On Sep 5, 1:12 pm, Highland Ham
wrote:
Is it possible to check the quality of a coax connection to a PL259
plug without taking the plug apart - i.e. simply by using a
multimeter?

Hi Andy,

With both ends in your lap:
shells, end to end - very low Ohms;
pins, end to end - very low Ohms;
shell to pin, either end - infinite Ohms.

===========================
The above is an electrical contact/insulation (DC) check

To check the quality of the complete coax cable including the plug(s)
a 'coax loss' check especially when operating at the higher frequencies
is important.

Some antenna analysers (like the MFJ 259/269 ) have this coax loss
measuring facility. These instruments enable the user to change
frequency which shows the overall quality of coax + fitted plugs.

The best type of PL259 plug is the one with a cable entry arrangement as
in N-type plugs . This provides an excellent and simple braid connection
,without having to apply heat other than soldering the centre conductor
to the top of the pin .
These plugs are somewhat more expensive than traditional PL259 plugs
(equivalent US$ 6 in the UK) but imho it is worth the expenditure.

Frank GM0CSZ / KN6WH

All

More on the nature of the problem. I have basically fitted a 1/2 size
G5RV. Its fitted at 30 ft high between a pole at the end of the yard
and the chimney at approx 30 ft high. The ladder line falls pretty
much vertically except for the very end where i have had to divert it
away from a steel cast iron style balcony which surrounds a roof
terrace on the first floor. I figured it would not be good to brush
alongside the balcony as its metal.

Anyway, i am getting some very weird SWR readings even when i am using
my automatic ATU (LDG Z-100. These range from close to 1.1:1 on
40metres all the way up to 3.1: 1 in the middle of the 20 metre band.
I am trying to work out where the problem may lie. So far i have come
up wiith:

1) its just the way the antenna works and the ATU cant do any better?
2) the ATU is not working properly (but it seems to get a decent match
elsewhere)?
3) there is a problem with the plugs (would this appear to make a
difference only on some frequencies)?
4) somehow the stell balcony / balustrade is causing a problem even
though i am keeping the ladder line approx 12 inches away from it.
Also would this only cause a problem on 20M?
5) running the coax along the steel balustratde and into the house is
causing a problem (is this possible)?

Confounding factor is that it seems to be working ok even with the
high SWR and i have made some decent contacts on both 40 and 20
metres.

I thought i should start with the plugs but any other thoughts welcome
- all very odd!!

Regards

Andy