[TowerTalk] Tdr reading with dc grounded antenna?

[Michael Tope]

If you are trying to determine if the high VSWR problem is with the 
feedline or the antenna, then the TDR can help with that. If the 
feedline is good, the TDR should show a single strong reflection at a 
distance consistent with the length of the feedline. If you are seeing 
multiple strong reflections that are a significant distance apart, then 
it could be pointing toward a feedline problem. The devil is in the 
details of course (type of coax, length, etc). Can you plot the TDR 
results and share them with the group along with info on the type of 
coax and its approximate length?

Of course, at best about all you will get from the TDR is distance to 
fault which may help sort out whether it is a feedline problem or an 
antenna problem. If it is an antenna problem the TDR plot is unlikely to 
tell you anything about the nature of the problem except perhaps if a 
4:1 VSWR is what you would expect to get in the shack (given the loss of 
the coax) if the feedpoint of the antenna was shorted or open. BTW, this 
is a good example where having a baseline TDR plot or impedance versus 
frequency plot of known working antennas could come in handy toward 
troubleshooting them if they start acting up.

73, Mike W4EF...................

On 9/17/2021 6:23 AM, WW3S wrote:
> Using a AA-230 tdr, trying to diagnose a Diamond dual band antenna prior to climbing. SWR is 4.*:1, ….should the tdr see a short when it hits the antenna?
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