In a couple of blog posts, we discuss the phasing of vertical pairs for directivity. In one post we discuss phasing from the perspective on one specific FCC pool question. In the other blog post we give an overview of what the nature of vertical phasing of antennas is all about. However, in this web page we will discuss an actual case of vertical-pair phasing to gain a directional advantage. We will take it from cradle to grave, showing the theory and its practical implementation with regard to a mobile rig configuration.
The procedure may change slightly but here is what we have in mind.
- A pair of matching mag-mount quarter-wave antennas will be obtained.
- How do you hook up that pair of 50 Ohm antennas to your 50 Ohm transceiver? You could use a Tee but it wouldn’t work. We are going to present the Wilkinson Power Divider concept. It’s just a couple of coax cables and a terminating 100 Ohm resistor. Simple as pie.
- One antenna will be mounted on the car
- We will tune the antenna for minimum SWR.
- and we will take field strength measurements.
- Then, the pair of matching mag-mount quarter-wave antennas will be mounted on a car.
- We will tune each individually for a minimum SWR before hooking together via a T-connector.
- We will verify that the two transmission lines for each match in length or at least record any differences.
- The precise distance between the mounted radiators will be measured as mounted on the vehicle.
- We will then take some field strength measurements for comparison purposes later.
- We will then solve for the required additional 50 Ohm coax needed for one of the mag-mounts and install it.
- The earlier field strength measurements will then be repeated so that we can compare the two.
It is coming soon so stay tuned. We might have to wait for warmer weather, though.