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BiggarDigger

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About BiggarDigger

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    Nebula

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  • Gender
    Male
  • Interests
    Astronomy (obviously!), IT (work - ugh), electronics and radio engineering, meteorology, fresh air and wide open spaces.
  • Location
    Biggar, Scotland
  1. BiggarDigger

    Antenna grounding..?

    Checking that the antenna is protected against lightning is essential. Michael Faraday nearly paid the price for overlooking that step. However pretty much any practical radio astronomy antenna should be grounded intrinsically. For radio astronomy, either a set of long yagis or, much more likely, a dish will be used. The antenna will be mounted on a substantial base, a post, mast or similar. The mounting system itself forms the grounding section. I guess an exception to that might be if a large dish antenna is mounted on a flat roof of a tall building. Such an arrangement would need additional lightning precautions. Lightning protection is a basic requirement of pointing anything metallic at the sky, but it won't improve the performance of the system, as noted in my comments about groundplanes. Richard
  2. BiggarDigger

    Antenna grounding..?

    For almost all purposes in radio astronomy, no you don't need to worry about antenna grounding for performance. Any benefits with respect to the antenna efficiency will be negligible: the frequencies are so high that the length of any ground plane is very small and the superstructure of the antenna mount will more than compensate for the lack or formal ground plane. Ground planes and antenna earthing is more often used at frequencies below 30MHz where unbalanced wire antennas can be used above a conducting plane. For most radio astronomy, waveguides or long yagis are used in a balanced mode and there should be no common mode currents to speak of. Here's a quick article that covers the basics if anyone is interested. https://www.electronics-notes.com/articles/antennas-propagation/grounding-earthing/how-to-ground-earth-antenna-aerial.php Towards the bottom of page 2 it is recommended to employ a 3λ/2 ground plane for wire antennas. In the KU band that equates to around 45mm ground plane and the dish is several metres wide. Even for Hydrogen Line, the recommended ground plane for an unbalanced feed is 330mm and your yagi or dish is still much bigger, even if it operates unbalanced. Note however, that in some phased array systems the antenna can be fixed and ground mounted. A metallic ground plane forms an integral part of the antenna, but these tend to be wide area, low frequency antennas covering several hundreds of square metres. I think the pictures I've seen of the receiving antennas at the 143MHz GRAVES radar site look like such an array. From Wikipedia: https://en.wikipedia.org/wiki/Graves_(system)#/media/File:Silo_du_plateau_d'Albion.JPG, but it's difficult to be sure what is presented in the picture. Be aware however that for any radio astronomy antenna you will have a large metallic object pointing at the sky and you will need to take basic lightning precautions.
  3. MRGC in Plymouth in 1985. Topped out at 44wpm CW and operated G (and latterly) GM4WKN until children and other priorities came along. Never went to sea: a life playing with radio and electronics in the civil service in central England beckoned. I was active on EME and MS as well as several others. Nowadays, I use those experiences to play around with meteor detection using an RTL-SDR. If/when I get more time and if/when resources allow, it would be good to do some other radio astronomy too. Meteor detections are pretty straightforward with low end kit, but if you really want, you could engineer an EME array on 23cm you should be able to run some very healthy Hydrogen line observations with both az/el controls. Richard
  4. Ahh, I didn't catch that rather important observation Ian! Taking your trace on the 11th, there is a 2Khz change in frequency in 17 approximately seconds. Cropping mine to the same 2Khz vertical window (centred on the 0Hz Doppler shift point), I recorded it for 40 seconds. In the image below, I've scaled my horizontal axis to the same as your's and crudely overlaid the two images. My image is very wide at that scale, so I've aligned the two at the -1Khz point (the point at which it drops off the bottom of the waterfall plot). That point is somewhat dependent on the accuracy of the RF tuning - hence the misalignment of the GRAVES azimuth switching pulses. Also, there's some scaling errors left to right across the image, but even with those and the crude overlay, you can see a very large difference in radial velocity between your trace and mine. Perhaps with more time (and an earlier evening) it may be possible to make a better job of the alignment. Visually, I'd estimate that the ISS ran across about 90° of your sky compared to approximately 60° of mine at the same absolute velocity, meaning the magnitude of your radial velocity was much higher than mine. I think! Richard
  5. BiggarDigger

    Computer Suggestions

    \IT SysAdmin Mode == On While Ryzen is undoubtedly the best bang for your buck right now, think of the bigger picture. If this is for your business, supporting heavy lifting such as Desk Top Publishing, CAD and GIS work, you need a lot more than low cost grunt, good though that stating point is. Anything in the enterprise class CPU will be fine, an 8th gen i7, Xeon, Ryzen - the choice is yours. But don't loose sight of the bottlenecks. The disk subsystem is critical and as a minimum you need an SSD or RAID 1 spinners in a machine that's going to adequately run those applications over the long term. If you go single ended, 2TB SSD are pretty cheap these days, or go for a hardware RAID controller and a couple of fast SAS drives. If you want reliability (which you normally would for business use) go RAID 1 for OS and RAID10 for data. Consider off-board storage connected via iSCSI or similar. 32GB Ram would be the minimum I would look at for those applications, ideally 64GB and above. Graphics cards are essential to lighten the load on GIS and CAD, especially over the long term and in business use. Perhaps look at mid range tower server chassis and drop Windows 10 or Server 2012R2 or above. Server 2012R2 or above gives you two free Hyper-v installations, so you can completely isolate your business stuff from your AP. Protect it with a UPS and suitable backup software. Remember to not loose sight of what pays the mortgage: AP processing is a nice sideline, but it's a business tool first and foremost, so don't treat it like a gaming rig, or shiny new toy in the corner: invest in it like any other business tool. \IT SysAdmin Mode == Off Richard
  6. That's an interesting one Ian. I captured the same two passes, but didn't notice the difference in Doppler until I saw your post. I will need to think about this a bit: the gradients (i.e. the rate of change in Doppler shift), appear on face value to be different to yours. However, I think this is to be expected. Since my range to the ISS was greater, yet the absolute path taken by the ISS was the same, it traversed a smaller angle of my sky than yours in the same amount of time, so the radial velocity would have been lower and the gradient less steep.....I think. Richard
  7. BiggarDigger

    Team Viewer Query

    You can adjust the quality of the link to give better colour representation. Your's is probably set to the default "Low". It's a not obvious to find though. From the TeamViewer app, go to Extras > Options > Remote Control > Quality > Custom Settings > Cutsomise Colours Richard
  8. BiggarDigger

    Horsehead with an 8 inch Dob

    Reflecting on the observation today, I have to admit that visually B33 is, at least with my gear, rather underwhelming. A vague finger of dark sky protruding into a line of slightly less dark sky. However, to be able to observe an object at the limits of my and the equipments' ability was something special. Particularly so, having seen many times over the images that seem fill the internet. Akin to, but a whole level tougher than, observing M1 for the first time. A special evening indeed...but for now it's cloudy again and a forecast of snow for tonight. Ho hum. Richard
  9. BiggarDigger

    Horsehead with an 8 inch Dob

    It was a cold, raw day yesterday, with a strong biting wind and mostly overcast skies. However the ClearOutside app suggested that the clouds would roll back by 18:00 and the wind drop. Suitably prepared then, I took a peek outside at around 19:00 only to find the clouds were as heavy as ever. Some gaps were appearing just after 20:00, so I waited until 21:30 and took another look outside to find a glorious clear sky with only a few low clouds skirting the horizon. The dob had long since cooled and Orion was hanging at a nice elevation to the South, so I retreated inside to get kitted up into my thermals, winter hat and gloves. Outside by 21:45, I popped in the 27mm Starguider and align on Alnitak. NGC 2024, The Flame, was very clear, with the central division and a couple of "branches" visible without filters. Move down towards my quarry and I can see NGC 2023, again without filtering. NGC 2023 is placed at one end of an arc of stars; the central star points towards the HorseHead. Looking South, about the same distance between NGC 2023 and the central star should be where my quarry lay. Nope, nada, diddly squat. I've read many times that patience is a virtue with IC 434 and B33, so I spent quite a while teasing out details. Without filter, I think I could just about see IC434 as wisps of nebulosity ooze in and out of visibility. After a while I popped in a H-Beta filter on the same 27mm EP. The sky is instantly much darker. The Flame still visible as too was NGC 2023. I can see a very slightly lighter patch of dark sky to the east of NGC 2023, being located slightly East and South of two faint mag 10/11 stars. It's IC434, but B33 is still illusive. More time passes and I wondered if B33 is beyond my scope's capability, even at this dark site. It's a work night and it's getting late, so my mind considers calling it a night, when a slightly darker finger of darkness oozed into sight very slightly north of the two faint stars. I blinked a couple of times and it's still there. I nudged the tube and it almost disappears then re-establishes its form when the scope settles. It's not shaped like the photos; more like an outstretched thumb pushing blackness into a patch of graphite grey. I can't see the "head", just the "neck". After about 15 seconds, it disappeared. Did I just see The Horsehead? Am I imagining things; are my eyes and mind playing tricks - is this "averted wishing"? I stood up and took in the sky for a while. The MilkyWay visible from South East to North West. Praesepe looking beautiful to the naked eye; Leo above the horizon and Virgo rising. I think briefly about taking in some galaxies, but I'm cold and I need to return to the warmth of the house soon. I gather myself again and return to the eyepiece, still with the H-Beta and 27mm. It's there again! IC434 marginally lighter than the pitch black background sky. A soft notch, north of the two faint stars. This time, I'm sure it's there and it isn't wishful thinking. After a bit, I nudge the scope again; the grayness of IC434 consumes the notch and this time it doesn't return: the grayness is fading a bit, almost as if to say, "I've shown you my secret and that is all you get". Very happy, I bring the scope inside to defrost and I gush like a fan-girl at Mrs Digger, who sympathetically makes me a cup of tea and returns to her book, not knowing the amazing site I've just seen. It is, by far, the most difficult object I've bagged to date and one that is worth taking 15 minutes out of a Monday morning to write up. Richard
  10. Thanks Ian, Yes, now I've added a definition for the cfg.SpecFreqMax and cfg.SpecFreqMin constants in the conditional actions script, the logger isn't missing much. In fact, arguably, for my site and system, it's too sensitive. Generally speaking, I don't think I've got too much RF noise. However, in addition to events of the order of a second or more, I recorded a fair number of extremely short duration and weak events overnight (<0.1s and ~15dB SNR), My original script didn't detect many of these. Given my range to GRAVES, I have no reason to think these are not meteoric in nature, but I suspect they may be very low in mass, which almost instantaneously vaporise creating a very weak and short duration events. I suppose that for a complete picture these should be included, but it would make post analysis of the events more difficult. As a result, I've tweaked the SNR threshold and duration up to 16dB and 0.1s. I'll see what effect that has on filtering out these extremely short duration events over the next day or so. If I can find the time, I might also have a play with a second spectrum, with a narrow window, to record the head echoes and see if I can deduce information about incoming velocity. Richard
  11. Progress! Reviewing the .USR file, I can see there are a number of configuration variables which are passed to the conditional actions script. Primary for my concern is the cfg.SpecFreqMax and cfg.SpecFreqMin. These were set outside the tuning range of my dongle - remember I'm running the dongle driven by SDR# and not Spectrum Lab. Adding those variables into the conditional actions text file plus tweaking some minor SNR and duration settings and I'm now recording meteors with this new script: I'll monitor the output for a few days and see what the script records, particularly in the small hours when background rates and duration tend to peak. Richard
  12. Ian, A brief update on some tests I ran with the script. Since my RTL-SDR dongle appears not to like Spectrum Lab, or more specifically, I haven't been able to find a driver dll to interface the two and need to drive it from SDR#, I had to fall back to testing only the conditional actions in the text file. These imported fine, but I couldn't get the script to trigger correctly. I can see it reading the average SNR, but upon an incoming meteor, it steadfastly refuses to trigger any further. I have adjusted the SNR trigger point down to a couple of dB, at which point it should be triggers almost continuously, but still nothing. Oddly enough, when there is an incoming strike, I see the green icon on the main display briefly flash to yellow and then back to green, just as it does when executing my current script: I need to spend more time reviewing the new script to see if there's a configuration in SL that I need to adjust to get the new script to recognise the peaks in the spectrum. Given that I'm only using the conditional actions and not your full setup, is there something in the initial configuration of SL using your method that specifies the incoming frequency range over which the conditional action script should search for a peak? Anyway, I'll try find some more time over the next week to run some more tests and checks. Richard
  13. I had a little play with this just now and encountered the usual pernickity Spectrum Lab. I've never been able to get SL to drive my RTL-SDR directly, and so it was today. I use a virtual cable (from vb-audio.com) to connect the SDR output to SL and use SDR# to drive the rf functions of the SDR. Nonetheless, I'm interested in the features in this script and tested it with a 1kHz local oscillator in SL to fine tune the conditional actions. For now, I've reverted back to my original script as I don't have enough time to tweak much further tonight. However, with a bit of luck I can find time in the week to merge the conditional actions text file into my hardware specific setup. I'll report back in a few days. Richard
  14. BiggarDigger

    LED vs. sodium street lighting?

    Our village was converted to LED lamp heads a couple of years ago. We have a street light directly outside our property, about 10 metres across the driveway from the front door, which faces north. The lamp heads are tightly focussed on the road. Often, on clear nights, when on dads taxi duty, I can see the Milky Way as I walk to or from the car even though the street light is just a few metres away. The I can't comment on imaging, but I can say that I've seen more auroras since the upgrade and the rear of the house, where I do all my visual observing is very dark. Richard
  15. Good piece of work Ian! I'll need to make time to experiment with the new script. Richard
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