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LF: Re: Speclab, GBR and loop antennas

To: [email protected]
Subject: LF: Re: Speclab, GBR and loop antennas
From: "g3ldo" <[email protected]>
Date: Wed, 30 May 2001 09:04:57 +0100
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Wolf, DL4YHF, said:
".......the system does receive below 10kHz but I don't know how good. I
don't have a commercial receiver which goes below 10kHz, so I cannot compare
my RX system to  a professional RX. I don't even know a (reliable) signal
between 1 and 10kHz to listen for. The RX antenna is a heavy bundle of 19
ferrite rods, insulated from each other to avoid currents in the
semiconducting material, and 400 turns of wire. Total inductivity about 30
millihenry, parallel caps for resonance between 15..20kHz and a high-current
JFET as impedance converter (no voltage gain required for the MIC input of
the PC). With more C's shunted it will work on even lower frequencies, but
not very good I suppose".

I tried Speclab for the first time yesterday and it worked fine with a
receiver audio output - with lots of interesting features that will take me
a long time to explore.

Tried it as a VLF receiver for the purposes of receiving GBR. Seemed to work
OK after an an itial hitch and all the relevent function boxes were green.

Problem now no signals even though there is noise in the speaker. The signal
generator produces a signal. Nothing on the input box. I have also lost the
colour palet so everything is in monochrome. Furthermore Speclab wont set
back to 'normal'.

Abandonded Speclab and used D2155 Level Meter, connected to the superloop
described on my Web page. Loop resonated (aproximately) to 16kHz using 90nF
good quality capacitors. When GBR transmitted it was -75dBm and the CW was
very easy copy. The loop exibited 24dB symetrical nulls but deepest part of
the nulls masked by noise.
Later did the test using the signal on 138kHz with loop accurately resonated
and got 32dB symetrical nuls.
A good day out in the sunshine experimenting with LF!

Peter, G3LDO

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