Bloody 7db mag mount antennas from eBay!

These were both said to be 7db antennas for 2.4ghz.. The cost the same
and both came from Hong Kong. An email sent back to the seller of the
4.5db looking ant was no good as he thinks its a perfect 7db for
wifi.....

http://img182.imageshack.us/my.php?i...oto0023ja1.jpg

On May 30, 8:14 pm, AdamO <wepl...@gmail.com> wrote:
> These were both said to be 7db antennas for 2.4ghz.. The cost the same
> and both came from Hong Kong. An email sent back to the seller of the
> 4.5db looking ant was no good as he thinks its a perfect 7db for
> wifi.....
>
> http://img182.imageshack.us/my.php?i...oto0023ja1.jpg

After wandering his feedback(most happy with antenna) i'm guessing
alot of people are using 1.2ghz antennas on there gear :/

On May 31, 1:58 am, AdamO <wepl...@gmail.com> wrote:
> On May 30, 8:14 pm, AdamO <wepl...@gmail.com> wrote:
>
> > These were both said to be 7db antennas for 2.4ghz.. The cost the same
> > and both came from Hong Kong. An email sent back to the seller of the
> > 4.5db looking ant was no good as he thinks its a perfect 7db for
> > wifi.....
>
> >http://img182.imageshack.us/my.php?i...oto0023ja1.jpg
>
> After wandering his feedback(most happy with antenna) i'm guessing
> alot of people are using 1.2ghz antennas on there gear :/

Well if he says it's 7dbi, you'll have to believe it, unless if you
want to get it tested in a laboratory and prove otherwise.

We carry a 7dbi on our catalog as well, which has 2 coils:
http://www.confero24.com//product_in...-mount-antenna

Length of the filament is about 24cm.

HTH / c24

Half an idea of wavelength and antenna theory should do it.. But it
looks like that is more rare then first thought.

AdamO <(E-Mail Removed)> hath wroth:

>These were both said to be 7db antennas for 2.4ghz.. The cost the same
>and both came from Hong Kong. An email sent back to the seller of the
>4.5db looking ant was no good as he thinks its a perfect 7db for
>wifi.....
>
>http://img182.imageshack.us/my.php?i...oto0023ja1.jpg

Ummm, I don't think so. I can model the antennas easily enough if I
had accurate dimensions. Just looking at both and guessing, I would
give the one on the left about 5.0 dB gain. The problem is that the
gain peak may not be where you expect. Both antennas are intended to
be operated over a ground plane. That will reflect the signal upwards
to a considerable degree. You may have 5dB of gain, but it might be
at an angle of perhaps 20 degrees or more above horizontal (uptilt).
In the horizontal plane, the gain may be considerably less.
Fortunately, it's not much of a problem with such low gain antennas
because they have side lobes and mysterious gain peaks all over the
place.

However, that's not the real problem. It's the coax cable loss. That
looks like RG-316 on the right and RG-175 on the left which are both
very lossy at roughly 1.5 dB/meter at 2.4Ghz. My guess(tm) is about 3
meters of coax on the left or about 4.5dB loss in the coax. That
subtracts from the antenna gain resulting in no net gain. That might
be why you claim it was "no good". It's not, but might offer an
improvement by virture of an improved location. It's also false
advertising for the vendor to not include the coax loss in the specs,
but everyone does that so it's difficult to change.



--
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

On Jun 1, 3:00 am, Jeff Liebermann <j...@cruzio.com> wrote:
> AdamO <wepl...@gmail.com> hath wroth:
>
> >These were both said to be 7db antennas for 2.4ghz.. The cost the same
> >and both came from Hong Kong. An email sent back to the seller of the
> >4.5db looking ant was no good as he thinks its a perfect 7db for
> >wifi.....
>
> >http://img182.imageshack.us/my.php?i...oto0023ja1.jpg
>
> Ummm, I don't think so. I can model the antennas easily enough if I
> had accurate dimensions. Just looking at both and guessing, I would
> give the one on the left about 5.0 dB gain. The problem is that the
> gain peak may not be where you expect. Both antennas are intended to
> be operated over a ground plane. That will reflect the signal upwards
> to a considerable degree. You may have 5dB of gain, but it might be
> at an angle of perhaps 20 degrees or more above horizontal (uptilt).
> In the horizontal plane, the gain may be considerably less.
> Fortunately, it's not much of a problem with such low gain antennas
> because they have side lobes and mysterious gain peaks all over the
> place.
>
> However, that's not the real problem. It's the coax cable loss. That
> looks like RG-316 on the right and RG-175 on the left which are both
> very lossy at roughly 1.5 dB/meter at 2.4Ghz. My guess(tm) is about 3
> meters of coax on the left or about 4.5dB loss in the coax. That
> subtracts from the antenna gain resulting in no net gain. That might
> be why you claim it was "no good". It's not, but might offer an
> improvement by virture of an improved location. It's also false
> advertising for the vendor to not include the coax loss in the specs,
> but everyone does that so it's difficult to change.
>
> --
> Jeff Liebermann j...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

Yes clearly Not and that being my point. Leaving coax out of this as
it will only be cut to a very short length and connected to a usb
dongle.... At first glance i would be expecting 6db from the right
and 4.5 from the left based on antenna theory and practice. The ground
plane is a not a worry as usualy a mag mount is on a large metal
roof....

The right antenna being for a very different band is the kicker....
More and more people put a nice little spring on the bottom of there
477mhz antenna, yes it looks nice and i'm sure your radio loves it!

AdamO.

>>> These were both said to be 7db antennas for 2.4ghz.. The cost the same
>>> and both came from Hong Kong. An email sent back to the seller of the
>>> 4.5db looking ant was no good as he thinks its a perfect 7db for
>>> wifi.....

>> Ummm, I don't think so. I can model the antennas easily enough if I
>> had accurate dimensions. Just looking at both and guessing, I would
>> give the one on the left about 5.0 dB gain...

All these dbi numbers and other WiFi antenna talk brings back memories
of the glory days of CB. What a waste.

Jim <(E-Mail Removed)> wrote:
> >>> These were both said to be 7db antennas for 2.4ghz.. The cost the
> >>> same and both came from Hong Kong. An email sent back to the seller
> >>> of the 4.5db looking ant was no good as he thinks its a perfect 7db
> >>> for wifi.....
>
> >> Ummm, I don't think so. I can model the antennas easily enough if I
> >> had accurate dimensions. Just looking at both and guessing, I would
> >> give the one on the left about 5.0 dB gain...
>
> All these dbi numbers and other WiFi antenna talk brings back memories
> of the glory days of CB. What a waste.

And memories of you Pace 123A?

--
..

Jim <(E-Mail Removed)> wrote:
> >>> These were both said to be 7db antennas for 2.4ghz.. The cost the
> >>> same and both came from Hong Kong. An email sent back to the seller
> >>> of the 4.5db looking ant was no good as he thinks its a perfect 7db
> >>> for wifi.....
>
> >> Ummm, I don't think so. I can model the antennas easily enough if I
> >> had accurate dimensions. Just looking at both and guessing, I would
> >> give the one on the left about 5.0 dB gain...
>
> All these dbi numbers and other WiFi antenna talk brings back memories
> of the glory days of CB. What a waste.

And memories of your Pace 123A?

--
..

On Jun 2, 8:25 am, /*..*\@/*..*\.:-) wrote:
> Jim <m...@null.net> wrote:
> > >>> These were both said to be 7db antennas for 2.4ghz.. The cost the
> > >>> same and both came from Hong Kong. An email sent back to the seller
> > >>> of the 4.5db looking ant was no good as he thinks its a perfect 7db
> > >>> for wifi.....
>
> > >> Ummm, I don't think so. I can model the antennas easily enough if I
> > >> had accurate dimensions. Just looking at both and guessing, I would
> > >> give the one on the left about 5.0 dB gain...
>
> > All these dbi numbers and other WiFi antenna talk brings back memories
> > of the glory days of CB. What a waste.
>
> And memories of your Pace 123A?
>
> --
> .

Pace 123A! You saying i'm old? :P