As of August 2009, much of the
material on this page has been updated and repackaged into a PowerPoint
the package click
Everything in radio is a learning process. The design and building of
antennas is no exception. When the outside work is done and it's time to
test the newest creation, one final step always remains -- the PL-259 coax
connector. Having done my share of these, I always wondered about the
mechanical integrity of the finished product. The application of heat in
the process of completing the connector can have some devastating effects
on even the best connectors.
This is a cross-section of a mil-spec silver barrel, gold
tip and Teflon core 'solder-on' PL-259 connector. Look closely and you can
the braid appears to have migrated somewhat with the application of heat.
There also appears to be significant deforming of the braid. Would you
really want 2 KW running through this connector?
So what's the answer to producing the absolute best
PL-259 coax connector? For all commercial work, the standard is crimp-on
connectors. The mechanical quality of these connectors is excellent and
they are easy to produce. The required tools are not that expensive, the
connectors are similar in cost and the end product is perfect each and
every time. Many well known DXer's and contest
operators have all transitioned to these mil-spec silver/silver and Teflon crimp-on connectors for one-hundred per
cent of their needs. Spend a few minutes and take a look at the process.
The terminology associated with coaxial
Note: the 'outer conductor' will be referred to as the
"braid" in this document and
the 'inner conductor' will be referred to as the
The construction process
This series of images details the construction process
from start to finish.
For best results, the steps must be executed in the order shown.
These are the basic tools. Key to the process in the
is the crimping tool and in the bottom right
is the Cablematic stripping tool. All items are available
from a variety
of mail order suppliers online.
This is the Cablematic DXE-UT8000
stripping tool for RG-8 and RG-213. It can be ordered
online from DX Engineering
in Tools section
A simple, but important modification to this tool is required.
The tool has a *blind plug in the centre that needs to be drilled
out before it can be used properly. Remove both cutting
blades. Secure the tool in a vise. Use a new 3/16" drill bit
and drill out the plug. The bore will be clear and
the tool will operate flawlessly. Replace the cutting blades.
the plug in place, the stripped length of the centre
conductor is too short. The centre conductor bottoms
out on the plug and becomes deformed as the tool turns.
RG58 cut length
RG-213 cut length
Note: these cut lengths are shown for information
purposes only. The Cablematic tool cuts to the proper length.
Use good quality coax cable
Use good quality crimp connectors that are
SST (silver body, silver barrel with a Teflon centre)
Slip a short piece (1½") of 3/4" shrink tubing
the crimp barrel onto the coax
Using the "First Cut" end of the Cablematic tool, smoothly rotate the tool
while applying even pressure towards the cable. All layers down to the
centre conductor will be cut in this single step. About 10 turns of the
tool should give you the correct length of exposed centre conductor. As you
release cutting pressure on the tool, the cutting action will stop.
Use non-slip gloves for a good grip on the tool and the cable.
Here is the trimmed RG-213
Using the opposite end of the Cablematic tool, trim
off the jacket of the cable. The tool will stop automatically
the correct length has been trimmed off.
The jacket has been fully trimmed off
Using very sharp nippers, carefully trim
back about 1/4" of the braid
Carefully slip the connector onto the prepared coax
and ensure the connector is fully seated. The braid
should just meet the edge of the connector.
Hold the assembly on a slight angle to solder the
centre conductor. While you can crimp the centre conductor,
a better mechanical connection is made if it's soldered.
to have a vise or support for the soldering iron.
Close-up view of the process
After the solder has cooled, slip the barrel up to
the connector. Ensure the barrel is fully seated
against the end of the connector body.
Using the crimp tool, apply even pressure until the
ratchet stops. Ensure the crimp tool sits very close
the body of the connector
The finished crimp!
The next steps are beautification
The excess centre conductor must be cut
Use line pliers to cut the centre conductor
Step # 10B
Apply even pressure in one cut
The finished cut should be just ahead of the connector tip.
Do not cut the connector.
Slip the piece of 3/4" shrink tubing into place
Use a good quality heat gun to shrink the tubing.
Be careful not to apply too much heat.
See note below about the heat gun
With the right touch, the shrink
tubing will run perfectly
Shrink is fully seated
File off the rough end of the centre conductor
Use a small fine file for this process
Apply short even strokes while holding the connector
Step #12 C
The finished job with a little of the centre
conductor showing beyond the connector
The finished connector!
This is a perfect connector in every way
Some connector construction
and tool tips:
If you want to make very short (say less than 6")
interconnect cables, start with a long piece of coax. Make the first
connector on the long piece of cable, then cut to the desired length and
make the second connector. This approach will prevent pulling the centre
conductor or braid through the jacket of a short piece of coax.
Buy a good quality crimping tool. The unit shown above
is the RF Industries RFA-4005. The crimp tool is sold with 2 dies that
cover most popular cables. The kit contains: (1) RFA-4005-20, Crimp Tool
Handle; (1) RFA-4005-01, Crimp Die Set for RG-58/U,
RG-59/U,RG-142/U,RG-8/X, LMR-195, LMR-200, LMR-240 & Proflex Coaxial
Cables; (1) RFA-4005-02, Crimp Die Set for RG-8/U, RG-213/U, LMR-400 &
Belden 9. Note: The
RF Industries RFA-4005
tool set can be purchased from a variety of suppliers or direct from RF
Make sure you have the correct die-set in the crimp tool
for the type of coax cable you are using.
During Step #6 (as shown above) dry fit the connector a
couple of times to ensure you have trimmed the correct amount of braid.
It's easier to trim the braid at this stage as opposed to once you have
the connector in place and the centre conductor soldered.
Once you have completed Step #6 and placed the connector
on the cable, hold the (seated) connector firmly in place while
soldering the centre conductor. It's important to have the connector
firmly seated before you solder the centre conductor.
The Klein cable cutters shown above are the ideal tool
for cutting coax. The tool cuts the coax without squashing the cable in
the process. It also make a very clean end cut.
Use caution working with this tool and make sure
you know where your fingers are all the time.
The Cablematic DXE-UT8000 stripping tool
can be ordered
in Tools section. Consider ordering several sets of replacement blades
when placing your order... there a very inexpensive.
The small side cutters shown above are the perfect tool
for trimming braid from coax. Try to keep one of these cutters for only
trimming braid, that will ensure the cutter is always sharp. Keep
another one of these for flush cutting plastic tie wraps... it makes a
very clean job.
The 3/4" shrink tubing used in the Step #11 of the
assembly process is not really required -- it's purely cosmetic, but it
makes a very professional looking finished product. Shrink tubing can be
used as a means of color coding cables for different applications.
In Step #9B, resist the temptation to re-crimp (or crimp
down) the raised portion of the barrel on the left. The raised portion
is above the jacket of the coax whereas the crimped portion is
against or crimped directly to the braid. Do
not crimp this small raised portion.
After Step #6 -- and before you begin Step #7, make sure
you have no tiny fragments of braid laying on the dielectric or touching the centre conductor.
Crimp connectors are usually packaged individually in
small plastic bags. If you are buying crimp connector inventory for
several different types of coax, label the plastic bags to ensure you
can tell the connectors from one another. Some of the connectors look
Always use the best crimp connector you can purchase.
There is no such thing as good quality cheap connectors. The
RF Industries brand of
connectors are very reliable, their quality control is excellent and the
technical support provided is superb.
connector demonstrated here (for RG-213
cable) is RFI part number RFU-507ST. The
ST stands for
Keep the entire connector assembly process as clean as
The heat gun used is a
with variable temperature output from 250 - 1100 F which is more than
enough heat to handle any type of shrink tubing. For the shrink tube
applications shown on this page, the gun is operated at about 500 F
which gives a very even flow of heat for running the shrink. This is an
industrial grade heat gun that will give many years of very reliable
service unlike many hobbyist grade units.
If you're looking for information about connectors for
LMR400 series cable, here are a few good links:
A few final comments...
process takes practice to perfect.
with the Cablematic stripping tool can be frustrating at first, but
steady even pressure towards the centre line of the cable will yield
nice results after a few test runs. For the best cutting action, the
tool must be started square to the end of the cable and a little more
pressure is required for the first couple of rotations. It takes
practice -- do not be discouraged with your first attempts. Cut off the
mess and start again.
crimp connector is far superior to any solder-on connector.
Yes I use these connectors for outdoor work... but like
any connector they are very well sealed. Living here in the Pacific
Northwest dictates that all outdoor antenna connections be waterproof.
A properly enclosed outdoor
connector at my station starts with a piece of 1" shrink tubing over the
entire connector. Next is the first
layer of plastic tape (over the shrink tubing).. and it extends at least
1" beyond the ends of the shrink tubing. Next is a
second layer of self vulcanizing 3M rubber tape -- applied
in the opposite direction to the first layer of tape. Finally I add
third layer of plastic tape in the
opposite direction to the second layer of self vulcanizing 3M
rubber tape. To achieve the best results, gently stretch the
tape during application to ensure all layers are very wrapped tightly.
In so doing, the tape will mold to the shape of the connector.
Some examples of weatherized outdoor connectors:
I have not had or experienced any water or moisture contamination
problems using this process. I do leave a small tab of tape folded over
at the end of each layer -- that makes it easy to find the start point
if I ever want to open up the connection.
If you have any questions after reading through this
page or trying your hand at making crimp-on connectors, please click my
email link below and I will try to help you.
All photographs in this series were taken with a Nikon COOLPIX
5700 digital camera (on a tripod).
My thanks to Jilly for her assistance during the
production of this page.
February 09, 2010
by Paul B. Peters, VE7BZ
Copyright © 2000 -2006 Paul B. Peters, VE7BZ. All rights reserved.