Beginners guide to network switches

[jrwalliker]

Quarter-wave monopoles can be made to give an excellent match to 50 ohms without needing any extra matching components.

John

[Johnny B Good]

Assuming my experience with the GS608 is typical and you include it amongst the "Usual Suspects" list of "Things that need to be reset" when things go weird with the network, it works very well for weeks/months at a time. :-)

Yes, "modern"[1] unmanaged ethernet switches are about as "Plug 'n' Play" as it gets. As someone else in this thread pointed out, it's about as easy as using mains lead extensions (but without the overloading/fire and electrocution hazards).

These days there's no compelling case for specifying Fast over Gbit ethernet switches on cost grounds, especially as entry level Desktop PCs and proper Notebooks have been equipped with Gbit lan ports as standard fit for the past 5 years or more. This is true even if you still have older kit or "Novelty Gadgets" (games consoles, mobile phones, tablets etc) with nothing faster than a fast ethernet port to connect up to your lan.

Unlike the bad old days of ethernet hub technology when connecting a

10Mbps gadget would slow the whole of a fast ethernet lan down to just that speed, a modern Fast or Gbit ethernet switch allows all kit to communicate at their own speed limit.

A link via a Gbps switch between a 100Mbps device and a Gbps device will limit the data flow rate to that of the slowest whilst still allowing the Gbps device to exchange data with yet another Gbps device at close to 90% of the Gbps speed limit. Indeed, data transfers in an 8 port Gbit switch could go at full speed between all 4 pairs of connected computers simultaneously depending on the switch's total "packet store and forward" performance capability.

A quick perusal of the specs[2] for the GS608 suggests two independent links (two pairs of computers) can go at full speed before a third link will start to slow things down.

[1] And by "modern", I mean anything designed during the past 15 years or so (essentially any such kit that *isn't* an ethernet hub). [2] It speaks volumes for how far the internet (and networking kit) has evolved when, contrary to the experience of 15 years ago (post dial-up, 128Kbps always-on cable broadband), it would have been quicker to walk across the hall to the next room, from which to retrieve the packaging to let you extract the user guide from, just to check such specs than it would be to google "GS608 specs" and click the second hit to instantly download the same user guide as a pdf file as I did just now simply on account ICBA to walk across the hallway. :-)

[The Natural Philosopher]

You may think there are no (extra components) , but there are.

Even if they look like twisted bits of wire..

[The Natural Philosopher]

Generally half a 75 ohm - 36 ohm,

See...

You MIGHT use 50 ohms for that, but it will suffer from some reflections.

[jrwalliker]

A useful reference is: Antenna theory analysis and design by Balanis. About 1000 pages long.

[jrwalliker]

There is no need for any twisted bits of wire to make a quarter-wave monopole with a 50 ohm impedance at resonance.

John

[The Natural Philosopher]

A quarter wave monopole is always 36 ohms. End of discussion

"Since a half-wave dipole has a gain of 2.19 dBi and a radiation resistance of 73 ohms, a quarter-wave monopole, the most common type, will have a gain of 2.19 + 3 = 5.19 dBi and a radiation resistance of about 36.8 ohms if it is mounted above a good ground plane.[1]"

[jrwalliker]

As you wish. I'll just carry on doing the impossible then. (I do have a vector network analyzer for doing the measuremnts.)

John

[John Rumm]

You want to try my broadband - sometimes it would be quicker by post!

[maurice]

It looks like a 5 year old Turnip must have been at home sick, on the day the teacher chalked the word "if" on the blackboard.

michael adams

...

[The Natural Philosopher]

If it isnt, it still wont be 50 ohms

You may still choose to feed it from 50 ohms, and accept a crap VSWR, but that doesn't make the monopole a '50 ohm impedance antenna'

[maurice]

It looks as if he was also off sick on the day the teacher chalked up "is always" and "If it isn't" on the board, and asked the children if both could be true at the same time.

A very sickly child, by the looks of things.

michael adams

...

[The Natural Philosopher]

I assume you are of the Left persuasion, as this all out ad hominem continues?

You do realise how unpleasant and stupid you are appearing?

[9pl]

Of course we never ever see any ad hominem from you.

Oh, the irony.

[polygonum]

For many, I agree. But after the first wave of "of course it's gigabit" machines came out, there was a period in which a considerable number of machines reverted to Fast. Was somewhat surprised how many I saw.

[News]

In message , News writes

Job done! Thanks all. The switch arrived, was connected and it just works. Delighted. That has kept Son happy, and cost me a fiver.

[Mike Tomlinson]

En el artículo , News escribió:

Are you sure you got a gigabit one? The D-Link one closest to 5 quid (QuickFind: 351558) is 10/100 only.

You would have been better paying a little more for the TP-Link gig switch at 13 quid IMO. QuickFind: 721574

[News]

In message , Mike Tomlinson writes

Sorry Mike! Yes, you're quite right - I looked at the wrong figure on the invoice. What I bought was 9.15 plus VAT, so just under 11 pounds.

It is a 'D-Link GO-SW-5G - GO 5-Port Gigabit Switch', now showing on ebuyer as out of stock.

I never normally think about ebuyer, and only used this time because I followed a recommendation posted in another thread.

[Mike Tomlinson]

En el artículo , News escribió:

Think you did well there :) Glad it does the job for you. It really would have been silly saving a couple of quid to get a slower 10/100 one. You'll never regret getting a gig switch, especially if you start streaming movies or flinging large files around.

Yes, that's the Dremel-type tool and kit I posted a link to a while back. Is it any good?

cheers :)

[News]

In message , Mike Tomlinson writes

Indeed. The switch is used by son, so he can connect PC, Xbox and Playstation. I monitor our usage regularly, and it is amazing how it plummets whenever he is away. How he manages, I don't know. We (self and wifey) watch movies and stuff, wifey plays online games yet our usage seems minimal.

Well, it looks excellent. Haven't used it in anger yet, but will report back, when I do.