The CHA M-COIL is an inductive loading coil used to lower the resonant frequency of vertical whip antennas, allowing effective operation on lower HF bands, such as 30 and 40 meters. It’s compatible with several Chameleon Antenna radiators, including the CHA SS58 (58 inches), CHA SS17 (17 feet), and CHA SS25 (25 feet).
With a power rating of 100W CW and 200W SSB, the M-COIL is well-suited for portable and field operations. These power limits ensure efficient performance without risking coil overheating or degradation, especially during prolonged transmission sessions.
Using the CHA M-COIL with Different Whip Lengths
CHA SS58 (58 inches)
- Best Bands: 20 and 30 meters with M-COIL
- Setup: Attach the M-COIL between the Blank Adapter and the SS58 whip. The M-COIL compensates for the shorter length of the SS58, effectively enabling lower-band operation.
- Applications: Ideal for compact setups, such as HOA-restricted environments and portable operations where height limitations apply.
CHA SS17 (17 feet)
- Best Bands: 30 and 40 meters with M-COIL; works from 20 to 6 meters without the coil.
- Setup: Extend the SS17 to 16 feet for 40 meters and attach it to the M-COIL. For 30 meters, adjust the whip to about 7 feet, 5 inches.
- Applications: This configuration provides a good balance of portability and low-band capability, suitable for field deployments and emergency communications.
CHA SS25 (25 feet)
- Best Bands: Optimized for 40 meters and potentially 60 meters with M-COIL; can operate on 20 meters without it.
- Setup: Extend the SS25 fully when using the M-COIL for 40 meters. For potential 60-meter use, tune the whip length and radials accordingly.
- Applications: This is a highly effective setup for field operations, offering strong performance on low HF bands and excellent signal reach.
Power Considerations for Safe Use
- SSB Mode: Up to 200W for voice communication, which is beneficial for clear, powerful transmissions on lower HF bands.
- CW Mode: Up to 100W, suitable for modes requiring continuous or digital signal transmission. Monitor SWR and reduce power slightly in extreme heat or for extended operation.
Tips for Optimal Performance
- Radials: Always use radials appropriate for the frequency. More and longer radials improve grounding, especially important on 40 and 30 meters.
- Environment: Changes in terrain, moisture, and nearby objects may affect tuning. Periodic checks and adjustments can ensure the best SWR.
- Safety: Keep the setup away from people and RF-sensitive equipment, especially when operating above 10 watts.
This versatile setup enables efficient communication across multiple HF bands, whether for emergency, recreational, or portable operations, making the CHA M-COIL a valuable tool in field-deployable antenna configurations.
