Ve6fi Amateur Radio
Wifi Links using Rangelan2 7521
We did not have high speed internet at Ve6fi since we are beyond reach of the high speed from the telephone company. So what should we do to get wifi at the contest site?
We designed a two hop microwave system that originates in the City of Edmonton at Denis's (Ve6AQ) home. The first hop goes to Evan's home which is 8 kms away. The last hop goes from Evan's house to VE6FI a distance of 10 kms. We did the path profiles, figured out the free space losses, calculated the required antenna gains and necessary power output required. The design called for 0.5 watt radio operating on the 2.4 GHz band using spread spectrum modulating technique. We wanted to have a data rate of 300 to 500 kbits/sec.
We wanted to have some fade margin on the system so that we could tolerate multi path fading. We designed a 20 db fade margin on each hop. The radio equipment we used was Proxim Ranglan2 7521 which are abundant on ebay. They sell for around $50.00 per radio. These radios are specified at 1.6 Mbits/sec but in normal life you do not get this. The antennas we used were 24 db gain grid antennas. They look like BBQ grills. The radios were mounted in a weatherproof enclosure right behind the antenna. This is advisable as the loss in the transmission line if one has to bring it down the tower into the shack is to high. A short two foot transmission lines between the antenna and the radio is all that is required.
This Rangelan2 radios have a Ethernet input which allow one to use CAT5 cable to provide the connection from the router to the input of the Rangelan2 radio. In most designs one would not require two hops of radio. When I checked with the radio manufacture as to whether I could tie them in series, they said it could not be done. Well it can be done. You merely connect the two Rangelan2 7521 radios back to back by a CAT5 crossover cable.
At the Ve6fi site (end of the two hop radio system) we run a piece of CAT5 cable from the top of the tower down into the shack. In the shack we have a hub and distribute the signal in that manner.