Meteor Pings on 30m Using a QRSS Signal from a Local Station

UPDATE on 25Jan2019   I just scanned 24 hours of ten minute grabs a found only 5 or 6 possible weak pings.  Plenty of airplane trails but no impressive pings.  At this time there we are in between meteor showers and that's how it should be.  I believe this further substantiates the technique described herein.

I am fortunate in having a local QRSS station about 10 miles north of my QTH.  The signal arrives via ground wave and is of moderate strength so as not to overload the waterfall display of my 30m grabber.  Patches of fuzz have were noted during the 2018 Leonids above and below the groundwave trace which I concluded are caused by backscatter from meteors.  The following observations were conducted during the December Geminids.

Meteors occur when the meteoroid (space rock) reaches the E layer where the atmospheric density is high enough to heat the rock to incandescence and produce a trail of ions and free electrons.  The recombination rate of electrons is relatively slow and allows reflection of radio waves up to a number of minutes.  The trail lasts longer as frequency goes lower.  Meanwhile the ion trail drifts with the resident winds resulting in a Doppler shift in the incident radio wave which is large enough to be seen relative to the trace of the incident signal on a waterfall display.  Figure 1 is from my 30m grabber showing the fskcw signal from KD5SSF along with a typical meteor ping and airplane reflection.

Figure 1.  Meteor Ping on KD5SSF's FSKCW QRSS Signal

During the recent Geminids I was doing an experiment with WD4AH to look for meteor pings from his signal with no thought of using the signal of KD5SSF. While looking for pings from WD4AH I could not help but notice the frequent pings on SSF whose frequency was about 10 Hz away.  I archive my 10 minute grabs and had available six days of data before, during and after the Geninids and decided to count all the pings and see if data could be presented in some way to yield information about the shower.  And lo and behold it did, as I shall now describe.

Pings vary from just a brief smudge to a lengthy, bright feature.  I considered only whether or not a ping was noted on a given 10 minute grab and made no effort to distinguish multiple pings on that frame.  I also tried to account for the stronger pings by assigning values of 1 for the regular ones and 2 and 3 for the progressively stronger ones.

Interference can produce "false pings" due to airplane reflections, other QRSS signals and pulses that come from Lord knows where,  The false pings can be identified relatively easily by their characteristic shapes.  For example, airplane reflections have a constantly curving shape which is sharp and distinct. Likewise the keying characteristics of other QRSS stations will be different from that of KD5SSF.  Most noise pulses will usually be spread across the frequency axis.  A possible ping was rejected when I could not be certain.  If anything I think I under estimated the number of pings.  The fsk keying of SSF's signal was a help also since the ping would follow the up and down shifts  which the other QRM would not.

A total of 122 ping events was counted and entered into a Google spreadsheet and grouped in several ways.  Figure 2 is a count of pings for each day.  Figure 3 is a histogram plot of pings versus time of day by dividing the 24 hours of time into 11 bins and totaling the number of pings in each bin for the six day period.  The scale is a little strange since it is divided 24 by 11 but you can see clearly that the maximum number of pings over the six day period was greatest between roughly 0900z to 1130z which is about 2 or 3 hours before Sunrise local time.

Figure 2.  Pings for Each Day

Figure 3.  Pings vs Time of Day

Figure 4.  Pings per Four Hour Period

I then counted the pings in successive four hour periods from the beginning to the end of the recording period, Figure 4.  I think the large spike on the 15th was augmented by the way I assigned higher numbers to stronger events.  That suggests there was a number of big rocks during that time.

Summary

It was a bit tedious examining all the 10 minute grabs in detail.  It took about 2 hours and 2 Salty Dogs.  I put on my reading glasses and got close to the screen to better judge each frame for pings and distinguish them from QRM.  I counted the pings using Notepad with four columns for UTC time and a "1" for a ping, a note on small, medium or large and in the fourth column the final adjusted ping number.  The final table was saved then entered into Google Sheets for analysis.  The analysis was easy and fun with Google Sheets doing all the work. 

The main thing you need for a similar project is a nearby QRSS station at just the right distance or antenna orientation to give a clean, stable, not too strong signal so you can see the fuzzy pings

QRSS Meteor Scatter on 30 and 17m During the November Leonids Meteor Shower

Introduction

During previous meteor showers W4HBK, WD4AH and WD4ELG have observed meteor pings on 17 and 20m using QRSS techniques at sub-Watt power levels.  As discussed in a previous blogs we needed to adjust our approach for our next shower and see if we could do better on 17m and  go one band lower to 30m.

During the November 2018 Leonids Meteor Shower we used the 17 and 30m QRSS bands to look for meteor pings .  We have previously had moderately good success on 17 and 20m and our goal this test was to improve our success rate using "lessons learned" and to go one band lower and see if pings were observable on 30m.

Experimental setup

W4HBK:  tx on 30m using a U3S running 700 mW to an inverted V antenna and rx on 17m
WD4AH:  tx on 17m using a U3S running 500 mW to a random wire antenna and rx on 30m
WD4ELG rx on 17 and 30m

HBK is 276 miles/444 km from AH and 580 miles/935 km from ELG
ELG is 466 miles/750 km from AH

Based on previous tests we found that a near continuous signal with minimum frequency shift made it easiest to identify pings and can be adjusted for as little dead air time as possible.  Hence we used fskcw with a 1 Hz shift with the dot-second time adjusted to transmit for 9 minutes and allow 1 minute to cool the finals at the end of a 10 minute frame.  The duration of the test was from just after midnight (0700z) to just past Sunrise (1300z).

I also used a program called SeqDownload to record the grabber screens at AH and ELG directly to my computer in real time so that it would not be necessary to download from their archives after the test, via the Internet.  This greatly simplifies and reduces the time to process the data and avoids confusion.

Results

     17m

We were able to record many pings on 17m between W4HBK and WD4AH.  Figure 1a is a typical ping and Figure 1b is a stitch of all grabs to give an idea of the total number of observed pings.

Figure 1a  Typical  ping on 17m from WD4AH at W4HBK

Figure 1b  Stitch of all 17m grabbs of WD4AH by W4HBK

WD4AH also had 5 pings on the WD4ELG grabber, Figures 2a and 2b show two examples.

Figure 2a  Meteor Ping of WD4AH received by WD4ELG

Figure 2b  Second example WD4AH at WD4ELG

30m

Only a few weak pings were recorded of W4HBK at WD4ELG, Figures 3a and 3b.

Figure 3a  W4HBK received by WD4ELG on 30m

Figure 3b   W4HBK received by WD4ELG ON 30m

WD4AH recorded a number of pings from W4HBK.  Figures 4a and 4b are representative.  Figure 5 is a stitch of all grabs to give an idea of the total number of pings.  Note at right the band begins to open and HBK's signal becomes a combination of meteor scatter and weak propagation.

Figure 4a  W4HBK received by WD4AH on 30m

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Figure 4b  W4HBK received by WD4AH on 30m

   

Figure 5  Stitch of grabs by WD4AH of W4HBK on 30m

     Special Event

At 0916z all four grabbers recorded pings.  In addition, judging by the long duration of W4HBK at WD4ELG (Figure 3b) this may have been a fireball event.

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Conclusions

Meteor scatter is very easy on 17m QRSS over a distance of 276 miles while difficult over  a distances of 466 and 580 miles.

On 30m it is fairly easy on the shorter path and difficult on the longer one.  Additional problems on the lower bands are QRM from other signals and modes of propagation.  Examples of the latter are tropo ducting and unexpected Sporatic E.

Great care must be taken to rule out false pings from these problems.  I do this by looking for letters of the call or elements of the letters as well as the characteristic signature of meteor pings. A single dit or dah at the right time can verify the sending station.