Wall Wart RFI Noise Filter

Bullet 50:800 (16:1) HF Balun, 3-30 MHz, 500/1500 Watts, T2FD, BBTD, ALE

SKU Bullet-16B-500EB
$89.95
Bulk pricing available for quantities of 2 units or more
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Bullet 50:800 (16:1) HF Balun, 3-30 MHz, 500/1500 Watts, T2FD, BBTD, ALE
Product Details
Country/Region of Manufacture: USA
Type: NEW
Input ohms/Output ohms: 50 in, 800 out (450-1200 ohms)
PEP Power Rating (watts): 500/1500
Input Connector: SO-239
Transformer Topology: Braodband Ferrite
Hardware Type: Stainless
Weight (pounds): 2/3
Antenna Compatability: T2FD, BBTD, ALE, Rhombic

The Bullet-16B is a multi core balun with a compact enclosure (looks like a bullet) enclosure that is lightweight and easy to transport for your fixed/portable ALE, T2FD or BBTD antenna systems. Also useful for low power rhombics and other wire antennas needing balanced 800 ohm output. Halyard hoist at top of balun for convenient attachment point. Input is via SO-239 coax connector and output with side eye bolt output.

This transformer requires a feed line choke to isolate the coax feed line from the antenna. A coax noise filter at the radio end of the coax is also recommended to reduce common mode noise current picked up by the coax braid.

Available in 500 watt and 1500 watt models

Tech Note: If you are building a T2FD/BBTD antenna and you need a matching resistor, use either the TR-800-600 or TR-1000-600. If you are making the 130 foot folded dipole version and you need wire, the DWK-160 will work nicely. To minimize feedline radiation use a choke at the antenna feed point with the Bullet-16B-500EB or use the hybrid 16:1 balun with built-in 1:1 choke, Part# BULLET-16-1-500EB. See related products for these items.

NOTE: We rate our Bullet baluns (and ununs) conservatively at 500 watts PEP with a 50% duty cycle (FT-8 or CW)). Some manufacturers selling low cost baluns may use a 5% duty cycle for their PEP rating to make it appear you get a higher rated balun for a lower price, but you may in fact be getting be getting less. Their 1500 watts PEP really means 75 watts continuous or 150 watts at a 50% duty cycle compared to our 250 watts at 50% duty cycle. Our baluns typically cover a larger frequency range under 2:1 SWR which make your transceiver happy and probably will last longer with less electrical stress.

Remember we over engineer our products, to out perform our competition - just compare the weight of our baluns to theirs and you will know we put much more into our products so you don't have to worry about failure at a critical moment.


Wall Wart switching DC power supplies that plug into the AC power line plug and provide DC power to laptops, routers, battery chargers, cell phone chargers, etc are a known source of broadband RFI (a.k.a dirty electricity) that effects many electrical devices including computers, radio receivers, HDTV systems, etc.  In many cases this extra RFI noise effects computer I/O speeds since they have to error correct the information packets many more times due to the noise interference causing packet errors.  A ferrite ring can often increase data throughput by reducing the error correction to normal rates.

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.

RFI WW Installation 300x288 - Wall Wart RFI Noise Filter

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