UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Tuners in Philips G6-G11 CTV chassis

Pieter H · 31st May 2018, 11:30 am

Hi Synchrodyne,

an interesting discussion, the UK VIF choice for 39,5MHz. Like you, I also haven't found any convincing technical reason, which makes me conclude it must have been political!

As my story on the first 10 year of TV development in Europe clearly shows, choices on line rates and the associated IF standardization were pure politics! This was the time that countries (i.e. the technical community, the big business management and politicians) still thought that for competitiveness and local employment it was still best to have national standards. With the well-known result of initially some 6-7 different TV standards in Europe (depending how you count, and including the Belgian versions). In the meantime we learned the had way that in consumer electronics that's not how it works!

With the introduction of 625 lines UHF and colour most countries complied (with the exception of France and its 819 lines) but not with respect to Vision-Sound frequency distance and the IF. So my guess is that UK policy makers were forced to accept the 625 lines (or maybe even were happy, who knows, the 405 lines had proven to be a pretty mediocre standard), but in order to keep some level of uniqueness imposed a larger bandwidth and 5,999MHz vision-sound distance ("the UK goes for higher picture quality" or similar). Essentially the same policy as the French, without going to the 11MHz 819 lines extreme.

Given this different VIF-SIF distance of 0,5MHz compared to the CCIR, one argument for a higher VIF could have been to move it 0,5MHz upwards in order to keep the SIF identical at 33,4. As we've seen in my tuner history, until the emergence of IC's, in general set makers tried to keep the SIF fixed as much as possible and then vary the VIF depending upon the standard. But this doesn't seem to be the reason, because it is moved upwards by 0,6MHz, making the SIF 100kHz higher at 33,5 vs. the 33,4 of CCIR. Strange and indeed unexplainable so far. So it looks the arguments for 39,5-33,5 seems to have been more political than economical.

But I'm sure that, given the desire to go to 39,5MHz, there was some technical analysis done that showed a slightly better interference performance under certain conditions, thus justifying the choice for 39,5-33,5MHz. And so it happened.

I admit, mostly speculation, but the best I can make of it. Looking forward to your thoughts.

Kind regards, Pieter

31st May 2018, 11:30 am	#8
Pieter H Tetrode Join Date: Sep 2017 Location: Waalre, Netherlands Posts: 67	Re: Tuners in Philips G6-G11 CTV chassis Hi Synchrodyne, an interesting discussion, the UK VIF choice for 39,5MHz. Like you, I also haven't found any convincing technical reason, which makes me conclude it must have been political! As my story on the first 10 year of TV development in Europe clearly shows, choices on line rates and the associated IF standardization were pure politics! This was the time that countries (i.e. the technical community, the big business management and politicians) still thought that for competitiveness and local employment it was still best to have national standards. With the well-known result of initially some 6-7 different TV standards in Europe (depending how you count, and including the Belgian versions). In the meantime we learned the had way that in consumer electronics that's not how it works! With the introduction of 625 lines UHF and colour most countries complied (with the exception of France and its 819 lines) but not with respect to Vision-Sound frequency distance and the IF. So my guess is that UK policy makers were forced to accept the 625 lines (or maybe even were happy, who knows, the 405 lines had proven to be a pretty mediocre standard), but in order to keep some level of uniqueness imposed a larger bandwidth and 5,999MHz vision-sound distance ("the UK goes for higher picture quality" or similar). Essentially the same policy as the French, without going to the 11MHz 819 lines extreme. Given this different VIF-SIF distance of 0,5MHz compared to the CCIR, one argument for a higher VIF could have been to move it 0,5MHz upwards in order to keep the SIF identical at 33,4. As we've seen in my tuner history, until the emergence of IC's, in general set makers tried to keep the SIF fixed as much as possible and then vary the VIF depending upon the standard. But this doesn't seem to be the reason, because it is moved upwards by 0,6MHz, making the SIF 100kHz higher at 33,5 vs. the 33,4 of CCIR. Strange and indeed unexplainable so far. So it looks the arguments for 39,5-33,5 seems to have been more political than economical. But I'm sure that, given the desire to go to 39,5MHz, there was some technical analysis done that showed a slightly better interference performance under certain conditions, thus justifying the choice for 39,5-33,5MHz. And so it happened. I admit, mostly speculation, but the best I can make of it. Looking forward to your thoughts. Kind regards, Pieter