Re: LF: MW Antenna [was:RE: Clemens on MF!!]

[Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>]

Hello Clemens,

What did i say...
So now you need a clean earth and maybe you can use a relay while 
transmitting. The relay switches both earths parallel and during RXing 
you just use the clean earth.
+6 dB, so now you're getting twice the antenna current with the same power?
Can you show us the image showing your house and the antenna again? I 
remember there was a coax of some 10m between TX and dipole feed point 
(?). If you can install an earth system directly below the feed point, 
then the RF current cannot cause TVI at home.
73, Stefan/DK7FC


Am 19.01.2014 16:11, schrieb Clemens Paul:
> Hi Wolf,
>
> I've tried the T-Antenna mode this weekend.
> It was excited against PE (protective earth of the house).
> Matching was surprisingly easy by a series C of around 1340pF,
> R (the real part)  happened to be 50 Ohm (in dipole mode it varies between 60 
> and 70 Ohm).
> The effect was dramatic in any sense.
> Ground wave signal strength went up by ~ 20dB as measured on a remote Perseus in
> Amberg (nr Nürnberg) this afternoon.
> Sky wave signal strength during last night went up by at least 6dB,maybe 10dB
> (diifficult to measure because of qsb while changing the configuration) in DL 
> as well
> in OH (1900km distance) on a remote Perseus.
> Now the downside:Rx noise level went up by roughly the same amount (day/night)
> and funny things happened when TXing with full power.
> The TV and some lights in the living room went off and on,there was hum in the 
> telephone
> etc.
> The RX noise problem could easily be solved by switching the two antenna modes
> automatically with the PTT line and a few relays.
> The EMI problem perhaps by a separate earth?
>
> 73
> Clemens
> DL4RAJ
>
>
>    
> > -----Original Message-----
> > From: owner-rsgb_lf_group@blacksheep.org
> > [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of wolf_dl4yhf
> > Sent: Saturday, January 11, 2014 11:32 PM
> > To: rsgb_lf_group@blacksheep.org
> > Subject: Re: LF: RE: Clemens on MF!!
> >
> > Hi Clemens,
> >
> >
> > Am 11.01.2014 22:58, schrieb Clemens Paul:
> >      
> > > The dipole is a horizontal 90°V, 8-15m high and according to
> > >        
> > EZNEC it has a spheroidal
> >      
> > > pattern with no nulls.
> > >        
> > Ok... that makes a difference.
> >      
> > > The vertical part of the feeder is only about 6m long.
> > >        
> > So the rainworms will be cosy and warm around the lower parts of the
> > antenna, hi..
> >      
> > > Tomorrow I'll check the impedance of the antenna aagainst
> > >        
> > ground with both feeder wires
> >      
> > > connected
> > > and see if I can match it to 50 Ohm,dependent on the available parts.
> > >        
> > That would be a good indicator for the ground conductivity.
> > At the local antenna farm, the total resistance (after
> > compensating the
> > reactive part with a series coil) went up from 26 to approx 35 ohms
> > within a few months.
> > During transmit, I simply use the PE (plus possibly the underground
> > cables) as counterpoise. During RX, the PE is disconnected from the
> > antenna's own 'ground' which consists of a few buried wires,
> > to prevent
> > QRM from the mains creeping in. Another remote RX antenna is already
> > planned, most likely it will be a small active loop or a system of
> > crossed loops.
> >
> > Cheers,
> >    Wolf.
> >
> > ( where is everyone .. now hearing only "  -...  ..  .-  "  ? )
> >
> >
> >      
>