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Modifying Conifer Antennas for Wireless Networking
part 3
Reassembly
The dipole can then be installed into the feedhorn. Use some
silocone or hot-melt glue on the ends of the dipole, to ensure it
won't become dislogded.
the dipole installed into the feedhorn,
and fixed into place with hot-melt glue
Glue the feedhorn into the metal base, using a high-strength glue,
such as 24hr Araldite.
the feedhorn glued into the base with Araldite
Glue the nose cone onto the end of the feedhorn.
Re-assemble the antenna, and use silicone or hot-melt glue to seal up the back
of the feedhorn (where the coax enters the feedhorn).
seal the base with silicone
Terminate the other end of your coax with a female N connector.
a female N connector
To minimise the stress on the coax where it exits the rear of the feedhorn,
use a cable tie to firmly attach it to the antenna mounting bracket,
as shown in the photo below.
The two U-bolts provide sufficient clearance for the coax between the mast and the bracket,
and you can use the existing holes in the bracket.
coax cable-tied to the bracket
The cable tie ensures the coax will not move inside the feedhorn. This is particularly
important when using a fairly stiff coax, such as CNT-400. Failure to properly secure
the coax in this way can result in the coax moving while you mount the antenna on a
mast, and this can lead to broken dipoles.
You're now ready to test it!
Note that most people using Conifer antennas for wireless networking
have them horizontally polarised - that is, they are rotated 90 degrees
compared to the way Galaxy mounted them (ie, long axis of the grid
is vertical for wireless networking, instead of horizontal).
18dBi modified Conifer
mounted for horizontal polarisation
Note, however, that the polarisation you should use will depend on the polarisation of the
antenna you are connecting to.
For example, a waveguide is horizontally polarised, while a collinear omni
is vertically polarised
Usage
For information on connecting an external antenna to a wireless radio, have a look at the page on
using wireless antennas.
Testing
We've modified a number of Conifer feedhorns, and have done
some testing in a controlled environment,
to determine which dipole modification achieves the best results.
The testing indicates that this dipole provides at least 3dB better
signal strength than the more common Galaxy modification (ie,
soldering coax onto the cut-off down-convertor PCB).
Details of the testing procedure and the results are available
here and
here.
These test results have been verified by other people's test results too.
Recently, a fellow WAFreenet member replaced the pcb dipole in his 18dBi
Galaxy dish with a dipole I constructed using the method described above,
and saw an increase in SNR of approx 4-5 dB.
References
ChrisK's Galaxy Mod
Leeming Wireless Network - Dish Mod
Conifer 2.4GHz Antenna Modifications for Wireless LAN
How to modify an Ex-Galaxy Antenna for Wireless Network
Conifer Antenna Testing (part 1)
Conifer Antenna Testing (part 2)
Credits
Photos by ,
graphics by .
navigation:
part 1
| part 2
| part 3
last updated 22 Oct 2013
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