Model CU-5-1500 - 5 to 1 Unun

(SO-239 in/Eye bolt hoist with output connector on top, side stud for ground/counterpoise)

Purpose. This unun is designed to match 250 ohms unbalanced to 50 ohms unbalanced up to 1500 watts PEP power from 1.8-61 MHz. It provides conversion from unbalanced 50 ohm coax to an unbalanced 250 ohm load/antenna feed point and gives a 5:1 impedance step-up to reduce VSWR on the coax feed line. The unun is housed in a 4” x 4” X “2 NEMA weather resistant box with SO-239 coaxial input and a ¼” stud terminal with wing nut on the top for output and another on the side for ground or counterpoise connection.

This unun is DC grounded and will bleed off static electricity but it is NOT A LIGHTNING ARRESTOR.

Model CU-5-1500 is a 50 ohm to 250 ohm (5:1) voltage unun used to translate a 50 ohm input up to 250 ohms at RF power levels up to 1500 watts PEP (30% duty cycle) when used with a matched load. With a matched 250 ohm unbalanced load SWR should not exceed 2.0 over the frequency range 1.8-61 MHz.

Application. For traveling wave, end fed or portable 30, 60 or 90 foot antennas the 5:1 balun makes a good transformer for converting 50 ohm coax to a 250 ohm feed point. If you use the antenna on multiple bands, the feed point impedance may not always be 250 ohms and use of the 5:1 unun at high (>350 ohms) or low (<100 ohms) will require reduced power input or the unun may have its power ratings exceeded and damage to the unun may occur. The 5:1 conversion ratio will change for loads other than 250 ohms unbalanced.

Typical Antenna System Using CU-5-1500 is usually 30, 60, 90 foot of wire end fed or rain gutter end fed (not connected to ground). Sometimes a 20-50 foot counterpoise (off side stud of unun) and laying on ground will help SWR on certain bands. Many HOA Rain Gutter antennas using 5:1 ununs like this on internet search.

Use a coax noise filter (CMNF-1500) to reduce noise from any vertical antenna or a line isolator (MC-1-1500) to suppress coax cable braid radiation on transmit.