Hi!
Since about 11:00z, I'm using DHO38 as a reference for my carrier on
8969.98. As it can be seen on your grabber, frequency is stable.
I'm using a 3,5mH surplus DCF77-Ferrite rod (20cm by 1cm) resonated to
roughly 22kHz with a 15nF capacitor. GQD on 21,4kHz also could be
received by this system.
Coupling to sound-card is done by a secondary winding of about 30turns.
No active parts required. Just fed into the Mic-Input.
The ferrite-antenna is in the garage where the Notebook is and about 5m
away from the loading coil. DHO is about 20db over noise in the
wide-band-view 0-24kHz when the rod is properly adjusted. GQD is about
the same. So in case DHO is on "breakfast-brake", GQD could be used.
73
OE3GHB
Gerhard
Am Samstag, den 26.02.2011, 15:17 +0100 schrieb Stefan Schäfer:
> Markus, VLF,
>
>
> Am 26.02.2011 14:27, schrieb Markus Vester:
> > DHO 23.4 kHz is received simultaneously by a small ferrite antenna
> > to lock the TX samplerate.
>
> Maybe this should be pointed out a little more detailed.
> While it was a quasi common thinking in the last months, that it is
> impossible to receive a VLF MSK transmitter (like DHO38 or GQD) during
> transmitting below 9 kHz (due to the very high field strengths near
> the TX coil and wire), your and Gerhard's experiments show that it is
> possible indeed, if a resonated ferrite antenna is used. I've built
> the same and can receive DHO38 at 20 dB SNR in 3 Hz. The attenuation
> of a 9 kHz signal against 23.4 kHz is about 40 dB. The dynamic range
> of the soundcard allows another 80 dB before overload occurs.
> Additionally there is a very narrow directivity of this antenna (-10
> dB at +-30 deg).
>
> The few VLF transmitting stations may use this method as an
> alternative to a GPS locked VFO, if SpecLab is used to generate the TX
> frequency. I will use this antenna as a redundant system to lock my
> VFO in the next experiment. Maybe there are some advantages regarding
> EMC.
> RX stations may use this method too since the strongest MSK
> transmitter can be choosen, even if the RX loop antenna points into
> another direction! (Stereo mode necessary)
>
> A photo of my simple ferrite RX antenna for DHO38 is here:
> http://dl.dropbox.com/u/19882028/DHO38%20ferrite%20RX%20antenna.JPG
> 34.3 nF is used to resonate to 23.4 kHz. The output winding has about
> 25 turns while the primary has about 200 turns.
>
> 73, Stefan/DK7FC
>
>
> > Markus (DF6NM)
> >
> >
> >
> > From: Gerhard Hickl
> > Sent: Saturday, February 26, 2011 11:55 AM
> > To: [email protected]
> > Subject: Re: VLF: OE5ODL and OE3GHB active on 8970 Hz
> >
> >
> > Hi Stefan and group!
> >
> > In the moment I'm running on GPS-Sync and will switch to DHO38-Lock
> > in a few minutes. I'm curious about the stability.
> >
> > Antenna-current is as usual about 550-580mA.
> >
> > Beside my plan to run a QRSS10 X-Band QSO with OK2BVG soon, no
> > further plans right now.
> >
> > 73
> >
> > OE3GHB
> > Gerhard
> >
> >
> >
> > Am Samstag, den 26.02.2011, 11:42 +0100 schrieb Stefan Schäfer:
> > LF,
> >
> > The season is slowly passing, the average QRN is significantly
> > rising. But today the QRN is low and both Austrian VLF TX stations
> > are transmitting. OE3GHB is about 15 dB above noise in 424 uHz on
> > 8969.98 Hz.
> >
> > Some new projects on your side? There's not much activity these
> > days...
> >
> > 73, Stefan/DK7FC
> >
> >
> >
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