08-08-2017, 10:04 AM
Full wave demodulators were used in many pre-war superhet TV receivers that employed a very low vision IF. Such receivers were the Murphy A42V and the GEC BT8161. In these sets the VIF was 4Mhz or thereabouts. Rediffusion employed a full wave demodulator in cable TV receivers, again the reason for the FW demodulator was because the lowest cable system frequency was only 4.95Mhz for 405 line BBC TV.
In 1938 Murphy introduced the 9" CRT A58V TV receiver, this set employed the same low VIF as the A42V but employed a half wave vision demodulator. Murphy cited the case for the simple demodulator was because the CRT was so small any 3.5Mz vision-sound beat pattern would be hardly noticeable at normal viewing distances.
Geordie McBoyne.
In 1938 Murphy introduced the 9" CRT A58V TV receiver, this set employed the same low VIF as the A42V but employed a half wave vision demodulator. Murphy cited the case for the simple demodulator was because the CRT was so small any 3.5Mz vision-sound beat pattern would be hardly noticeable at normal viewing distances.
Geordie McBoyne.
