WU1M Aeronautical Mobile Operations
My airborne ham radio operating is mainly on 2 meters in my Piper PA38-112 "Tomahawk" but as a Certified Flight Instructor/Commercial Pilot I sometimes operate from other aircraft and on other bands. Because I am using a "portable" for 2 meters as opposed to a permanently installed FAA approved radio, per FAA regulations I can only operate on the ham frequencies while in VFR (visual flight rules) conditions and not while in IFR (instrument flight rules) conditions.
The "portable" is a Vertex (Yaesu) VXA-700 which is the only portable aviation NAV/COM radio with 2 meters capability ever manufactured. It was only produced for a short time and was replaced by the model VXA-710 which substituted business band for the 2 meters band. Output power is 5 watts. I mainly use 146.52 simplex but do use repeaters...carefully. Even with PL it is possible to hit more than one repeater at the same time. Just to give you an idea of signal coverage, on a clear day the line of sight to the horizon from the cockpit window is 39 miles from 1,000ft above the ground, 55 miles from 2,000ft, 67 miles from 3,000ft, 86 miles from 5,000ft and 122 miles from 10,000ft. So, at 5,000ft on a perfect day my horizon to horizon visual span is 172 miles. Even taking into account low power, antenna type and location as well as possible ground terrain, my simple setup covers a very wide area.
The radio is mounted to the lower right side of the cockpit windshield using a modified suction cup GPS mount (see upper right corner of cockpit photo). I use the "rubber duck" antenna supplied with the radio placed against the windshield. The audio output of the unit runs from its aviation headset adapter cord to the plane's intercom "aux audio input" socket, mixed with the cockpit audio and into the headsets. It's too noisy in the cockpit to use the radio's built-in mic and the optional external mic must be an aviation type. I use a Telex 100TRA dynamic noise canceling handheld which plugs into the mic side of the radio's headset adapter cord. To have the transmit audio side of the plane's radio/intercom system modified to also feed the "portable", add a separate PTT switch and an external antenna for 2mtrs is cost prohibitive. The radio is powered from its internal battery pack or a 12vdc accessory socket on the right side of the instrument panel.
This setup allows me to communicate with my passenger(s), air traffic control (using the plane's radios) and operate 2mtrs. The VXA-700 also serves as an emergency backup aviation NAV/COM. It's easy to take in and out of an aircraft and meets all FAA requirements for equipment that is not permanently installed.
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