TRACING CHRISTCHURCH TV INTERFERENCE

Press, Volume C, Issue 29520, 23 May 1961, Page 14

TRACING CHRISTCHURCH TV INTERFERENCE

Equipment for tracing interference with television reception in Christchurch would probably be installed in a Post Office vehicle within the next fortnight, the senior radio inspector (Mr J. B. Dolan > said yesterday. Mr Dolan spent last W’eek in Auckland with radio inspectors there, noting what interference was encountered and how they dealt with it. Television has been operating in Auckland for about 18 ; months. ; “In the main, the troubles in Auckland are caused by ! high-tension power-lines.” said Mr Dolan. A great deal ! of interference resulted from the fraying of insulation on 6600 volt lines, but there were very few of these in Christ-

church. (Inquiries at the Municipal Electricity Department revealed that the last 6600-volt network in the city area, at Belfast, was due to be dismantled within two months.) The 11,000-volt high-tension lines, almost general in Christchurch, were bare, so no insulation trouble was possible, but interference could arise from the disctype strain insulator used for heavy wiring at line terminals and bends. However, there were methods of dealing with this, said Mr, Dolan

Thermostats of certain domestic equipment, such as electric blankets and butterconditioners in refrigerators, could also cause interference “Butter conditioners can very seriously affect television, causing large black bands across the screen and rendering viewing impossible.” said Mr Dolan. Interference Distinction

Unfiltered sewing-machine and vacuum-cleaner motors could also cause trouble. The Auckland inspectors could tell the difference between the interference caused by the various types of appliance. however, and Mr Dolan expected that, with a little experience, his own staff would be able to do the same. “The limits of intensity within which interfering equipment must be . suppressed have been laid down in the Radio (Television) Interference Notice. 1961.” Mr Dolan said.

“We hope that, with the cooperation of manufacturers, retailers, and users of domestic equipment, we shall be able to keep the noise level within these limits. All complaints will be investigated. Our aim is to assist the viewer to enjoy his programmes to the full.” A reasonably efficient, wellsited aerial was very desirable. even in central areas, and was absolutely essential in more distant places, added Mr Dolan.