The response is very flat because instead of an antenna, a sine source is used. I leave it up to you to calculate Z(in) of the contraption, and if physically it presents a realizable condition for reception. If so, it will be a piece of cake to receive the Japanese time station JJY-40 at 40 KHz.
https://www.sigidwiki.com/wiki/JJY
https://www.sigidwiki.com/wiki/JJY
Obviously this is an E-field antenna, a totally different beast compared to the magnetic loop antenna.
With my basic knowledge of radios I will play around a bit with the front end but not delve deep into antenna theory, this is beyond my scope.
Yes its impressive, all the VLF signals are there.
Have you tried simulating some capacitance (coming from the windings) in parallel with L5?
I am not familiar with SDR, but I begin to like the waterfall diagram. What is the sw you use, and is it available for Linux?
No, but as the linked article states, with the coil shorted inter-winding and other capacitances are without effect.
Yes of course looking into the Base of Q1 - not much voltage change there, so just the 26R for wire resistance so no Q no resonance just a flat response right up to 1MHz.
Mathematics and understanding of antennas is a specialist thing (a black art!). The Smith Chart was a thing to fear at exam time.
I know, so I always kept a safe distance to this😉
Looking for the Japanese time station, I did measurement in the range 39.9~40.1khz.
The first one with my standard test setup.
The second one with ferrite rod removed.
so what can we se?
There is a local carrier quite close to 40kHz, hiding the faint 40kHz-Signal.
Without the ferrite rod noise level drops about 5dB -
not very much, so there is room to improve noise of the circuit.
With some fantasy the 40kHz signal can be discovered...
Looking for the Japanese time station, I did measurement in the range 39.9~40.1khz.
The first one with my standard test setup.
The second one with ferrite rod removed.
so what can we se?
There is a local carrier quite close to 40kHz, hiding the faint 40kHz-Signal.
Without the ferrite rod noise level drops about 5dB -
not very much, so there is room to improve noise of the circuit.
With some fantasy the 40kHz signal can be discovered...
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If you could extend this to flat from 10kHz to 2 MHz it would more than cover all of the AM Medium Wave band.
A few times now I have come across reports that people have received SAQ and recorded it simply by connecting a long wire antenna to the sound input of their Computer. That's with no receiver electronics, no tuned circuit nothing just an antenna.
There is even a report from the USA that SAQ was recorded and Morse code read simply by throwing a tangled wire into a tree.
In the limit then, all that's needed is a long wire, a pair of headphones and a second carrier near the SAQ frequency that beats with it and makes the Morse code audible.
Can it really be this simple or are these fake reports?
I'm beginning to think that VLF gets everywhere.
There is even a report from the USA that SAQ was recorded and Morse code read simply by throwing a tangled wire into a tree.
In the limit then, all that's needed is a long wire, a pair of headphones and a second carrier near the SAQ frequency that beats with it and makes the Morse code audible.
Can it really be this simple or are these fake reports?
I'm beginning to think that VLF gets everywhere.
I doubt whether these reports are really true. On the other hand this will vastly depend on noise from the environment, and maybe there are remote places in the world where these things do work - who knows?
To extend the upper limit a faster transistor like 2n2369 looks promising in simulation. But I would not trust simulation in the upper region as the frequency dependency of ferrite core permeability is not modeled at all.
How you wind the tiny wire on that rod. Should I buy one of these Amazon clock antennas to play with
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- EverSet ES100 Atomic Clock Receiver Starter Kit including the receiver module, a breakout board, 2 fine-tuned antennas and the 90 degrees antenna holder bracket.
- EverSet ES100 is the only receiver designed for the new WWVB BPSK modulated time clock signal from Fort Collins, Colorado.
- EverSet ES100 delivers an up to 100x better reception than the old-school AM receiver technology, known from wall clocks and wrist watches.
- For detailed information, datasheets and example code see UNIVERSAL-SOLDER.ca official website.
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Most pics I posted are from my winradio's G31DDC. For specs, https://winradio.com/home/g31ddc.htm
Still one of the best but for Linux it looks there isn't comparable software, only devpacks: https://www.linradio.com
SDRplay offers more, has better noise blanker and offers Linux soft even for ARM. https://www.sdrplay.com/sdrconnect/
However, no full spectrum display nor very low BW. OTOH more support in the form of plugins including latest DRM.
HDSR can operate with soundcard as input but alas no Linux support.
It can be true. In a low EMI environment, a wire in a tree via an impedance transformer can deliver sufficient input signal. Once, 450 to 50 R wideband transformers were available and when connected to high Z receiver input, VLF reception was very good. Some 30 years ago in Belgium, in the village where I lived the only noticeable EMI was horizontal deflection circuit from TV. Grid was clean as a whistle.
I think these two antennas are combined to allow operation without adjusting the direction of antennas by elimination of the the minimum.