A good solution is to use a plastic pipe in which you will place the antenna and the usb Wifi key and then descent to the computer with a simple 5 m lenght usb cable.
This system will have the advantage to have nearly no lost and your signal will be greatly improved.
Here is my motorhome setup :
the antenna is a colinear with a gain of 8 db
It's attached to the motorhome by the use of a vaccum cup, I did not want to make holes in my camper.
The WiFi usb key is inside the chromed tube, direxctly connected to th antenna wire inside the white plastic tube and the cable is a 5 m lenght usb standard.
Signals are really stronger.
Here is picture of the mesured signals before and after
(mesured with Netstumber program)
As you can see there is no doubt about the efficiency of this little modification.
Improve your WiFi connection
The use of WiFi access points is very nice when travelling but their range is very short
It's easy to increase the range by the use of an external antenna but...
Antenna gain is mesured in decibels
A 6 decibel gain is equivalent to a power multiplied by 4
For exemple, if you have 90db with a 100 watts amplifier you will need 400 watts to get 96 db.
WiFi use a standard power of 100 milliwatts
thus, an antenna with a gain of 6 db will radiate 4 times more power and of course will also receive 4 times better
One should think it's enough to place an antenna on the vehicle roof to get that nice result and this is in theory true but Wifi connections use very high frequencies (2.4 Ghz) and at those high frequencies the lost in the cables and connectors are very high.
Let's take an exemple:
Let's say we use a 3db gain antenna placed on the vehicle roof by the mean of a 5 meters cable.
We use a very common RG58 cable and 2 connectors.
The lost in a connector is 0.5 db thus a total of 1 db for two connectors.
The cables are far from being perfect, here are the lost per 100 meters for the RG58 type
30MHz : 6.30dB 50MHz : 8.10dB 150MHz : 14.10dB 220MHz : 17.10dB 450MHz : 24.60dB
900MHz : 35.00dB 1500MHz : 45.60dB 1800MHz : 50.10dB 2000MHz : 53.00dB 2500MHz : 59.50dB
As you see the attenuation at WiFi frequencies is huge : 59.5 db per 100 m !
In the exemple we use 5 m and we will have an attenuation of 2.975 db !
this added to the connectors lost become 3.945 db
In other words using our 3 db gain antenna will give a worst result that using the incorporated antenna.
To improve the system we should use either a greater gain antenna either less cable lengt but sitting on the roof with the computer on the knees is not a very comfortable way.
There is a better solution :
Place the WiFi transmitter (or usb key) as close as possible from the antenna and use a low frequency to conduct the signal to your computer.
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Belgian radioamateur around the world