Interesting Quick Thought

Anthony Symons ant at
Mon Jan 21 12:11:57 EST 2002

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 
>   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 something?
>   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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