On 03/03/17 10:57, Harry Bloomfield wrote:
NY has brought this to us :
Do they use 2.4 GHz? I'd assumed/read somewhere that they didn't use a
resonant frequency of water for that very reason, and that 2.4 was
only available because no-one (eg military, broadcast) could use it
for anything else long-distance. On the other hand, with a dish aerial
to concentrate the available power into a narrower beam, maybe water
attenuation can be overcome sufficiently to transfer a usable signal
at 20 km range.

Much longer distances have been managed than that.

But probably NOT with *exactly* 2.4Ghz

When I was involved with this, the permitted power levels antenna gain
and rain issues meant a couple of klicks was pretty much the usable limit.

Long distance microwave hops are at a different frequency.


I really don't follow how a copper tank full of water, can attenuate a
signal more than the same tank, but empty.


Reflection and attenuation are different beasts


--
Canada is all right really, though not for the whole weekend.

"Saki"

On 03/03/17 11:16, Harry Bloomfield wrote:
What puzzles me, is that the signal strength graph show the usual slight
variations, but occasionally shows a massive spike in the signal
strength of some of the signals.

Multipath, reflections etc.

someone opening a metal fridge door behind the router, as seen from your
position.

etc.


--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".

The Natural Philosopher explained on 04/03/2017 :
But probably NOT with *exactly* 2.4Ghz

When I was involved with this, the permitted power levels antenna gain and
rain issues meant a couple of klicks was pretty much the usable limit.

Long distance microwave hops are at a different frequency.

It was an experiment with 2.4Ghz data link, as I remember staying
within the permitted power limits, but using some very specialised dish
antennas.

'In Flight Refuelling' rings a bell on this.

It was that experimental link, which prompted me to experiment with a
similar, though much shorter link across the village. I had it quite
successfully running for several months.

Lobster wrote:
On Thursday, 2 March 2017 21:54:06 UTC, wrote:
On Thursday, 2 March 2017 20:12:40 UTC, DerbyBorn wrote:
Daughter is trying to use WiFi instead of a wire travelling up the stairs.
What should she consider - and Extender that appears to boost the signal

Most respondent seem to be assuming that if you use a mains-borne ethernet signal, you're stuck with hard-wired internet rather than wifi. It's definitely not an either/or: eg I cured a wifi blackspot in my house (which has lots of thick stone walls) using one of these: http://tinyurl.com/jlagfrb) (or http://uk.tp-link.com/products/details/TL-WPA4220.html)

Extenders / boosters / repeaters boost the signal level, but because they share the same frequency band as the 'hub thing' they halve the speed.

I currently use my auxillary extender thingy on a completely different network to the main one, so my devices swap over to the best signal when necessary. I must admit I had a lot of grief getting it set up, and once it worked I just left well alone... I've never quite understood the whole speed-halving malarkey; am I avoiding it by what I'm doing? Or can I simply change the names of the two routers to match; or do they clash then? Ideally I'd much rather have just the one wifi network, for sure.

David


My wifi speed is 20X my broadband speed, so not important.

newshound wrote:
On 3/2/2017 11:27 PM, Harry Bloomfield wrote:
newshound was thinking very hard :
FWIW I have found the ring main units slow and unreliable. I can get
pretty much full speed (40 MB/S) with a wifi extender. I have two
cottages with a 2 to 3 foot wall in between (including the chimney
breast). There is a doorway knocked through, not line of site, but
signal diffuses / diffracts through it well enough. The master and
slave are both on the first floor, this provides coverage downstairs
and to the second floor above the extender. I had a fancy netgear
extender but this died after a few years, now I have a budget TP-link
one.

A 'cottage' suggests somewhere which maybe doesn't have many other wifi
signals to contend with. It is very different when there are lots of
other signals around, swamping the wanted one.

To be honest, I have never tried the mains units.

I can see the one from next door, and usually at least three from across
the road. They are well down on signal of course. I have no reason to
suppose they cause significant interference, I get much the same speed
cabled to the main router as on WiFi through the extender.

I worked on the design of mains data transmitting units some decades
ago. They suffer from 2 problems. They inherently generate radio
interference and the wired propagation distance can vary from a few feet
to hundreds of yards. I built the Spice models for various mains wiring
configurations. It was a very depressing scenario, particularly in
blocks of flats. The RF transmitting distances are inherently dependent
on the wavelength characteristics of the house wire lengths. You get the
same problems with longitudinal propagation in telephone cables.

On Fri, 3 Mar 2017 23:37:48 +0000, tony sayer wrote:

Try telling the 2.4 GHz point to point links that are here that.
One is 6 km the other only 4 km. Another site has around 20 km
and 15
km. Rain, hill fog, snow or all three didn't stop 'em working.

Do they use 2.4 GHz?

They certainly did, I'm not sure if they are still on 2.4 Ghz as
the
kit has changed a couple of times since the orginal installion 15
odd
years ago. That used Cisco Aeronet 350 series bridges, 15" dish
one
way and "long" yagi the other.

5.8 Band C is the preferred way nowadays works much better for longer
range links. We have got one in daily reliable use over some 18.7
miles...

Before the fibre arrived the backhaul was over a licenced 5 GHz link
of 25 miles. Was supposedly doubly rendundant but who ever selected
the kit didn't think as well as it did, as it found a way to fall
over. Only serious outage, possibly the only one short of (rare)
power loss at the sites, over several years. 100 Mbps IIRC.

--
Cheers
Dave.

On 04/03/17 10:05, Capitol wrote:
Lobster wrote:
On Thursday, 2 March 2017 21:54:06 UTC, wrote:
On Thursday, 2 March 2017 20:12:40 UTC, DerbyBorn wrote:
Daughter is trying to use WiFi instead of a wire travelling up the
stairs.
What should she consider - and Extender that appears to boost the
signal

Most respondent seem to be assuming that if you use a mains-borne
ethernet signal, you're stuck with hard-wired internet rather than
wifi. It's definitely not an either/or: eg I cured a wifi blackspot
in my house (which has lots of thick stone walls) using one of these:
http://tinyurl.com/jlagfrb) (or
http://uk.tp-link.com/products/details/TL-WPA4220.html)

Extenders / boosters / repeaters boost the signal level, but because
they share the same frequency band as the 'hub thing' they halve the
speed.

I currently use my auxillary extender thingy on a completely different
network to the main one, so my devices swap over to the best signal
when necessary. I must admit I had a lot of grief getting it set up,
and once it worked I just left well alone... I've never quite
understood the whole speed-halving malarkey; am I avoiding it by what
I'm doing? Or can I simply change the names of the two routers to
match; or do they clash then? Ideally I'd much rather have just the
one wifi network, for sure.

David


My wifi speed is 20X my broadband speed, so not important.

Is it 20x the speed your media server can download HD videos at though?


--
"When one man dies it's a tragedy. When thousands die it's statistics."

Josef Stalin

On Friday, 3 March 2017 20:53:54 UTC, Dave Liquorice wrote:
On Fri, 3 Mar 2017 09:28:24 -0800 (PST), Lobster wrote:

I currently use my auxillary extender thingy on a completely different
network to the main one, so my devices swap over to the best signal when
necessary. I must admit I had a lot of grief getting it set up, and once
it worked I just left well alone...

Is that another wired AP? If not how does it get it's connection to
the LAN?

Yep. Setup here comprises a Virgin Superhub 2, in modem+router mode, which spits out WiFi on SSID 1, connects to a conventional CAT5 LAN, and also to an adjacent 'Powerline' device which pumps my network signal into the mains. At the far end of my house is the TP-Link PowerLine device, which just provides WiFi for that area, on SSID 2

I've never quite understood the whole speed-halving malarkey;

On a given channel only one thing can transmit at a time. With a
repeater (aka extender) retransmitting on the same channel as the AP
each packet is transmitted twice, once from the AP then again from
the repeater. Thus halving the number of time slots available.

OK. Does that apply only to a wifi extender; ie one which sucks in a weak signal and boosts it over a wider range (if I'm getting that right?)

... am I avoiding it by what I'm doing?

Certainly if the two APs are on different channels. If on the same
channel and they can't hear each other there is potential for a
"mush" zone between them where a device can hear both and if the APs
transmit at the same time stomp on each other. Also the device may
start switching between them.

Or can I simply change the names of the two routers to match; or do they
clash then?

The SSIDs can be the same and even on the same channel provided the
traffic levels aren't high on both at the same time.

So (assuming low traffic, which is fair enough) are you saying there's no benefit to my current arrangement at all, and I'd be better off putting both on the same SSID, same channel then?

On Sat, 4 Mar 2017 05:47:06 -0800 (PST), Lobster wrote:

Yep. Setup here comprises a Virgin Superhub 2, in modem+router mode, which spits out WiFi on SSID 1, connects to a conventional CAT5 LAN, and also to an adjacent 'Powerline' device which pumps my network signal into the mains. At the far end of my house is the TP-Link PowerLine device, which just provides WiFi for that area, on SSID 2

I've never quite understood the whole speed-halving malarkey;

On a given channel only one thing can transmit at a time. With a
repeater (aka extender) retransmitting on the same channel as the
AP
each packet is transmitted twice, once from the AP then again from
the repeater. Thus halving the number of time slots available.

OK. Does that apply only to a wifi extender; ie one which sucks in a
weak signal and boosts it over a wider range (if I'm getting that
right?)

Yes.

So (assuming low traffic, which is fair enough) are you saying there's
no benefit to my current arrangement at all, and I'd be better off
putting both on the same SSID, same channel then?

Same SSID I pretty sure isn't a problem at all. If the coverage areas
of the two AP's overlap having them on different channels will stop
them stomping on each other or having to wait. It's also a bit
dependent on whether the two APs can hear each other if on the same
channel. If they can they won't transmit at the same time. If they
can't they might which will make things messy in the overlap area
when traffic levels are high.

If the total traffic from each AP is greater than the maximum
bandwidth available on one WiFi link. ie if the WiFi can support 40
Mbps, you could have one AP shifting data at 38 Mbps the other
shifting data at 2 Mbps without serious problems. But is that 2 Mbps
became 10 Mbps it would start to get messy.

--
Cheers
Dave.

The Natural Philosopher wrote:
On 04/03/17 10:05, Capitol wrote:
Lobster wrote:
On Thursday, 2 March 2017 21:54:06 UTC, wrote:
On Thursday, 2 March 2017 20:12:40 UTC, DerbyBorn wrote:
Daughter is trying to use WiFi instead of a wire travelling up the
stairs.
What should she consider - and Extender that appears to boost the
signal

Most respondent seem to be assuming that if you use a mains-borne
ethernet signal, you're stuck with hard-wired internet rather than
wifi. It's definitely not an either/or: eg I cured a wifi blackspot
in my house (which has lots of thick stone walls) using one of these:
http://tinyurl.com/jlagfrb) (or
http://uk.tp-link.com/products/details/TL-WPA4220.html)

Extenders / boosters / repeaters boost the signal level, but because
they share the same frequency band as the 'hub thing' they halve the
speed.

I currently use my auxillary extender thingy on a completely different
network to the main one, so my devices swap over to the best signal
when necessary. I must admit I had a lot of grief getting it set up,
and once it worked I just left well alone... I've never quite
understood the whole speed-halving malarkey; am I avoiding it by what
I'm doing? Or can I simply change the names of the two routers to
match; or do they clash then? Ideally I'd much rather have just the
one wifi network, for sure.

David


My wifi speed is 20X my broadband speed, so not important.

Is it 20x the speed your media server can download HD videos at though?



Irrelevant, wouldn't even try to download videos. Video transmission is
via modulators and UHF distribution network. Quality is well below SD!!
but as was found nearly a century ago, people will watch crap and not
notice.

In article , The Natural Philosopher
scribeth thus
On 03/03/17 10:24, NY wrote:
Try telling the 2.4 GHz point to point links that are here that. One
is 6 km the other only 4 km. Another site has around 20 km and 15 km.
Rain, hill fog, snow or all three didn't stop 'em working.

Do they use 2.4 GHz? I'd assumed/read somewhere that they didn't use a
resonant frequency of water for that very reason, and that 2.4 was only
available because no-one (eg military, broadcast) could use it for
anything else long-distance. On the other hand, with a dish aerial to
concentrate the available power into a narrower beam, maybe water
attenuation can be overcome sufficiently to transfer a usable signal at
20 km range.
2.4 is not used much for point to point. It is used for 'village wifi'
and can get a km or two with the right antennae, BUT it does tend to
stop working in rain

2.4Ghz is probably good for rain radar tho.

Point to point is at a lot of other frequencies.

Rain and microwaves is a very interesting subject. generally te higher
the frequency the worse the effect BUT there are as has been pointed
out, deep and narrow notches in longer wavelengths like 2.4Ghz.

Which is why 2.4Ghz is left for 'amateurs' use. In practice that means
microwaves, wifi, model radio control, some local telemetry and a few
other short distance uses.

Tony Sayer will be along with chapter and verse on what is used
professionally.


Well we do use 1.5 Ghz for a few links, very long ranges are possible
but the bandwidth isn't that much but 40 odd miles sometimes is
achievable.

Sometimes 18 Ghz, wide bandwidth at these frequencies. And yet to try
them but Ubiquity do have a Fibre link a gig odd thruput at 24 GHz


Have a play with this tool, it will show you what is possible using 2.4
and 5.8

https://airlink.ubnt.com/#/
--
Tony Sayer