Success with meteor detection by radio scatter from Graves on 143/049MHz at Lichfield Radio Observatory!

Fantastic news! We have successfully detected meteors again at LRO – and what meteors!! They were coming in thick and fast approx 1 every 1-2 minutes when Rhys and I left home today at midday. These are best detections we have ever achieved.

Credit for this must go to Bill Watson, our good amateur radio pal from Lichfield – without whom this achievement would not have happened.

If you have read previous reports, you will be aware that we have have been experiencing incredible difficulty detecting meteors at LRO for several months. Even before that, rates were a lot less than Peter Hill records with his setup. I could never work out why this should be. Then, last year, LRO stopped picking them up at all. I put this down to the old ICOM R7000 receiver giving up the ghost……

Having been on holiday for the last two weeks, this seemed to be an excellent opportunity to explore why we were experiencing these problems and to try and find solutions. The icing on the cake is that this weekend is the predicted peak of the annual Lyrid meteor shower. Wouldn’t it be wonderful if we could detect meteors again in time for this shower. The weather forecast was not good for visual observations but radio detection can still work with clouds! (Although note the forecast has now changed and predicts a clear night on Saturday so a great opportunity to observe this shower is now available).

The problem with working out where the difficulty was is that the Graves signal is not normally detectable – unless it bounces off a meteor. Therefore it is very difficult to be sure that the radio is correctly tuned – and of course if it isn’t then low meteor detection rates will be obtained regardless of other issues in the setup. To make matters worse, our investigations in the first week of our Easter holiday demonstrated that meteors can be detected all the way between 143.049MHz and 143.050MHz BUT that rates vary. Graves transmits on 143.050MHz but this does not mean that this is the best frequency to use – I must admit that I have not quite worked out why that should be but in the first week we demonstrated that it was very difficult for us to detect meteors at 143.050MHz and Bill confirmed this will his own radio equipment – which acted as gold standard for us throughout this exercise as he can detect meteors approx. one every 2 minutes even outside of meteor showers.
Therefore, there were several potential reasons why we might be experiencing difficulty detecting meteors:
(i) The radio was deaf
(ii) The radio was incorrectly tuned either because we were using the wrong frequency or because the tuning was off on the radio.
(iii) We were using the wrong band (needs upper side band).
(iv) The aerial was incorrectly tuned for 143.049MHz.
(v) The aerial was pointing in the wrong direction.
(vi) The aerial was horizontal when it needed to be vertical or vica versa.
(vii) The material used for the aerial mast (old steel poles from a trampoline) was interfering with the aerial.
(viii) There is a problem with the aerial feeder cable (e.g. water has got in to it).
(ix) The aerial is not mounted high enough.
(x) Our house is located in a radio dead-spot.
(xi) Software settings problems – we are using Spectrum Lab and we are finding it complex to get our heads around it.

Bill confirmed that the best frequency to use (using his own gear in Lichfield at his house) is 143.049MHz, upper side band. Detection rates are high here and even if this is not the best frequency it is very close to it with more than enough meteors detected for our purposes.

The next step was to use a radio that was proven to be sensitive enough to detect meteors and to confirm this. We opted to use our Yaesu FT-817 for the initial tests – a modern sensitive radio. We took this to Bill’s house and disconnected his radio and confirmed that the Yaesu is more sensitive than his own rig and easily detected the Kent beacon on 144.430MHz (www.gb3vhf.co.uk, the website of the 144.430 MHz and 432.430 MHz amateur radio beacons located at BT Fairseat on the North Downs in Kent) using his aerial in his garden.

I was also able to use my own laptop to record meteors at Bill’s house, so that I could demonstrate successful use of WSJT-10 and Spectrum Lab for this purpose (at least successful enough to be able to see meteors although I have problems with the programming script in Spectrum Lab software still).

Taking this Yaesu FT-817 back to LRO, we found that detection rates in the log cabin were poor using the Moxon homebrew on top of the cabin and we could not detect the Kent beacon. This should have been possible and suggested that either the aerial, feeder cable or position/location were at fault.

The next step was to take the 5/8 vertical (Bill has tuned this for 143.049MHz) and today we tried this in the garden at LRO using the computer in the log cabin and Bill’s feeder cable – success! The best meteor detection rate we have detected ever!

I also found a small program which works under Windows 8 (on computer in log cabin) called IrfanView which can be easily configured to record screenshots automatically – just by starting the program and then pressing “C” and putting in appropriate settings on the box that appears. This is much easier to use than Spectrum Lab’s scripting software and also allows screenshots of both WSJT-10 waterfall graph and Spectrum Lab to be simultaneously recorded together.

Our next step is to remove some of the poles on the 5/8 aerial to see how high it needs to be (wife and neighbour don’t like tall aerials), then to move it to the top of the log cabin in exchange for the Moxon there. If that works, we will then try out the feeder cable from the log cabin (currently using a new one from Bill) – as it is possible that water has got in to the feeder cable and is the cause of our problems). We then would like to try the FunCube Dongle Pro Plus as we do not wish to leave the Yaesu FT-817 permanently turned on – it is an expensive machine and we prefer to keep it in good condition, particularly as there is a risk of lightening damage to any radio connected to an aerial.

Andy & Rhys

Bill with his homebrew 5/8 aerial erected outside his house in Lichfield – this gives a sense of perspective on how high he mounted it:

Meteors being detected today at LRO using the 5/8 aerial:

IrfanView recording screenshots directing into a folder of our choice:

Settings on IrfanView for automatic screenshot recording every 30 seconds:

I think (but am not sure) this might be carrier from Graves which can appear sometimes for short while, depending on atmospheric conditions (Bill has confirmed this can happen):

WSJT-10 is useful to demonstrate that the input gain is 0dB – I set it to -1bD as it can vary by 2 dB and it is important not to let it go much above 0dB (better to be -1 to 0bD):

Possible Graves carrier signal:

Frequency on the Yaesu FT-817 which worked well for detecting meteors today at LRO:

Bill’s homebrew 5/8 aerial at LRO today – I have added a choke by winding the feeder cable into a loop:

The strange trace below is what happened when Bill changed the aerial outside his house!

The dial below shows the best aerial directional setting for Brams in Bill’s experience from Lichfield:

The dial below shows the best aerial direction for Graves:

Bill has also had success detecting meteors from Brams – this is the frequency he used:

Meteor detection at Bill’s house (shown on waterfall on WSJT):

The following is an alternative aerial Bill has made – a Slim Jim:

More meteors being detected at Bill’s house:

The frequency Bill uses for Graves (143.049MHz USB):

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