03-12-2020, 03:33 PM
(This post was last modified: 03-12-2020, 03:35 PM by Geordie McBoyne.)
The second generation post-war HMV and Marconi TV sets had TRF circuits, HMV models 1805 and 1806 and Marconi VRC52. The design of the receivers differed from the previous range of models which were superhets with low IFs, most common models were the HMV 1804 and Marconi VT50.
The HMV 1806 was an expensive set and was considered well worth conversion to band 3 reception. In order to install the EMI fourteen position tuner the factory solution was to convert the TRF receiver to superhet operation. The sound retuning was easy from 41.5Mc/s to 38Mc/s. To retune the vision TRF circuits from 45Mc/s to 34.5Mc/s small value capacitors were connected across the coils. Doing this did peak up the response somewhat.
Birmingham models were introduced in 1949 had superhet circuits with IFs of 34.5Mc/s vision and 38Mc/s sound, almost BREMA values.
Geordie McBoyne.
The HMV 1806 was an expensive set and was considered well worth conversion to band 3 reception. In order to install the EMI fourteen position tuner the factory solution was to convert the TRF receiver to superhet operation. The sound retuning was easy from 41.5Mc/s to 38Mc/s. To retune the vision TRF circuits from 45Mc/s to 34.5Mc/s small value capacitors were connected across the coils. Doing this did peak up the response somewhat.
Birmingham models were introduced in 1949 had superhet circuits with IFs of 34.5Mc/s vision and 38Mc/s sound, almost BREMA values.
Geordie McBoyne.
