> I now have become even lazier. I no longer terminate the antennas
> with open or short circuits for these measurements. Instead, I
> measure with an antenna connected, and using a range of frequencies
> different to that favoured by the Yagi. As long as you stay off its
> working range and secondary resonances, its SWR is close enough to
> infinity to provide a very good approximation. Of course, a
> better-than-infinite-SWR match will reduce the reflected power, making
> the cable look more lossy than it really is. In other words, if you
> obtain the original (unterminated) reading over a range of
> frequencies, you can accept those readings even if there is an antenna
> connected to the feedlines.
>
> The advantage is that I can now measure the integrity of all the
> feedlines in the station within a few minutes, and without having to
> leave the shack.
This is almost the same thing I now do with all my receiving
antennas. I recorded the return loss on all the systems. I simply
scan through the antennas (all 30 or so) and check them on one
frequency...and scan back through again at a higher frequency. In
this case, since the antennas are mostly terminated. I look for a
change in return loss from normal...either up or down.
By using the distance-to-fault program, I can find a problem within
a few feet of distance even on 2000 foot long feedlines if it is a large
deviation from the normal impedance at that point..like an open
shield.
73, Tom W8JI
W8JI@contesting.com
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