WDØM - Pagosa Springs, CO

Pagosa Springs, Colorado




Antenna System Overview

In addition to the SteppIR 4 element beam antenna for 40 - 6 meters, I also wanted to be able to work on the lower frequency ham bands, 160 and 80 meters. There are SO many options to consider. I have the good fortune of living on 5 acres, with no restrictions on wire antennas.

Using the microHAM Station Master, I can select which antenna I want to use manually - or the Station Master will select them automatically, in conjunction with the Alpha 87a amplifier.

I also used a Palstar ZM-30 Antenna Analyzer to ensure that all of the antennas were tuned to the resonant frequency where I intend to operate. I HIGHLY recommend using an antenna analyzer when putting up wire antennas. It makes short(er) work of tuning an antenna, and lets you actually see what is happening. You'll know whether you need to lengthen or shorten the wire to get it to resonate at the frequency you desire without having to guess.

Before we get to work, please understand that this information is intended to give general ideas about installing wire antennas - not to provide specific guidance or technical information on the length of each wire, or the relative performance between antenna types. Please consult other sources for those details. A Google search will provide an incredible amount of technical information. The ARRL Antenna Handook is an excellent reference document.


Junction Box at Base of Tower

  • I purchased a weather proof electrical junction box large enough to contain the antenna relay system, adequate space for connections and a lightning protector, then placed it at the base of the tower. The benefit of a remote antenna switch/relay box is that I only need one coaxial cable from this location into the house to my transceiver. If I had to run six coaxial cables, it would easily have cost as much as the relay system (I use a high-quality LMR400 cable, by Times Microwave). Adding or deleting an antenna now is far easier, because all I need to do is to add/remove a short coaxial cable at the tower junction box.

    • Junction Box Contents

  • The "Six Pak" antenna switch/relay box is made by Jay, WXØB, of Array Solutions. The relays are high quality, and provide considerable isolation between the antennas. The Digital Antenna Selector by Alpha works in conjunction with my Alpha 87a amplifier and controls the relay box, thereby selecting the appropriate antenna. I installed an I.C.E. Model 303 Lightning/EMP protector for the coaxial cable on the back panel (left side/middle). The panel is connected to the ground system at the base of the tower by #4 copper wire. You will also notice that the coaxial cable running to the ICE lightning protector has 10 ferrite beads on it (by Palomar Engineering) to prevent common mode currents from flowing back to the house. This significantly reduces static and noise which otherwise may be induced on the coax, and carried to the receiver. I highly recommend this, particularly if you operate on the low bands.

    • Palstar ZM30 Antenna Analyzer

  • Putting up an antenna can be a real challenge. Without using an analyzer, the only way to tell if it's tuned to the right frequency is to fire up your transmitter and check the SWR over the band you want to operate on. If the antenna isn't resonant within the band your transmitter covers, about all you might be able to tell is that it is resonant above or below the band. With an analyzer that operates on frequencies outside the ham bands, you can tell exactly what adjustment to make without taking the antenna up or down or running back and forth to your antenna. An analyzer will tell you the resonant frequency and determine exactly how much to shorten or lengthen your antenna after only one measurement. For example, if you're shooting for a 14 Mhz resonance, and the SWR is lowest at 14.56 MHz, this is 4% higher than desired, so you know to lengthen the antenna by 4%. There's no need to keep cutting the antenna and raising and lowering it many times. This saved me a LOT of time and is well worth the price for anyone putting up an antenna.

    • microHAM's Station Master

  • The microHAM Station Master is the controller for the antenna relay box at the tower base, and interfaces between my Alpha 87a and the relay box. The Station Master provides a radio control interface, automatic antenna switching, automatic band pass filter switching, selective SteppIR tuning, computer controlled rotator interface, interface for automatic power amplifiers, sequencer for receiving antennas and many additional unique features.

    • Antenna Choices

  • My goal was to work on the 160 and 80 meter bands with a selection of wire antennas. My SteppIR antenna covers 40 - 6 meters (40 and 30 meters with the add-on SteppIR system), and does an excellent job. To get started, I placed fiberglas tubes across the top of the tower so that it extends about 3 feet on either side, then installed two pulleys, one on either side of the tower. The pulleys allow me to raise and lower the wire antennas using a rope, making maintenance and adjustments far easier than having to raise or lower the tower each time I wanted to work on them.

  • The picture on the left doesn't reflect the wire antennas very well due to the limitations of photography, but gives you an idea that there are a lot of wires in the air. As a result, I'll resort to a few line drawings that will help you visualize how the antennas are installed, and give you a few "tricks" on how to put them together.

    • The next page discusses the actual antennas installed at WDØM.