26 May 1994
Norman McLeod
For a change, this week sees a littlequiz to find out who's been paying attention. Try these technical questions. The answers are all to be found in back issues from number 90 to date.
1 Roughly how many stereo programmes must be transmitted at a time with DAB?
(a) one
(b) three
(c) six
(d) twelve
2 What is the formula for deriving the left channel from a sum-and- difference signal?
(a) 2 fL
(b) (L+R) + (L-R)
(c) (L+R) - (L-R)
(d) 0.1 cost
3 Roughly how many stations could a reasonable FM radio potentially distinguish without interference across a truly full city FM dial?
(a) eight
(b) 20 - 30
(c) 40 - 50
(d) 100
4 What is the now quiet AM frequency which used to be occupied by the massive German transmitter at Langenberg?
(a) 1260 kHz
(b) 873 kHz
(c) 1440 kHz
(d) 1593 kHz
5 What is the maximum aerial height currently permitted to FM RSL's?
(a) 5m
(b) 10m
(c) 20m
(d) 40m
6 What is the frequency used by the recently-opened Virgin relay at Lydd in Kent?
(a) 1197 kHz
(b) 1215 kHz
(c) 1224 kHz
(d) 1260 kHz
7 FM broadcast audio needs treble boost, otherwise known as pre- emphasis, before transmission. The amount of boost that needs to be applied at 10 kHz is about:
(a) 3 dB
(b) 6 dB
(c) 10 dB
(d) 14 dB
8 How much power was permitted at the first-ever RSL broadcast in 1984?
(a) 50mW on AM
(b) 50mW on FM
(c) 1W on AM
(d) 1W on FM
9 What is the approximate audio bandwidth transmitted by AM stations in the UK?
(a) 3.5 kHz
(b) 6.5 kHz
(c) 10 kHz
(d) 15 kHz
10 What is the audio bandwidth transmitted by FM stations?
(a) 10 kHz
(b) 15 kHz
(c) 19 kHz
(d) 22.05 kHz
The first volunteer to fax ten correct answers to me on 0273 700 526 will be offered the chance to set ten questions of his (or her) own to see how smart the rest of us are. And, of course, untold fame in these hallowed columns.
The answers and explanations will appear next week. In the meantime, your news, views and questions are always welcome.
Any readers wishing to comment on what I have said are welcome to call me on 01 273 684 172 or send e-mail to normac@fastnet.co.uk
Copyright NJ McLeod 1995