Detachable antennae: PMR446 vs. Wifi

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Detachable antennae: PMR446 vs. Wifi

Post by troffasky » 26 Jul 2011, 13:54

Why is it that the above is verboten on PMR446, but OK for the arguably more heavily contended 2.4GHz wifi band?

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Re: Detachable antennae: PMR446 vs. Wifi

Post by 26CAB40 » 26 Jul 2011, 13:58

Not really comparable.
One is for short range voice comms over 1km or so, the other is to provide wideband data services within a short range.
Chalk & cheese.
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Re: Detachable antennae: PMR446 vs. Wifi

Post by troffasky » 26 Jul 2011, 15:17

Sorry I wasn't clear in my OP. I meant in regulatory terms, not technical ones.

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Re: Detachable antennae: PMR446 vs. Wifi

Post by 26CAB40 » 26 Jul 2011, 15:27

Domestic Wi-Fi installations are not usually the target for hi-gain external antennae, we must presume they are for commercial installs.
The antennae available over the web, being sold to consumers probably exist within a 'grey zone' in that respect.
They are usually from international sources where regulations may vary.

Microwave equipment installed in commercial premises has to conform to many regulations of course.

External antennae for PMR446 are illegal.
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Re: Detachable antennae: PMR446 vs. Wifi

Post by Guzzy » 26 Jul 2011, 16:57

A lot of PMR446 radios use really pathetic and very lossy 'coiled spring' type antennas, if you put a 'proper' UHF antenna on them, you get a significant improvement in performance. Illegally, of course. ;)

There is quite a lot of experimentation with improvised WiFi antennas. You can have loads of fun extending WiFi ranges! :D
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Re: Detachable antennae: PMR446 vs. Wifi

Post by wind in the antenna » 26 Jul 2011, 19:51

The FCC were concerned about people using high gain antennas with WiFi. They brought about what I recall was a voluntarily manufacturers' agreement to use reverse SMA and TNC etc. RF connectors. This duly brought out a market in reverse gender antennas and adaptors and achieved nothing for their cause.

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Re: Detachable antennae: PMR446 vs. Wifi

Post by andykirby » 26 Jul 2011, 20:13

Agreed with that Guzzy! I can remember years back I bought a little 2.4Ghz magmount to connect to the wifi card in my old PC. Suddenly I could pick up some crazy fast AP from down the street :o

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Re: Detachable antennae: PMR446 vs. Wifi

Post by wind in the antenna » 27 Jul 2011, 00:29

Converted radio equipment
PMR446 users are reminded that their radios are only licence-exempt if they are built and
operated within the conditions of the exemption regulations. If modifications are made to the
equipment, such as adding an antenna connector, the overall maximum ERP or other technical
parameters must not exceed the permitted levels set out in the Interface Requirement.

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Re: Detachable antennae: PMR446 vs. Wifi

Post by bigbloke » 27 Jul 2011, 05:35

Hmmm...I've often toyed with the idea of recycling my old pair of Pye PF1's and nightcall unit onto 446 channel 8.

The antenna is definitely built in! :) The power can be wound down to 500mW , but the deviation would be a bit wide.

Have to work out the crystal frequencies and give it a go for some fun.

As for Wifi, before 4W video senders and similar powered CCTV camera senders in 2.4GHz I've had 5mb connections at
around 15 miles and 2Mb (when the tide permitted) at over 35 miles. the problem wasn't the RF signals, but having to use
atheros chipsets with a wireless router distro called Star-OS to enable the round trip ACK timers to be pushed out far enough
to get packets through reliably. And before anyone cries "Foul!" this was on channel1 ...under my ham callsign :)

Regards

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Re: Detachable antennae: PMR446 vs. Wifi

Post by wind in the antenna » 27 Jul 2011, 09:26

TX xtal freq (MHz) = fc / 36
RX xtal freq (MHz) = fc + 10.7 / 5

Crystals in both units are HC18u wire ended

The RX unit was fitted with either FC03219 filters for 25kHz spacing or for earlier issues, FC03208 for 50kHz spacing.

The antenna was often said to be built into many an unwitting rookie coppers right nostril. :lol:

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Re: Detachable antennae: PMR446 vs. Wifi

Post by Guzzy » 27 Jul 2011, 20:20

andykirby wrote:Agreed with that Guzzy! I can remember years back I bought a little 2.4Ghz magmount to connect to the wifi card in my old PC. Suddenly I could pick up some crazy fast AP from down the street :o
WiFi homebrewing at it's best:

http://cruftbox.com/cruft/docs/cantenna.html

http://www.turnpoint.net/wireless/cantennahowto.html

The only antenna project that comes with a free novelty lunch on the inside. :lol:

The original intention with these designs was to leach off other WiFi users, not so easy these days, most people have become much more aware of WiFi security.
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Re: Detachable antennae: PMR446 vs. Wifi

Post by bigbloke » 28 Jul 2011, 12:27

Cantenna ??? PAH !!! :lol: :lol: :lol: :lol:

WAY better off adding a new feedpoint to an old 60cm ASTRA sky dish !
and inverting it so that it looks as though its pointing at the sky not at the
ground .

A good 17dB of gain to be had !!

Wimo in germany used to make a circular polarised feedpoint for OSCAR sattelite
working that used to be a direct replacement for the LNB on these type of dishes.

[edit] couldnt find my picture so here's one from Wimo on an 80cm [/edit]

Image


1m dishes were even more fun :))

Regards

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Re: Detachable antennae: PMR446 vs. Wifi

Post by fez » 28 Jul 2011, 14:53

love playing with wifi, Got all sorts of antennas from helical, dish to yagi.

My fav is my commercial 2.4ghz dish.

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Re: Detachable antennae: PMR446 vs. Wifi

Post by Guzzy » 28 Jul 2011, 16:29

fez wrote:love playing with wifi, Got all sorts of antennas from helical, dish to yagi.

My fav is my commercial 2.4ghz dish.
I'm sorry, but I think you will find it damn hard to beat a Pringle's can.

Sure, it may not have as much gain as some of your fancy shmansy helical, yagi and dish antennas, but the construction process tastes much nicer! :D :lol:
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Re: Detachable antennae: PMR446 vs. Wifi

Post by wind in the antenna » 28 Jul 2011, 22:44

wind in the antenna wrote:
Converted radio equipment
PMR446 users are reminded that their radios are only licence-exempt if they are built and
operated within the conditions of the exemption regulations. If modifications are made to the
equipment, such as adding an antenna connector, the overall maximum ERP or other technical
parameters must not exceed the permitted levels set out in the Interface Requirement.

I'm a radio armature who made the switch to ariel none-bio
New Face in Hell

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Tony in Brighton
26TM9480
26FB298
G7TXU
----------------

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