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<DIV>Chris:</DIV>
<DIV> </DIV>
<DIV>I wonder if you may be correct that there could have been a change in
later years. Manuals for the VR-1200, 1200B, 1200AFC, VR-2000B and TR-70
all agree on 5.00/5.54/6.8 mhz for 625 low band.</DIV>
<DIV> </DIV>
<DIV>But the AVR-2 and TR-70C agree on 4.95/5.54/6.8 mhz</DIV>
<DIV> </DIV>
<DIV>So the sync tip frequency is slightly different between early models and
late models. Perhaps there was a change in the spec for the sync amplitude
that resulted in the change in deviation? I was able to find this
illustration that confirms the 70/30 ratio <A
href="http://www.pembers.freeserve.co.uk/World-TV-Standards/HBI.pdf">http://www.pembers.freeserve.co.uk/World-TV-Standards/HBI.pdf</A> but
I did not locate any documentation on a change in the early to mid 70's.</DIV>
<DIV> </DIV>
<DIV>Don Norwood<BR>Digitrak Communications, Inc.<BR><A
href="http://www.digitrakcom.com">www.digitrakcom.com</A></DIV></DIV>
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<DIV><B>From:</B> <A
href="mailto:Chill315@aol.com">Chill315@aol.com</A><BR><B>Date:</B> November
21, 2013 at 9:36:32 PM EST<BR><B>To:</B> <A
href="mailto:quadlist@quadvideotapegroup.com">quadlist@quadvideotapegroup.com</A><BR><B>Subject:</B>
<B>FM standards in 525 and 625</B><BR><BR></DIV></BLOCKQUOTE>
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<DIV>I just hung up the phone with Ted Langfell, our illustrious
secretary. We are having a discussion about the standards used for
recording signals on a quad. This came about because a manual for an
AVR-1 had a frequency for blanking different than a VR-1200 manual. He
believes it was 5.3 vs 5.6 MHz. He is driving so can not check the
email. </DIV>
<DIV> </DIV>
<DIV>So here is the research that I did while on the phone. I
continued after we hung up. Both RCA and Ampex tell us that they
conform to the SMPTE and EBU standards. The referenced standards are
SMPTE RP-6 for Modulation Levels. The RP-10 standard describes the
Signal Specifications. The 625 system conforms to CCIR Document DOC.
X/27E-3 as set forth from the EBU.</DIV>
<DIV> </DIV>
<DIV>525 Low band mono is from 4.28 for sync tip, 5.0 for Blanking,
and 6.8 for peak white. Pre / post emphasis is 4 db at 4 MHz.</DIV>
<DIV> </DIV>
<DIV>525 Low Band Color is from 5.5 for Sync, 5.79 for Blanking, and 6.5 for
peak white. Pre / post emphasis is 9.54 db at 4 MHz.</DIV>
<DIV> </DIV>
<DIV>625 low band is sync tip at 5.0, 5.54 for blanking, and peak white
at 6.8 MHz. Unknown emphasis curve. </DIV>
<DIV> </DIV>
<DIV>I did a math solution and came up with 5.54 MHz for the blanking.
This was based upon a linear relationship based upon the .7 to .3
ratio of video and sync as published by Ampex. This is the
specification that is in question. </DIV>
<DIV> </DIV>
<DIV>But the top frequency is for PEAK WHITE. does that mean over 100
units of video? If not, how much? If 120 video plus
sync, then blanking is lower in frequency. An interesting math
problem. And a good discussion. Also the modulators clamp at
Blanking so in reality the deviation is kind of controlled by the video
level alone.</DIV>
<DIV> </DIV>
<DIV>525 High band is 7.06 for sync. 7.9 for blanking, and 10.0 for peak
white.</DIV>
<DIV> </DIV>
<DIV>625 High Band is 7.16 for sync. 7.8 for blanking, and 9.3 for peak
white.</DIV>
<DIV> </DIV>
<DIV>Super High Band is 9.2 for sync and 12.2 for peak white.</DIV>
<DIV> </DIV>
<DIV>All information is from VR-1200 and TR-4 manuals. I also referred
to Ennes's book on VTR theory.</DIV>
<DIV> </DIV>
<DIV>So what is the reason for the discrepancy? A misprint? The
sales literature does not list the frequencies. Or was there a change
by the EBU or SMPTE in the standard after the design of the AVR-1?</DIV>
<DIV> </DIV>
<DIV>As a side note, we know that there were different standards when both
AMPEX and RCA first introduced the machines. That is why there was a
special setting on the TRT series demod's that allowed you to screwdriver
adjust the curve to get proper playback. This also appears on the
TR-22 and other low band quads from RCA. The standards were settled
early on by the SMPTE as the governing body. Both RCA and AMPEX
licensed each other so that the machines would be compatible. So if
one developed a new standard, the other had to adopt it for
conformity. We did not need the Beta vs VHS was in broadcasting
quads.</DIV>
<DIV> </DIV>
<DIV>Chris Hill</DIV>
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