[NLRS] SWR infinite on 432.....rats!

[Doug Reed]

Hi David.

If you have little or no test equipment, then you have pretty much
expressed your only option. Personally, I'd want to take the power
meter up the tower with you so you can directly measure power at the
far end of the coax. That will let you verify cable RF loss while you
are doing all this.

The other alternate is to make a good solid RF short with whatever
connectors it takes, and screw that on the far end of the coax when
you check return power from the transmitter end. Don't try to prove
anything with the dummy load until after you've proved the coax and
connections are good. You can of course do a DC ohms reading on the
dummy load from the shack to prove it isn't shorted or partially open
along the way.

A better option might be to attach the dummy load to the coax in the
shack before you climb the tower. Then use the DVM to measure the DC
resistance back to the shack as you get to the different connecting
points. You should see a few extra ohms on the far end of the coax,
but if resistance is wildly higher or lower, you're starting to
localize the problem. I wouldn't take an expensive DVM up the tower,
one of the "free with coupon" cheap DVMs from Harbor Freight will be
fine for this job and you can laugh if it takes the fast way down from
the tower.....

<https://www.youtube.com/watch?v=Il_eju4D_TM>
The #37 video explains how to do a basic TDR measurement with a simple
scope and square wave generator. Doing the TDR measurement with the
fast square wave from W2AEW's #88 video will be more accurate but
finding the 74AC14 to build it could be a problem. Anything that
generates a waveform with a fast rise time would do the job. But I
haven't tried this myself so I don't know what works in real life
instead of theory.....

Good luck!
73, Doug Reed, N0NAS.