna since the RX is
> overloaded anyway. Now it is easier to identify eventual phase glitches
> (could be on the RX side as well, though).
>
> 73 and thanks for watching.
>
> Stefan/DK7FC
>
>
>
> Am 15.12.2013 14:49, schrieb PA1SDB, Peter:
> > Stefan,
> > Signal is O.K., but stabillity is'nt :-(
> > To much spread around center frequency.
> >
> > (I know.... I'm complaining about 0.01 Hz drift..........)
> >
> > 73's Peter
> >
> >
> > ----- Original Message ----- From: "Stefan Schäfer"
> > <[email protected]>
> > To: <[email protected]>; "Paul" <[email protected]>
> > Sent: Sunday, December 15, 2013 4:14 AM
> > Subject: Re: LF: A short VLF experiment at DK7FC
> >
> >
> > Since 4:10 UTC, the signal is available without interruptions now on
> > 8.97000500 kHz.
> >
> > 73, Stefan/DK7FC
> >
> > Am 14.12.2013 20:50, schrieb Stefan Schäfer:
> >> Hi all,
> >>
> >> Tomorrow the rain probability is just 10% and so i think i can risk
> >> to run a short VLF experiment on 8970.00500 Hz. I'm using the fixed
> >> antenna at JN49IK00WD. These days, the QRN is very low for quite a
> >> long time! The plan is to run about 500W RF power, or more, depending
> >> on the voltage limit of the antenna. And the plan is to start
> >> transmitting tonite, after the experiment with VO1NA, i.e. i'll come
> >> on air arround 2 UTC, hopefully. I will run the test until the late
> >> afternoon. First i'm TXing a stable frequency until 9 UTC, later some
> >> DFCW-600, and then maybe some tests in OPDS32.
> >> Suggestions welcome.
> >> BUT it all depends on the WX. If it starts to rain then i have to stop.
> >> Will someone give it a try and watch for me?
> >>
> >> 73, Stefan/DK7FC
> >
>