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From: Dimitrios Tsifakis <dtsifakis@gmail.com>
Date: Sun, 10 Feb 2019 08:37:11 +1100
Message-ID: <CAKvcm2dMFaQcsr9FQVZrKAeBjhnBPQrO1r5Of5Y0b4i7BGoBiw@mail.gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: VLF: in VK?
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Hi Stefan,

> Can you tell more details?

Yes, see answers below!

> How much power was used?

The amplifier output power was about 50 W.

> How much antenna current?

Calculated current based on measured parameters about 2.2 A RMS

> Was it the 3 turn loop?

Yes!

> What type of receiver was used on the RX site?

E-field antenna (miniwhip) to an upconverter and HF receiver.

> Is that site in a quiet location?

Not particularly (it's in the suburbs) but VK1DSH reported it was a
relatively quiet morning.

> Which bandwidth or mode?
> Was it actually QRSS-10 (Which i would watch in 122 mHz)?

He was using spectran at QRSS30 setting,  0.042 Hz.

> What was the SNR?
> Is there a screenshot for us to see?

yes, see here: http://people.physics.anu.edu.au/~dxt103/pics/Dimitris_0004.jpg

Not stellar SNR but the radiated power I reported originally (7.5 uW)
is not correct. I think the capacitors have sustained some damage
because they seem to introduce a series R of about 6 ohm! After I
adjusted for that extra R, I now think that my radiated power was
closer to 2.3 uW. No wonder they got hot, poor things!! So if I fix
that problem I will gain another ~ 5dB for the same amplifier power.

> What is your plan for today? :-)
> Who is the next distant station?

The plan is to try to improve the SNR at the same location by using
better capacitors. Now that we are certain we are in the far field
(over 2 lambda), we can easily calculate how the signal will attenuate
over greater distances and eventually, when I am happy with the
stability of the system, I will get Edgar to do his magic!

> This could be the beginning of a growing worldwide VLF activity, if you
> can 'mobilise' a team of stations who build up RX and TX systems arround
> VK.

Yes, I have that in my mind. I am planning to donate a few of the
large ferrite bars to local hams that are interested in setting up a
VLF RX station. The relative immunity of the H-field antenna to noise
in the urban environment gives it a small advantage compared to the
E-field ones. I found that about 150 turns of wire on that ferrite
make a good general purpose untuned antenna which if desired can be
tuned to achieve better results.

What do you think of the plan? :-)

73, Dimitris VK2COW