Re: 30 DB directional..

Most (but not all) of the below is true.   The issue is that the limits 
here are strict level limits, not relative. The bands
are not "forbidden", but "restricted".  The details can be found in 47 
CFR Part 15.205.

All 802.11 signals have side-lobes, as antenna gain goes up, the side 
lobes come with it.  This
is typically more of an issue when running on ch1 and ch11.  Ch1 has a 
center frequency of 2412MHz,
while Ch11 is centered at 2462MHz.   The nominal channel width of an 
802.11b signal is 22Mhz, so ch1
starts at 2401 (while the band starts at 2400), and ch11 ends at 
2473MHz (the band stops at 2483.5MHz)

The restricted bands of particular interest to 802.11b/g are 
2310-2390MHz and 2483.5-2500Mhz.  The limit
for both is 500uV/m (47CFR15.209).    Note the 10Mhz on both sides.  
(Do the math.)

Many here (and elsewhere) have heard me say that the real issue of 
attaching antennas with more gain
is not the EIRP limit but the potential for out of band emissions.  You 
have to knock the sidelobes down at
least as much as your antenna gain brings them up.

I don't agree that the limit for 100mW is 10dBi of net antenna gain.  I 
just happen to have seen two systems
FCC certified at higher levels than this.  One has a 25dBi antenna 
attached to a 20dBm transmitter (and this *is*
the power input to the antenna (ahem)) the other has a 29dBm 
transmitter, pulled back to 23dBm, attached to a 21dBi antenna.   Both 
passed (but both are expensive, essoteric designs.)   You'll need a 
very nice I/F or BP filter to duplicate the results.

On Jul 7, 2004, at 4:40 AM, Norm Nelson wrote:

> The antenna gain limit on all 2.4 Wifi gear 802.11b/g is determined by
> the forbidden band edges. On the low channel 2412 MHz the forbidden
> band edge starts at 2390 MHz.  Because of the Wifi modulation
> envelope, emissions in the forbidden band at the sides of the skirt
> goes up and down with antenna gain. The limit for 100 mW (advertised)
> +18 dBm (for real) is 10 dBi of net antenna gain. That  is antenna
> gain compensated for cable loss. On the top end the channel is 2462
> MHz and the forbidden band starts at 2483.5 MHz. The limit for all
> emissions in the forbidden bands around 2.4 GHz is 54 dBuV/m.
>
>
>
> On Wed, 30 Jun 2004 00:43:49 -0700, Jim Thompson <[email protected]>
> wrote:
>
>> 300mW (24.77dBm) + 30dBi = 54.77dBm EIRP.
>>
>> The maximum tx power you can *legally* run with 30dBi of antenna gain
>> PTP is
>>
>> 30 - (30 - 6) / 3 = 22dBm, or 158.49mW.
>>
>> In other words, you're about 2X (3dBm) too high in tx power.
>>
>>> -----Original Message-----
>>> From: [email protected]
>>> [mailto:[email protected]] On Behalf
>>> Of
>>> blitz
>>> Sent: Tuesday, June 29, 2004 4:32 PM
>>> To: [email protected]
>>> Cc: [email protected]
>>> Subject: Re: [BAWUG] 30 DB directional..
>>>
>>> Yes, they're good, and deliver plenty gain, just make dammed sure
>>> they're
>>> fastened to a SOLID structure, the pattern is very tight. They're
>>> heavy.
>>> You will want to inspect them regularly for mounting bracket
>>> tightness. I
>>> lost a mounting bracket in the snow one winter when it came loose. 
>>> The
>>> wind
>>> beat the snot out of the dish before I could get up to make repairs. 
>>> I
>>> shot
>>> 53 miles with a pair from a 535' building in a downtown to a mountain
>>> top
>>> with them with 300mw in commercial service. They're big, they 
>>> wind-load
>>> like hell, and they collect ice, and wind makes them sing, causing a
>>> lot of
>>> vibration. I double nut every bolt. They're a knock off of the 
>>> Prodlin
>>> (I
>>> think thats the spelling) dishes from the 1980's. Good stuff.
>>>
>>> At 16:19 6/29/2004, you wrote:
>>>> Hello everyone..
>>>>   Anyone ever use one of these?
>>>>
>>>> http://www.hyperlinktech.com/web/hg2430d.php
>>>>
>>>> 2.4 GHz 30 dBi High Performance Reflector Grid Antenna Model: 
>>>> HG2430D
>>>>
>>>> If so, got any real stats on em?
>>>>
>>>> Thanks..
>>>> C.
>>>>
>>>>
>>>>
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