03-04-2017, 09:00 AM
(This post was last modified: 03-04-2017, 09:03 AM by Murphyv310.)
Hi.
One other thing I have just remembered was a discussion I had with Henry Chmiel (British Relay area Engineer) around 1971-2. I remember asking him about the poor BBC2 pictures before we duplicated and his answer (rather long winded if I remember) was that it was down to the vision level on 625. The peak white was only 80% that of the VIT signal and black level was around 5% above what it should have been.
In the 60's British Relay used a UHF all valve receiver in the stations (MR754) and this initially was thought to have been the problem. The designers in Croft Street along with Murphy came up with a fully transistorised receiver with synchronous detection PLL & AFC the MR756 and the result was the same. Later on after the 405 line receivers were ditched after duplication all stations used the all valve receiver in the BBC2 position and the only issue's with them was a slight increase of noise and reduced top end response with the 2T pulse being about 7% down.
One other thing I have just remembered was a discussion I had with Henry Chmiel (British Relay area Engineer) around 1971-2. I remember asking him about the poor BBC2 pictures before we duplicated and his answer (rather long winded if I remember) was that it was down to the vision level on 625. The peak white was only 80% that of the VIT signal and black level was around 5% above what it should have been.
In the 60's British Relay used a UHF all valve receiver in the stations (MR754) and this initially was thought to have been the problem. The designers in Croft Street along with Murphy came up with a fully transistorised receiver with synchronous detection PLL & AFC the MR756 and the result was the same. Later on after the 405 line receivers were ditched after duplication all stations used the all valve receiver in the BBC2 position and the only issue's with them was a slight increase of noise and reduced top end response with the 2T pulse being about 7% down.
