Re: Longdistance 5.8GHz p2p links: Low signal with17dbm :-(

I have some old WRAP 2C boards and I only use CM-9 cards with those.
I remember reading that WRAP boards can have problems when using high 
powered radios.

See the bottom of this page:

http://madwifi-project.org/wiki/UserDocs/Ubiquiti

Also see this:

http://madwifi-project.org/wiki/UserDocs/WRAP

Recent Alix 3D2 boards have enhancements made between the C and D revs 
where Pascal Dornier of PC Engines added some resistors and/or 
capacitors to make the board work well with the high powered radios.  I 
would recommend using Alix D series boards over the WRAP board for UBNT 
radios.  (WRAP is end of life anyway)

Like Tom says -- there is a power offset, so you should be getting a lot 
more power than what you are setting it to.  Search the UBNT forums / 
knowledgebase for info on the proper power offsets for SR5 and XR5

I'd be curious to hear how you do with a pair of Backfire dishes at each 
end and either UBNT XR5's, SR5's, or CM-9's since the backfire has 
something like 17 dBi of gain.
You can get one on the cheap from FlyTech USA here:

http://www.flytecusa.com/details.cfm?wid=223&wb=HG5817D

These have a 25 degree beam width for easy aiming -- you can also look 
right down the mounting bracket that comes with it like a gun sight 
before mounting the antenna to the bracket to get a good starting point 
when aiming.

In a point to multi-point setup I've done where I use a Pacwireless 
12dBi omni and XR5 on one end and a Backfire dish w/ XR5 on the other 
end where the radios are about 0.5 miles apart w/ clear line of sight I 
get readings of about -45 on both ends w/ 48 or 54 megabit rate and 
easily over 20 megabit throughput w/ radios at full power -- plenty of 
link margin there, but I haven't had the opportunity to add mileage 
between the stations (it's a temporary setup once a year anyway).  
Another unit off that omni that was a WRAP board with a CM-9 and 
backfire dish was picking up the omni at signal of about -60 on both 
ends and it was also about 0.5 miles away.

Now I can't say that setup would work with them separated by 20+ miles, 
but if I were to attempt it I would at least go to a backfire dish 
replacing the omni so there are dishes on both ends and use XR-5's for 
max power.  The units I use w/ UBNT cards are Alix 3d2's using the MMCX 
connector and a pigtail from L-com that is good through 6 ghz with 
LMR-400 coax 5 feet or less.  Perhaps a good very high gain grid mesh 
antenna on each end would be even better.  I've always liked the 
backfire dish though.

Hopefully some day I can try some long distance stuff -- I haven't had 
the opportunity yet but I have the gear if anyone in Massachusetts has 
access to places that can get line of sight several miles apart.

Good luck.

--
Eric Malkowski
BVWireless, LLC

Tom Sharples wrote:
> The Ubiquiti cards add around 9db internally to the reported level, if you 
> set the madwifi output power to greater than about15db. So you are getting 
> full output with txpower set to 17.
>
> Tom S.
>
> ----- Original Message ----- 
> From: "Beat Meier" <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, April 20, 2010 4:57 AM
> Subject: [Madwifi-users] Longdistance 5.8GHz p2p links: Low signal with17dbm 
> :-(
>
>
>   
>> Hello again
>>
>> I'm still stucking with the output power of 5.8GHz links.
>> Is there anyone who has modified madwifi hal to use full power of 5.8GHz
>> band of ubiquity cards (SR5)?
>> I need a 25km link in 5.8GHz and I really want to use my wrap boards
>> with madwifi driver.
>> I tried to modify the madwifi hal but the output did not change :-(
>> Nobody is using longdistance 5.8GHz p2p links which needs more than 
>> 17dbm???
>> I have 81dbm and as we now madwifi won't be able to work with this in
>> 5.8GHz :-(
>> It needs a level of at least 70-74dbm to work realiable...
>>
>> Thanks a lot for any hint!!!!
>>
>> Beat
>>
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