Brian Kelly wrote:
I'd like to build a compact antenna/100W rig patch panel instead
getting involved with big expensive coax switches. Could be done
nicely with BNC connectors & RG-58. Does anybody have a link to a site
which provides freq (160M-440) vs. power handling ratings for BNC
connectors?

I don't know about a website, but it has often been discussed here. Try
searching through
http://groups.google.com/advanced_group_search

It all comes down to the RF current through the center connection. This
is partly about skin effect and surface conductivity, but equally
important - and less predictable - is accurate assembly of the center
pins.

If at all possible, use connectors with captive center pins. This
removes the biggest source of inaccuracy in amateur assembly.

All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out.

Bottom line: BNCs in good condition are fine for 100W at 440MHz, so
they're good for that power level at any lower frequency too.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

BNCs are almost universally used for non microwave test equipment. So, I
have used them a lot. My biggest problem has been the shield not making good
contact with the body of the connector after a while. By far, I have had the
fewest problems with the kind where a sleeve is crimped over the outer
insulation to provide strain relief. On the better connectors, this sleeve
is about an inch long. You do not want to allow any flexing of the bare
shield.

Tam/WB2TT
"Brian Kelly" wrote in message
om...
I'd like to build a compact antenna/100W rig patch panel instead
getting involved with big expensive coax switches. Could be done
nicely with BNC connectors & RG-58. Does anybody have a link to a site
which provides freq (160M-440) vs. power handling ratings for BNC
connectors?

Tnx,

w3rv

Crazy George wrote:
All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out.


Ian, you need to chop one apart again and look at the construction.
The contact pressure is provided by the wavy washers behind the
shoulder. The rubber washer, which is on the other side of the
shoulder, if anything opposes the contact pressure direction as it
'seals' against the end of the female cylinder.

Well, thank you, George - they do say "Learn a little every day"! I've
sawn up several BNC plugs, but never in that particular way.

Even though it's a wavy washer, the fact remains that the spring
eventually weakens (it happens it in C plugs also).


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Hm, I assembled about a gazillion BNC connectors in a previous life.
They were whatever brand the Air Force bought, and they didn't contain a
wavy washer. The pieces were the shell, the tip, and the screw end; and
to hold the braid on the inside there were only the rubber washer, a
strange-shaped washer, and a flat washer (to go between the screw end
and the rubber washer to reduce the friction when tightening). One
surface of the strange washer was flat (actually, stepped), and that was
where the braid was smashed against the boss inside the shell. The other
was tapered in such a way that it would force the rubber washer to
expand outward to squeeze tightly against the shell. When disassembling
one, we'd often find that the rubber washer would be cut nearly in two.
The only pressure on the braid was from the rubber washer via the force
of the screw end.

A common mistake was to put the strange washer in upside down, since it
just looked right that way, with the braid nicely cascading over a sort
of angled surface. When that was done, the washer wasn't properly
expanded by the tapered end of the strange washer, and you could easily
yank a connector off. When properly assembled, there's no way you can
yank one off.

I have a bunch of connectors in my junk box which are essentially the
same as I've described, but with a couple of more parts relating to the
tip and insulator. I assemble one from time to time when needed and,
like their military counterparts, they've been very trouble free.

Roy Lewallen, W7EL

Ian White, G3SEK wrote:
Crazy George wrote:

All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out.


Ian, you need to chop one apart again and look at the construction.
The contact pressure is provided by the wavy washers behind the
shoulder. The rubber washer, which is on the other side of the
shoulder, if anything opposes the contact pressure direction as it
'seals' against the end of the female cylinder.


Well, thank you, George - they do say "Learn a little every day"! I've
sawn up several BNC plugs, but never in that particular way.

Even though it's a wavy washer, the fact remains that the spring
eventually weakens (it happens it in C plugs also).

Roy:

Take an unwanted BNC and the biggest pair of diagonal cutters you have.
Clip the latching collar off the shell at the rearmost point of the two
latching slots. May take a couple of tries on each side depending on the
cutters and amount of force you can muster. Inside you will find the
components which create the mating pressure, usually including several half
washers which immediately fall out. If you have never cut the latching
collar off of a BNC, you have never seen that part of the construction,
which is hidden inside the knurl. And, yes, all the BNCs the Air Force
purchased had the wavy washer inside, or they would not stay latched. You
are describing the cable retention hardware, an entirely separate issue.

BTW, after you remove the latching collar, you now have a universal plug
which will mate with female BNC, TNC and N. Depending on brand, the
retention is iffy, but I find them very useful for quick connect/disconnect
applications. Trompeter plugs, with their machined sleeve, are quite good
without the latch.

--
Crazy George
Remove NO and SPAM from return address
"Roy Lewallen" wrote in message
...
Hm, I assembled about a gazillion BNC connectors in a previous life.
They were whatever brand the Air Force bought, and they didn't contain a
wavy washer. The pieces were the shell, the tip, and the screw end; and
to hold the braid on the inside there were only the rubber washer, a
strange-shaped washer, and a flat washer (to go between the screw end
and the rubber washer to reduce the friction when tightening). One
surface of the strange washer was flat (actually, stepped), and that was
where the braid was smashed against the boss inside the shell. The other
was tapered in such a way that it would force the rubber washer to
expand outward to squeeze tightly against the shell. When disassembling
one, we'd often find that the rubber washer would be cut nearly in two.
The only pressure on the braid was from the rubber washer via the force
of the screw end.

A common mistake was to put the strange washer in upside down, since it
just looked right that way, with the braid nicely cascading over a sort
of angled surface. When that was done, the washer wasn't properly
expanded by the tapered end of the strange washer, and you could easily
yank a connector off. When properly assembled, there's no way you can
yank one off.

I have a bunch of connectors in my junk box which are essentially the
same as I've described, but with a couple of more parts relating to the
tip and insulator. I assemble one from time to time when needed and,
like their military counterparts, they've been very trouble free.

Roy Lewallen, W7EL

Ian White, G3SEK wrote:
Crazy George wrote:

All the contact pressure in a BNC derives from the rubber washer
inside
the bayonet ring. A good BNC should need quite a hard twist to make
the
bayonet click into place... and in old surplus plugs, this springiness
does wear out.


Ian, you need to chop one apart again and look at the construction.
The contact pressure is provided by the wavy washers behind the
shoulder. The rubber washer, which is on the other side of the
shoulder, if anything opposes the contact pressure direction as it
'seals' against the end of the female cylinder.


Well, thank you, George - they do say "Learn a little every day"! I've
sawn up several BNC plugs, but never in that particular way.

Even though it's a wavy washer, the fact remains that the spring
eventually weakens (it happens it in C plugs also).

Well, Roy, here is cut and paste from Ian's post:

"All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out."

"....rubber washer inside the bayonet ring." sure doesn't sound like cable
retention to me. Sorry for the confusion, I guess.

On the other hand, when the rubber washer deteriorates, the connectors mate
much more easily once, as the female contact is destroyed in the process.

Ian, I suspect that is your failure mode, as I have chopped up some very old
connectors, and the spring washers still seem to retain their shape, while
the rubber is rotten. On the other hand, I have seen some cheapies which
are soft from the manufacturer. I send those back.
--
Crazy George
Remove NO and SPAM from return address
"Roy Lewallen" wrote in message
...
Ah. We're talking about two different things. I thought that the subject
had come up about securing the braid within the connector. Ian's initial
response was along the line of what I've observed. And that's what I was
talking about. But you're talking (I think) about what secures the male
connector to the female, another issue altogether.

Yes, I've never broken the latching collar off a BNC, so I've never seen
the associated components. I fully believe you that there's a wavy
washer to apply the pressure.

Roy Lewallen, W7EL

My mistake. Sorry.

Roy Lewallen, W7EL

Crazy George wrote:
Well, Roy, here is cut and paste from Ian's post:

"All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out."

"....rubber washer inside the bayonet ring." sure doesn't sound like cable
retention to me. Sorry for the confusion, I guess.

On the other hand, when the rubber washer deteriorates, the connectors mate
much more easily once, as the female contact is destroyed in the process.

Ian, I suspect that is your failure mode, as I have chopped up some very old
connectors, and the spring washers still seem to retain their shape, while
the rubber is rotten. On the other hand, I have seen some cheapies which
are soft from the manufacturer. I send those back.
--
Crazy George
Remove NO and SPAM from return address

On Mon, 4 Aug 2003 22:06:49 -0500, "Crazy George"
wrote:


On the other hand, when the rubber washer deteriorates, the connectors mate
much more easily once, as the female contact is destroyed in the process.


Hi All,

Another failure mode is mixing HV BNC (quite rare) with standard BNC.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Mon, 4 Aug 2003 22:06:49 -0500, "Crazy George"
wrote:


On the other hand, when the rubber washer deteriorates, the connectors mate
much more easily once, as the female contact is destroyed in the process.


Hi All,

Another failure mode is mixing HV BNC (quite rare) with standard BNC.

Yes, if you're hamfisted enough, you can easily connect a BNC signal
lead to an MHV high voltage supply. They're rare compared with BNC, but
they do appear at hamfests.

Whoever invented this booby-trap should have been connected to it! As
amateurs, we only need to know two things about the MHV series:

1. Plugs and sockets look like a "stretched" BNC.

2. Avoid.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

I used to think crimp on connectors were just the lazy mans way of putting
on a BNC. After 15 years of using them I have come to believe they are
better than the old style. I just removed an old radar system from service
whith hundreds of BNC connections. None of the crimp ons were bad, not so
for the others. I am sure this was the cause of many of the intermitent
problems that had plagued this radar.

"Tarmo Tammaru" wrote in message
...
BNCs are almost universally used for non microwave test equipment. So, I
have used them a lot. My biggest problem has been the shield not making
good
contact with the body of the connector after a while. By far, I have had
the
fewest problems with the kind where a sleeve is crimped over the outer
insulation to provide strain relief. On the better connectors, this sleeve
is about an inch long. You do not want to allow any flexing of the bare
shield.

Tam/WB2TT
"Brian Kelly" wrote in message
om...
I'd like to build a compact antenna/100W rig patch panel instead
getting involved with big expensive coax switches. Could be done
nicely with BNC connectors & RG-58. Does anybody have a link to a site
which provides freq (160M-440) vs. power handling ratings for BNC
connectors?

Tnx,

w3rv