Helpful Technical Guides
Helpful Technical Guides — Free Expert Downloads
Knowledge you can put on the air!
Palomar Engineers has been helping radio operators, installers, and RF professionals solve noise and interference problems for over 60 years. Our free technical guides give you practical, field-tested information to help you choose the right ferrite products, chokes, filters and antennas for your specific application.
Each guide is written by our engineering team — short, easy to follow, and designed to educate first and simplify selection. Best of all, every download is free (registration required) so we can keep you informed with new updates and product improvements.
📘 Available Guides
| Guide Title | Summary | Related Products |
|---|---|---|
| Choosing a Feedline Choke | Understand where and why to install feedline chokes for best performance. Includes placement diagrams and product recommendations for common antennas. | 1:1 Baluns & Feedline Chokes › |
| OCF Antenna Confidence Guide | Learn how hybrid transformers improve balance and reduce noise in off-center-fed antennas. Explains how to match feedline and transformer ratios for best efficiency. | OCF: Why, What and How › |
| Noise Filter Selection Guide | Discover how to isolate and stop RFI noise from AC, DC, and coax lines using Palomar’s noise filter families. | Noise Filter Products › |
| Ferrite Mix & Application Guide | A quick reference to ferrite material mixes (31, 43, 61, 75) and how to choose the right type for your frequency range. | Ferrite Cores › |
| AC/DC Power Noise Solutions | Learn how noise from power lines, supplies, and inverters couples into your station — and how Palomar filters eliminate it. | Power Line Filters › |
| RFI / EMI Suppression Fundamentals | A foundational guide on identifying, measuring, and fixing common RFI and EMI issues in radio, audio, and digital systems. | RFI / EMI Solutions › |
💡 Why Download These Guides?
- Written by Palomar’s Ferrite Application Experts
- Easy to follow — includes diagrams, use-cases, and model recommendations
- Updated regularly to reflect new products and installation practices
- Every download helps us keep you informed of future tips, updates, and product innovations
📥 Get Your Free Guides
All guides are free — simply add them to your cart and check out at no cost. You’ll receive instant access plus email updates when new guides are released. Note: You can add multiple guides to your cart at the same time as other items.
Palomar Engineers — Ferrite Application Experts since 1965.
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