Interesting Quick Thought
falkle at sunsbeacshs.qld.edu.au
Mon Jan 21 12:33:19 EST 2002
i probably didn't make my comment on the pigtail from the usb wlan device to
the dipole mounted on thetv antenna boom should be of foam filled 50 ohm
cellflex or equivilent coax
----- Original Message -----
From: Anthony Symons <ant at sa.pracom.com.au>
To: Len Falknau <falkle at sunsbeacshs.qld.edu.au>
Cc: <smithy at mobsoft.net>; <wireless at lists.samba.org>
Sent: Monday, January 21, 2002 11:11 AM
Subject: Re: Interesting Quick Thought
> What about the co-ax? TV is 75 Ohm, and Lan (and most radio apps) are
> 50ohm. Also TV co-ax is usually very low grade. As for the RF switch, Ive
> seen people use a shielded relay (about $55) to switch so that when they
> transmit on one radio it switches the aerial to the transmit section, and
> then when they want to receive it would swap back to the receiving unit.
> But, it probably a) wouldnt be fast enough, and b) would drop out the TV
> on TX.
> Also, recieving and transmitting are a different kettle of fish. For
> transmitting you need a multiple of the wavelength. Preferable is exactly
> one wave length, but if size is/isnt a contraint you can half it, and
> probably double it, im not sure. 2.4ghz is pretty high frequency which
> gives it a small wave length. I have seen someone hook up a low frequency
> cordless phone to their tv aerial on a farm, get an SWR meter (tells you
> how much of your signal is reflecting off the aerial and coming back at
> your equiptment, which is bad) and then they trimmed the ends of their tv
> aerial untill it had a good SWR. Apparently it worked pretty well.
> But to take this approach with 2.4gz would require a very expensive SWR
> meter, as prices go up with frequency.
> Finally, Im not a ham, just a hobbyisit, and most of this comes from my cb
> days, so if any ham knows better please correct me.
> On Mon, 21 Jan 2002, Len Falknau wrote:
> > leaving aside the technical aspects the concept is great
> > you could use a usb wlan device and mount it in the waterproof enclosure
where the amplifier is (wonder how mush hash it would introduce into the tv
picture) then a pig tail out with a small dipole with reflector mounted on
the end of the tv antenna
> > cheap and easy with some braising rod
> > len
> > ----- Original Message -----
> > From: Ben Smith
> > To: wireless at lists.samba.org
> > Sent: Sunday, January 20, 2002 7:07 PM
> > Subject: Interesting Quick Thought
> > Hi Everyone,
> > I had a brief thought today. Everyone's main concern with wireless
networking is cost, It's great new technology and is actually reasonably
cheap to setup in comparison to other typical communication networks.
Anyway, my thought was is it possible to use existing TV antenna's on
peoples roofs for wireless networking, would it be possible with some
tweaking to enable the antenna to be used to both TV and WLAN? They run at
2 completely different frequencies but considering most TV antenna's pick up
both UHF and VHF then I'm assuming it might not be a problem. The other
thing would be WLAN needs literally no interferace between the antenna and
the WLAN card and good line of sight. There are also other issues to
consider such as If the TV and the WLAN is being used at the same time,
would it be possible to creat some dual connector similar to an RF switch or
> > There are several things to think about and consider, most people
would look at it and think it's not possible and that it's a waste of time,
but surely if we could eliminate the cost of the user installing an all new
antenna then the possibilities when it comes to expanding our wireless
networks would be limitless!
> > I myself will be doing some research into the concept and hopefully
come back with some interesting results. If anyone else has some thoughts
on this subject please tell me about them.
> > Best Regards,
> > Ben Smith.
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