DComTalk.com

Any idea why it is it referred to as RG-8 all over the internet? I
wondered if thick ethernet had a special dielectic so as to be easier
to cut a hole into than normal cable would be, and whether my vampire
tap would be able to make it into the center conductor of normal RG-8.

Where does that leave the tranceivers I have which have a pass through
path for something the size of RG-8 using PL259 coax connectors, and
were sold to me as thicknet tranceivers?

If thicknet is larger diameter than RG-8, does that mean the PL-259
coax won't fit the thicknet? Were their special coax connectors? Or
are the three tranceivers I have that have a pass through connection
appearing to be for RG-8 actually a variation on thinnet? Or did later
installations use REAL RG-8 and these tranceivers but not use vampire
taps? The more I learn the more ignorant I become...

In article <1110302957.715105.211120@g14g2000cwa.googlegroups.com>,
"sqrfolkdnc" <carey.schug@gmail.com> wrote:

Any idea why it is it referred to as RG-8 all over the internet?

Probably because most hams consider any (roughly) 0.4" diameter, 50 ohm
cable to be "RG-8". Don't believe everything you see or read on the
Internet. ;^)

I
wondered if thick ethernet had a special dielectic so as to be easier
to cut a hole into than normal cable would be, and whether my vampire
tap would be able to make it into the center conductor of normal RG-8.

We took great pains to make the dielectric soft enough to allow easy
penetration, yet firm enough to prevent movement of the center conductor
when the cable is bent, which would affect the characteristic impedance.
The foam dielectric makes the cable somewhat thicker than RG-8.

Where does that leave the tranceivers I have which have a pass through
path for something the size of RG-8 using PL259 coax connectors, and
were sold to me as thicknet tranceivers?

One can always build a transceiver that, instead of attaching through a
vampire tap, requires cutting the cable and inserting the transceiver
through standard connectors. The advantage is that the complexities of
the vampire tap are avoided; the disadvantage is that the network must
be brought down to install each new station.

If thicknet is larger diameter than RG-8, does that mean the PL-259
coax won't fit the thicknet? Were their special coax connectors?

PL-259 (UHF) connectors were never used, at least not according to the
Ethernet standard. PL-259s are not constant-impedance connectors; they
are fine for non-demanding applications, e.g. ham radio. Ethernet uses
Type N connectors; these are more expensive, but specified at 50 ohms
impedance. They are also quite a bit more rugged.

As a ham myself (KE1B), I would have liked PL-259s, since I could have
gotten all I wanted as vendor samples from Ethernet cable manufacturers!
Instead, I started using N connectors myself for amateur applications,
and never went back. PL-259s are simply awful at GHz frequencies.

Or
are the three tranceivers I have that have a pass through connection
appearing to be for RG-8 actually a variation on thinnet? Or did later
installations use REAL RG-8 and these tranceivers but not use vampire
taps? The more I learn the more ignorant I become...

No standards-compliant installation used RG-8, or PL-259 connectors.
Some commercial products used Type N inline connections, but most used
the vampire tap.

By the way, there really is no single standard for "RG-8"; this is one
of the problems we wanted to avoid. There is RG-8, RG-8/A RG-8/C, and a
variety of others. Lots of manufacturers make "RG-8 style" cable; all of
these vary in dimensions, attenuation, shielding effectiveness, etc.
Ethernet installation would have been a nightmare if we just said "Use
RG-8 cable".


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com

Rich Seifert wrote:

As a ham myself (KE1B), I would have liked PL-259s, since I could have
gotten all I wanted as vendor samples from Ethernet cable manufacturers!

Another one here, VE3ZU. I wonder how many people here, realize that many
of the first computer hobbyists were hams? The first popular computer
magazine, Byte, was originally published by Wayne Green, who also published
73 Magazine, among others, for amateur radio. There were many computer
articles in 73, along with the ham radio stuff.

Incidentally, I have every issue of Byte on the shelves behind me. I bought
the first three issues in person, from Wayne, at the 1975 Radio Society of
Ontario Convention, in Ottawa.

In article <GPSdnVsLU-oJrrPfRVn-2A@rogers.com>,
James Knott <james.knott@rogers.com> wrote:

Incidentally, I have every issue of Byte on the shelves behind me.

You will find an article I wrote in the January 1990 edition,
chronicling the 10th anniversary of the Ethernet ("Blue Book")
Specification. A group of the original designers got together in my home
for a reunion party, which resulted in the article.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com

Rich Seifert wrote:

(snip)

are the three tranceivers I have that have a pass through connection
appearing to be for RG-8 actually a variation on thinnet? Or did later
installations use REAL RG-8 and these tranceivers but not use vampire
taps? The more I learn the more ignorant I become...

No standards-compliant installation used RG-8, or PL-259 connectors.
Some commercial products used Type N inline connections, but most used
the vampire tap.

The first 10base2 installations I saw used those transceivers
with N to BNC adapters on them. At one point I did use one
at the end of a thick ethernet cable with type N connectors.

If you want to add to your collection, I have some 100baseT4
transceivers.

-- glen

Rich Seifert wrote:

(snip)

You may have problems trying to use RG-8 or any standard cable with a
vampire tap. The dimensions/geometry are simply wrong. Also, the tap is
designed to work only with a solid center conductor (not stranded) and a
foam dielectric. The standard solid polyethylene dielectric of RG-8 is
much too dense for the tap probe, and the higher dielectric constant
reduces the diameter of the cable, i.e., the tap probe will be too long.

I did it once. We bought some Suns that we were told would have built
in 10base2, but didn't. We ordered some transceivers, but I wanted
to get the machines running. I put two vampire taps on some
RG8 (probably RG/213, actually) soldered BNC connectors onto
each end, and had it running for some weeks. The only problem
was that once one of the BNC connectors shorted out (they were panel
mount connectors). The clamp was tight enough not to wiggle too much,
but I probably wouldn't put it in the wiring tray.

-- glen

100baseT4 "tranceivers"!! ???????

OK, the more I learn, the more I learn I don't know.

I'm interested. Unless the tranceiver is 100baseTX <--> 100baseT4, in
which case I am VERY interested.

A web search...if I learned correctly, there is a DB40 AUI connector
for 100 megabit ethernet, from which one can connect a 100baseT4
tranceiver or a 100baseF tranceiver (and maybe others), but it never
caught on and interface cards nearly all have RJ45 ports for 100baseTX
only.

So it would be nice to have as a display item, but unless I can get
network interface cards with drivers (I think I saw a reference to a
list of cards supported by some linux driver including some 100baseT4
cards) and maybe a hub/switch, it is not something I could set up and
have running live.

As I understand it, 100baseT4 is 3 pairs transmit, 1 pair
control/collision/receive I can see that meaning either a hub is a
requirement or any cable can connect two DTE devices together without a
hub and a crossover is not required, but I could not find anything on
the web to explain how it works (probably a shortcoming in what to look
for on the web, I'm sure its there somewhere)

Rich Seifert wrote:

Incidentally, I have every issue of Byte on the shelves behind me.

You will find an article I wrote in the January 1990 edition,
chronicling the 10th anniversary of the Ethernet ("Blue Book")
Specification. A group of the original designers got together in my home
for a reunion party, which resulted in the article.

Actually, it's the Jan 1991 issue, page 315.

"Ethernet: Ten Years After"

"Imagine a world without networks: no Novell/3Com/TOPS,..."

Perhaps you could post the text or a link to it here. I'm sure others would
find it interesting.

glen herrmannsfeldt wrote:

No standards-compliant installation used RG-8, or PL-259 connectors.
Some commercial products used Type N inline connections, but most used
the vampire tap.

The first 10base2 installations I saw used those transceivers
with N to BNC adapters on them.   At one point I did use one
at the end of a thick ethernet cable with type N connectors.

The first ethernet network I worked on (or even saw), was a DECNET,
connecting several VAX 11/780 computers and used vampire taps. However
that's not my first experience with networks. That would be on a system
built by Collins (part of Rockwell). They had a network, that instead of
using packets, used time slots (time division multiplexing). When a device
(computer, tape drive, disk etc.) wanted to send data, it would be assigned
a time slot on the ring. The destination would then listen to that time
slot. While the time slots could have been assigned dynamically, in the
systems I worked on, they were permanently assigned. IIRC, the Collns
8500B had a 2 Mb/s ring over RG-58 cable, while the 8500C ran 8 Mb over
triaxial cable. There were also adapters to convert between the two
speeds. The ring had relay boxes, for connecting the various devices and a
loop sync box, to retime the signal. As I recall, this technology was
developed in the mid '60s. I was working on it in the late '70s, a few
years before ethernet was created.

In article <vOudnfmdqNKZjLLfRVn-jg@rogers.com>,
James Knott <james.knott@rogers.com> wrote:

glen herrmannsfeldt wrote:

No standards-compliant installation used RG-8, or PL-259 connectors.
Some commercial products used Type N inline connections, but most used
the vampire tap.

The first 10base2 installations I saw used those transceivers
with N to BNC adapters on them.   At one point I did use one
at the end of a thick ethernet cable with type N connectors.


The first ethernet network I worked on (or even saw), was a DECNET,
connecting several VAX 11/780 computers and used vampire taps. However
that's not my first experience with networks. That would be on a system
built by Collins (part of Rockwell). They had a network, that instead of
using packets, used time slots (time division multiplexing). When a device
(computer, tape drive, disk etc.) wanted to send data, it would be assigned
a time slot on the ring. The destination would then listen to that time
slot. While the time slots could have been assigned dynamically, in the
systems I worked on, they were permanently assigned. IIRC, the Collns
8500B had a 2 Mb/s ring over RG-58 cable, while the 8500C ran 8 Mb over
triaxial cable. There were also adapters to convert between the two
speeds. The ring had relay boxes, for connecting the various devices and a
loop sync box, to retime the signal. As I recall, this technology was
developed in the mid '60s. I was working on it in the late '70s, a few
years before ethernet was created.

I worked for BigBank in NYC in the late 70's and the CTO was really
big on pre-standards channel-oriented broadband LAN for buildings and
ISO (meaning mostly X.25) WAN. The cable plant for the BB was
identical to any CATV system except we didn't have telephone poles or
manholes. Our engineers joked that if/when the got downsized they
could all go home and get jobs with the local cable TV company and
have a shorter commute.

Many of the engineering issues for our BB and an outdoor CATV system
were similar because we were in a very high EMI environment (a couple
thousand feet LOS from the Empire State bldg) and interference was
always leaking into all sorts of stuff. Years later I could hear AM
radio on my PC before streaming was invented.

The CTO later went on record as "ethernat can't work" and BigBank
became a huge TokenRing operation. I had to jump thru hoops to get
ethernet in for my DEC datacenter. We spent MILLIONS on OSI stuff and
it was a PITA to get it connected to all the types of DEC gear I had.
OTOH, I had thousands of users, worldwide, by 1982. TCP/IP, What's
that ?





--

a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.

Al Dykes wrote:

I worked for BigBank in NYC in the late 70's and the CTO was really
big on pre-standards channel-oriented broadband LAN for buildings and
ISO (meaning mostly X.25) WAN.  The cable plant for the BB was
identical to any CATV system except we didn't have telephone poles or
manholes.  Our engineers joked that if/when the got downsized they
could all go home and get jobs with the local cable TV company and
have a shorter commute.

Many of the engineering issues for our BB and an outdoor CATV system
were similar because we were in a very high EMI environment (a couple
thousand feet LOS from the Empire State bldg) and interference was
always leaking into all sorts of stuff. Years later I could hear AM
radio on my PC before streaming was invented.

The CTO later went on record as "ethernat can't work" and BigBank
became a huge TokenRing operation. I had to jump thru hoops to get
ethernet in for my DEC datacenter.  We spent MILLIONS on OSI stuff and
it was a PITA to get it connected to all the types of DEC gear I had.
OTOH, I had thousands of users, worldwide, by 1982.  TCP/IP, What's
that ?

That Collins 8500C system that I worked on, was part of the Air Canada
reservation system. That system ran on a Univac computer, and the Collins
network was the communications processor for it. As I mentioned in the
other note, devices such as tape drives and disks were connected to this
network. There were also about 2 dozen PDP-11s connected, each with 3 or 4
serial I/O cards, each card containing a Motorola 6800 CPU and 8 UARTs,
which were then connected to modems, to talk to terminals around the world.

It was quite a system in it's day.

Hello,

RHS> As a ham myself (KE1B), I would have liked PL-259s,

since I could have gotten all I wanted as vendor
samples from Ethernet cable manufacturers!

JAK> Another one here, VE3ZU.

I'm in good company then :-)

I've seen coaxial Ethernet used in places where EMC was an
issue. I've thought about using it in the shack for this
reason (well, that and I'm likely to have reels of it
sculling about the place anyway ;-)

I like BNC for low power connections, N for heftier stuff.

73, Andy, KB9YLW

Hello,

Besides 10base2, I also have a 10baseF hub...
^^^^^^^

Which 10baseF? As I understand it there was 10baseFP
(fibre passive, not widely deployed), 10baseFB (for backbone
link segments, I don't know much about this) and 10baseFL,
which is more common and can interwork with the earlier
FOIRL standard. I've been on the lookout for a small
10baseFL hub or switch, perhaps one that supports single-
mode links.

- Andy Ball

Hello Rich,

RHS> The forced spacing was to prevent lumped capacitive

loads on the system, which could cause unacceptable
signal reflections.

I understand that you wrote this about original 'thick'
Ethernet, but I'm wondering if there are preferred lengths
for 10base2 cables. Would certain lengths minimise the
effect of any reflections from the BNC connectors? I don't
remember 10base2 being especially fussy, but an ounce of
prevention...

- Andy Ball

Andy Ball wrote:

I like BNC for low power connections, N for heftier stuff.

I haven't got anything that requires N connectors, but I like using BNC. If
any gear comes with an SO-239 connector, I use an adapter to convert to
BNC.

Incidentally, one thing that really gets me, is all the names for a BNC
connector. It is not "British Naval Connector" or that other common one
with a couple of people's names. According to what I read in Ham Radio
Magazine, several years ago, a guy from Amphenol (IIRC) said it's derived
from:

B - bayonet lock
N - N type (you can actually plug a male BNC into a female N, though the
lock won't work
C - compact (version of N series)