Description

EARCHI End-fed HF Matchbox Antenna 6–40 Meter Multiband HF Antenna This is a used piece of equipment . Ships via USPS Ground Advantage International sales welcomed and ship through the eBay Global Shipping Center. Shipping times will vary if going out of the country. Specified delivery times listed on the ad is to US addresses and will also vary. The eBay Global shipping center is included in that and not the final destination outside of the US. The information listed below was found online and does not reflect what is included in the sale. It is for reference use: Introduction This EARC project produces an inexpensive, multiband, end fed HF antenna matchbox that is quick and easy to setup and use. The end fed feature adds portable convenience, but does present another issue. The problem with an end fed half wave antenna is that the antenna presents high impedance, creating a significant miss match with the usual transceiver impedance of 50 ohms. This miss match is significantly greater than typical tuners can accommodate without a matching transformer. This project creates a trifilar wound, 9:1 UNUN (unbalance to unbalance) toroid matching transformer that will match the high input impedance of an end fed antenna into the range where most antenna tuners can produce good performance. The matchbox handles 100 watts of power. This project requires an antenna tuner to achieve satisfactory SWR . If you need an auto tuner, we recommend the LDG line of auto tuners, shown to work well with these matchbox antennas, and highly rated by users. They are reasonably priced and available at most ham stores. The matchbox project uses readily available common hardware and materials listed below. Matchbox Parts List 1 small plastic enclosure (shown right) 1 powdered iron toroid T130-2 3 20” pieces of 18 AWG solid insulated copper wire in red, green, and black 2 # 8-32 x 3/4” hex head machine screws 2 # 8 lock washers 2 # 8 ring wire lugs 2 # 8 flat washers 2 # 8 lock washer/nut combination 2 #8wingnut 1 SO-239 panel mount connector to fit keyed enclosure opening 30’ # 18 AWG insulated stranded wire antenna with ring lug attached Small amount of clear silicone caulk to secure toroid in place Preparing the MATCHBOX Plastic Enclosure The enclosure needs one 5/8” hole for the SO-239 connector, and one 11/64” hole for the counterpoise wing nut on the lower side of the enclosure. An 11/64” hole on the upper right side of the box facilitates antenna connector mounting. TOROID WINDING First, wind the three 20” pieces of insulated solid wire onto the toroid. Place the wires as shown green-black-red, and wrap the toroid 9 turns so that it looks like the photo on the right. Notice there are three wires extending from the left winding and three wires extending from the right winding. As the connections are completed, the steps refer to the specific wires by left or right and color. NOTE: Count turns by counting the number of times the wire goes thru the toroid center. Crimp together and solder the left black wire with the right red wire When the step is completed, it will look like the right photo. The next three steps should appear as shown in the first photo on page 3. Crimp and solder a # 8 lug to the left red wire about 2” from the toroid. The completed lug will later connect to the antenna connection bolt on the upper inside of the enclosure. Twist the left green wire with the right black wire. Strip the ends of the two wires and twist together at about 2”. This twisted pair will solder to the center connection of the SO-239 connector in a later step. Trim and strip the remaining right green wire at about 2”. wire, and crimp and solder both wires to a # 8 lug. The 2” green wire will connect to the ground Cut an additional 2” piece of green connector on the SO-239 already installed in the enclosure. Strip remaining green wire end 3/8” and bend into a hook for connection to the SO-239 ground connector. The SO-239 connector and ground lug should be installed through the keyed hole in the lower right with the mounting nut securely tightened. Solder the green and black twisted pair to the SO-239 center connector. Solder the green wire hook to the ground lug on the SO-239 connector. From inside the box, place an 8-32 machine screw through a lock washer, the # 8 lug on the green wire, then through the lower 11/64’” mounting hole. Place a flat washer on the outside protruding machine screw followed by # 8 lock washer/nut and tighten securely. Place a # 8 wing nut on the machine screw to finish the counterpoise connector . Position the toroid inside the box to allow connection of the red antenna wire lug to an 832 machine screw and lock- washer on the upper box side. Place a flat washer on the outside of the box followed with a # 8 lock washer/nut. Tighten the nut securely. Next, place the wing nut on the antenna connector and your project appears as shown above. A small spot of clear silicone compound is used to secure the toroid from movement in the enclosure. The final assembly step is to secure the box cover in place with four screws. Preparing the Antenna Wire Matchbox performance will be determined by two factors: The length of the antenna wire, and the capability of the tuner. The length of the antenna wire should be between 24 and 60 feet for best performance. Additional counterpoise is not normally required, as the coax shield provides the counterpoise function. Wires longer than 60 feet may have excessive impedance for some tuners to properly match. Wires shorter than 24 feet may not radiate as effectively. A 30 foot insulated 18 gauge stranded wire antenna and connecting lug is included with the project and should meet most requirements without need for any counterpoise. Experience has shown that most external tuners and some internal tuners will tune 80–6 meters with an antenna length of 24’ to 30’. If a longer antenna is desired, the provided antenna can be lengthened. Some tuners, in particular internal tuners, may not tune the full 80-6 meter range. You may need to try different wire lengths to optimize your antenna configuration. If you are having difficulty getting your rig to tune, start with a 26’ wire. This should produce good results on at least 40-6 meters using the narrowest performance range of internal tuners. Best performance is achieved with a coax of 16’ or longer, with the coax shield providing the counterpoise function. Additional counterpoise is usually not required in this design, although the lower wing nut provides a convenient counterpoise connector if needed. The end fed antenna system works well in horizontal, sloper, and vertical configurations. Observe established safety practices when working with antennas, and avoid proximity to power or utility wires. Permanent installations should be equipped with appropriate static and lighting protection. Keep amateur radio safe and fun! Coax center INPUT Coax S hield Toroid Wiring Schematic ANTENNA CONNECTION Red wire Black wire