BNC connectors 75 Ohm versus 50 Ohm?
 

On Sun, 06 Jun 2010 19:19:42 -0400, John Passaneau
wrote:


*Snip*

No the size of the center conductor pin is different between 75 and 50
ohm connectors and will either make bad contact or damage the socket.

*Snip*

John Passaneau W3JXP


Not in years, they used to be made with different sized pins but now
rely on different dielectrics for impedance.

H.

Who used to get yelled at by his boss for inserting 50 ohm males into
75 ohm females.

BNC connectors 75 Ohm versus 50 Ohm?
 

[Sorry for being a little late to the party, but I was off newsgroups most
of this week.]

This thread had some discussion of adapters and I want to share my bad
experience with some low-cost items, proving, once again, that you get what
you pay for.

I am testing all my adapters and discarding some because the assemblies are
pulling apart with very little force. One manifestation: tightening the
threaded ring on a PL-259 (either cable end connector or adapter) and having
the ring just continue all the way on, separating from the connector body.

One test for a future failure has been any lack of smoothness when I rotate
the ring while tugging it gently. If it binds, rather than turning smoothly
in my hands, it's going to fail. Also, some of the cheap connectors are
press-fit together very poorly; they pull apart with only a few pounds of
pull.

Most of my early exposure to coax connectors was in and around the US Navy,
where reliable connectors are the rule, so I was a spoiled child.

"Sal"
(KD6VKW)

BNC connectors 75 Ohm versus 50 Ohm?
 

On 06/13/2010 01:50 PM, Sal M. O'Nella wrote:

[Sorry for being a little late to the party, but I was off newsgroups
most of this week.]

This thread had some discussion of adapters and I want to share my bad
experience with some low-cost items, proving, once again, that you get
what you pay for.

I am testing all my adapters and discarding some because the assemblies
are pulling apart with very little force. One manifestation: tightening
the threaded ring on a PL-259 (either cable end connector or adapter)
and having the ring just continue all the way on, separating from the
connector body.

One test for a future failure has been any lack of smoothness when I
rotate the ring while tugging it gently. If it binds, rather than
turning smoothly in my hands, it's going to fail. Also, some of the
cheap connectors are press-fit together very poorly; they pull apart
with only a few pounds of pull.

Most of my early exposure to coax connectors was in and around the US
Navy, where reliable connectors are the rule, so I was a spoiled child.

"Sal"
(KD6VKW)

PL-259's I can handle.
BNC's drive me nuts trying to get a good connection.
I gave up and just buy my cables now.
Bill

BNC connectors 75 Ohm versus 50 Ohm?
 

In article ,
says...

On 06/13/2010 01:50 PM, Sal M. O'Nella wrote:

[Sorry for being a little late to the party, but I was off newsgroups
most of this week.]

This thread had some discussion of adapters and I want to share my bad
experience with some low-cost items, proving, once again, that you get
what you pay for.

I am testing all my adapters and discarding some because the assemblies
are pulling apart with very little force. One manifestation: tightening
the threaded ring on a PL-259 (either cable end connector or adapter)
and having the ring just continue all the way on, separating from the
connector body.

One test for a future failure has been any lack of smoothness when I
rotate the ring while tugging it gently. If it binds, rather than
turning smoothly in my hands, it's going to fail. Also, some of the
cheap connectors are press-fit together very poorly; they pull apart
with only a few pounds of pull.

Most of my early exposure to coax connectors was in and around the US
Navy, where reliable connectors are the rule, so I was a spoiled child.

"Sal"
(KD6VKW)

PL-259's I can handle.
BNC's drive me nuts trying to get a good connection.
I gave up and just buy my cables now.
Bill

Sal's right - it's down to the quality of the item. I've seen some poor
BNCs, but many PL-259s which were REAL rubbish. I expect it's because
many of them are used for CB - and price is the usual decider there.

I've standardised on 50R BNCs for everything. Usually Amphenol or
Greenpar - the extra cost is insignificant, compared to rig prices these
days. Why 50R - the only reason is that the sockets are more robust.

Ready made BNC cables have been a disappointment - they are usually
crimped, and the crimps seem to relax with age. Cables can pull out,
given a bit of a tug. I use solder/clamped connectors and always solder
the braid to the clamping sleeve. Never had a failure.....

BNC connectors 75 Ohm versus 50 Ohm?
 

"Gaius" wrote in message
...
In article ,
Cables can pull out,
given a bit of a tug. I use solder/clamped connectors and always solder
the braid to the clamping sleeve. Never had a failure.....


After I got out of the Navy, I worked as a Marine Electrician, installing
equipment on Navy ships. My foreman told me that it is rarely done, but the
Navy can perform a Quality Assurance "pull test" of 25 lbs on a connector.
I think that's a lot of pull for a connector to withstand.

BNC connectors 75 Ohm versus 50 Ohm?
 

Sal M. O'Nella wrote:

After I got out of the Navy, I worked as a Marine Electrician,
installing equipment on Navy ships. My foreman told me that it is
rarely done, but the Navy can perform a Quality Assurance "pull test" of
25 lbs on a connector. I think that's a lot of pull for a connector to
withstand.

In a previous life I was tasked with tailoring a large number of RG-58
cables connecting radar scopes at a new installation in Korea. This
involved cutting the cables to length and installing clamp and solder
type BNC connectors. The rumor was that the Korean troops were supposed
to be helping us, but we never saw them -- until one day, when they
showed up. The one assigned to help me sat down and, neither of us being
fluent in the other's language, I proceeded to show him how to assemble
the connector.

Now the job of one of the several pieces, a metal ring, is to push
against and expand a rubber washer, which is mainly what holds the
connector together. This piece looks like it should go upside down from
the correct orientation, but if put on that way, the rubber washer won't
expand and the connector will come off very easily, with only a gentle
tug. If assembled correctly, it'll take a lot of pulling, as Sal says,
to get it off. I've never seen a correctly assembled connector come off.

Getting back to the story, I carefully demonstrated the correct assembly
method to the Korean troop, emphasizing the orientation of the ring.
After putting the connector on, I showed him our standard test. We would
grab the connector in one hand and about two feet down the cable with
the other. Then we put our hands together, making a loop of cable, and
briskly yanked them apart, resulting in a really good sharp tug on the
connector. A properly assembled connector had no trouble with this test.

So I gave him the parts and went to work on a connector. After a while
he handed me the cable with attached connector. I gave it the tug test
and the connector snapped right off. So I repeated the mimed
instructions, with extra emphasis on the ring orientation, then put him
to work again and got back to what I was doing. When he was finished he
handed me the connector, I did the yank test, and again the connector
popped right off. He shrugged, muttered something under his breath, got
up, and left. Guess he figured he'd had enough of that game, where he
assembled connectors and I pulled them off. We never saw the Korean
troops again.

Roy Lewallen, W7EL

BNC connectors 75 Ohm versus 50 Ohm?
 

Roy Lewallen wrote in
:

I've never seen a correctly assembled connector come off.



Another story, but with a different outcome.

I worked in a training school at one stage, and we thought we would get
trainees to make up BNC RG58 patch cables as a practical exercise, and we
would feed the output into our satellite labs where cables didn't seem to
last long (trainees pulled equipment trolleys around by the coax if it
didn't reach the desired socket).

Total failure, the BNC field serviceable connectors were just too
complicated for dissinterested trainees more interested in discussing
fast cars than concentrating on the job... and they had no stake in it,
if the cables didn't work, it didn't matter too much.

Solving the problem of the connectors pulling off led me to the Amphenol
specs, and I found that the pull out spec for the field serviceable
connectors was *much* lower than the spec for the crimp connectors.

So, I bought a quality crimp tool (in those days, it was a few hundred
dollars), and some Kings crimp connectors, and we switched the classes to
use the crimp components and a trim jig. The outcome was much better,
fewer faulty cables, and the crimped cable retention was much better and
consistently so.

No I know that one of the large suppliers to hams advertises "crimped,
not soldered", but that is just a blatant case of playing to the market.
A bit like the single core 4:1 Guanella balun that manufacturers
attribute to Sevik's assurance that it will work fine on a fully floating
load... whan antenna system is a fully floating load. The theme is the
customer is always right, if he wants something that doesn't make sense,
see Rule 1.

An interesting new connector type is the "compression connectors", "Snap-
n-Seal" is a proprietary name. I tried some of these on RG6, and a bit
suspicious of the cable retention mechanism, every one I tested using
different types of RG6 (including QS), hung on until the cable tore apart
some distance from the connector.

Owen

BNC connectors 75 Ohm versus 50 Ohm?
 

Owen Duffy wrote in news:Xns9D9948E3052AFnonenowhere@
61.9.191.5:

No I know that one of the large suppliers to hams advertises "crimped,
not soldered", but that is just a blatant case of playing to the market.


Got that back the front, didn't I.

DXE advertises "soldered, not crimped", but that is just a blatant case of
playing to the market.

Owen