- Bob KØNR
A VHF FM Station at Home
In our Technician License classes, we encourage people to get a 2m/70 cm handheld transceiver as their first ham radio. This gets them on the air and using their new Technician privileges quickly. But, of course, this pipsqueak of a radio can only do so much.
The next step in radio equipment depends on where you want to go with your ham radio activity. One avenue is to establish a more capable VHF/UHF FM station at home. Sometimes we refer to VHF/UHF FM as the Utility Mode for ham radio. While we don’t normally work DX with this mode, a lot of fun and useful ham radio activity gets done this way. A handheld transceiver is a start but with limited power and antenna, its range will also be limited. Working through repeaters helps a lot but it is important to have useful simplex coverage. Think in terms of a worst case scenario, with all repeaters off the air due to severe weather or some other emergency situation.
Some people will argue for just getting a single-band radio for 2 Meters. This is a less expensive way to go but I recommend getting a dual band radio that covers the two most popular FM bands: 2 Meters (146 MHz) and 70 cm (440 MHz). In most areas of the country, this sets you up to access a lot more repeaters and simplex frequencies.
A VHF/UHF radio installation consists of:
VHF/UHF FM Transceiver: You will need a dual band mobile transceiver that covers the 2 Meter and 70 cm bands (Figure 1). Some popular transceivers to consider: Yaesu FT-7900, Kenwood TM-V71A
13.8 Volt DC Power Supply: VHF/UHF FM Transceivers are mobile rigs set up to be powered by your vehicle’s 12 volt power system, which actually delivers more like 13.8 Volts. To use these radios inside the house, we use a DC power supply that delivers the required 13.8 volts DC from our standard AC house power system. See these power supplies from Astron and Samlex.
Coaxial cable and connectors: 50-ohm coaxial cable is used to connect the antenna to the transceiver. Normally, PL-259 connectors are used on both ends of the cable. There are a variety of cable types, with larger diameter cables generally having lower loss (Figure 2).
VHF/UHF vertical antenna: You’ll need to install an antenna that covers the 2M and 70 cm bands. Ideally, this antenna is located high up, on the outside of your house but we may have to settle for a compromise installation such as an antenna in the attic. Some popular antennas are the Comet GP-3, Cushcraft AR-270 and Diamond X-50A.
Configuring the Station
Connecting the radio to the power supply is not that complicated, but make sure you get the polarity right! (Black is negative, Red is positive.) Make sure the power supply can deliver the required current for your transceiver (typically, 9 to 13 Amps). You might want to get a power supply with extra current capacity to be ready for future use (in the range of 18 to 20 Amps).
The bigger challenge is figuring out where and how to mount the antenna and route the coaxial cable. Your first choice should be to get the antenna outside the house and as high as possible. Modest size VHF/UHF antennas can be mounted using standard TV mast and hardware (Figure 3). Figure 2 shows two common coaxial cable types. On the left, is the larger RG-8 size cable that will deliver lower loss but may be more difficult to route through restricted locations. The cable on the right is RG-8X, which is about ¼ inch in diameter, suitable for cable runs of 25 feet or less at UHF frequencies.
Your antenna system should be grounded for lightning protection. This usually means installing a ground rod into the ground and running a thick ground wire from the ground rod to the antenna. Antenna grounding is a complex subject, so see this paper for much more information.
If you can’t put your antenna on the outside of your house, you can try an attic installation. This is not ideal but many radio amateurs go this route. Keep the antenna as far away as possible from electrical wiring and large metal objects.