Hi Oliver.
AHHH, those old Tektronix oscilloscopes, about the size of 2medium suitcases with a very long 5" CRT. I have used many of these including the one pictured with an unbelievably fast time base. Beautifully built equipment (which was reflected in the price). All termination points and even the solder had a percentage of silver in the alloys. The instruments even had a coil of this special solder rolled up inside the top of the case for repair work. I had a mains transformer fail (green/brown smoke) and would you believe this type of component was guaranteed for the life of the instrument and we had one delivered free in 48 hours. Quality and service we don’t see very often now.
That video should be a compulsory view for anyone involved or are going to be involved with transmission of intelligence from point A to anywhere. It would be good if you can put it up separately so it is not confined to readers of this post. That is exactly what I was on about some time ago and I mentioned above. A very important point often overlooked or completely ignored.
That measurement technique is termed Time Domain Reflectometry. During my 22.5 years with AWA I got involved with Television transmitting antennas, Yes the ones on 500 to 700 ft towers (TCN9 is 785ft)
and this method was used to measure the return loss of the plumbing at the end of the cable. That video shows a return loss of about 6db open circuit which means that length of cable has about 3db loss at the frequencies involved. The TV cable is 3.25 or 4.5 inch diameter and cable losses are very low. We were able to accurately measure return losses of the antenna at something like 40db or a VSWR of about 1.02:1 or reflection co-efficient of about 1% whichever measurement type turns you on. Not bad for an antenna which had 96 full wave or 192 half wave elements as the transmitting medium at the top of that tower. You would have to see it to believe the plumbing and cabling involved.
Silicone Chip some time ago did an article on oscilloscope leads. Especially the higher frequency ones. This is a good read if you can find it. If you have ever measured these leads in the X 1 position you will find the centre conductor is a resistance wire of quite a few ohms. The article goes into the reason behind this and acknowledges the skills and patience of the design engineer at the time who did not have the luxury of computers and transmission line modelling. All done on paper.
Cheers Bob
