Introduction

Better Low Band Reception for DXpeditions by George Wallner, AA7JV, focuses on noise reduction and effective receive antenna systems for improving 160-meter CW performance during DXpeditions.  Most DXpeditions enthusiastically announce 160m CW operation. Too often they don’t deliver. They spend valuable days battling noise, but eventually fall back to FT8, or just work 80 meters. But that does not satisfy the demand for 160m CW.

Key Article Highlights:

1. Importance of Low Band RX Systems
   Effective 160m CW operation requires noise reduction and a good RX antenna. Without these, only "big guns" can be worked, and QSO rates drop quickly.
2. Noise Challenges
• Local Noise: From generators, power supplies, computers, etc.
• Thunderstorm Noise: Significant in tropical zones, especially in monsoon areas.
• Inter-station Noise: From nearby TX antennas, harmonics, and wideband emissions.
3. Noise Mitigation Techniques
• Grounding: Use water-grounded stakes or multiple radials for RF grounding.
• Filters and Chokes: Add AC line filters and RF chokes to block noise currents on cables.
• Station Layout: Separate TX, RX, generators, and cables to minimize coupling.
4. RX Antenna Systems
   Good RX antennas improve signal-to-noise ratio (SNR) by focusing on desired signals. Key options include:
• Flag: Rectangular, loaded-loop with ~7.3 dB directivity factor (DF).
• Delta Loop: Single-support antenna with ~7.5 dB DF and low complexity.
• DHDL: Modified delta loop with excellent 9.3 dB DF but very low gain
  (~31 dBi).
• Beverage: Excellent performance (~11 dB DF) but inconsistent results near water.
5. RX System Components
• Pre-Amplifiers: Essential for low-gain antennas like the DHDL. Place them at the antenna to preserve SNR.
• Coax Feedline: Use quad-shielded RG-6 to avoid noise pickup.
• Powering RX Systems: Inject well-filtered DC power through the coax (bias-T method).
6. Generator and Power Supply Noise
• Shield ignition systems and use filters on generator outputs.
• Bury AC cables in wet sand for noise reduction.

Conclusion
This article provides a detailed, experience-based guide for DXpeditioners aiming to excel on 160m CW. Preparation is key for noise-free 160m CW operation on DXpeditions. Effective noise mitigation, thorough station planning, and using directional RX antennas ensure success. Operators should optimize for high SNR and be ready to capitalize on rare, magical low-band conditions where high CW run rates are possible. 

The full article can be downloaded in PDF format from the NCDXF website HERE

Shielded Box	DC Power Injector