100m might be fine for 1.8 MHz (160m band) antennas but for 17.2 KHz it's about 100 times smaller in terms of wavelength. If you know how to utilize a piece of wire of 1m as receiving antenna for 160m, the same applies for the 100m horizontal wire at 17.7 KHz.
It will work, for this kind of circuits up to 20k I always used this topology. Thanks to to the symmetry no issues with "antenna effect" that requires shielding.
What kind of laptop are you using? I thought to isolate RX and computer with optical USB interface and that produced more interference than what was intended to disappear ;-)
What kind of laptop are you using? I thought to isolate RX and computer with optical USB interface and that produced more interference than what was intended to disappear ;-)
Another option would be to record the sound output on my mobile phone or Samsung Tab.
The + - 5V supplies can be battery, two Lithium 18650 cells would avoid any noise. As regards the Laptop again it has Lithium battery.
Yes the symmetry of your circuit looks great. I can't think of a better way to design this.
The + - 5V supplies can be battery, two Lithium 18650 cells would avoid any noise. As regards the Laptop again it has Lithium battery.
Yes the symmetry of your circuit looks great. I can't think of a better way to design this.
Small (in terms of WL) antennas exhibit high impedance and are capacitive. Hence for reception, the easiest way is to feed it to the top of a tuned LC with a high Z amplifier (or mixer).
My laptop uses Li batteries as well but most of the time runs on AC grid power. In the battle against EMI I designed and built a simple MW receiver, useful input 0.1 uV, with possibility to plug in magnetic field and electric field antennas. Works great to find the source of the problem. It appeared that the PC is a source of radiation that would require shielding. An alternative might be a physically very small one in a metal case, to be used only for radio.
I am familiar with 15 kHz equipment in my ancient past. They were using Baudot code, not Morse.
Software decoding works well. I would use as long a wire as possible or a very big loop and high pass it to a PC soundcard, to reduce mains pickup. After capture, Audacity can bandpass filter - You are talking about 50 Hz B/W.
Software decoding works well. I would use as long a wire as possible or a very big loop and high pass it to a PC soundcard, to reduce mains pickup. After capture, Audacity can bandpass filter - You are talking about 50 Hz B/W.
@davidsrsb Thank you for adding some confirmation to some items that we have been discussing. As I understand it the 17200 Hz carrier when transmitting Morse is either present or absent. So a very binary form of AM modulation then. My plan was to use a Ferrite rod tuned to 17200 Hz probably with a wire attached. In the literature Grimeton SAQ talk about vertical polarization. Do you know if we are better off with a long horizontal wire or a not so long vertical wire? I have see photos/designs on the Alexander Association website showing a portable receiver that uses a telescopic aerial?
Thanks for your engagement in how to receive SAQ Grimeton on 17.2 kHz, very interesting discussion!
At World Heritage Grimeton Radio Station in Sweden, the Alexander association is responsible for keeping the only remaining, and still fully functional 200kW Alexanderson alternator in running condition. Nowadays we don't magnetize the alternator very hard, so the output to the antenna is about 80kW. The very unique Alexanderson multiple antenna, with six 127m tall towers, has an efficiency of about 12%, so about 10kW reaches the ether, enough to be heard in many parts of the World. Listeners in Europe can receive SAQ with a small simple receiver and antenna, but if you are in the US, you will need a very sensitive receiver and large, correctly tuned antenna.
See what other listeners are using on our interactive listeners map: https://drive.google.com/open?id=18nSI0tfCQsxGJo9x7YA7tqBSHYopmGpU&usp=sharing
You can follow our our work on our website https://alexander.n.se.
There are also some tips on how to listen to SAQ at https://alexander.n.se/en/the-radio-station-saq-grimeton/lyssna-pa-saq/
Subscribe to our newsletter where we post info on our upcoming transmissions.
Best of luck!
Fredrik / Alexander association
At World Heritage Grimeton Radio Station in Sweden, the Alexander association is responsible for keeping the only remaining, and still fully functional 200kW Alexanderson alternator in running condition. Nowadays we don't magnetize the alternator very hard, so the output to the antenna is about 80kW. The very unique Alexanderson multiple antenna, with six 127m tall towers, has an efficiency of about 12%, so about 10kW reaches the ether, enough to be heard in many parts of the World. Listeners in Europe can receive SAQ with a small simple receiver and antenna, but if you are in the US, you will need a very sensitive receiver and large, correctly tuned antenna.
See what other listeners are using on our interactive listeners map: https://drive.google.com/open?id=18nSI0tfCQsxGJo9x7YA7tqBSHYopmGpU&usp=sharing
You can follow our our work on our website https://alexander.n.se.
There are also some tips on how to listen to SAQ at https://alexander.n.se/en/the-radio-station-saq-grimeton/lyssna-pa-saq/
Subscribe to our newsletter where we post info on our upcoming transmissions.
Best of luck!
Fredrik / Alexander association
The shortest VLF antenna is an active whip. It requires to be located as far as possible from sources of interference and needs a good ground. Described with installation details also in
https://www.pa3hcm.nl/?p=1232 as mini-whip
https://www.pa3hcm.nl/?p=1232 as mini-whip
Bloody hell, Rich. I wish I'd seen this earlier. My wife's from Cardiff and I've been there a few times now and still have family and friends there. I'm going to read up on this pronto. I wonder if I might have a crack at hearing this next year - or are we just TOO far away? Let's hope it keeps going!
When the wavelength is 17 km, any practical wire or loop is electrically short.
That makes 12% antenna efficiency look pretty good.
That makes 12% antenna efficiency look pretty good.
You might consider making a transformer to match the (presumably high) audio input impedance to the 375 Ohm impedance of RF in air. A long wire antenna positioned in the same polarization mode (probably horizontal at this freq?) as the transmitter might also be helpful, though I'm no expert on VLF receiver antennas.
To get an audible 500 Hz signal, consider heterodyning the carrier with a 16.7KHz audio source.
To get an audible 500 Hz signal, consider heterodyning the carrier with a 16.7KHz audio source.
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I get this:
300 Mhz/ meter x 1/17.2 KHz = 17.441 km wavelength
100m /17441 m = 0.005733
I'm a little rusty on this stuff though; haven't been doing RF stuff since I retired. I'm sure somebody will correct me if I slipped up somewhere.
You are correct.
Lambda = c/f
Taking c (the speed of light) as 299792458 m/s and f (frequency) as 17200 Hz Lambda is 17429.79407 metres
or Lambda (wavelength) is 17.42979407 km
This is dubious. It is not the only way, see previous discussions. Please don't confuse this thread.
Not too far away! There are listeners reports from Australia see:- https://drive.google.com/open?
This is recording from near Perth:- SAQ 24.10.23 (6.5m loop) West Australia
Thank you for taking time to post on our thread, it is much appreciated. It surely is that many people are in awe of what you are doing at Grimeton SAQ. Watching the YouTube videos and reading yours and others websites brings the realisation of what the early pioneers of radio were doing around the world and how valuable their contribution was to international communications and safety at sea. It is a great thing that Sweden has looked after and preserved this last Alexanderson Alternator for future generations.
Please accept my apologies for mis-quoting the power output of the Alternator as 250 MW rather than 250 KW and more accurately the power level actually used today of 80 KW.
This thread is about "Tuned Sound Amplifier/Receiver" I wanted to look at receiving and processing the signal from Grimeton SAQ as purely a signal in the audio spectrum rather than the more conventional receiver approach. Notably most of the receiver designs I have seen (historical and recent) use a frequency mixing to make the Morse code more audible and often show an untuned front end.
Essentially what I am proposing to construct (and other posts above have elaborated on similar, notably @Aridace ) is as follows:-
- tuned front end (Ferrite rod / Capacitor) with high Q
- optional vertical antenna/earth connection input
- high impedance sound preamp
- buffer amp feeding directly into the sound input of a mobile phone or Laptop PC
- mobile phone or Laptop PC recording sound input into standard audio wav file or similar (with high sampling frequency).
- optional processing of the sound file
- replay of the sound file at slower speed (0.5x or less) such that the Morse code is clearly audible