Experimenting With 2m Simplex

Experimenting With 2m Simplex

For the past couple of W1HLO meetings, the club has been experimenting with 2 meters and communicating with the newly-formed E.O. Smith Ham Radio Club. This exercise has been a very good lesson in understanding simplex communication, yagi antennas, and power. To start, we used Google Earth to see what direction E.O. Smith High School is from NFA. We found that E.O. Smith is approximately 20 miles (32km) away at a compass bearing of 336 degrees. The roof of the NFA ham shack is about 40 feet off the ground, so we weren't sure how much of the terrain would be a factor.

First Test

Our club used a four element yagi antenna and a 40W mobile VHF radio for our first experiment. We chose a yagi antenna due to its directional properties and aimed it (as best we could) to 336 degrees. We called CQ on 147.450MHz but did not hear anything in response. E.O. Smith was using an HT (handheld transceiver) with an Arrow yagi antenna and 5W of power. They did not hear us and we weren't sure if we could hear them over the noise. Afterwards, we used the W1HDN repeater so we could still make a QSO.

Second Test

A couple weeks after the first test, we went back to the drawing board and tried something else. For the second test, we decided that more gain and more power might help us. We erected a 9-element 2m yagi that has about 12dB of gain. We used our 40W 2m radio again and this time, we placed an rfConcepts 2-315 2m amplifier between the radio and antenna. This combination gave us roughly 100W of transmit power. To ensure RF safety, the transmitter was placed in our shack, to keep our operators far away from the antenna on the roof. The antenna was pointed towards 336 degrees, in the direction of E.O. Smith.

Amazingly, E.O. Smith was able to hear us from their parking lot using their Arrow yagi antenna and an HT. You can listen to a recording of what E.O. Smith heard when we were transmitting. Unfortunately, we couldn't hear E.O. Smith respond, probably because of their location (low to the ground on the parking lot) and power (roughly 5W with their HT).