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WIRELESS. >
VOLUME CONTROL.
" 'Most of t'ie receivers which are sold
I ;.r constructed in the home are designed
to Pve loud-speaker reception, and it is
'necessary that some form of volume con-
ttol be used in order that' the music or
speech can be toned down to suit any
sail room. , , . .
A method of volume control which is
vapidly being adopted is the use of a
toping resistance connected across the
jeconditry of one of the audio-frequency
transformers. In the case of a two-Btago
amplifier it is usually connected across
the secondary of the first transformer.
The damping resistance is variable, and
is such that when at maximum resistance
its value is 1 megohm, and if this ' is
variable down to zero or a very low value
the volume call be varied from maximum
to a mere whisper.
The use of such control is very con
venient in any receiver. It will be found.
that the damping- resistance '.will improve
the quality of the reproduction, os it limits
iuy tendency towards overload by harsh
nolC6, &c. Alany people attempt the
tontrol of volume by either detuning or
by turning down the filaments of one or
more of the valves; this is .not a good
imciiec, us operating the filament control
of the valve may cause distortion. The
filaments, once set in the .correct posi
tion, should bo left untouched.
Relay Stations for Victoria.
While nothing definite has been made
inotvn by the Broadcasting Co. of Aus
tralia (3L0) in regard to the establish-
ment of relay stations in' Victoria, it is
ilmost certain that in the near future the
louatry listeners will have the benefit of
relay stations, which will be situated in
land. A brief outline of the system used
by the British Broadcasting Co. in Eng
land will perhaps help those interested in
the subject to understand the working of
the relay system,
Tn England all broadcasting is run by
i company known as the B.B.C. There
are 51 stations in the B.B.C. system. Of
these, nine are main stations of medium
power, eleven are. low-powered relay sta
tions, and one is a highrpowered station
capable of reaching out all over the
islands. The policy of the B.B.C. Beems
to have been to so cover England with
broadcast signals that there is not one
spot where a programme cannot be picked
up by a crystal receiver.
Listeners in Victoria will remember
ibat England and Victoria are, roughly,
about the same areas. In .Victoria the
area is served by two stations of -the -A,
class, which are perched on .the edge of
the State. To cover the same aVea the
B.B.C. employs 21 broadcast stations. All
these stations can be connected together
by means of land lines, and simultaneous
broadcasting by all the stations is a regu
lar feature of the organisation. While
/this arrangement is beneficial for the
broadcasting of intelligence of a national
character, it nevertheless restricts the
listener to only one programme when such
a feature is in progress. It is hoped that
in Victoria 3LO will arrange for a variety
of programme by running local pro-
srsmmcs from the relay stations on oc
casions.
The largest station- hi England, which
is situated at Daventry, is located in the
centre of the organisation,, and it is: said
that the signals from this station can be
picked up on a crystal receiver in any
part 'of the country. This station employs
a transmitter which works with a power of
23 kilowatts, , which can be inereused lo 30
kilowatts if desired. The antenna is sup
ported between two masts each 500 feet
high. The wave length used is 100C
meters.
In. the light of experience there does
not appear to be any great advantage to
be gained from such an enormous broad
cast station. As. far, as Australia is con-.
:«nied.Trc' will be very" much better served
Hf, .number of smaller-powered stations
"scattered. throughout, the. States'.
At_ present the crystal receiver'' limits
are very small— within 20-30 miles of '3LC
and 3AR. In some of the larger inland
towns, there must bo thousands of. people
- who ivould instal a crystal receiver, where
as the cost of a three or four valve re
ceiver, whicli is required to receive from
Melbourne at present, is beyond thein.
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