On 3/8/23 05:33, Dave Wade G4UGM via cctalk wrote:
   
 Our
Honeywell H3200 had 1200BPI NRZI 7-track drives.....
 
http://www.bitsavers.org/pdf/honeywell/datapro/70C-480-01_7404_Honeywell_20…
 page 13 onwards... Needed chrome tape....
 Dave 
 
The reason NRZI topped out at 800 BPI on 9-track was skew. 
If you ever adjusted the skew using a skew tape, you could
clearly SEE on a scope how close 800 BPI came to the limits
of tape weave (and it WAS close).
Jon