Model CU-5-1500EB- 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 20-31 foot vertical 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 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
Use a coax noise filter to reduce noise from any vertical antenna or a line isolator to suppress coax cable braid radiation on transmit.
A simple ferrite ring filter on the DC power line can help suppress the RFI noise affecting the victim device or keep the DC power cord from acting as an antenna and radiating RFI into other victim devices. This kit is also useful on laptop computer supplies, routers, cable modems, wireless phone charges, etc.
Installation is quick and easy: Just wrap the DC power cord through the center of the ring filter as many times as you can and reinstall. For best results with long DC power lines, use one at the ring filter at the wall wart end (to prevent the wall wart power supply from using the DC line as an antenna) and another at the DC plug end (to prevent the electronics in the powered device from using the DC power cord as an antenna). Typical installation is shown below:
The filter suppresses RFI in from .1-100 MHz. Inside diameter is 3/4 inch/19 mm.
Since most households and office environments have multiple wall warts we offer the Wall Wart RFI Filter kit in bulk quantity packages.
Known RFI Generators include Roku/Sling-TV power adapter - Interference heard in the AM broadcast band and harmonics. Also many ethernet Cable/DSL modems, cell phone chargers, computer power adapters have the same issue: using the AC or DC side of the power supply as a radiating antenna. RFI solution is to use a linear power supply, change adapters or wall wart ferrite filters