View Single Post
Old 27th Dec 2015, 3:09 am   #327
ORTF_&_Co
Retired Dormant Member
 
Join Date: Mar 2007
Location: Nantes, France
Posts: 35
Default Re: 405-Line VHF Aerials 2013 to the present day.

Quote:
Originally Posted by Synchrodyne View Post
Quote:
Originally Posted by SteveCG View Post
I was wondering whether the later 625 line L3 allocation was rooted in the mists of time with the 819 F3 allocation?
That I don’t know. It certainly seems to be an odd allocation, though. Perhaps ORTF & Co can help here. (...)
Hello, sorry I could not reply sooner.

In fact, 819 lines ch F3 was never used in France. Only one transmitter was initially planned in Tours with this channel, but it was never built and this channel was not even incorporated in the receivers' channels selectors.

I presume that the previous experience of regular long distance reception of 441lines band I transmissions, incited the RTF tp avoid the risks of severe interferences in using a channel overlaping both channels F2 and F4.

With 625 lines system L' on VHF in the Eighties, the problem was slightly different because most of former 819 lines band I channels had been replaced by new band III channels (in Troyes, Caen, Nantes and Limoges), except for transmitters received in neighbouring countries : Bastia (Eastern Corsica) on ch L2 (49.25-55.75 MHz) and Ajaccio (Western Corsica) on ch L4 (57.25-63.75 MHz), both received in Italy.

Both other band I transmitters formerly on ch F4-V, Besançon and Carcassonne, were retuned to new ch L3-V (54.00-50.50 MHz) instead of ch L4-V (57.25-63.75 MHz). I presume this was intended to reduce possible interferences with neighbouring Swiss transmitter at La Dôle, and Spanish one in Barcelona, both using ch E4-H (62.25-67.75 MHz), furthermore French
transmissions were mostly encrypted.

Please note that for a better comprehension above, I mentioned French L' frequencies in the same way as for 'E' channels, that are infradyne (audio = video freq.+ 5.5 MHz) while French band I 'L' channels were supradyne (audio = video freq. - 6 MHz).
Attached Thumbnails
Click image for larger version

Name:	French_band_I_819_to_625 _channels_switch-over_1984.jpg
Views:	286
Size:	132.5 KB
ID:	117470  
ORTF_&_Co is offline   Reply With Quote