Author Topic: The whole wifi con  (Read 10617 times)

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Offline IanMacdonald

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Re: The whole wifi con
« Reply #100 on: November 22, 2017, 10:06:48 am »

They already do... sort of. A lot of houses are built with foil backed foam insulation board in the walls like this stuff.

If they manage to install a smart meter here (Which will call for an armed escort) then some of that is definitely going in. At least I have an excuse that I was being 'green' by adding insulation, when they lose their spy signal.  :-//
 

Offline tooki

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Re: The whole wifi con
« Reply #101 on: November 23, 2017, 07:14:27 pm »
If no other devices are using the WiFi spectrum, channel 6 is the most likely to give the best performance but if the air is not empty, 6 will probably suck  ;D
In a totally vacant spectrum, why would 6 perform any better than any other channel? The channel bandwidth is the same for all the channels, afaik.
 

Online Ice-Tea

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Re: The whole wifi con
« Reply #102 on: November 23, 2017, 08:11:06 pm »
This.

Offline Monkeh

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Re: The whole wifi con
« Reply #103 on: November 23, 2017, 08:33:46 pm »
You may want to check where the channels sit in relation to that.
 

Offline tooki

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Re: The whole wifi con
« Reply #104 on: November 24, 2017, 06:27:42 am »
 

Offline borjam

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Re: The whole wifi con
« Reply #105 on: November 24, 2017, 07:08:40 am »
This.
Not all antennas are created equal :) Some are broadband designs that work well regardless of the channel you are using.
 

Online Ice-Tea

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Re: The whole wifi con
« Reply #106 on: November 24, 2017, 08:42:25 am »
Antennae (and other RF components) do not have flat return loss, insertion loss etc etc. As the middle of the band coincides with channel 6 (wel, rather somewhere between 6 and 11 actually...), this ussually means RF performance is a bit better there...

No need for a source: take any wifi antenna.

Offline borjam

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Re: The whole wifi con
« Reply #107 on: November 24, 2017, 09:14:06 am »
Antennae (and other RF components) do not have flat return loss, insertion loss etc etc. As the middle of the band coincides with channel 6 (wel, rather somewhere between 6 and 11 actually...), this ussually means RF performance is a bit better there...
Of course not, but there are broadband antennas with a broader region of low enough return loss, and there are narrow band anntenas.

Unless you are using a narrow band antenna tuned to a certain channel the difference will be negligible.
 

Online Ice-Tea

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Re: The whole wifi con
« Reply #108 on: November 24, 2017, 09:35:02 am »
The above is a typical wifi antenna. Wouldn't call it negligeable.

Offline wraper

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Re: The whole wifi con
« Reply #109 on: November 24, 2017, 09:45:14 am »
The above is a typical wifi antenna. Wouldn't call it negligeable.
Intentionally making antenna like this would not even make much sense as it works best at around channel 13. And it actually contradicts to what you said about channels 6 working the best.

 

Offline borjam

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Re: The whole wifi con
« Reply #110 on: November 24, 2017, 09:53:08 am »
The above is a typical wifi antenna. Wouldn't call it negligeable.
First: Typical antenna, in which context?

Second: RL below 8 dB can be considered quite harmless. Or am I missing anything?

 

Online Ice-Tea

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Re: The whole wifi con
« Reply #111 on: November 24, 2017, 10:08:23 am »
The above is a typical wifi antenna. Wouldn't call it negligeable.
Intentionally making antenna like this would not even make much sense as it works best at around channel 13. And it actually contradicts to what you said about channels 6 working the best.

You'll note I already requalified my statement: "(wel, rather somewhere between 6 and 11 actually...)  ;D

The above is a typical wifi antenna. Wouldn't call it negligeable.
First: Typical antenna, in which context?

What do you mean? Not sure I understand but lets turn this around: can you show me a wifi antenna that does not have RL dip in the 2.4-2.5GHz band?

Quote
Second: RL below 8 dB can be considered quite harmless. Or am I missing anything?

Depends on what you call harmless. At 8dB, 15% of your output power is lost. At 20dB (the 'dip') something like 1%.

Offline wraper

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Re: The whole wifi con
« Reply #112 on: November 24, 2017, 10:37:19 am »
The above is a typical wifi antenna. Wouldn't call it negligeable.
Intentionally making antenna like this would not even make much sense as it works best at around channel 13. And it actually contradicts to what you said about channels 6 working the best.

You'll note I already requalified my statement: "(wel, rather somewhere between 6 and 11 actually...)  ;D
No, if we say like this, then somewhere in between of 12 and 14 :).
 

Online Ice-Tea

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Re: The whole wifi con
« Reply #113 on: November 24, 2017, 10:45:29 am »
What about this: surely not Channel 1?  :popcorn:

Offline borjam

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Re: The whole wifi con
« Reply #114 on: November 24, 2017, 10:52:59 am »
Depends on what you call harmless. At 8dB, 15% of your output power is lost. At 20dB (the 'dip') something like 1%.
Which means a loss of .7 dB.

Economists think in percentage terms. RF engineers think in dB terms  :horse:  :box:
(I'm not an engineer myself, but a Physics drop-off, but certainly not an economist at all!).

Attached is the S11 graph of a really narrowband antenna. A HF tuned loop. You must retune even if you are making a 2 KHz change :)

(A MFJ-1788 loop)
« Last Edit: November 24, 2017, 10:56:47 am by borjam »
 

Offline wraper

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Re: The whole wifi con
« Reply #115 on: November 24, 2017, 10:53:35 am »
What about this: surely not Channel 1?  :popcorn:
:box: :-DD

 

Online Ice-Tea

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Re: The whole wifi con
« Reply #116 on: November 24, 2017, 11:16:20 am »
Depends on what you call harmless. At 8dB, 15% of your output power is lost. At 20dB (the 'dip') something like 1%.
Which means a loss of .7 dB.

Economists think in percentage terms. RF engineers think in dB terms  :horse:  :box:


*shrugs* Call it what you want. It's lost.

What about this: surely not Channel 1?  :popcorn:
:box: :-DD


 |O :palm:

Joking aside: not exactly the kind of antenna you'll find in off the shelf wifi equipment.

*waits for wraper to dig up an off the shelf piece of wifi equipment that has this antenna*

Offline borjam

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Re: The whole wifi con
« Reply #117 on: November 24, 2017, 11:35:21 am »
Joking aside: not exactly the kind of antenna you'll find in off the shelf wifi equipment.

*waits for wraper to dig up an off the shelf piece of wifi equipment that has this antenna*
Of course you can find good, reasonable and crappy antennas. I remember some antennas I tested a couple of years ago. Granted, they were cheap despite being attached to an (COUGH!)"N"(COUGH!) (*) connector, and the "radiating element" was just a more or less random piece of wire inside a plastic piece.

I tested 20 of them with a VNA and there were no two equals. But fine, the person who asked me to try them told me the cost was a hefty dollar a piece or so. These antennas were sold as "3G antenna" and they are all part of the same batch. Out of 20 I think that maybe 5 didn't even have a piece of wire inside.

This is more or less the equivalent of the fake ferrite suppressor you find in bottom of the barrel USB cables. Just a cylinder of plastic.

Note for the curious, that awesome VNA is not mine, it's at the University. My own VNA is cheaper than that VNA's calibration kit.


(*) The cough is due to the fact that the connectors were N compatible (you could plug them!) but they were more like a copy of an N connector. The quality of the centre ring was apalling.
 


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