Topband: fixing beverage

Jim Brown jim at audiosystemsgroup.com
Tue Nov 24 16:18:59 EST 2015


On Mon,11/23/2015 2:06 PM, Mike Waters wrote:
> Maybe things have improved lately, but AIM would not be my first choice.

There are multiple ways to do TDR. I like the way that this unit does it 
-- an inverse FFT of a frequency sweep.

http://sdr-kits.net/VNWA3_Description.html

To expose small perturbations in the feedline or system, make the sweep 
at VHF/UHF. To see only the more gross defects, sweep from about 50-150 
MHz. To understand this, remember that a linear frequency sweep will 
spend more time in the high octaves than the low ones, so the greatest 
contribution to the display will be that higher octave, whatever you 
have chosen.

In the example posed by the question about varmint damage, I'd set it 
for 200 - 1,000 MHz to see small nicks in the braid, 50 - 150 MHz to see 
the connectors and splices.

73, Jim K9YC




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