Version 4 - 2nd February 2002

QUADRANTIDS 2002 ADDED

I have been monitoring radio wave propagation, aurorae and meteors using radio techniques since early Year 2000. During this time I have improved my knowledge and techniques by experimentation, trial and error and discussions with other interested observers.

The main improvements have been in converting the received traces to greyscale images, and in the use of two receivers on different frequencies. The greyscale images show detail much better than the original colour images. (They are also much smaller files for storage and transmission). The use of two receivers enables monitoring of meteor trail reflections from transmitters on two different frequencies in two different locations. I thought that it may be possible to estimate the direction of the meteors using two traces. The results so far are a bit ambiguous and inconclusive. I think that if I could triangulate using a third receiver I might get a better estimate of direction and may be able to estimate meteor speeds.

The main equipment I use is a Kenwood Transceiver TS-440s. The antenna is a 90ft doublet at average height of about 38ft running East-West. The antenna is fed into the receiver through an MFJ antenna tuner. A good stable receiver with fine tuning is absolutely necessary because the doppler signals being received vary by only a few Hz in several MHz. I have found however that it is not necessary to have such a large antenna as I use. Satisfactory signals have been recorded on each receiver with antennas consisting of only 10metres of wire at a height of 3 meters above the ground and without an antenna tuner.

The second receiver is a Racal TR1772.

My computer is a 130 MHz Pentium and the software I use is R_meteor from COAA in Portugal. Full details of the theory and principles of recording radio meteors are available on the COAA website at www.ip.pt/coaa . There are other freely available FFT software packages but in my opinion none gives traces as clear as R_meteor.

The shortwave signals I monitor are from the BBC World Service transmitters at Skelton, Wooferton and Rampisham - all in the UK. I can receive groundwave signals from each of these stations. These transmitters use a variety of frequencies and antennas at different times of the day and night. At my location I have found that the frequencies of 12.095 MHz, 15.565 MHz and 17.640 MHz give the best continuous coverage during the daytime. Unfortunately, I have not found any station that gives good coverage during the early morning hours just after midnight. Several are available for short periods during the night but to keep up with them requires adjusting the receiver frequencies throughout the night - not my idea of fun.

The following traces are samples of my records showing various meteor, aurora, propagation and other phenomena. If you would like to see records for other dates/times please ask (e-mail contact info below)

Many of the traces show 'S' shaped curves. I live in an area with two international airports within 25km and with major airlanes overhead. The reflections from the aircraft complicate the recordings but are no great problem when you get used to them. At least I know that the system is working when I see the trails. It is interesting to compare trails reflected from two transmitters at different frequencies to try to determine the flight path.

Perseids 2000

Perseid meteors with long duration tails. Reflections affected by auroral activity. Also transmitter/antenna switching at 07:12. Recorded 12 AUG 2000 on 17.640MHz at 50 Hz bandwidth

Orionids 2000

On the night of 27th to 28th Oct 2000 the BBC transmitted a 300kW continuous carrier at 17.640 MHz beaming 140 degrees. This trace shows the high level of Orionid meteors at this time - mostly very fast and with only a few giving ionisation reflections reater than a few seconds. Recording bandwidth was 50 Hz

Leonids 2000

The BBC again put out a constant 17.640 MHz carrier for four hours on the night of 17th to 18th November 2000 when this fireball was recorded using 50 HZ bandwidth. Note the reflection from the ionised tail which lasts for several minutes. The longest trail recorded during this shower was greater than 10 minutes.

The above traces were recorded later that night. Activity was high for several hours until dawn.

Geminids 2000

Recorded on 15 December 2000 at 11.895 MHz and 50 Hz bandwidth. The period 22:00 to 22:50 UTC appeared to be the peak of the radio meteor shower. Notice that the doppler shift is less at 11.895 MHz than it is for those recordings made at 17.940MHz. This is because the amount of doppler shift is directly proportinal to the frquency of the transmitter.

Perseids 2001

Recently I have tried combining the signals from two transmitters on different frequencies on to a single trace as above during the Perseids on 11 August 2001. The top trace shows reflections from a transmitter on 17.640 MHz ( North of the receiving location) and the bottom one is at 12.095 MHz (South East of the receiving location). As can be seen there appears to be little correlation between the results from the two recordings. The two signals are seeing different meteors and aircraft. The record below does however show some correlation of an ionospheric disturbance.

The record was made on 10 August 2001 during the Perseids. Top trace is 15.565 MHz (South of the receiving location) and bottom is 12.095 MHz (South East of the receiving location).

Leonids 2001

Click here for Leonid 2001 records

Quadrantids 2002

Click here for Quadrantids 2002 records

Break up of signal due to ionospheric disturbance, possibly aurora. Recorded 18 October 2000 on 12.095 MHz with 50 Hz bandwidth

During the Leonid shower on 18 November 2000 these effects of an aurora were recorded at 17.640 MHz and 50 Hz bandwidth. A few meteor reflections and the start of an aircraft trail are also seen.

IF ANYONE CAN EXPLAIN SOME OF THESE PHENOMENA PLEASE CONTACT ME AT g3nfb@warc.org.uk

Recorded 12 AUG 2000 on 17.640 MHz with 50Hz bandwidth. Evidence of a possible second carrier approx 1Hz from the ground wave together with what may be beat frequencies. It has been suggested that the bars may be due to second order distortion in a transmitter where the transmitter carrier level tracks the modulation level for power economy reasons

Recorded on 21 October 2000 at 12.095 MHz with 50Hz bandwidth. The Trace shows two sets of horizontal bars - one set about 2Hz wide and the other about 4Hz. More transmitter economy measures?

This trace shows a mirroring effect of the aircraft traces. This was seen often in the earlier records I made. I was advised that this resulted from the AGC action of my receiver and that the AGC should be turned off or the RF gain turned down so that no AGC action occured.

The set of 2 Hz bars may in fact be two sets of mirrored 4 Hz bars.

Since turning down the receiver RF gain I have recorded no more mirror imaging.

It should in theory be possible to see reflections from satellites but I have not seen any traces yet that I could be certain about. However, the long curved line going from bottom left to top right in the Orionid record above may be a satellite.

Transmitter site switched either power or antenna direction at 16:59. In this case reflections continued to be received after the action. Other cases occur when no further reflections are received.

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