cisco dish v grid antenna

I want to get a high gain directional wlan antenna (it will be mounted in a fixed
position, not mobile) and I was thinking about a Cisco AIR-ANT3338 solid dish - they're
pricey but I expect excellence from Cisco. I've also seen these grid antennas about which
are a fraction of the price and yet advertise the same gain levels and narrow beamwidth.
Is there an advantage to getting the Cisco or am I just paying for the name? Thanks for
any advice.

tg wrote:
> I want to get a high gain directional wlan antenna (it will be
> mounted in a fixed position, not mobile) and I was thinking about a
> Cisco AIR-ANT3338 solid dish - they're pricey but I expect excellence
> from Cisco. I've also seen these grid antennas about which are a
> fraction of the price and yet advertise the same gain levels and
> narrow beamwidth. Is there an advantage to getting the Cisco or am I
> just paying for the name? Thanks for any advice.

why ?
what will it be locally connected to, and how far is the cable run ?
what will it be pointed at ?

On Fri, 6 Jun 2008 11:29:01 +0100, "tg" <(E-Mail Removed)>
wrote:

>I want to get a high gain directional wlan antenna (it will be mounted in a fixed
>position, not mobile)

It takes more than a dish to make a wireless network. What else you
got?

>and I was thinking about a Cisco AIR-ANT3338 solid dish - they're
>pricey but I expect excellence from Cisco.

Ouch. You must have money. About $700 plus shipping.

>I've also seen these grid antennas about which
>are a fraction of the price and yet advertise the same gain levels and narrow beamwidth.

Yep. About $60 plus shipping.

>Is there an advantage to getting the Cisco or am I just paying for the name? Thanks for
>any advice.

Solid dishes are usually slightly heavier than grid dishes, making
installation easier for the grid. In this case, it's not the weight
of the dish, but the weight of the mounting. The Cisco dish is made
from spun aluminum. The grid is made from either steel or cast
aluminum.

The solid dish will have a higher wind load than the barbeque grill
dish and therefore requires a more solid mount. However, if the grid
ices up, the wind load is higher for the grid (due to ice surface
roughness).

The solid dish has almost no pickup to the sides or rear, in the
direction of the dish, and is therefore better for RF crowded roof top
and mountain top installations. Solid dishes also block signals
coming from the rear at all frequencies. Grid dishes pass higher
frequency junk coming from the rear.

Solid dishes are usually made of aluminum, which will last for a long
time on a mountain top. Grid dishes are made from coated steel, which
doesn't do as well in a corrosive environment. One grid dish lasted
three months after getting installed in the exhaust stream of a diesel
generator.

Solid dishes can handle optional covers, which are useful for heating
and prevent snow accumulation. You can probably craft some kind of
cover and heater for a grid dish, but I've seen no commercial
versions.

Some solid dishes are more difficult to align, as the grid dish can be
bore sight aligned by removing the feed.

When dinged in shipping or during installation, solid dishes are a
pain to repair (I use the local body shop). Grid dishes are much
easier to pound back into some semblence of a parabola.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"ps56k" <(E-Mail Removed)> wrote in message
news:Pnb2k.7827$(E-Mail Removed)...
> tg wrote:
>> I want to get a high gain directional wlan antenna (it will be
>> mounted in a fixed position, not mobile) and I was thinking about a
>> Cisco AIR-ANT3338 solid dish - they're pricey but I expect excellence
>> from Cisco. I've also seen these grid antennas about which are a
>> fraction of the price and yet advertise the same gain levels and
>> narrow beamwidth. Is there an advantage to getting the Cisco or am I
>> just paying for the name? Thanks for any advice.
>
> why ?
> what will it be locally connected to, and how far is the cable run ?
> what will it be pointed at ?

the dish will be connected to a PCI wireless card in a pc
cable run will be about 10 meters or less
it will be pointed at another location that has an access point - I want a direct
connection to the other building, independent of the internet.

tg wrote:
> "ps56k" <(E-Mail Removed)> wrote in message
> news:Pnb2k.7827$(E-Mail Removed)...
>> tg wrote:
>>> I want to get a high gain directional wlan antenna (it will be
>>> mounted in a fixed position, not mobile) and I was thinking about a
>>> Cisco AIR-ANT3338 solid dish - they're pricey but I expect excellence
>>> from Cisco. I've also seen these grid antennas about which are a
>>> fraction of the price and yet advertise the same gain levels and
>>> narrow beamwidth. Is there an advantage to getting the Cisco or am I
>>> just paying for the name? Thanks for any advice.
>> why ?
>> what will it be locally connected to, and how far is the cable run ?
>> what will it be pointed at ?
>
> the dish will be connected to a PCI wireless card in a pc
> cable run will be about 10 meters or less
> it will be pointed at another location that has an access point - I want a direct
> connection to the other building, independent of the internet.
>
>
If your PCI card has a power output of approx 13 dBm.
The Cisco Antenna is 21dBi.
If you use 10 metres of LMR400 to connect them, say 2.5dB loss.

That would give you 13+21-2.5 = 31.5dBm which is 11.5 dBm more than you
are allowed in the UK.

You will need to consider changing antennas on both ends of the link to
stay within the limits, and for the link to be viable.

"ps56k" <(E-Mail Removed)> wrote in message
news:Pnb2k.7827$(E-Mail Removed)...
> tg wrote:

ps: I also have a fairly strong access point so I might at some point swap the ends around
and connect the dish/grid to my access point. It's just a case of spending my money wisely
that's all - I don't want to spend hundreds of pounds on a dish antenna if a grid antenna
will do exactly the same thing.

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Fri, 6 Jun 2008 11:29:01 +0100, "tg" <(E-Mail Removed)>
> wrote:

lots of info here Jeff, thanks very much.
On reflection I think a grid might be better for my needs as wind speeds do worry me. My
proposed outside installation location isn't dish-in-a-hurricane proof so I may have to go
for the grid simply out of safety and I'd much rather a storm wreck a £60 grid antenna
than a $700 dish antenna. If I mount the antenna inside then I'm back to deciding if the
expensive dish will be better than the grid antenna.

On Jun 6, 10:54 am, "tg" <t...@nospamevereverever.net> wrote:
> "ps56k" <pschuman_no_spam...@interserv.com> wrote in message
>
> news:Pnb2k.7827$(E-Mail Removed)...
>
> > tg wrote:
>
> ps: I also have a fairly strong access point so I might at some point swap the ends around
> and connect the dish/grid to my access point. It's just a case of spending my money wisely
> that's all - I don't want to spend hundreds of pounds on a dish antenna if a grid antenna
> will do exactly the same thing.

Nobody's saying this outright, but no, you don't even need to spend
$100 to get a decent antenna.

Our 12 dbi panel antenna cost $34 shipped, is tiny (4" cube) and
unobtrusive. Our farthest client on the antenna is a laptop about 500
meters away.

Just out of curiosity, how did you to conclude how much gain you need
for your system? Have you done any link calculations or tests? Do
you know what cable you are going to use and what it's loss is?

I suspect that all too often people just decide to "get the best"
which they imagine is the strongest or most powerful. But you really
need to match the tool to the job. You don't buy a sledgehammer to
drive a 16p nail, and you don't need 21 dbi dish/grill antenna to
connect with the building across the street.

Another comment: Running a fat antenna (LMR400) cable into a PCI
card could lead to damage. You may want to consider using a pigtail
as a strain relief - if you go with LMR400. With LMR2xx not likely a
problem, depends on length needed.

steve

tg wrote:
> Is there an advantage to getting the Cisco or am I just paying for the name?

You're paying for the name. Just because it says Cisco does not mean its
better - case in point, someone took apart a $500 Cisco radome yagi and
discovered it was identical to another one with a different branded
label for only $45.

Cisco AIR-ANT3338 2.4 GHz 21 dBi dish - $700
2.4 GHz 24 dBi Grid Antenna - $55