I've been doing FFT-based measurements since 1982. I suggest that you try
a technique before you criticize it. Your analysis is badly mistaken.
Jim,
Factually, the little bumps or even big bumps on VHF are meaningless for
active problems on lower frequencies. They might predict a future issue,
but on 160 meters even crushing a cable flat for five feet would be
meaningless for receive loss unless the center actually contacted the
shield.
This is just the way things work, and it is important we get our heads
around the way things work.
If I wanted to find the reason for high signal loss on 160, the last thing I
would ever do is look at the system on 150 MHz or even 30 MHz. I would
first look at the system down around where the problem is, or as close as I
could to that frequency.
I can go out and slice half of the shield off for 10 feet and not tell a
difference in receive 160 signal, but it would be terrible on VHF. VHF
certainly tells us a future problem or a defect nicely, but it will not
directly point reliably to the LF issue unless by chance there is only one
bad spot.
I use a TDR when applicable, and that is about once every three or four
years. I can find and fix any cable system for HF with a cheap common SWR
analyzer, and so can anyone else. I can sit in my house and find a bad
connection 1000 feet away by sweeping the SWR between 1.8 and 5 MHz, and get
within a foot, and not spend $500 on equipment.
73 Tom
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