Issue 30 Six News, June 1991
BY G3CCH & SM7AED
Some years ago we had a number of regular weekly tests on the 144 MHz band using Meteor Scatter with good results, Soon after the 50 MHz band was available to Swedish amateurs, arrangements were made for regular weekly one hour tests. Times chosen correspond to the daily peak of random meteors around 0600 GMT.
Over a period of 18 months all but 3 of the 50 MHz tests have resulted in complete 2-way QSOs. Twice some other form of propagation masked most meteor bursts, probably sporadic E, and the third failure was due to a lack of meteor reflections, not helped by local interference. Although such QSOs are basically just an exchange of call-signs, report, and acknowledgments we find it possible to send additional information. Alternate 5 minute periods of transmitting and receiving are used, but also by utilizing semi-break-in, QSOs can be completed often quite quickly. Sked periods longer than 30 minutes are very rare.
We consider that an efficient and non-stressing maximum keying Speed is where CW can still be read by ear, that is in our case around 30 wpm. Any slower is just time wasting during non shower periods -bursts only last at most several seconds. Using higher speeds requires a variable Speed tape recorder, and re-playing of tape recordings is time consuming but may be an advantage when the meteor count is low.
At G3CCH a memory keyer with fixed length memory has been in use for several years, but recently the CMOS keyer as described in QST Nov 1990 with 4 pre-programmable memories has given considerable more versatility.
A keyboard keyer, described by VE3OBE has also been constructed, sending at 30 wpm is quite easy. At SM7AED a memory keyer, with 8 pre-programmable dynamic RAMs and with possibilities to put in a pause of 5 to about 50 bits after each sequence of callsigns plus report, has given good service for at least 15 years. The aerials used are 5-element Tonna, at G3CCH 14 mtrs AGL and at SM7AED 8 mtrs. Large buildings and houses obscure the takeoff at both stations, results would no doubt be far better with a clear view of the horizon aiming aerials directly at one another. This has been confirmed at SM7AED when operating from his second QTH about 200m ASL with clear horizon towards the UK. Trying other beam headings reduced the signal strength noticeably, plus the weak background signal, that is often present, disappeared. This weak background signal is frequently noted, mostly during the summer months, usually only just at noise level. It is presumably not due to tropospheric conditions as it can be present when tropo is most unlikely, but from meteor reflections that are far from optimum angles.
The distance between us is 910 km, 50 for a meteor trail of average height (85 km) a take-off angle of 8 degrees is required. Aerials at 12 mtrs AGL would satisfy these conditions, but with the obstructions already mentioned best results are obtained with aerials as high as possible. The number of bursts and pings in any one 5 minute duration can be as low as 10 up to a maximum where it is difficult to count owing to many overlapping bursts, About 2% of all bursts have noticeable Doppler shift but using normal CW bandwidths no information is lost. 50 MHz seems to be the ideal band for meteor scatter. Results can be achieved without waiting for sporadic-E or aurora. SSB may be used but it is very tiring during non-shower conditions. During major showers it is often possible to make one (or more) complete QSOs in a single burst. So if you hear a station calling CQ via a meteor reflection, answer by giving both callsigns and a report. Trying to add locator, name, and so on, is to be avoided if you wish to the QSO.
Give meteor scatter a try! It is fascinating!
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