Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

[OH7HJ]

Most of these Moscow TV aircraft scatter (AS) dopplers were from near the Rx-Tx baseline midpoint which is within common radio horizon of Rx and Tx for high flying aircraft. However, among these usual dopplers were some very short dopplers that were plotted at too steep angle to be from usual airliners. Steep doppler angle at baseline midpoint would mean aircraft crossing at supersonic speed. It was not likely that there would be many supersonic flight so evidently something else should cause these yet unknown dopplers.

With most cases of the unknown steep dopplers there was no aircraft scatter explanation for them in the usual area of reception of Moscow TV baseline midpoint. Plotted doppler baseline crossing angle is steep close to Rx or Tx, and mild far away from them.

Supersonic flights is not practical explanation so another reason for steep dopplers might be aircraft crossing baseline closer to Rx or Tx. That meant that the unknown dopplers might came from somewhere else than near Moscow TV baseline midpoint that is within or near common radar horizon from both Rx and Moscow TV Tx. The problem about close to Rx or Tx baseline AS crossings is that the aircraft would be far away from the supposed VHF radar range limits of Rx or Tx radio horizons.

Seeking for Steep Doppler Origin

First, I checked 26 of these unknown steep dopplers on Moscow freq from during about 2 days with Planefinder playbacks and found that in 14 cases of 29 unknown steep dopplers there were no planes near the baseline midpoint area of usual visible Moscow crossings. In the cases of aircraft near the area of visible crossing, there usually was usual mild aircraft doppler for it showing separately from the unknown steep doppler.

Antti OH7DI has previously introduced bistatic radar equations showing that strongest bistatic scatters appear with planes near Rx or Tx. In this case planes over Moscow Tx are far out of radio horizons of each other as the Moscow TV Tx is abt 892 km away from Rx. It is also known that aircraft crossing Rx-Tx baseline closer to Tx or Rx plot steeper dopplers than those crossing near midpoint of baseline.

To check if these mystery steep dopplers could somehow propagate over-the-horizon (OTH) from somewhere near Moscow Tx maybe with help of signal boosting baseline forward scatter effect and occasional tropo scatter, I added a check of close to Moscow district to this survey. Not really believing that these crossings could propagate from so far away.

Plane Crossings from Near Moscow…!

The results of plane search appeared suprising. There indeed was a plane on the Rx-Tx baseline in 23 of the 26 cases of these unknown steep dopplers.

The spot was on an almost transverse to baseline air route crossing Rx-Tx baseline near city of Kolakovo about 135 km before Moscow. This crossing point appeared to be close enough to Moscow TV Tx to produce about as steep dopplers as these observed unknown dopplers.

Regarding scientific credibility, the trouble with these findings is that the point of crossings is far beyond receiver radar horizon. It would mean that observed aircraft dopplers propagate from a radar range of about 757 km. That is a clearly over-the-horizon (OTH) observation which has this far been not supposed to regularly happen on VHF…!

Reasons Contributing to OTH Observation

If these really are over the horizon crossings, then we need to explain what would bring so distant low VHF band aircraft dopplers visible. It might be a combination of these favourable factors:

• Very high ERP power of Moscow TV Tx,
• baseline forward scatter effect that increases AS doppler signal level by 20 … up to 30 dB,
• recently configured high resolution Spectrum Lab receiving FFT settings,
• help of occasional tropo scatter, and
• the rather large 12-element receiving yagi array.

I remember having seen a few such steep short dopplers with the previous Moscow TV receiving arrangement but back then with the default wide band receiving Spectrum Lab FFT settings they were not yet sharp and regular enough to catch attention like they now are.

With the powerful 6-over-6 6m receiving yagi array and with the Spectrum Lab FFT settings improved sensitivity of reception the Moscow TV carrier is now visible and plotting practically continuously on its strip. With earlier smaller receiving aerials Moscow TV plotted without visible carrier as a chain of those short and wide electric discharge scatters (EDS) only on its spectrum strip.

Baseline Forward Scatter Effect

The forward scatter effect of baseline crossing is experimentally known to momentarily increase aircraft scatter doppler intensity up to the level of the TV carrier itself, or sometimes even a little stronger than the carrier.

Because the Moscow TV carrier is now practically constantly visible at Rx Spectrum Lab strip, it may be possible that the forward scatter baseline effect boosted crossing are momentarily as strong as the TV carrier, which would bring them visible from over the horizon distance of 757 km from receiver.

Bistatic range of this forward scatter observation is not increased because the crossing occurs right on the 892 km Rx - Moscow TV Tx baseline.

OTH Crossing Screenshots

Below are examples of many of similar crossings near Kolakovo. First attachment illustrates Rx-Tx baseline near receiver (Rx) and near Moscow TV transmitter (Tx) shared to two Planefinder playback maps. Map at left shows that there appear no aircraft near the usual crossing point of baseline midpoint area. Map at right shows aircraft crossing baseline near Kolakovo, abt 757 km from Rx and 135 km from TV Tx in Moscow. Its steep doppler crossing at SL strip shows at right. Pic: 2017-09-28-1554 FT - PF playback - Moscow TV ant Y12H 140 - Steep doppler - No aircraft near baseline midpoint - OK191 near Kolakovo © OH7HJ.JPG

Next attached screenshot shows another example of a plane crossing Moscow carrier near Kolakovo with simultaneous steep doppler. Baseline and range from receiver (Rx) to this crossing point are marked on the map at left: 2017-09-28-2242 FT - PF playback - Map of crossing point on baseline - Moscow TV ant Y12H 140 - Steep doppler - Aircraft near Kolakovo 757 km away © OH7HJ.JPG

Third pic shows Rx - Tx baseline on map with its midpoint near Boksitogorsk and the steep doppler baseline forward scatter crossing point near Kolakovo marked: Moscow TV Rx-Tx baseline length 892 km 145 degr KO85TT Tx from KP42QP Rx - Kolakovo forward scatter crossing point © OH7HJ.JPG

Regards,

• Juha -

Links

Online multi-static radar screenshot archive for doppler originals: maanpuolustus.net/muut/tutka/kuvat/
AS dopplers on Moscow TV carrier - Part 1: oh7ab.fi/foorumi/viewtopic.php?f … =120#p1912
AS dopplers on Moscow TV carrier - Part 2: Facebook OH7AB
AS dopplers on Moscow TV carrier - Part 3, 469 km: viewtopic.php?f=21&t=295&start=150#p2359

Spectrum Lab Manual: qsl.net/dl4yhf/speclab/index.htm
2 x 6 -element 50 MHz yagi array for AS doppler spotting: oh7ab.fi/foorumi/viewtopic.php?f … t=30#p1852
Locator map for measuring distances and baselines: no.nonsense.ee/qth/map.html
Planefinder: planefinder.net/#

Natural Scatters

Radar Aurora Compared to Sodankylä Magnetogram - Part 1. openstreetmap - ilmaisia karttoja!
Radar Aurora Compared to Sodankylä Magnetogram - Part 2. openstreetmap - ilmaisia karttoja!

Electric Discharge Scatter EDS - Yläsalamat aiheuttavat radioheijastuksia viewtopic.php?f=21&t=295&start=100#p1782
TV-lähetteitä aurorassa ja ES-kelissä viewtopic.php?f=21&t=295&start=100#p1892

Natural EDS ‘Doppler Hooks’ may be scatters of spreading high altitude lightnings:
‘Dopplerkoukkuja’ Moskovan TV:n jaksolla - Osa 1. viewtopic.php?f=21&t=295&start=100#p1893
‘Dopplerkoukkuja’ Moskovan TV:n jaksolla - Osa 2. viewtopic.php?f=21&t=295&start=110#p1900
‘Dopplerkoukkuja’ Moskovan TV:n jaksolla - Osa 3. viewtopic.php?f=21&t=295&start=110#p1901
‘Dopplerkoukkuja’ Arkangelin TV:n jaksolla - Osa 4 viewtopic.php?f=21&t=295&start=110#p1903
‘Dopplerkoukkuja’ Pietarin TV:n jaksolla - Osa 5 Facebook OH7AB

Aurora and EDS - Radiorevontulia ja sähkönpurkausheijastuksia 6m bandilla - 1.
viewtopic.php?f=21&t=295&start=140#p2250
Radiorevontulia ja sähkönpurkausheijastuksia 6m bandilla - 2 viewtopic.php?f=21&t=295&start=140#p2289

Tavallisia sähkönpurkausheijastuksia (EDS) viewtopic.php?f=21&t=295&start=140#p2251
Yläsalamapurkauksen synnyttämä ukkos-Es-keli viewtopic.php?f=21&t=295&start=110#p1895

50 MHz Es-keliavauksia viewtopic.php?f=21&t=295&start=140#p2248
50 MHz Es-keliavauksia - osa 2. viewtopic.php?f=21&t=295&start=140#p2249

[OH7HJ]

“LIVE ROCKET LAUNCH - Watch as the European Space Agency (ESA) launches the Sentinel-5P satellite from northern Russia at 5:27 EDT (10:27am BST). The satellite will track global air pollution from orbit.”

The liftoff trajectory of this rocket launch was directed over East Carelia so it appeared possible to plot on the bistatic ‘ham radar’ experiment strips. Checking monitor strip of Arkhangelsk TV carrier, there were signs of a rather faint very fast doppler crossing among usual aircraft doppler traces. The time of the fast doppler trace at 12:27 FT matched with liftoff time told in the video link below.

Range limit for aircraft on high altitude with the VHF bistatic radar experiment is radio horizon about 420 … 450 km away. A high rocket launch has of course longer radio horizon but it has an altitude limit regarding TV transmitter low radiating aerials. Rocket may plot a doppler until about 100 km altitude when flying between receiver and TV transmitter like the Rockot in this case did. Very high flights like satellites above 100 km are above TV transmitter vertical patterns of radiation so they are not visible on these bistatic doppler strips.

No Launch Trajectory Info

It is very uncertain to prepare for spotting dopplers of these rocket launches because there is no advance info available about their initial launch directions, trajectories, altitudes and velocities. This launch information would be needed for proper receiver setups and aerial directions to catch a clear rocket launch doppler. Launches are rare and usually directed to east away from reach of this doppler experiment. This launch had been delayed 6 times so it was not evident that it would be launched now, either. Because of all this it is a matter of good luck to have freqs and aerials oriented correctly for catching a rocket launch doppler from the part of launch trajectory that is within altitude and bearing limits of reception setup.

A couple of common aircraft dopplers are marked on the attached screenshot along with the circled faint tracks that appear Rockot doppler crossing traces on wide and narrow spectrum strips. The strip speeds are set for aircrafts and I was no prepared for very fast objects like a rocket so got only a short and flat doppler trace.

Aerial of this bistatic radar experiment is a 6-element yagi. Receiver is a cheap RTL SDR dongle plotting on laptop screen with HDSDR and Spectrum Lab softwares on Arkhangelsk R1 TV channel carrier frequency. Time stamps on Spectrum Lab strips are UTC + 3 h Finnish local.

Launch Links

Science Video of Rockot-Sentinel liftoff: facebook.com/IFeakingLoveSc … 150278820/

Prior launch info:
Schedule: Oct. 13 Rockot • Sentinel 5p
Launch time: 0927 GMT (5:27 a.m. EDT)
Launch site: Plesetsk Cosmodrome, Russia
A Eurockot Rockot vehicle will launch with the Sentinel 5 Precursor Earth observation satellite for the European Space Agency and the European Commission. Sentinel 5p carries an instrument to measure air quality, ozone, pollution and aerosols in Earth’s atmosphere. Delayed from Oct. 31, early 2017, June, August, Sept. 21 and Oct. 9. [Sept. 21]

spaceflightnow.com/launch-schedule/

earth.esa.int/web/guest/mission … entinel-5P

• Juha -
  
  

[OH7HJ]

The Nyandoma TV plots fairly long dopplers of about 20 minutes from east of Lake Ladoga. Looking for farther range, there is a flight route east of Lake Ääninen about 375 km away from receiver. Aircraft crossing here plot repeatedly doppler tracks of about 5 minutes. Here are examples of them.

Two of the examples are from the North-South route with planes crossing Nyandoma TV carrier abt 375 km away and one from NE route of aircraft crossing at abt 395 km away from the receiver. The funny ‘feathers’ occasionally visible around TV carrier and AS dopplers are curious side bands distinctive to Nyandoma TV Tx.

Receiving aerial is the usual 6 over 6 element 6m band yagi array pointing direction 100. Time stamps are Finnish local, UTC + 3h. Doppler strip archive with originals of these strips is arranged by time and date at: maanpuolustus.net/muut/tutka/kuvat/

The online bi/multistatic radar demo with fresh strips updating every half an hour is here: maanpuolustus.net/pages/tutka/

• Juha -
  
  
  

[OH7HJ]

OIRT-TV-kanavan 2 kuvakantoaalto on nimellistaajuudeltaan 49.750 MHz. Tässä on dopplerohitus Petroskoin (Petrozavodsk) TV:n R2-jaksolla 59249,998 kHz.

Petroskoi on varsin lähellä, joten lentsikoiden lähiohitusten dopplerit näkyvät melko voimakkaina sen kantiksen jaksolla.

Oheiskuvan ohitus on kopitettu 50 MHz jagilla, joka toimii näin etäällä nimellistaajuudestaan lähinnä ympärisäteilevänä dipolina. Dopplereita se näkee silti kohtuullisesti.

Taajuuksia:

Jürgenin kopittamistaan asemista kokoama OIRT-kanavalista tarkkoine taajuuksineen ja tuntomerkkeineen: dx.3sdesign.de/tv_offset_list.htm
Kokonainen OIRT-TV-lista, ilman tarkkoja taajuuksia: vcfm.ru/radio/fais2015_11_1+2ch.php

T: - Juha

[OH7HJ]

Karshevon pienitehoista n. 10 watin paikallislähetintä voisi ehkä merkitä tämä neljän sarja dopplereita, heikolla kantiksella 29 Hz Pietarin kantiksen yläpuolella? Lentsikkasuuntimalla (ASDF) tarkistettaessa, kaikki neljä lentoa osoittivat samaa suuntaa. Ohessa esimerkkikuva lentsikkasuuntimasta spektrinauhalle ympyröityine dopplerohituksineen.

Jakutinon TV on myös samalla suunnalla, mutta niin kaukana, että sen kantiksella pitäisi näkyä EDS-heijastusten helminauhaa. Nyandoman TV:n jokin sivunauha on kolmas vaihtoehto, sekin kun on lähes samalla suunnalla.

Tämä on kopitettu RTL-tikku vastarina suoraan Spectrum Labissa Yaesun välitaajuuden kautta, joten taajuudet näkyvät peilinä, koska en vielä ole löytänyt SL:n asetuksista taajuuden peilausoptiota. Antennina on 6-yli-6 vaakajagi suuntaan 100 astetta.

Linkki lokaattorilaskentasivulle: k7fry.com/grid/

T: - HJ

[OH7HJ]

Looking at natural phenomenon viewpoint, the curious orbital Nasa photo might be from a cloud of high altitude electric discharge. It appears transparent, and either weakly luminous or lighted up by the aurora discharge. The natural 50 MHz scatters on the R1 TV channel usually plot radio scatters dividing to two or three or even more directions. These ‘radio flares’, ‘doppler hooks’ or ‘fork scatters’ may be born by scattering from such dividing streamers of natural high sky electric discharges.

Photo is found with keywords ‘Nasa aurora arrow’ search. Photo link to it is youtu.be/9yCustQ4Zqg

The natural Electric Discharge Scatters (EDS) appear have spread doppler components that may present speed vectors of spread spectrum of accelerated ions and dividing natural discharges in very low pressure air.

After igniting, these discharges spead and create hot enough plasma or cloud of ionized air which is conductive enough to reflect and scatter VHF radio waves. As soon as the high atmosphere electric discharge is over, the temporary semiconducting ionized cloud cools down again fading away their ED radio scatters.

Spectrums Spread by Altitude?

Observing radio scatters of these natural discharges show radio scatters lasting from less than a second to a few minutes. Long lasting EDS usually have wider spread spectrums than short ones. This suggests that air ions or plasma accelerated in the electrostatic field of discharges gets faster and makes wider spread EDS spectrums in lower pressures of higher altitudes. So both duration and spread spectrum width of EDS’s may be related to their altitudes.

One of the highest altitude electric discharges and usually the only visible by eye from here on ground is the Aurora Borealis or Northern Lights, with its distinctive wide spread noise spectrum it causes on radio scatters. The wide spread spectrum aurora scatter is the longest lasting high altitude radio scatter with duration of hours.

There are yet no established words for these high sky electric radio scatters. The curious ionospheric “high-altitude plasma irregularities in the E region” mentioned in this FM bistatic radar paper from 1997 appear same as high lightning discharges that seem to cause the EDS: onlinelibrary.wiley.com/doi/10.1 … S02454/pdf

Articles, Studies and Observations

Already somewhat known spreading and dividing natural high altitude electric discharges are ‘sprite’ lightnings. Sprite photos by Thomas Ashcraft: heliotown.com/Catalog_Transi … vents.html

“Sprites, Elves and Intense Lightning Discharges”, Nato Science Series II: books.google.fi/books?id=XagIZh … es&f=false

Upper-atmospheric lightning: en.wikipedia.org/wiki/Upper-atm … _lightning

The Manastash Ridge radar: A passive bistatic radar for upper atmospheric radio science - onlinelibrary.wiley.com/doi/10.1 … S02454/pdf

EDS - Yläsalamat aiheuttavat radioheijastuksia: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Sähkönpurkausheijastus EDS - Electric Discharge Scatter: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Yläsalamapurkauksen synnyttämä ukkos-Es-keli: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

‘Doppler hooks’ - ‘Dopplerkoukkuja’ ‏Moskovan, Arkangelin ja Pietarin TV-jaksoilla:
Osa 1: viewtopic.php?f=21&t=295&start=100#p1893
Osa 2: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Osa 3: viewtopic.php?f=21&t=295&start=110#p1901
Osa 4: viewtopic.php?f=21&t=295&start=110#p1903
Osa 5: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

Online bistatic radar demo listening to R1 TV channel carriers at maanpuolustus.net/muut/tutka/kuvat/

• Juha -
  
  
  
  

[OH7HJ]

Nadvoitsy TV Tx near Segezha is told to have ERP power of 13 kW, which is less than 1/10 of St. Petersburg TV Tx power. However, also this medium power R1 channel Tx allows see fairly long off-baseline backscatter aircraft scatter (AS) dopplers of airliners traveling on Far East route through Kainuu waypoint. Here are a couple typical examples of them.

With very low power transmitters (Tx) aircraft doppler scatters are usually visible near baseline between Rx-Tx only because of the baseline forward scatter effect that boosts aircraft scatter as strong or even stronger than the Tx signal at the moment of aircraft crossing Rx-Tx baseline. In such baseline forward scatter cases aircraft scatter doppler crossings have been momentarily observed with VHF transmitters having less than 1 W of transmitting power with receiver 100 km away from transmitter.

With medium strong Tx’s like the Segezha Nadvoitsy AS doppler are visible also away from baseline. Not as far away as with strong transmitters like St Petersburg TV and Moscow TV, which allow observing AS dopplers up to the theoretical common radio horizon of Rx and Tx. With help of baseline forward scatter effect, sometimes even over the horizon (OTH).

These dopplers were observed with an inexpensive RTL dongle receiver and north pointing 6-element 6m band yagi. Softwares used are HDSDR and Spectrum Lab, with FFT set for decimation of about 8 … 16 to allow high resolution and reception sensitivity with good tolerance against noise interference like aurora scatter. Time stamps are Finnish local. Sector of aircraft doppler visibility from doppler appearance to its fadeout is drawn on the pics as lines from Segezha Nadvoitsy TV transmitter (Tx). Aircraft course adjustments are visible as notches in their plotted doppler tracks.

Radar Range and Tx Power Experiments:

East: St Petersburg TV, Äänisjärvi 360 km: openstreetmap - ilmaisia karttoja!
Nyandoma TV, Äänisjärvi 395 km: viewtopic.php?f=21&t=295&start=150#p2370

South: Moskova TV, Tikhvin 469 km: viewtopic.php?f=21&t=295&start=150#p2359
Cherepovets TV, Tikhvin 440 km: viewtopic.php?f=21&t=295&start=110#p1898

West: St Petersburg TV, Ähtäri 300 km: openstreetmap - ilmaisia karttoja!

Low Power: OH5IY lentsikkaheijastukset 0,1 W majakasta OH5ADB 144 MHz: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

• Juha -
  
  
  
  
  

[OH7HJ]

Continuing with another example of aircraft scatter doppler on Segezha Nadvoitsy TV Tx. First pic show plane location at its doppler appearence on the spectrum strip and the second pic at the fadeout of its doppler from the strip. Next plane doppler is already appearing while the first plane doppler is fading.

Previous pics: AS dopplers from Kainuu - 297 km, part 1 - viewtopic.php?f=21&t=295&start=150#p2379

• Juha -
  
  
  
  
  

[OH7HJ]

Arkhangelsk TV Tx is supposed to have 8 kW of ERP power, so it is lower powered than Segezha Nadvoitsy. However, the Onega Bay of White Sea helps to boost its signal strength so rather long aircraft dopplers are available at it.

Here is an example of flight that despite of its rather low flight level of 10058 m was visible for up to 458 km from receiver. The route of this flight kept close to Rx-Tx baseline, so the baseline forward scatter effect improved its signal strength. The plane was flying almost parallel to Rx-Tx baseline so it plotted a parallel type of doppler close to the Arkhangelsk TV carrier.

Receiving setup is similar to the previous Kainuu experiment, with RTL as Rx 6-element 6m band yagi pointing NEE. Softwares are HDSDR and Spectrum Lab, with FFT set for decimation of about 8 … 16 to allow high resolution and good reception sensitivity. Doppler shift scale is Hz and time ticks are every 10 minutes. Time stamps are Finnish local. Aircraft course adjustments are visible as angles or notches in the doppler. Two pics were saved direct during the flight and one screenshot was created later with Planefinder playback.

Next: Arkhangelsk TV AS dopplers - 426 km, part 2 - viewtopic.php?f=21&t=295&p=2382#p2382

• Juha
  
  
  
  
  
  

[OH7HJ]

Next set of screenshots on Arkhangelsk TV carrier frequency illustrate typical doppler of flight arriving from Far East.

First screenshot is from doppler appear location and next from doppler fadeout location. Sector of doppler visibility is drawn with lines from Arkhangelsk TV Tx.

Date and local time of observation is marked to each file name. Doppler shift scale is Hz and time ticks are every 10 minutes. Receiving setup is the same as in previous experiment.

Previous: Arkhangelsk TV AS dopplers - 458 km, part 1 - Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

• Juha
  
  
  

[OH7HJ]

Two subsequent flight dopplers. Experiment setup as with earlier two reports.

Previous:

Arkhangelsk TV AS dopplers - 458 km, part 1 - Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

Arkhangelsk TV AS dopplers - 426 km, part 2 - posting.php?mode=reply&f=21&t=295#pr2382

• Juha
  
  
  

[OH7HJ]

Here is a series of 4 pics of aircraft dopplers crossing Arkhangelsk TV carrier with transverse to the Rx-Tx baseline flight path.

The transverse crossing is much steeper than the parallel crossings of previous examples so now using narrow spectrum scale. Time ticks are every 5 minutes.

Otherways receiving and file name documenting setup is the same as with previous Arkhangelsk TV AS doppler reports.

Continued in next report: Arkhangelsk TV AS dopplers - transverse crossing 2 - Kerhon kaluston lainausvihko

• Juha -
  
  

[OH7HJ]

AS doppler pics series continued from previous message. Aircraft coming from north is flying lower which makes its doppler weaker.

Previous observation reports:

Arkhangelsk TV AS dopplers - 458 km, part 1 - Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Arkhangelsk TV AS dopplers - 426 km, part 2 - posting.php?mode=reply&f=21&t=295#pr2382
Arkhangelsk TV AS dopplers - 416 km, part 3 - Kerhon kaluston lainausvihko
Arkhangelsk TV AS dopplers - transverse crossing 1 - Kerhon kaluston lainausvihko

• Juha
  
  

[OH7HJ]

These are aircraft scatter dopplers on Nyandoma TV Tx carrier east of Lake Onega (Äänisjärvi). Nyandoma is supposed to have a medium power TV transmitter with ERP of 46 kW.

There were more similar dopplers in Nyandoma spectrum strips but because many domestic flights do not use locating ADS-B transponders these flights are not visible on online radar servers like PF and FR24 they could not be identified.

Rx aerial is a 6 over 6 element 6m band yagi array (Y12H) pointing at dir 100. Time stamps are Finnish local and time ticks at spectrum strip are 5 minutes apart. Doppler archive with copies of these spectrum strips is arranged by date and local time at: maanpuolustus.net/muut/tutka/kuvat/

Previous: AS dopplers on Nyandoma TV carrier - 395 km- viewtopic.php?f=21&t=295&start=150#p2370

• Juha
  
  
  
  
  

[OH7HJ]

Luonnolliset radioaaltojen hajaspektriheijastukset yläsalamoista saavat joskus hupaisia muotoja. ‘Kovista’ ja ‘kylmistä’ keinotekoisista kohteista, kuten lentokoneista heijastuvat radioaallot näkyvät yhtä kapeina dopplerjuovina, kuin niiden lähetinkin. Luonnollisista sähköisistä ‘kuumista’ ja ‘pehmeistä’ lyhytaikaisia plasma- ja ionipilviä muodostavista sähkönpurkausilmiöistä heijastuvien aaltojen tunnusmerkki on hajaspektri, eli kaiku ‘leviää’ enemmän tai vähemmän. Joskus kohinana, joskus kuvien kaltaisina haarautuvina kiharoina tai ‘dopplerkoukkuina’.

Nämä sähköskatterit on tallennettu Cherepovetsin TV:n kantoaaltotaajuudella n. 49739,583 kHz. Lähekkäisellä taajuudella on myös Arkangelin eli Vienan TV. Nauhoilla näkyy myös näitä kaukaisempien TV-lähetteiden kantoaaltojen tai sivunauhojen heijastuksia. Viistoviivat nauhoilla ovat lentsikkadopplereita Cherepovetsin TV-sivunauhakopioineen.

Otoksissa Spectrum Lab -softan taajuusasteikko yläreunassa on hertseinä, Cherepovetsin TV-kantoaallon kohta likimain nollana, muutaman hertsin ryömintätoleranssin puitteissa. Aikaleimat vasemmalla ovat Suomen aikaa. Radiospektrinauhan liikesuunta on ylhäältä alas. Vastaanotin on tavallinen halpa RTL-SDR-tikku kuuntelemassa 50 MHz 4-el ympärisäteilevää dipolimattoantennia (D4H) radiosoftan HDSDR ja virtuaaliäänikaapelin kautta.

Linkkejä taivasheijastuksiin ja yläsalamiin

Electric Discharge Explanation of Nasa ‘Aurora Arrow’ Photo - viewtopic.php?f=21&t=295&start=150#p2374
Already somewhat known spreading and dividing natural high altitude electric discharges are ‘sprite’ lightnings. Sprite photos by Thomas Ashcraft: heliotown.com/Catalog_Transi … vents.html

“Sprites, Elves and Intense Lightning Discharges”, Nato Science Series II: books.google.fi/books?id=XagIZh … es&f=false
Upper-atmospheric lightning: en.wikipedia.org/wiki/Upper-atm … _lightning
The Manastash Ridge radar: A passive bistatic radar for upper atmospheric radio science - onlinelibrary.wiley.com/doi/10.1 … S02454/pdf

EDS - Yläsalamat aiheuttavat radioheijastuksia: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Sähkönpurkausheijastus EDS - Electric Discharge Scatter: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Yläsalamapurkauksen synnyttämä ukkos-Es-keli: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

‘Doppler hooks’ - ‘Dopplerkoukkuja’ ‏Moskovan, Arkangelin ja Pietarin TV-jaksoilla:
Osa 1: viewtopic.php?f=21&t=295&start=100#p1893
Osa 2: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.
Osa 3: viewtopic.php?f=21&t=295&start=110#p1901
Osa 4: viewtopic.php?f=21&t=295&start=110#p1903
Osa 5: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

Online bistatic radar demo listening to R1 TV channel carriers at maanpuolustus.net/muut/tutka/kuvat/

Briefly in English: High sky radio scatters sometimes plot curious patterns on these R2 TV channel spectrum strips. Here are a few examples of these natural dividing spread spectrum scatters.

[OH7HJ]

Kirkkaana tulipallona maiseman valaiseva tähdenlento havaittiin Lapissa illalla 16.11.2017. Ursan asiantuntijan mukaan tähdenlennon arvioidaan pudottaneen kymmeniä kiloja, jollei jopa satakunta kiloa meteoriittikiviä Inarinjärven etelä- tai kaakkoispuolelle. Tässä 50 MHz bandin monipaikkatutkan tallenteessa näkyy ehdokas tulipallon tutkajäljeksi ympyröitynä, lähinnä sopivan tapahtuma-ajan perusteella.

Jannelta sain tulipallon tarkan alkuajan 18:40:15.241, joka on peräisin Panu Lahtisen Ivalossa olevasta allsky-kamerasta. Kiitos! Tulipallon tarkka syttymisaika näyttäisi sattuvan tutkanauhan lukematarkkuuden puitteissa yhteen tämän tutkatallenteen kanssa. Spectrum Labin hitaalta nauhalta pystyy ajan arvioimaan noin 10 sekunnin tarkkuudella.

Vaikka tutkakaiku näyttää hyvin samanaikaiselta, se voi silti olla jokin tästä tähdenlennosta riippumattomista lukuisista korkean taivaan sähkönpurkausheijastuksista (EDS, Electric Discharge Scatter), joita vastaanotin havaitsee jatkuvasti tällä Arkangelin TV:n taajuudella muutaman minuutin välein. Nauha on tallennettu on pohjoiskoilliseen katsovalta 6-elementtiseltä PA50-6-6 -jagiantennilta HDSDR- ja Spectrum Lab -softilla Arkangelin TV:n kantoaallon taajuutta 49739,586 kHz kuuntelevalta RTL-vastaanottimelta. Nauhan aikaleimat ovat Suomen aikaa.

Liitteet ja linkit:

Video tulipallosta: m.facebook.com/story.php?story_ … cation=ufi

Uutisartikkeleita: mtv.fi/uutiset/kotimaa/arti … gs.JyxwLmQ

Silminnäkijäkomentteja: satakunnankansa.fi/kotimaa/ … 200542207/

Jannen kertoma alkuaika: facebook.com/groups/luonnon … 22R9%22%7D

Ursan Taivaanvahtiin ilmoitetut havaintoajat vaihtelevat n. 18.35 … 18.40 välillä: taivaanvahti.fi/observations … _id/desc/0

Monipaikkatutkan online demonäyttö: maanpuolustus.net/pages/tutka/

Liitekuva tutkanauhasta: LP HDSDR Y6E 030 Arkhangelsk TV © OH7HJ - 2017-11-16-1800 - Bolide in Lapland at 184015 FT - Unknown radar trace at abt 184010 FT.jpg

T: - Juha -

[OH7HJ]

Näihin HDSDR-softaradiolla havaittuihin tyypillisiin spektreihin 6m TV-bandin R1-kanavalta merkkasin ympyröiden ja viivoilla yhdistäen joitakin esimerkkejä samanaikaisista luonnollisista heijastuksista, jotka ovat yhtaikaisia eri TV-lähetinten jaksoilla. Samanaikaiset luonnolliset radioskatterit näkyvät useina erilaisina yhdistelminä eri TV-lähetinten taajuuksilla. Koska radioheijastukset ovat voimakkaimpia lähetinten suunnilla esiintyvistä korkean taivaan kohteista, näiden samanaikaisista yhdistelmistä voi arvioida korkean taivaan heijastusten aiheuttajien summittaista tapahtumissuuntaa TV-lähetinten suuntiin vertaamalla.

Esimerkkiskattereden alussa ei näy meteoriheijastusten tuntomerkkiä, meteorivanan nopean lineaarisen liikkeen head-echo-doppleria, joten ne lienevät tavanomaisia spontaanisti syttyneiden luonnollisten korkean taivaan sähkönpurkausten radioheijastuksia (Electric Discharge Scatter EDS). Tällaisia sähkönpurkausheijastuksia näkyy ala-VHF-bandeilla jokseenkin jatkuvasti, kun taas meteoridopplerit (MS) ovat varsin harvinaisia.

Pitkäaikainen seuraaja saattaisi havaita spontaanien luonnonskattereiden seasta satunnaisia nopeita meteoridopplereita, ja käyttää niiden voimakkuusvertailua meteorivanan tapahtumasuunnan arvioimiseen tunnettujen TV-lähetinten suuntien perusteella. Vielä tarkemmin heijastusten radiosuuntiminen onnistuu tietenkin interferometrialla, jos käytössä on koherentti tuplavastari ja -antenni.

Tunnistetut parhaiten näkyvät TV-lähettimet taajuuksineen, lokaattoreineen ja karttasuuntineen on merkitty spektrikuvan yläreunan asteikolle. Muita etäisiä TV-lähettimiä, joiden luonnollisia heijastuksia nauhoilla myös satunnaisesti näkyy, on toki paljon näitä merkittyjä enemmän. Taajuusasteikko yläspektrin ja vesiputouksen välissä on kilohertseinä (kHz). Aikaleimat vasemmassa reunassa ovat Suomen aikaa, ja päiväys sekä vastaanottosetuppi on merkitty kunkin otoksen tiedostonimeen.

Linkkejä

Oheiset esimerkkiotokset on kopitettu hamssivastarin välitaajuutta kuuntelevalla RTL-SDR-tikulla tällä itään katsovalla jagikaksikolla: viewtopic.php?f=21&t=599&start=30#p1853

Sekä luonnollisia radioheijastuksia, että lentsikkadopplereita voi käyttää myös kaksisuuntaiseen kusoiluun. Tässä yksi softa lentsikkaskatteriyhteyksien harrastajille: AirScout is a Software for Aircraft Scatter Prediction - airscout.eu/

Lentsikkaheijastusten käyttäminen tuntemattomien radiolähetinten suuntimiseen (Aircraft Scatter Direction Finding, ASDF) - Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

Radiosuuntiminen kahden tai useamman antennin ja koherentin vastaanottimen interferometrialla: Simple Interferometer for Radio Direction Finding (RDF) - itr-datanet.com/~pe1itr/sate … ometer.htm

[b]In English:

How to tell the approximate direction of a natural high sky radio scatter? Here is how I estimate the general direction of strong 6m TV band scatters with single aerial and receiver method of known TV transmitters used as radio scatter beacons. [/b]

It is known that the baseline forward scatter effect greatly increases scatter intensity when the scattering target is close to the Rx - Tx baseline. This applies both for natural and artificial radio scatter targets. When scattering target is farther away from Rx - Tx baseline the signal strength of scatter decreases.

With very powerful TV Tx’s as beacons, radio scatters are visible from far away from baseline high sky targets as off-baseline backscatters. With small power TV Tx’s as beacons, only targets close to Rx - Tx baseline create observable scatters because the baseline forward scatter effect boosts their signal intensity.

Direction Estimate of Radio Scatters by TV Tx’s

On the R1 (OIRT1) TV carrier freq of 49750 kHz there are many TV Tx’s a few kHz apart from each other. Looking at the attached R1 TV channel spectrum strips, one can see that some natural scatters appear simultaneously on some of the known TV Tx carrier freqs marked at the scale above the screenshots.

By the directions marked to the TV Tx’s on the scale, one can make a rough estimate about the general direction of each scatter by which Tx freqs they appear on simultaneously.

I have marked and joined with lines some examples of the simultaneous natural high sky electric scatters on the spectrums. There are lots of natural scatter occurring every few seconds on this R1 TV channel so it is rather easy to spot them with modest equipment.

High sky electric discharge scatters seem occur at about similar altitude as Es scatter and be related to them, so their visibility range is comparable to 50 MHz Es ranges. So, Central Europe is not away from R1 TV electroscatter observing range.

73, T: - Juha -

[OH7HJ]

With aerials in low interference station location a long time observer could spot meteor scatter head echo scatters triggering some of these electric discharge scatters. For example, Esko OH2AYP has managed to spot some nice narrow doppler meteor scatter (MS) dopplers preceding spread spectrum electric discharge scatters (EDS).

Attached are a few pics of Esko’s MS dopplers on two TV Tx freqs. The upper one is St. Petersburg TV and the lower one is Moscow TV, both on 6m band R1 TV channel. Freq scale is about the width of receiver SSB filter. Much wider doppler shift indicating very high velocity together with short duration of the doppler distinguishes meteor scatter dopplers from usual aircraft scatter (AS) dopplers.

The actual meteor trail scatter is visible as narrow doppler (head echo). In some of his pics, the meteor trail appears to trigger a typical irregular spread spectrum electric discharge scatter following the actual narrow meteor doppler. In another pics, there is no electric dischage scatter following the meteor doppler. So a meteor trail may usually initiate a natural electric discharge that shows as a spread spectrum scatter.

The electric discharge scatter is usually much stronger and longer lasting than the preceding meteor scatter trace that appears to trigger it. However, usually there is no evidence of any meteor trail doppler preceding the ED scatter. So it appears that meteor trail may initiate a natural atmospheric electricity discharge but not always. There are a lot more natural ED scatters than meteor dopplers so most high sky natural electric discharges seem to be initiated spontaneously.

Spotting MS from among ED scatters - 2: viewtopic.php?f=21&t=295&p=2497#p2497
Spotting MS from among ED scatters - 3: viewtopic.php?f=21&t=295&p=2498#p2498

73, - Juha

[OH7HJ]

A sequence of strong and wide EDS flare or burst natural high altitude scatter occurring on the R1 TV channel. The strength of this flare scatter was strongest on the NEE pointing yagi of my aerials. So I guess this scatter originated from somewhere in North direction. The scatter starts and strengthens quickly and fades gradually in a few minutes which is usual to wide strong flares like this. Momentary spectrum of the flare at top appears to be a symmetric one of an analog TV, with weak center carrier.

The TV Tx of this scatter is unknown and its center frequency of abt 49749.5 kHz is unlisted. Might be some of the Kola dirstrict local TV Tx’s. I added to one of the pics the ‘scale’ of known TV Tx’s. Such wide flares as this occur irregularly from every tens of minutes to every few hours. Sometimes their rate increases before high sky electric activity periods like before aurora borealis spread noise spectrum discharge scatters begin.

These are slow moving monitor strip pics so I can not tell if there were any MS doppler head echo triggering the burst. By shape it is a usual wide TV Tx scatter flare that appears be caused by ionizing high altitude electric discharge. Compared to the Segezha Nadvoitsy TV visible on the same spectrum with sharp side band lines, the wide natural scatter burst has its side band lines merged together. This is a distinctive spread spectrum effect of high sky electric discharge scatters (EDS).

Time stamps at left are UTC + 2 hours. Aerial is a 6-el yagi pointing abt direction 030. Receiver is a RTL dongle working with HDSDR software. The Segezha Nadvoitsy TX is constantly visible with sidebands strong in freezing subzero during night and fading when temperature is rising above 0 C in daytime. An earlier less intense wide EDS flare visible on the strip has occurred less than an hour earlier.

Strong 6m TV High Sky Scatter - Part 2: viewtopic.php?f=21&t=295&p=2421#p2421

• Juha -
  
  
  
  
  
  
  
  

[OH7HJ]

Soon after I had reported about the wide strong natural scatter there appeared an aurora scatter. The aurora was a short burst lasting for a couple hours only. After aurora had stepwise faded out, there appeared one more wide natural burst following it. After this there were no similar strong natural wide bursts for hours.

It might be possible that these wide strong scatters were once again related to high sky electrostatic discharge activity, like accumulating high voltage ionospheric charges that seem to be related to birth of aurora borealis (Northern lights), too?

Solar wind is known to constantly bring positive static high voltage charges to the upper ionosphere. Electrostatic explanation of Northern lights discharge suggests that aurora borealis is a high voltage discharge between polar rims of ionosphere opening (aurora belt) and charged solar wind environment. This model explains easily the curtain shapes of visible aurora discharges in the sky, as well as aurora discharge movements along with night time movement of polar opening of ionospheric layers.

Strong 6m TV High Sky Scatter - Part 1: Aircraft Scatter - Lentokoneheijastus ja sen doppleri.

• Juha -