<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><br><br>Chris Hill</div><div><br>Begin forwarded message:<br><br></div><blockquote type="cite"><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><blockquote type="cite"><div>
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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.
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<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>
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<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>
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<div>Chris Hill</div>
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