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HN50

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About HN50

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    Nebula

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    Surrey
  1. HN50

    VLF radio receiver build

    Hi, Thanks for the post. Unfortunately, a whole load of non astronomy things have gotten in the way of my work on this since (Gulp! Can’t believe it...) last November. I had been having a bit of trouble building a band pass filter to tune to a single station. It should be a case of a high pass and a low pass in series, but I think that something was not quite right with my workings, and I was investigating a different radio entirely. Anyway I am hoping to get back on to this soon, and if nothing else I have a hankering to build a table top VLF radio. Out of interest, what range of frequencies can the Arduino frequency counter detect? Dave
  2. HN50

    Reflector vs refractor

    Hi, I have the ST150 and for low/medium power it is a great telescope, so if you use it for the role it is intended I don’t think you would be disappointed. An 8” dob would be more cost effective and allow me to see deeper into the sky, but these choices are not always totally rational as there is something I love about a large aperture refractor. I can only agree with what others have said around the mount. I acquired the ST150 when I traded it with a friend for my old ST102, and the size difference is significant. I tried it initially on my AZ4; I have seen comments on here from people who are fine with that but I found it a too shaky and upgraded to the Skytee 2. I have no experience of the F8 version, but the F5 is no lightweight so you would want to take into account the cost of a suitable mount if you go for it. But otherwise I love it. Sweeping about the sky hunting down DSOs is very pleasant. The above are just my opinions, others might disagree. Hope that helps. Dave
  3. HN50

    COMPLETED - Celestron X-Cel LX 7mm £45

    Hi, Pm sent. Dave
  4. It has been nearly a year since I updated this (!!!) but I have had a hankering to get back to it. I had some time off recently so decided I would build a bigger aerial, using the method in the S@N article. I had some pine beam kicking about and I bought a spool of doorbell wire. The hatch into my loft at its widest is just over 1m, so I figured an aerial with 1m sides was the biggest I could build. After several hours of working I was left with this; Not pretty, but it looks like a loop antenna to me. I had slightly forgotten how to use SpectrumLab, but once I had got it working again I was confronted with the following plot; SpectrumLab seems to have decided to use different settings, but I don't remember seeing the transmitters like they appear with the 45cm sided aerial. It is still noisy, but I can definitely see two, maybe 4 transmissions. I even dared to believe that it looked a little like some of the other screenshots I had seen online. I reset the plotter settings (below) and left it to run for 24 hours. When I came back, I had the following; A few of the signals are below the strength of the background noise (so I assume might as well be ignored), and most of the stronger signals are quite noisy, however I saw that 22.1k is looking rather smooth. So I might have one signal that is usable. I am currently writing a powershell script that will pivot the data into rows rather than columns to make analysis easier in a spreadsheet; SpectrumLab is determined to log max, min and average; and I will also have to think about aligning the antenna to see if that will improve some of the other signals (I plonked it down just to get going), but at the moment the increase in antenna size does seem to have been helpful. So I will keep logging and see how things progress.
  5. HN50

    VLF radio receiver build

    Thank you Alan. Working with Arduino is rather fun, it feels a bit like old school programming when getting it to interact with home brew electronics. Dave
  6. HN50

    VLF radio receiver build

    Another slightly underwhelming update approaching, but I am feeling a bit chuffed. I have been learning how to program an Arduino ('Exploring Arduino' by Jeremy Blum) and have been able to; 1) Detect a varying voltage (used a spare potentiometer) 2) Get time from a real time clock 3) Log results from #1 and #2 to an SD card every minute 4) Use a transistor as a switch to turn on an LED My thinking is that if I can master all the above I have the basic ingredients for my logging module. Today I have been trying to get #4 modified to turn a radio on and off; the bit in the red box below is the transistor switch (2N3904 transistor). I gather these can take a maximum of 200mA - the radio seems to draw 150mA so I think it might be okay. Anyway, I got the radio hooked up to spectrum lab and several weeks of work/frowning gave me this; The radio comes on at ~57.75 seconds, is on for a second, then goes off. Hahahahaha! A little underwhelming, but baby-steps and all that. Next I will try tinkering with the radio output so that it goes into the Arduino and gets logged, though at the moment I am trying to get the new version radio laid out and the narrow band filter working. Dave
  7. HN50

    VLF radio receiver build

    Hi Alan, Thank you. It has been quite a slow piece of work but I have enjoyed it. Dave
  8. HN50

    VLF radio receiver build

    After a bit of work today the potentiometers got sorted. Well, they took 10 minutes to change, the following 2.5 hours was me trying to work out why the radio had stopped working. In the end I traced to it a loose connection caused by me tugging on one of the leads. I had plans to make a nice insulated shoe for the circuit and battery to sit in, but in the end I opted to use silicone sealant and glue them in place. Further down the line I am going to redesign the circuit so that the potentiometers are soldered directly to the veroboard, but I am happy enough for this version to have flying leads all over the place. Anyway, this is the latest pdf after some post build changes; BBB-4 VLF radio with headphone amplifier.pdf I have compared the physical size versus the first one I made, and I think the boards are comparable in size, looking at it now I just needed the larger case be able to handle two potentiometers (left pot is gain, right pot is on/off and volume). So if the amplifier was given a fixed gain, it would be possible to squeeze it into the smaller case. I also have fired up SpectrumLab in my back garden to see if me messing about with filters has made a difference (the BBB-4 with the filters certainly sounds more pleasant than the unfiltered Peanut Butter VLF radio). First screen capture is the unfiltered peanut butter radio; Mains hum is very obvious right at the bottom of the plot, and it really overpowers all but the loudest sferics when listening. The BBB-4 with high pass filter attenuates a lot of this (little signal below 1kHz). There are still harmonics, but they are not as loud. Gain is set to minimum. From a visualisation point of view the filters do not seem to make much of a difference, but for ease of listening they do. Both plots show sferics (vertical lines), VLF transmitters (solid horizontal lines), and I think the intermittent horizontal lines are Russian Alpha transmissions. So, all in all I am quite pleased. I have a few ideas for how I want to improve the layout in future versions, but for the moment I will leave it as is. The next stage is to clear the prototyping board as I want to put together a version of this radio that is tuned to just one of the VLF transmitters. That way I can see if I can get the variation in voltage logged by an Arduino datalogger and use that for SID detection. So the radio and filter will be posted eventually here, but I might start a separate Arduino data logger thread. Hope you enjoyed the post. Dave
  9. HN50

    VLF radio receiver build

    After more than a lot of frowning the radio is now 90% working (I wired the capacitors up wrong so both controls work backwards). I have also had to spend more than a bit of time debugging the circuit as I now realise the board had several important ommissions and would not work. Mainly the +9v line to the op amp was going to the wrong leg. A little reminder to myself of what happens when I rush or don’t pay attention. But then again I have had voltmeter out comparing values to the prototype and also checking connectivity so it has been useful practice. I have a few days off this week so I will sort the potentiometers and insulate the underside of the board. And maybe make that second headphone socket do something. That case looks huge!
  10. HN50

    VLF radio receiver build

    This is today’s work, about 3 hours of soldering. I think once again I have made the layout too snug (the inductors were a bit of a squeeze to get on), but otherwise so far I am pleased. Will stop now as I am starting to make mistakes, but the next job is getting the flying leads on to the potentiometers and battery holder.
  11. HN50

    VLF radio receiver build

    It has been a bit of a while getting the layout done, but I am starting to assemble the new circuit. Have got the circuit board cut out and cut rails as per plan. So I will get soldering tomorrow. Not the most exciting of updates, but after a bit of a break due to work it is nice to see the build progressing again. I am also keen to get the prototyping board cleared as I have started tinkering with an Arduino and have bought a data logging shield.
  12. HN50

    VLF radio receiver build

    I am still working on converting the schematics into a layout on StripboardCAD, but in the meantime I went out into the South Downs and a slightly more radio quiet location to try listening and recording with the prototype. There is significantly less mains hum, though you can hear a little interference from longwave (I think) radio in the form of faint garbled speech. However the low pass 24kHz filter is helping to remove some of that. I played around with the gain on the radio and spectrogram, but the above is certainly better than in my back garden. Tweaking the settings more and I could see quite a few more VLF transmitters (horizontal lines) from about 12kHz up; I heard lots of sferics but no tweaks or whistlers, though I don't think midday is a good time to listen. The iPhone can be a bit temperamental in knowing when the the radio is plugged in, but my first version will be headphones only so I am not too fussed about solving this now. Anyway, back to getting that circuit layout complete.
  13. HN50

    VLF radio receiver build

    I have been playing around again with SpectrumView and I found that it does have a gain control in settings, so by adjusting it you can display a fainter signal better, as below; I tried running it out the headphone amplifier again, however one thing I have found is that the plot does/can become a bit erratic (overload/feedback? - limit of my electronics knowledge) as below; So maybe it might be better to run any recordings from the second transistor as per the original BBB-4 design and have a dedicated radio for this (another project!). I have also found that I can either run the headphones or the microphone at any one time. Again, probably a simple fix for someone with electronics knowledge but at this stage I am just happy to have a functioning radio. Given that this is intended as an audio project I have decided that the first iteration will just have a socket for headphones. For the moment I have gone as far as I want with the prototyping, so I will fire up StripboardCAD and start laying out the circuit. Dave
  14. HN50

    VLF radio receiver build

    I had a play this morning by rewiring the 4 pole socket to run from the second transistor rather than from the lm386 audio amplifier. The BBB-4 is designed to plug into a recorder or laptop directly, however the visual settings on the iPhone spectrogram are basic and you can't alter the colour distribution to handle a weaker signal. Anyway I wanted to see what the difference looked like; Versus the plot from yesterday out the headphone amplifier; I am sure this would not be a problem in SpectrumLab, but for the purposes of what I am trying to achieve I prefer the second. So I think I will have the socket(s) out the headphone amplifier. Dave
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