Company network slowdown

"The Specification" says this is supposed to be a 32 to 48 bit time jam - content not specified except that it must not make a valid CRC if by some bizarre reason the collision is detected that late. The detection to jam delay is supposed to be no more than two bit periods.

Collision backoff should only effect the two (or more) systems who collided. Others on the wire shouldn't be effected, and they can slip in 9.6 usec after the wires stop vibrating.

It's a good HF cable, but isn't rated for voltage (given that the normal signals are about 2 Vpp), and of course has the different jacket, solid center conductor, and double shielding.

We also had problems with the people not cleaning the outer braid out of the tap holes. As far as the N connectors, there were only two per run, and we tended to take special care when putting them together (though not the kind of care you used with RG-9 or 214 at 3+ GHz.).

Didn't have much of that, but then we left the transceivers in place once they got installed.

The rise/fall spec was 20-30 ms, though the spec also required the harmonics down (second/third down 20 dB, fourth/fifth down 30 dB, sixth/seventh down 40 dB, higher down 50 dB) which really limits the resolution of TDR. Funny thing is, no-where in the spec do they give a required VSWR/return loss, whatever. I guess it's implied with the transceiver loading.

Even late model hardware didn't report it. That's why we needed the NetGen sniffer. (Well, that was one reason.)

Wowser! We just had a pretty good tape backup (yeah, I know) program. We knew the tapes were good, because they were verified during the day following the backup, and we had enough user mistooks that we were restoring files on a regular basis. There was off-site storage as well.

Huh? What kind of transceivers had built in terminations?

We had very little twisted pair, and once the orange cable was in (and working), the rest of it was stringing four pair, and poking pins into DB15s, which we often fobbed off on the interns.

Naturally. We tried to pre-mark the drop cables so that there was both a plastic marker, and a felt tip marking at the transceiver end. The drop end had a felt tip marking and a Dymo label that went on the face plate. Early on, we also marked the transceivers with felt tips on masking tape, but the heat killed that. When we started installing fiber, this was outsourced, but one of the contract requirements was that the fibers had to be marked with serial numbers every ten feet and within a foot of each end, and the serial numbers had to be entered into "the book" with full location information not later than noon of the next day. We randomly tested this as part of the acceptance inspection. This seems to have worked, though I have no idea how much it added to the tab.

The spec was ALSO 2.5 meters between transceivers - we violated that to heck and gone. ;-)

Not so. There could be a maximum of two repeaters (or four half repeaters or what ever) between any two "stations". If you wanted to have a 250 meter cable with repeaters every 2.5 meters feeding

100 OTHER segments, that was OK. Well, it was permitted - not that having 100^2 hosts in one collision domain would work worth a darn. ;-)

Old guy

Oh yeah. That too. I carried a sharp awl and cleaned out the braid before shoving in the probe. Lot of ways to do it wrong.

Nope. I wasn't looking at the ethernet waveforms although those were interesting to look at. I was sending a pulse down the line and looking for discontinuities. There was considerable magic in interpreting the trashy waveforms that were returned. However, it would detect shorts between the braid and the probe, water incursion, crushed coax cable, kinks that cause the dielectric to migrate, and crappy connections. I still use the same home made TDR for checking phone lines, coax cables, and CAT5 cable.

The transceiver loading is fairly light. A few PF at most. The VSWR at 10MHz is controlled mostly by the terminators and the coax cable characteristics. They weren't too critical for proper operation. My idea of "VSWR" testing was to put an ohms guesser on one of the probes. If it read 25 ohms, it's ok.

Want me to post my pile of DDS-1 through DDS-3 DAT tape drives and juke boxes with fried heads? I just tossed my pile of DC-600 style tapes and a few drives. In my extensive experience with these abominations, tape was at best a necessary evil, and at worst a very bad parachute.

No. BNC T connectors at the end points connected to a transceiver. The transceiver is usually a 10base2 to 10baseT media converter, or a cheapo 8 port 10baseT hub with an extra 10base2 port. If there's a Cisco router at one end, then it's a 10base2 to AUI adapter. I crimp a common F connector on the RG-6/u and then use a BNC to F adapter to the T connector. The terminators are both 50 ohms. Want details?

Oh, it's not that bad. As long as I keep it at 10baseT and not try for 100baseT, 25 pair telco bundles work just fine.

The tool that we use to bore the hole was usually pretty reliable in cutting the braid as long as you didn't force it - slow worked fine. We would then give the hole a puff of dry air from a spray can and inspect. The problem usually occurred with newbies (we had interns doing most of this work as it really isn't complex). The mentor was supposed to explain all this, but some interns didn't work out.

[TDR on 10Base5]

The rational is that the DIX specification isn't really covering the higher frequencies because what happens up "there" doesn't have the effect as the 10/20 MHz frequencies. Some of what you see on a 5 nano rise/fall time (200 MHz = about 2 foot resolution) isn't there as far as the Ethernet signal is concerned. None the less, having the sharp rise/fall really does help in multiple mismatch conditions. A long time ago, I had something similar (a NE555 driving half of a 74S74 driving an LH0002) when I was looking at a number of coax runs in a data acquisition trailer, and it certainly was useful in locating the fault, but we used VSWR meters to go/no-go the lines.

Putting it mildly

Major problems, and breaks in the cable itself.

That would have to be a pretty wicked bend - certainly down below the MIL-C-17 bend radius requirements. For the orange stuff, we never had bends shorter than about 2 foot radius.

At one time, I had the specs/schematics of the common transceivers we were using. They were a mess, given the isolation required, but there was a lot of ECL in there.

Two puff max - shunt resistance over 100K

Terminators speced as 49.9 Ohms +/- 1 percent, at 0 to 20 MHz with the phase angle of the impedance not to exceed 5 degrees, which is relatively good. The coax is allowed to have sinusoidal +/- 3 Ohm ripple at spacing of two meters or less (on top of the 50 +/- 2 Ohms of the cable), and that's probably dominant, I've seen people hand select MIL-R-11 carbon composite resistors for "50" ohms, and then wonder why the VSWR is so gross at higher frequencies. They might as well have used a wire wound.

First time I'm working at Ames - I ask a tech to build a six foot long cable of RG-214 with UG-21 type N's for a radar test (5 GHz). He comes back about an hour later with a nice looking cable. I ask him "did you test it?". He whips out his Simpson 260, center-center, shield-shield, nothing (open) from center to shield. "Yup - it's OK." We had a nice half hour lesson as I showed him how to use a slotted line and VSWR meter, and how to measure insertion loss with a shorting plug, and how it differed from the results using an open.

Oh, so you don't like my Exabyte 8205s and 8505s? ;-)

I dunno - we've been using it for years, and it hasn't killed us yet. (I know, I know - it will).

Gotcha

Actually, I shouldn't complain - my "RF" tool box has more adapters than you can shake a stick at, though I am missing my WR-112 to clip leads. ;-)

When I moved to this house, I initially set up using 10Base2, because it was quick. The following winter, I spent one weekend in the attic pulling CAT 5 to each room (why not), including eight drops in the den. Only when I was finished did I think it might have been a good idea to replace the US$2/mile cable that the klowns had for the phones.

Old guy

Well, that's correct. The 802.3 MPE (Manchester Phase Encoding) waveform concentrates most of it's power around 10MHz. The

10Mbits/sec data rate only requires about 30Mhz or bandwidth to operate. I don't see any reason to characterize the cable beyond its highest operating frequency.

Mine was a bit fancier. 555 driving some ECL gates to a fast switching xsistor with a clamp diode to prevent saturation (which would trash the risetime).

This one seems to be too crude:

does explain the principles involved.

I never had to deal with breaks in the cable. However, damage to the cable was a major cause of extended troubleshooting exercises. In one warehouse, the yellow cable was snaked through the overhead. No problem getting to the cable except that it was 20 ft off the floor which was about 3 ft too high for my tallest ladder.

The yellow coax was so stiff that it wouldn't bend with less than a

1ft radius anyway. However, that didn't stop anyone from trying to bend it across a sharp corner. The problem was always the same. Someone's workstation was a bit too far from the probe transceiver. DB15 extensions were impossible to find. The culprit certainly was not going to re-arrange their office layout for the convenience of the cabling. So, they give a good hard tug on the cable and try to brute force into giving them a few extra inches of cable length. If the cable bend radius started out at 1ft, it was now about 1 inch. Some of the buildings had metal studs in the walls and were capable of cutting the cable in half. I recall one 300ft run that had 3 or 4 cable splices installed. Cheapernet installs had exactly the same problem except that the cable was even more fragile. The problem didn't go away until we went to 10baseT.

As I vaguely recall, 4PF maximum. Very lightly loaded considering that the coax cable was about 25PF/ft.

Major overkill. I don't think any of my junk VSWR test equipment or directional couplers are accurate enough to measure that at low VSWR's. I would have to use a bridge to get the accuracy over the frequency range.

The reason for the tight specs had nothing to do with VSWR. 10base5 and 10base2 both use the DC levels on the coax for collision avoidance. The transceiver has a current source and uses the two terminators as a load to get the exact voltage required. Variations in typical production and installation, plus coax copper losses, caused the tolerance accumulation to potentially cause this voltage to drift out of spec. Rather than transfer the cost of a high tolerance current source to the transceivers, it was cheaper and easier to demand that the terminators were close to perfect. Eventually, everyone figured out how to make cheap precision current sources, so the terminator tolerances didn't need to be that critical. However, once written, such specs tend to be cast in stone.

The 10base2 Cheapernet terminator specs are something like 51 ohms,

+/- 5 percent. 10% will work. Unfortunately most of them were built with carbon composition resistors, which a slightly hygroscopic and will therefore tend to drift over time. I recently tested my pile of 50, 75, and 93 ohm terminators and found many of them were way out of spec. A quick bake in the oven solved that problem.

Sigh. You must work in a research or government environment. Nobody else I know could afford or has any interest in such details. Carbon comp resistors are terrible at higher frequencies but are probably just fine up to 30MHz. I vaguely recall tearing apart a 10base5 terminator and finding a single 51 ohm carbon comp resistor in parallel with something to get it down to 49 ohms. Resistor lead length inductance is probably the real killer.

I still have some slotted coax and waveguide lines floating around. I use them for skool demonstrations. These days, I use a network analyzer. It's nice to have everything displayed on a single Smith chart.

I'm not going to try and justify my use of crude tests. I was looking for continuity, not compliance with specifications. I don't have a test lab available at the customers. I also can't do much if I find something wrong with the terminator except replace it with another one. Also, knowing exactly why the specs are so tight on the terminator was a big help in knowing what I could get away with. I did find a few failures with the ohms-guesser method. Shorts were common. Defective transceivers were a problem. 117VAC on the coax shield (long story here) was found with a volts-guesser.

Incidentally, I still have about 4 Simpson 260 voltmeters in various levels of functionality. However, these days, I use a DVM.

I have an 8205 somewhere. I never got into the 8mm drives. Too expensive at the time and they had already developed a rather bad reputation. I didn't see it as much of an improvement of DC-600 size drives except for capacity. Instead, I went directly to 4mm drives and jukeboxes. Big mistake as it took a few years to demonstrate their shortcomings. I later went to AIT which seems to have fixed most of my complaints.

Have you ever had to do a massive restore from tape (while under pressure)? I have and I can assure you that reliability is not one of the better features of tape. I have a small collection of recovery tools that I use in case I get the all too common read errors. I've also had to use a tape recovery service to deal with tape errors, where the tape head had worn enough to be unable to read an old tape or where a new replacement drive would not read an old tape. For a time, one customer would put the old DDS-2 drive in the safe along with the tapes just to be sure they had the hardware to read the tapes. To add a challenge, HP was constantly screwing around with the tape format so that a random version of their firmware would not necessarily read tapes made with a different version. Sony was doing a heroic job of trying to stay HP compatible but eventually gave up.

This brings back nightmares of baby sitting tape restores that took all night and had to be watched constantly. I'm glad those days are over.

Oh, be serious. I have about 20 lbs of adapters and connectors. I would visit the local hamfests and retired hams and buy up all the adapters I could find. It didn't matter what type or flavor. Best investment I ever made. Every Field Day, about a dozen adapters evaporate, but I have spares. In this case, BNC to F adapters are very common in CATV work to interface to the test equipment. I carry a pile of them. There's almost no loss but admittedly, they are a rather bad 75 ohm to 50 ohm match. At 10Mhz, it's tolerable.

Incidentally, a demonstration I like to give at radio club meetings is grabbing one of my adapter boxes and stringing as many adapters in series as possible. I usually have a string about 6ft long. I attach a VSWR meter at both ends, dummy load, and 450Mhz transmitter. I then ask the assembled horde what they would predict for the loss. Conventional wisdom says that adapters are evil abomination and should be avoided at all cost. It turns out that the adapter chain has about the same loss as an equivalent length of RG-8/u. So much for the lossy adapter theory.

I use CAT5 for everything including video. About 5-7 cents per ft which is cheaper than coax. I did a remodel in about 1995 and was able to run conduit to various places. The size varies from 1/2" to

1" schedule 40. If I need to run something, I just add it to the tangled mess. Of course, I ran the conduit from where I needed it least, to where I thought it might be useful. That resulted in more cables under the desk and along the floor. I also have about 500ft of fiber in the pipes, which has yet to be useful. If I had to do it today, I would use the blue flex plastic wiring conduit instead of schedule 40.

Neither did the guys at DIX. There were tradeoff - the solid center conductor is to provide a constant depth target for the stinger in a vampire clamp. That was one of the changes between the original 3Base5 (which did spec RG-8/U) and version 2 (10Base5). In theory, skin depth would prefer stranded, or if solid, a silver plating, much as the better hard lines use.

The LH0002 has the drive capability - it's meant as a 50 ohm cable driver, but it's only categorized to 50 MHz (though it's capable of 150 MHz with a little tweaking).

Well, that should certainly keep it out of the way of the janitors. In most of our installations, it's tie-wrapped to the suspension for the false ceiling. The electricians and HVAC guys are all aware of the cable, and avoid it. Wish they'd do the same with the fiber.

We have extension cables out the whazoo - it's how we train the interns every quarter. Two foot steps from 2 to 16 feet. Rarely need longer.

Absolutely

Don't have the problem. All of our overhead drops go to wall plates. We only have one room with under-floor cables, and nearly all of those also go to wall plates. The few that were not were knotted around the false floor supports.

That was the main reason we never went to thinnet. That, and the vanity type who didn't like all those cables running around. Still have a secretary in mahogany row like that. We had cables ties to the underside of tables and desks so she wouldn't see them and complain.

That's about a 1.01:1, or a 46 dB return loss. Directivity of less than

40 dB would make it undetectable. Accurate measurements at that level are extremely difficult.

Two out of three

And number three - I had my 1st class phone with radar endorsement at 18. Of the RF type projects I've worked on, 1 was VLF, a large handfull were VHF, but the vast majority were above 5 GHz. And yes, I did moonlight several times as a transmitter engineer at broadcast stations. Even a

1.1:1 gets warm when you have 10 KW forward. ;-)

As you mention, 10 MHz isn't that critical. If you have ever looked at the applicable MIL specs, you'd know that plenty of other things are allowed and will significantly effect the observed resistance and reactance of resistors. The one time thermal shock when soldering the resistor being just one example.

When I was in this racket for keeps, I had three lines for 100 MHz to

18 GHz. Below 100 MHz (which I didn't work to much), we had to make do with couplers.

ACK that - the best coupler I had access to for 10 MHz had a directivity of around 18 dB - meaning a 1.28:1 could show as perfect (or as a 1.66:1) depending on phase angles. And finding a sliding load that is accurate at that frequency...

We didn't do that much "new work", meaning installing a completely new coax. When we did, we were testing at every step, so it was a simple "what did you just change". Adding drops were much the same. You knew the link was satisfactory when you started, if it was borked when you were finished - it was probably what you did.

We had/have a reasonable failure rate.

That's what interns were for. ;-)

I broke my last VOM about 8 years ago - been using DMMs ever since.

How 'bout the time the registrar was deleting expired accounts, and fumble fingered. The speed at which a mistyped command executes is directly proportional to the amount of damage done. She didn't mess around just wiping an entire partition - NO!!! She got the whole d4mn drive. It only effected about 200 users, but everything they had done between the nightly backups and the little typing error was gone. Took nearly three hours to restore, and was only that quick because the drive she erased was one that had a full backup overnight, rather than something earlier in the week, and nightly incrementals since then. There were a bunch of severely unhappy users. The registrar quit that week, and went back to hustling tables at the TGIFridays.

Good old UnSureStores. We used them for a while, but I think we're using Seagates now. "Not my problem"(tm)

No longer in the RF business, so my selection is much limited. But I had every 50 Ohm connector known to man from HN down to SMC, including APC-7s Most of my work was in N or SMA, and neither is rated very high on insertion cycles. We used the adapters, because when they got old, we could just toss 'em. It was a lot cheaper than replacing the connector on the test equipment.

There actually is a 75 Ohm BNC as well as a type N - Amphenol builds 'em. I did virtually zero work at 75 Ohm, except as matching sections. Even that was rare.

RG-8 at 450 MHz is within spec, but I'm starting to prefer RG-214 at that frequency for more consistent VSWRs. Some people actual tolerate RG-8 up to one or even three GHz. Not me. The double braid makes a substantial difference. Same for RG-142 vs. RG-58. The usual problem of multiple adapters is VSWR, rather than insertion loss. If they're quality adapter, neither the loss or VSWR should be that bad.

I wanted to do that. The boss here said no. I was actually planning on one inch everywhere. She didn't like the concept of me bashing holes in the wall to get it in.

When I have to go to fiber, that's probably how I'm going to go. Right now, I've run tests with Gigabit copper, but I see a lot (10%) of packet errors.

Old guy

How lavish. All of my early 10base5 and 10base2 installation were in "industrial" environments. That's where nobody cares about what it looks like as long as it works. Cables hanging from the overhead were standard. I don't recall ever running ethernet through the walls to wall plates. Everything was exposed, ugly, and messy. Works better that way.

Those are still around. I stock 4 boxes of CAT5, where the only difference is the jacket color. White, beige, grey, and blue. Well, actually there are two other boxes with plenum wire and a roll of red stranded CAT5 for making jumpers. I give the secretaries the choice of colors and invariably, they want some color I don't stock. Last week, I had to buy 1000ft for green CAT5 just to satisfy one inferior decorator. Also, if they're into Feng Shui, run away. I've had to negotiate the exact location, direction, color, and termination on the basis of how it affects the flow of chi.

2nd phone at 18. 1st phone with radar at 19. (Took me a while to find the old licenses).

Mostly VHF/UHF land mobile for me. Some HF design. 9 years working for Intech Inc on marine radios. 2 years for Granger Assoc on microwave. Everything else are various small business adventures and consulting. Got tired of RF and dived into computers, where I successfully repeated all my previous mistakes.

At the first FM transmitter I baby-sat, there was a warning that if the VSWR meter (Bird) every moved from the peg, the final would probably blow. At a different nightmare, I had to risk my life grabbing radios out of the building as blocks of ice the size of desks came down from the TV tower because the automagic VSWR meter relay had failed to start the de-icers. Wheeee...

I also have some "line stretchers". However, I'm a big fan of using bridges for precision measurments. While not exactly precision, that's how the Bird and MFJ antenna analyzers work. It's difficult to build a really broadband HF directional coupler that is flat from 1.6 to 30Mhz. I did that for a VSWR sensor and power guesser in one of the HF radios I designed and had to use two different types of ferrite materials to get the bandwidth flat. No fun.

Gaak. I charge by the hour so everything was a rush job. Throw everything together and hope for the best. Test only when done. I don't like doing it like that, but the labour content would have been double if I had stopped to test every connection as I went along.

That's what I really liked about 10base2. If you made a mistake in the cabling, everyone crashed simultaneously. I never had a problem with nobody noticing a problem. The entire company would be up in arms screaming at me. I kinda missed that with 10baseT and switches, where I could totally screw up a segment, and nobody would notice.

They're not disposable. They would have died finding that one.

10base2 run between two buildings. Coax grounded at both ends to AC power ground. We lost the ground (or neutral) in one of the buildings making the 10base2 coax the AC power ground return for the entire building.

Medical office database server was trashed when the vendor installed a program update while everyone was still logged in. Only option was to restore all the data. DDS-2 drive took about 6 hours (i.e. most of the day) to restore from backups. I had to sit there and accept verbal abuse from the entire medical staff because it was taking so long. I didn't have time to do a proper verify or CRC on the data files, so we just went live with what was restored. I was lucky that time, but not every time.

I forgot to mention DLT. That worked fairly well with few errors. However, it was rather expensive and the drives needed constant cleaning and ocassional rebuilds. In general, the tapes were transportable between different drives and error rate was very low. Recommended.

I did some work with CATV. Actually, I setup and built a bootleg CATV system in about 1975 around the neighborhood. At its peak, we had about 15 house on the system. It got shutdown because the local cable company got irate and claimed I was breaking numerous rules and ordinances. Long ago, I also worked for Subscription TV in Smog Angeles. The 75ohm BNC's are exactly the same dimensions as the 50ohm BNC's in the area around the center pin, PTFE sleeve, and shield fingers. However, the cable crimp diameters are different. Not exactly 75 ohms, but close enough for video.

My string of adapters showed almost no VSWR at 450Mhz. However, I cheated a bit. I avoided UHF connectors and right angle adapters. I also didn't use any non-characterized adapters such as phono. Another fun test was a long string of BNC "T" connectors in series. The short stub cause a small amount of VSWR and possibly some leakage, but the effects were rather small. I think I had about 50 connectors in series.

They're not. The point was that the various pundits that proclaim that ALL adapters are lossy or evil are totally wrong. For most applications, adapters a fine.

So far, I haven't had to do drywall rework. The main vertical pipes and splice boxes are hidden behind removeable wood panels. Another is under the stairs. Nail plates over all the fire breaks and some studs. However, FNT flex non-metallic tube (smurf tube) would have been much easier. However, the stuff is not up to code for many applications which might cause problems with the building inpsectors.

That's awful. I don't see anything that bad. Almost all my gigabit stuff is monitored with SNMP based managed switches. I just logged into one of my busier installations and noted less than 0.5% error rate for about 300GBytes or traffic per day. Gigabit has FEC (forward error correction). If you're getting 10% uncorrected errors, then you've got a wiring problem. My guess is split pairs or rotten connections. I've also had problems where I ran the CAT5e (before overpriced CAT6) next to large metal objects (rack rails) or near magnetic interference sources (flourescent ballasts, motors, ferroresonant xformers, etc). I also had problems with stranded wire patch cables and gigabit. Borrow a cable certifier and run some cable tests.

Everything was exposed, ugly, and messy. Works better that way.

Our industrial areas were limited, but even there the stuff was mainly out of sight. Tends to reduce accidental damage.

We didn't have that much CAT5, and it was almost always a gray, with some older stuff beige. We also had a limited supply of green, but they were cross-over cables only.

We follow the Ford Mantra - any color you want as long as it's black^Wgray.

I don't know if it's hiring policy or what, but we don't seem to have any of those.

Got the 2nd + radar, then the 1st - about a month apart. Was in the service in Denver, and had to fit the tests in between official duties.

I was doing computers in the 1960s as part of the system I was tech-repping in Japan.

I mainly did AM and UHF TV repeaters. I lucked out in not having much hardware problems, so it was mainly just keeping the logs up, and making sure the air filters got changed regularly. Chief engineer would peak the tuning quarterly, whether it needed it or not ;-)

I was raised in the North East, but starting in the mid-1960s, spent most of the time in warmer climes. Yes, I did have one occasion when I was driving in snow (Sunol pass on I-680 between Fremont and Livermore - a whole 980 feet above sea level), and there were occasions when I saw snow on the hills above San Jose, but I've mainly forgotten what snow and freezing drizzle is. Not missing it one bit, either.

More than an octave is always going to be difficult. Nearly all of the stuff I worked on was narrow band - 10% was wide band. Still stuff like the slotted lines could cover an appreciable range. The last FAA project I worked on was MLS, and we had a 1 percent bandwidth. Waveguide everywhere and dual directional couplers (loop) that had been hand tweaked to provide

46+ dB directionality. I'd hate to be the poor sod who was assembling those.

I dunno - the initial install and termination was one step, and as soon as we had the first drop working, we had a system on the wire to ping. Our "standard" was 'ping -s 8192 -c 25' which results in 150 packets. If we saw a single drop (and don't forget that with a -s 8192, that results in six packets that need to be faultless), we'd try again. A second "failure" or more than a single drop in the initial ping was rework time.

A bad vampire install on 10Base5 was the same. Had that happen a couple of times - no thank you.

That's why we wanted that first drop running something to ping. As soon as the drop was wired, and the far end connected to the central point - we'd throw a test set on and watch the lights. This detected the common wiring errors. Then a lap doggy, and a ping test. If that worked, on to the next mess. If not - find and fix.

They're not???

Wowser! The facility wire bender was trained by Edison or Tesla, or somebody, and he was rather dogmatic about wiring safety. Every training course I've ever encountered has demanded one and only one ground. Actually, between buildings, we ran twisted pair to isolation transformers on both ends, and used half repeaters. About

1992, that got replace with fiber.

news://comp.risks/ - that's common place, and people NEVER seem to learn.

That's normal. The network can be down for ten minutes, and we hear about it from Corporate on the East Coast, even if it's midnight here.

Tape drive cleaning is a given here. I'm no longer involved, but with

8mm drives, we were running about 7 hours a night per drive, so every Tuesday was cleaning day. Every drive in the place. Tuesday is also the day that tapes go/come off site, so the guy who collects tapes is the one who does the cleaning.

At home, I've recently switched to redundant drive backups. I have two cheap systems each with two 120 Gig hard drives, that have multiple partitions - each one mirroring one of the drives on the servers. Hard drives are getting reasonably cheap - I paid US$50 each for these. The important stuff still gets burnt to CD, and lives off site.

I don't use them, but my understanding was that the dielectrics were different in order to bring the impedance in line, while maintaining the same intermatability.

UHFs were never spec'ed for impedance, although they've been used in RF since before WW2. Right Angles? Yeah, they've never been able to get a decent VSWR. There was a company (might have been Omni Spectra) that used to advertise pre-built cables of 141 semi-rigid with impossibly short radius turns that fit the same space as a 90 degree connector, but had VSWRs down in the 1.02 + 0.007GHz :1 VSWRs which was little worse than the guarantee of an SMA straight plug. I've also seen it done with quarter inch hard line in a type N, but vaguely remember that the cost was astronomical.

As long as you're low enough in frequency, that's true. Things start to go south on you above 3.0 GHz, when that 16 mm stub becomes a significant part of a wavelength.

Single floor slab, and relatively low attic space (most rooms have cathedral ceilings). The boss isn't interested in extraneous wood trim strips - yeah, I thought of that too. I did hide some of the runs to points on the outside walls behind the base molding.

If we ever build a new house, there will be some added features. If you look back, it wasn't that long ago that phone wires went to one (at most two) places in the house, and the TV lead came through the window. My neighbor, who is a retired school principal still can't figure out why we need six computers in the den (neither can I). The other neighbor is a CIO with a major bank, and she can't understand why there are three networks in the house. (1 is company, 1 is the normal one, and the third is for play and backups.) One of the guys I work with just built a new house. Conduit in every room with two fibers - the "den" has six drops. The patch room is an air conditioned closet in the garage.

Only tried once - I had to borrow Gigabit gear, as I haven't seen the need to buy it yet. Our network isn't that busy.

Magnetic - no, but the air ducts are steel, and bonded. They're also huge.

I suspect some of the problems are the patch panel, which is in a closet along with the firewalls and routers. I'm _reasonably_ sure I've got the pairing correct, and did take care to keep the pairs twisted as close to the terminations as possible (less than an inch), but I'm not sure that punchdown blocks go that well with Gigabit. The 10BaseT performance is OK - virtually nil errors.

Old guy