Geminids

There is not much rhyme or reason with interference - someone or something turns on a piece of noisy electrical kit, it starts to radiate, it warms up and frequency changes and then switched off (hopefully). It coud be a TV, USB charger, led lights etc etc - you will (or may:-) get to know the different types. It may be that you are the culprit so look out for kit turned on near your antenna. There are things that can be done to improve the G4CQM antenna you are using to reduce RFI - location of cables and balun. A very good start though !

Actually, the ISS exercise we are conducting shows where the GRAVES signal is reflected by the ISS. We project the ground location back to the altitudes where the "radar beam" could meet a meteor and scatter. The meteor radio map is therefore only an indication of regions with the potential to have meteor scatter. You will understand that these results are dependent on ISS orbit - it only goes as far N as about London latitudes which work back to the meteor areas of Northern France latitudes. Video match could be supplied by French video networks eg BOAM. If we have other satellites with large reflecting surfaces that travel further North we will expand out field of video/radio match possibly to UK video coverage.

Although the times are similar, it actually depends on where the meteor was. Do you get tajectory details from you voisual observations? This is essentially correct - it does depend on a bit of geometry; for seeing what is called specular scatter from the trail it is neccessary for the path of the meteor to touch an ellipse with foci at GRAVES and your location. Thus, the geometry is unique to your location and it is not likely applicable to other locations. However, it is possible for anyone to see a head echo, if strong enough. There are also the really long duration events that are "non-specular" and are not dependendent on the geometry - so can be seen in many locations. You may want to look at this https://www.imo.net/observations/methods/radio-observation/intro/ which explains some of the ins and outs. Unless you have a very high gain antenna with a very narrow beam-width, it will not make too much difference.

Actually Gav, there are many of us with the same ambition of trying to understand waterfall or spectrogram displays. The links to video or still images is tenuous, not suprisingly as the direct light captured on camera is totally different to GRAVES scatter from ionisation trails. Head echoes such as the one on your 01:15:01 spectrogram can tell us something, but with a lot of effort. In the spectrogram following, the event looks like an underdense meteor. The longer duration events may be the specualar trail or sometimes longer lasting ionisation drifting in upper atmosphere winds. If you capture more ISS passes on your radio you may be interested in sharing them with this group here https://radiometeordetection.org/radioproject

Hi Morinmau, a pretty basic question but are you sure of the frequency of that signal and that it is GRAVES? I do not know the Noolec NESDR SMArTee v2 dongle but the ubiquitous FCDP+ can be a few hundred Hz off frequency - having said that, I have just looked at your last spectrumlab plot and the meteor ping is around 900 Hz with the "GRAVES" signal is just below.

Your reasoning for elevation angle is sound, but if you are still getting the main beam signal directly as it seems you are, then I would suggest that you are seeing the main beam through one of the antenna side lobes. Try higher angles of elevation, changing antenna polarisation or pointing away from GRAVES. From your location I would think you get very strong pings from meteors wherever you point. By the way where did you get the map that you have drawn your directions on? Mike

Yep - a good idea to do that !

My understanding of these functions is that, time returns a value that can be subject to the vagueries of processor busyness speed etc. and will be subject to variable delays (the author of Spectrum Lab explained this in Spectrum. Lab User Forum iogroups some time back). Now was introduce to overcome these problems and gives the most accurate report of time at the time the function is called. Your processor must be very busy 🙂 for such a difference. Seriously, there difference you talk about seems wrong. It will also be dependent on the context of where it is used in your conditional actions script - if the functions are side by side in a long loop process or the FFTs are large for example.

Not bad work for seven days work! Sorry I cannot help you with Pi 😞 Spectrum Lab has had many years of dedicated development - probably many more years that Raspberry Pi's have.

Hallo Ken, I am not familiar with your particular set up for Spectrum Lab. However, it does look as if the settings for the spectrogram display are set too low. The conditional action script seems to be capturing something. I do not know what the dispaly on the spectrum display graphs at the top indicate. Perhaps red for noise and green for signal? But I cannot see the levels. I would normally adjust the amplitude range (the numbers below the colo(u)r palette on yours they are set to about -110 to -60dB) of the lower limit so that the noise level is just occassionally poking into the spectrum graph and then set the upper limit to 40 dB above that. Then it is a matter of adjusting the colour sliders up and down. A good indication is when you get a purple-blue background and red-blue noise spots - meteors will be orange to yellow to white. I hope this helps. Mike

They look like good data. According to IMO information there are two showers that are at a maximum on 29 th July - Southern Delta Aquariids and Alpha Capricornids. (these have negative declinations - does that mean they are below the horizon and we don't see them?) They have Zenith Hourly Rates of 25 and 5 respectively . There is also the Perseids which were starting to become active on July 17th and going through to 12 August with ZHR of 100. Those results suprise me (nicely) for such Northerly monitoring; your background noise and interfence are probably good in such a remote(? 🙂 ) place. Do you have a good line of sight over the sea?

Hi Storm Chaser You've been running for a while now and I am wondering what kind of hourly count rates you've been getting in Stornaway?

Agreed.

Do you have a balun on the antenna down lead? This can significantly reduce cable pick up. I use commerically available ferrite baluns from the company that supplied the antennas. I have found monitor screens are still picked up by antennas.

It is nice to see the streaming data. I think I saw dim moon scatter at 1075 Hz. Where is 143.050 (zero Doppler for your RTL? Oh I can see on your clip it is at around 1065Hz. Your background noise looks quite steady with no nasty sproggies.

Welsome back! That is a really strong one. Keep on with the study - all valuable information. ISS is one of the biggest targets we see but unfortunately I think, from memory, its orbit is limited to something like 51 deg N. I did start to think about other large satellites that come further N - and hence help map out the side lobes - but 😞 I was sidetacked on another project.

According to the link below sporadic E contacts were highest 16:00 to 18:00 but still plenty of them between 18:00 and 20:00 UTC. https://www.mmmonvhf.de/es.php?year=2020&month=05&day=29 I learnt that mid-latitude sporadic E occurs between 100 and 120 km altitude (the altitudes we look for radio meteors) and is possibly casued by wind shear sweeping up long-lived metal ions from meteor disintegration. I haven't been able to ascertain whether VHF is refracted back or forward scattered? It seems a possible mode for GRAVES signals of the type and duration but I can't say (yet) if it is probable. It appears to be a different manifestation to that of tropo scatter. Any thoughts Mike

That is very interesting - I was looking for some kind of ionospheric effect. I will have to think and take advice on how trhat may allow signals like that. Thanks

A number of us who regularly monitor for meteors on the GRAVES radar frequency noticed an event at 29/05/2020 18:09:02 lasting here at Hayfield for almost four minutes, and with particularly high signal strength. Other than the long event there is no evidence on my records to identify it as a meteor. There is no head echo. The GRAVES pulses can be readily seen but apart from that there does not appear to be any general fading. Does this suggest high altitude with slow dispersion/recomination of the ionised cloud? How far wide spread was this seen? How strong (compared to avearge meteors) was the signal? Were there any space junk ionising the atmosphere.

I had noticed these effect on a few days now and happened to be watching the radio waterfall rather than spectrum lab when it happened today again. The streaks turn out to be a source of wandering frequency local QRM I first noticed several years ago and had hoped it had gone away. As for the bright spots from what you say they are not the more distant QRM from Starlink! I will investigate further. Thanks for the information.

Amongst my monitoring of daytime Arietids along came a herd of starlink satellites (I think). Two questions - has anyone seen the streaks that seem to be associated with the times of the bright events and how long before the herd are dispersed?

Jeremy - thanks for the announcement - much appreciated

Hallo Ian Out of interest do you know whether they were in the mainbeam or side/rear lobes of GRAVES? Mike Hayfield

I think that the wavy signal you see is interference from electrical equipment as it warms up or the load changes. I was about to add "faulty" equipment but with the sensitive receivers we have nowadays and the "relaxed" view by the RFI enforcers it could be a RFI approved. If this is the first time you have seen it you are lucky. It would be nice to know something of your radio set up there, but it almost definitely wouldn't help (me at least) with identification. It could be sproggies (spurious signals from broadcast transmitters), emissions from computer monitor or TV or even the ever present "wall warts"

This looks as if it might do the job. I need to get used to the jargon of TLEs and to convert ISS Azm and Elv to ground Lat and Long. I am checking a GRAVES recorded scatter from 20160729 that was verified at the time with ISS Tracker. At that time I had Time Lat Long 01:38:00 46.84 0.37 I have set the location to this Lat and Long and running the predictor (sat elevation >0 and min flare mag of 5.0) and using the current TLE (Keplers) the prediction is way, way off at 22.5N ~62E . For a LEO would I be right to assume this to be expected for that far back.