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From: Dennis on 9 Jun 2008 21:03
Lots of good info there Jeff, thanks its appreciated.

For fun I went out and grabbed a $20 omni antenna, it claims to be 9
dBi... I figured for $20 it was worth a shot... Until I realized I'd
also need an SMC cable.. the new antenna needs to be raised away from
the case of the computer like the old 2 dBi one was.... surfing the
net I'm now realizing the cable is going to cost more then the antenna
did :(

Which brings me to my next question: How much loss is there per foot
of cable (50 ohm) I use? Is it significant enough for me to want to
get the shortest cable possible, or can I give myself some leeway and
get a 20-30 foot cable?



From: ps56k on 9 Jun 2008 21:22
Dennis wrote:
> Lots of good info there Jeff, thanks its appreciated.
>
> For fun I went out and grabbed a $20 omni antenna, it claims to be 9
> dBi... I figured for $20 it was worth a shot... Until I realized I'd
> also need an SMC cable.. the new antenna needs to be raised away from
> the case of the computer like the old 2 dBi one was.... surfing the
> net I'm now realizing the cable is going to cost more then the antenna
> did :(
>
> Which brings me to my next question: How much loss is there per foot
> of cable (50 ohm) I use? Is it significant enough for me to want to
> get the shortest cable possible, or can I give myself some leeway and
> get a 20-30 foot cable?

at the Wifi freqs - 2.4Ghz microwave - there is a LOT of loss per foot.
Here's a chart for common LMR type cables ...
http://www.universalweb.com/CustomCablesUSA/PDF/RF-LMR-Cables-Specs_CustomCablesUSA.pdf



From: seaweedsl on 10 Jun 2008 14:44
On Jun 9, 8:03 pm, Dennis <dennispub...(a)hotmail.com> wrote:
> How much loss is there per foot
> of cable (50 ohm) I use? Is it significant enough for me to want to
> get the shortest cable possible, or can I give myself some leeway and
> get a 20-30 foot cable?


Short answer is: LMR 400 loses .25 db per meter or 6.6 for 100 feet.
30 foot cable is only 2 db. Hawking has a 30 ft 400 that can be
found for $30. Will need a pigtail-adapter, too.

You can use this to determine loss for a given cable:
http://www.timesmicrowave.com/cgi-bin/calculate.pl

Enter 2400 Mhz for frequency if you using B or G.

>. the new antenna needs to be raised away from
>the case of the computer like the old 2 dBi one was....
>I'm now realizing the cable is going to cost more then the antenna
> did

You could use your existing cable for testing and just get an adapter
to start?
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