Comparision of HT, Mobile and Base Coverage

by Richard Duncan NF114CP / WD5B

There is been a lot of discussion about whether to use a HT, mobile or base to get onto Yankee Romeo repeater. Here is some information to help you determine which coverage out be prefered. Note: Having a HT during a patrol is very helpful even if not directly involved with communications. You will have the advantage of being able to hear the communications and directives when out of range of the comms radio.

For the purpose of this page the following general attributes are used:
HT In Car	Running 4 watts. It is generally agreed that a HT on your hip or inside a car has a 20db loss over handheld.
HT	Holding a HT running 4 watts at about six feet and a rubber duckie. (Rubber duckie typical -3DB gain.
HT With Antenna	Running 4w watts on a mobile antenna at 3 feet and 3db gain.
Mobile Station	Running 40 watts with a 3db antenna at 3 feet.
Base Station	Running 40 watts with a 3db antenna at 21 feet.

Polar Coverage

The first group of photos shows the polar coverage from Channel Islands based on different radio setups. The worst case is using a HT inside the car to the best case of running a base station with antenna at 21 feet. Typical of my installation.

These computations are not completely accurate but setting actual ground conductivity and environment was not the goal, rather showing the different communications setup and their differences based on the same set of data. In otherwords, we are looking at the difference in coverage which should stay proportionate based on the equipment not the conductivity, etc. Due to local terrain, buildings and many other factors moving just a foot or two could and probably would result in different patterns. That's the characteristics of VHF/UHF. However, again, we are looking at different setups in the same exact locations.

[Click On Image For Larger Size]

Base Station 40w @ 21 feet.

This first image is a Base Station running 40w with a 3db gain antenna at 21 feet. A easy setup for most.

Good coverage exist out ot Anacapa Island and the waters to east Santa Cruz as well as most of the land facing the coast. The Oxnard plane and up the coat to Santa Barbara although there are a few weak spots.

This pattern is coverage from the base station in Channel Islands.

HT Inside Car 4w @ 3 feet.

This is the worst case. Running a HT inside the car with no outside antenna. An HT in the car or on one's belt typically exhibits a -20db to -23db loss!

HT Handheld 4w @ 6 feet. Rubber Duckie

Above is coverage using a 4 watt HT held at six feet. A "Rubber Duckie" antenna has -3db of gain, but being outside the car and up in height is far better than inside the car.

HT With Car Antenna 4w @ 3 feet 3db Antenna

Range is increased using a HT radio with a 3db mobile antenna. While not significant as the power is still low.

Mobile System 40w @ 3 feet. 3db Antenna

Mobile coverage is increase using 40 watts which is 10db gain over using a HT. Not quite as much as a base system due to the lower antenna height, but still good coverage.

Coverage from Channel Islands to Yankee Romeo

This set of charts shows the received signal strength expected from Channel Islands to Yankee Sierra repeater.
The green is good signal, yellow is fair signal and red is no or unusable signal.

HT Inside Car 4w @ 3 feet.	HT Handheld 4w @ 6 feet. Rubber Duckie
Mobile System 40w @ 3 feet. 3db Antenna	Base Station 40w @ 21 feet.

Coverage from Channel Islands to Anacapa Island

This set was done between Channel Islands and Anacapa Landing. Again, The green is good signal,
yellow is fair signal and red is no or unusable signal. Note the curvature of the earth is apparent and
the major reason for reduced coverage. Other than the loss due to operating a HT inside the car, most
coverage is a function of line of sight.

HT Inside Car 4w @ 3 feet.	HT Handheld 4w @ 6 feet. Rubber Duckie
Mobile System 40w @ 3 feet. 3db Antenna	Base Station 40w @ 21 feet.

The choice of station depends on a person's budget and desired coverage. There is a place for using an HT, mobile or base station. Unfortunately, one system will not cover all the requirements of the others.