Hi Dimitris,
Interesting, theat LIPD class. So you could even try higher frequencies
than 8.3 kHz. Here we are not allowed to transmit above 8.3 kHz.
However, i have a special licence to transmit arround 17.47 kHz, with 5
mW ERP. On that frequency i have been received by Edgar and we
transferred a 3 character message successfully some months ago. A 5
character message almost decoded but in the end we failed.
Why is there is a gap between 19.95...20.05 kHz? No idea but i would
have expected a gap arround 19.8 kHz, because of NWC
https://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt
200 uW on 8.27 kHz is a good signal but with the space you have, you
could get up to 20 dB more so it is a pity. But anyway, many people
could detect you at 200 uW, at least in a radius a few 1000 km.
73, Stefan
Am 07.02.2019 01:52, schrieb Dimitrios Tsifakis:
Ciao Marco,
yes, the grass is indeed greener on the other side but I am not
complaining about that! If there is no time now, perhaps there will be
later! More things to do when I retire, there is nothing worse that
people that retire and do nothing...By the way I do look at the legal
aspects. We are lucky in Australia our local spectrum authority has
made it clear how much we can radiate in the various parts of the
spectrum. There is a class licence known as LIPD (low interference
potential devices) which tell you how many microwatts you can radiate
on VLF and below and it is very generous I think. Here is what we are
allowed to do:
0 kHz to 14 kHz 200 uW EIRP
14 kHz to 19.95 kHz 50 uW EIRP
20.05 kHz to 70 kHz 7.5 uW EIRP
(note I cannot transmit between 19.95 kHz and 20.05 kHz, not sure why
there is that gap)
I can live with that!
73, Dimitris VK2COW
Στις Πέμ, 7 Φεβ 2019 στις 5:46 π.μ., ο/η [email protected]
<[email protected]> έγραψε:
Hi Stefan, Dimitris,
room is sure a thing that is not missing in VK :-)
I remember a vacation I had there some years ago ... a lot of km between "adiacent
places".. so ideal place for LF, VLF and even close to DC frequencies!
During my travel, just for fate, I drove close to Holt Navy Base sporting an
antenna just a bit larger than your loop ;-)
Anyway you know the grass of the neighbor is more green...
Dimitris has room but not a lot of time..
I have more time but less room
somebody else has room and time but no money...
What an hard life!
But... we all have fun!
73 Marco IK1HSS
P.S. who's looking the legal aspects?? ;-)
----Messaggio originale----
Da: [email protected]
Data: 5-feb-2019 23.40
A:<[email protected]>
Ogg: Re: VLF: in VK?
Dimitris,
Am 05.02.2019 21:14, schrieb Dimitrios Tsifakis:
G'day Stefan and Edgar,
My house is on QF44OX00OR and the property extends to QF44NX (50 acres
or 200,000 m^2). I do have permission from some neighbours to lay
wires into their properties, so an extra large (over 1km) ground wire
is entirely doable but not at this point in time.
Wow, i'm envious and happy that you have such possibilities!!!!!!!!!!!!!!
Not at this time, ok. I would suggest to start in small steps anyway, then you
can be happy about many improvements, not just a single big one :-)
I often imagine to live in Canada or Australia and do such experiments exactly!
The reference loop
is from the shed, about 100 metres south of the house, to the tractor
shed.
100m is very close, the far field begins at about 5.7 km distance at 8.27 kHz.
A RX in that distance is only useful to check and observe the signal stability
and compare levels. A feedback monitor like my tree which is 3.5 km distant
from my INV-L antenna in the city. From my ground loop antenna in JN39WI it is
57.6 km distant, which is already an interesting distance and can be
challenging below 3 kHz.
I have mains in the shed and I also have a 200 W audio linear
amplifier to get things started.
Excellent, just excellent! Your signal could be the stongest of the radio
amateurs! 200W is just fine for the first steps. But be careful with those
audio amplifiers, they do not seem to like to much reactive power.
For tuning the antenna you will only need a capacitor in series. For my
portable VLF system i built a current transformer to produce a small voltage
that goes to the soundcard. Then, using SpecLab, i can calculate the antenna
current directly and even keep the phase of the current stable, even if there
should be a soundcard glitch. For the signal generation i also use SpecLab and
a cheap GPS module. It all works very reliable, there were no problems so far.
With a house at one of the ends of the antenna you are in a very comfortable
situation! You may already have a ground system there, so the effort is at one
end only.
I can build a class-E kilowatt if
necessary later. I like the roughly north-south loop configuration as
it favours many large cities (Melbourne, Sydney, Brisbane and Tassie)
and most importantly Canberra which is only 30 km to the South. I will
try to get some signals received in Canberra before I start asking
people further away to have a listen.
Yes, this is a very good distance to observe your own signal. If you have
internet access there and can leave a small PC/notebook/tablet ... then you
could build up a webpage and run a grabber from there like i do from my tree
(still under maintenance). That would be ideal and it just feels good to see
the own signal very clearly on a real RX in a short distance. You are then
independent.
I currently have assembled an XO
clocked DDS controlled by an arduino to do the initial tests but later
when I decide to go QRSSSSSI can dig out and use the old rubidium
clock as a reference for extra stability. For receiving I use a 24
bit, 192 kHz USB sound card and spectrum lab (thanks Wolf!). The
antenna I will use for receive is one of those monster ferrite rods.
Amplification may not even be necessary, the signals I get when the
antenna is tuned seem to be already quite good. Once I have a decent
RX antenna I think I will start gifting these rods (I have a few) to
interested amateurs in the region and help them get started with
receiving on VLF. Make a small army of receivers, that would make life
much easier when evaluating antennas!
Oh yes! Fortunately there are a few arround here. These days this is (sorted by
distance to my VLF loop): DK7FC, DF6NM, DL0AO, DL4YHF, IK1QFK, Paul Nicholson,
SQ5BPF and RN3AUS. Oh and W1VD, K3SIW and Edgar J.T. This is about the complete
VLF group worldwide, at least those who prooved to detect narrow band (sub mHz)
signals close to the limits, in the last 3 years until now.
Hey, you should document your experiments even if it is a summary of
the activities and nothing more. The list is great but perhaps we are
missing out on many other potentially interested people that may have
not discovered the list.
Yes, you are right. I had the same thought sometimes. Certainly there are many
amateurs who would feel like having a new life when starting at VLF, It is an
unknown spectrum for 99.9 % of the amateurs. Actually it is not even amateur
radio because it is not a spectrum allocated to amateur radio. So everyone
could operate there.
But there is a risk, you know. There are those people who do not simply start to
transmit/receive there and feel good. There are those who prefer to ask if this is legal
at all. And then they ask here and there, as long as they find someone who triggers their
fears and phobs, and then they do nothing at all! Beware of such people, they are
contaminating your free mind. Concentrate on ideas and wishes, like for example detecting
your own signal in Canberra. And then the question "Will this also work on lower
frequencies", for example.
When writing an article in a radio magazine, what will be the result? Will it
actually lead to more active people on the band, who transmit and/or receive
for a longer time, say at least 5 to 10 years? Or will it rise a short interest
only, dominated by people telling it is not legal and so on... I'm not sure
about that. It could be even better to stay in a smaller group who can do what
it wants instead causing a decision / regulation by an 'authority'.
You are clearly not lazy having achieved so
much on MF and below :-)
Thanks but i'm lazy into a certain spectrum. On the other side, there are
people who write many articles over the years but it is simply impossible for
them to even imagine to wind a coil which has more than 100 turns. Maybe it is
good that there is a variety of people, the article writers and the coil
winders and something inbetween :-) Oh, and the programmers! Very important.
Without Wolfgang and Paul and Markus we would do nothing at all!
Oh BTW maybe i'll transmit on my loop again the next weekend. I can't await it,
it is more than 2 weeks ago, a very long time!!
I have played with ground loops before and had some good results in
LF.
On VLF it should work much better (relative to a vertical E field antenna). The
idea is that the current runs back in a deep layer (skin depth), depending on
the ground conductivity. So it should work better on poor conducting ground.
Once I establish a reference system, I can compare antennas
including ground loops. Unlike Europe where you have plenty of people
around you, I have to do both the TXing and the RXing and that
requires effort and time. The latter is a very scarce resource!
Anyway, looks like a nice day today to do some more outdoor work. We
had lightning storms and plenty of rain the past few days, so I
haven't made any progress.
RR, good luck and fun with the new challenges.
Looking forward to your next steps and reports.
73, Stefan
73, Dimitris VK2COW
|
