ARLA/CLUSTER: Episodio 145 da série " Foundations of Amateur Radio" - Coax Loss vs Connector Loss

[João Costa > CT1FBF]

Foundations of Amateur Radio #145

Coax Loss vs Connector Loss

A question that comes up regularly is one about loss, specifically
loss in the coax and connectors between your radio and your antenna.
The general wisdom is that better coax gives you better results and
more connectors is bad.

Anything with double joiners, or such like is really bad.

So, essentially we've been taught that we should have the shortest
coax possible with as few connectors as possible. Pretty fair and
reasonable, right?

During the week I was introduced to a video made by Jim W6LG. Jim has
a YouTube channel going back a couple of years with about a 100
videos.

One video is loosely called Jim measures the loss in coax connectors
and 100 foot of RG8X. In case you're wondering, 100 foot is 30m and
48cm of coax. I know this because the United States of America despite
appearances to the contrary is actually metric, they defined the inch
as being 2.54cm back in February of 1964. Other than driving on the
wrong side of the road, they're not too strange and they talk on the
air, a lot, so there's that.

Back to Jim.

He rummaged through his bits box, the one you have, the one that every
amateur has, and if you don't then you clearly need to spend some time
being with an Elmer and learning the ropes. Jim pulled out 30 odd
connectors, SO239 and PL259 by the looks of things and daisy chained
them all together. Jim has been around the block a few times and he
has connectors going back to World War 2, so he really did find the
bottom of his box to make his video.

Anyway, he rigged up a testing tool to compare a single connector to
30 connectors. Measuring the difference, showing pretty graphs, lines
and scales, the whole bit.

He even compared 20m to 6m and tested both extensively and even re-did
the tests with a kilowatt.

Then as icing on the cake, you know the one, with a cherry on top,
whipped cream on the side, he did the same test with the 30 odd meters
of RG8X coax.

I could leave you hanging here and let you go and find Jim's video,
but that wouldn't be fair if you're currently in the middle of your
commute to work like several people I know, so I'll share the outcome,
but if you get the chance, the 5 minutes of your life that you'll
spend with Jim are worth every second.

So, what was the outcome of Jim's test you ask?

Surprisingly, there was no discernible difference between one
connector and 30 connectors in-line, not at 14 MHz, not at 50 MHz, not
at 50 microvolts and not at 1 kilowatt, about 223 and a half million
microvolts.

Using RG8X coax, which sits about halfway between RG58 and RG213 in
terms off loss, there was however 22% loss at 14 MHz and 40% at 50
MHz.

Does make me wonder if it's the coax manufacturers who have been
telling us to buy more coax rather than join two bits of coax together
with a connector.

Might have to do that test myself. Better go and start digging through
my bits box.

I'm Onno VK6FLAB