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VK5QX > INFO 26.07.02 00:25l 146 Lines 5919 Bytes #999 (0) @ WW
BID : E70297VK5QX
Read: DB0FHN GUEST
Subj: Re: Plugs and Sockets
Path: DB0FHN<DB0ZWI<DB0HOT<OK0PBX<OK0PHK<OK0NAG<9A0BBS<VK6BBS<VK3AVE<VK5BRC<
VK5SPG<VK5TTY<VK5LZ
Sent: 020725/0819Z @:VK5LZ.#ADL.#SA.AUS.OC #:39937 [Elizabeth] $:E70297VK5QX
From: VK5QX@VK5LZ.#ADL.#SA.AUS.OC
To : INFO@WW
JUST A TIP
G6KUI wrote;
_________________
Are there any other radio amateurs that don't know how to assemble an 'N'
type plug ?
_________________
Having had a fair amount to do with RF installations I have seen many
botched jobs done on "N" type plugs and sockets.
The sockets that I refer to are the "female" in line type and fixed type
with the clamped cable entry at the rear.
Much of the trouble concerns the treatment of the outer braid and
resultant clamping of it against the ring inside the connector.
Many people sit there working away with some sort of a pointed tool trying
to prise and separate the strands of the metal braid and bend them back
across the ring. Generally something like a pointed metal scriber is used.
This can be a most time consuming process.
I saw, very early on in my career, a method used which I always found to
be very effective.
The outer covering of the cable was trimmed back, making sure not to nick
the strands of braid underneath.
(The length trimmed back needs to be somewhat longer than that required
for final fitting. This to allow a little more flexibility during the
termination process.)
Next, the end of the braid is opened up a little allowing around 5
millimetres of the poly insulation and inner conductor to be cut off. (The
reason for this will be explained a little later in this dissertation.)
The braid is then gradually "brushed" out using a File Card until all
strands are lying relatively flat and even along and around the line of
the cable. Begin brushing at the ends of the braid wires, working back
along the cable until all the braid is suitably separated.
_____
Now, some may not recognise the term "File Card".
This a wire brush, usually in the form of a pad through which small stiff
wires are interwoven and protrude through the pad material. Such a brush
is commonly used to clean the striations in files and remove the filed
metal particles.
_____
The braid ends then protrude beyond the end of the inner conductor and
poly insulation. This allows them to be temporarily twisted together
forming a more less "pointed" end. (Hence the reason for cutting back of
the inner portion of the cable.)
The fact that this can be done makes it easy to pass the back nut, and
flexible compression washer over the end of the cable and the clamping
ring to also be passed over the braid to the point where the outer cover
has been stripped.
At this time most of the excess braid can be trimmed off. The remaining
ends of the braid can then be "brushed back" over the clamping ring. Final
trimming of the outer braid at the back of the clamping ring than then be
carried out using a suitable pair of side-cutters (snips).
Using the file card for the purposes described results in a very even
spread of the braid around the connector components and a much tidier
result than is generally obtained.
There can be some criticism of this method if one takes a purist approach,
as brushing of a plated braid with the metal file card can remove some of
the plating. This could, of course, allow some deterioration of the braid
plating in situations where the cable is exposed to the elements, moisture
etc.
The answer to this is that the connector and cable should be suitably
water proofed using, preferably, self amalgamating tape with a layer of
PVC insulating tape as a final covering.
Such authorities as NASA would never allow such a method to be used for
termination of cables, however, I do not believe that the average Amateur
Radio operator would require achievement of such high levels of quality
assurance as needed by NASA.
I once did a relatively short QA course under NASA auspices and, although
I cannot claim an expert knowledge of this subject, I did learn quite a
lot regarding such aspects.
If I remember rightly, the NASA approach to cable termination required
that the braid of a cable, if terminated by manual means, should be
"picked" and prised apart using only a plastic tool. (this was so that the
plating of the individual wires would not be damaged.)
The single strands of braid must be laid parallel and flat along the cable
with no more than (I think it was) 3 or 4 strands in each 100 strands
crossing each other.
(This is because, when the connector is tightened up, the resultant
pressure on the crossed wires can cause them to cut into and possibly
through each other.)
This approach to cable termination, as required by NASA, means not only
time, but exceedingly great patience to achieve the final result.
(Soldering technique, as required by NASA is yet another interesting but
also involved matter.)
In this day and age an up-to-date well equipped workshop would undoubtedly
have suitable tools to allow a more automatic method (generally a crimping
approach) of cable termination. However, the manual method would still
undoubtedly apply to most of us as individuals.
I might add that the method described applies to such as the "N" type
connectors fitted to RG8 and RG213 type cables as well as the fitting of
"BNC" connectors to the smaller diameter cables. Means of fitting (so
called) "UHF" type connectors can vary according to connector design.
I have not, in this description, explained just how to determine the
various lengths to which the cable components, braid, insulation, centre
conductor etc., should be trimmed and soldered etc.
Such details can usually be found in instruction sheets often supplied
with the connectors or described in various Amateur Radio handbooks and
manuals.
I can only assure you that the method which I have described does allow
you to terminate cables in a much better and easier manner way than
usually occurs with other manual methods.
I trust that this information will be of some help to you.
Regards,
Ian
__________
73 de Ian, VK5QX
@ VK5LZ.#ADL.#SA.AUS.OC
25 July 2002
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