Yes, I understand your point. Also, just wondering were you work? As to your
application verses mine. At work we need a good, fast, and yet 100% foolproof
way to do them. But, I don't agree you would get an impedance discontinuity
with my way of installing them. At least when I sweep some of the cables I make
for combiners I have not seen it being any different, the ID/OD ratio is
basically the same either way. If you can keep from it, you don't use PL's on
UHF anyway, .
At work we are using "DS" RG58 coax using center foam dielectric, not solid
dielectric, (ours are mostly used on 800 MHz) and foam is very easy to melt
when you are upside down in a Taxi cab. Some of our government installs are
specked-out on exactly how to do theirs.
At work we use "N" connectors on our RG213, 9913, 400 etc. 99% of the time, all
our base antennas have "N". And we use crimp connectors most of the time with
"N" or 7/16 DIN.
The main problem we have had with connectors put on by others people for cement
trucks, etc. is when they are wooled around a lot, over years copper ends can
break off and short them out. With the shield folded over the out side of 213
this is an non issue. On anything that an impedanance discontinuity would
matter, like 800 radios we would be using "N". On our 2.4 or 5.8 microwaves, we
would of course be using hard-line or at least supperflex, and above that wave
guide, so this would be a non issue to us.
You NEVER use a PL259 on UHF if you are worried about impedanance
discontinuities. These are only good for HF and not great at VHF. But, we are
forced to use them when the radio has them on the back. Have you ever swept
them on UHF or 800? They are horrible when you get to 800 no mater how you
install them. I use "N" or 7/16 DIN when ever possible for all my ham radios,
and 7/8 for all coax I use www.kc0ll.net. But, the bottle neck is the back of
the radios.
Anyhow, that is my input, I am sure I have bored everyone at this point.
End of discussion..
David F. Branson
Senior Technician
Action Communications, Inc.
Tucson, AZ
520.792.0326
520.792.2709 fax
KC0LL@comcast.net
www.kc0ll.net
www.ActionCommunications.com
"America will never be destroyed from the outside.
If we falter and lose our freedoms, it will be because we destroyed ourselves."
--- Abraham Lincoln
Freedom isn't Free, Support our Troops
----- Original Message -----
From: Steve Katz
To: David Branson KC0LL ; TowerTalk@contesting.com
Sent: Tuesday, May 05, 2009 10:45 AM
Subject: Re: [TowerTalk] Fw: Amphenol PL259
At work for over 26 years we put a small washer in the PL259 so the reducer
mashes the shield tight between the body and reducer as it is screwed in. We
never solder the shield. After all, even the center pin of the PL259 is only a
pressure fit in the SO239. In 26 years and 1000's of mobile coaxes installed we
never had a problem doing it this way. This is much more foolproof than
soldering and heating (melting) the center insulation. Larsen antennas use to
come with a Teflon washer in the PL259 bag! Teflon or plastic worked fine, but
I have also used very small metal washers.
::I've never had any problem soldering the braid through the solder holes,
flowing solder through the braid and into the surface of the reducer. It takes
five seconds with the right soldering equipment and results in a very strong
bond without overheating anything. Keywords, "right soldering equipment." :-)
As for RG213 or RG8, we ALWAYS fold the shield back over the outside jacket
and screw the outer body of the PL239 over the shield, smashing the shield
between the outer jacket and the body's threads, then cut the shield that
sticks out with a knife held tight against the body and turn the body, it cuts
it nice and flush. We (of course) solder the center pin. This has been 100%
reliable and works better than soldering. Also, it is easer to get new guys to
do it right 100% of the time than the soldering/melting way. On antennas up in
the air it holds the coax in the connector MUCH better than it hanging from
only the shield, poorly soldered at best. I know you need a strain relief, but
on mountain tops with ice you need all the help you can get.
Not wanting to start a debate, but this works, I know it works, and for us it
works best.
::No debating. But this introduces a larger impedance discontinuity than
doing it the way the connector was designed to be used, where the cable's outer
conductor continues up inside the connector body until it is within 1/16" or
less of bottoming out against the dielectric material inside the connector. On
HF, it probably makes no difference one way or another. At VHF, it makes quite
a difference. I routinely sweep UHF cable assemblies to 300 MHz, and with a
1.2 GHz Termaline for a termination, get ~30 dB return loss at 300 MHz on most
dual-UHF connector cable assemblies (short patch cables); using the "fold the
shield back over the jacket" method described above, that drops to 10-12 dB at
300 MHz. Still not "terrible," but not nearly as good as 30 dB. The
difference is obvious and repeatable. For those of us using these connectors
at 144 and 222 MHz, it's worth doing it the old fashioned way.
WB2WIK/6
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