Comet Antenna HFJ-350M - User Manual

Instruction Manual
MODEL
【 Features 】
● It is a 3-division structure that is convenient to carry.
● Telescopic antenna for multi-band HF to 50 MHz band, whose frequency can be easily changed by short plug.
● Round-shape solderless Terminal for counterpoise is included. (Stranded wire: 3.5 sq [AWG12] compatible)
【Product image】
accessories
Short plug
Cautions on installation
◆ This product is not suitable for mobile use. Please do not set it on the vehicle and drive.
◆ If there are other antennas or obstacles such as buildings near this antenna, this will cause
SWR degradation and resonance frequency shift. In that case, please change the mounting
position of the antenna.
!
◆ Make sure that the connector of the connection cable and the antenna connector are of the
same type. If it is a different type, it can not be connected or it may be damaged.
HF-50MHz Portable Telescopic Antenna
For : 3.5 / 7 / 10 / 14 / 18 / 21 / 24 / 28 / 50 MHz
Handling and operation precautions
!
Base Coil
with connector
Product configuration
3.5 MHz expansion coil
connection & Telescopic
element shortest
HFJ-350M
M-P (PL-259)
Connector
3.5MHz
Expansion coil
Telescopic
Element
Thank you for purchasing our products.
For your safety :
Read this manual carefully for proper handling and operation before using.
Keep this manual in a safe place for future reference.
【 Specifications 】
Antenna type : 1/4 λ base loading type antenna
Frequency : 3.5 / 7 / 10 / 14 / 18/ 21 / 24 / 28 / 50 MHz 9-Bands
Max.Input Power : 75W (SSB) [3.5MHz] , 100W (SSB) [7 - 50MHz]
Impedance : 50Ω
Length : Min. 370mm , Max. 1665mm
Weight : approx. 260g (included 3.5MHz expansion coil)
Antenna Connector : M-P (PL-259)
● When installing or removing the antenna or adjusting the element, be careful not to open your
eyes at the end of the rod.
● Do not touch the antenna during and immediately after transmission. The fever can cause burns.
● Tighten the fixing screws firmly so that there are no accidents.
● When extending the rod, always keep in mind that there are no obstacles in the height direction.
● Do not use it outdoors when it is wet, as it is not waterproof.
● Do not use when the surface is wet, and use completely dry.
◆ To use this product, capacitive coupling with grounding or counterpoise is required.
Note that if the ground capacitance is insufficient, the VSWR characteristics will deteriorate,
especially in the low frequency band, and there is a high possibility that adjustment will not be
possible.
◆ On the structure shortened by the loading coil, the tuning band is narrow. If you want to check
where the tuning frequency is, we recommend using an antenna analyzer such as CAA-500Mark II.

Summary

Safety Precautions

Manual Handling and Reference

Read this manual carefully for proper handling and operation before use and keep it for future reference.

Product Features and Specifications

Key Features

Features include a 3-division structure for portability, multi-band HF to 50 MHz capability, and a solderless terminal.

Technical Specifications

Details include 1/4 wave base loading, frequency range, max input power, impedance, length, weight, and connector type.

Installation and Handling Guidelines

Installation Cautions

Requires capacitive coupling, tune band may narrow, check connector compatibility, not for mobile use, avoid obstacles.

Operation Precautions

Handle elements carefully, avoid touching antenna during transmission, secure screws, be aware of extension obstructions, and avoid wet conditions.

Connection and Adjustment Procedures

3.5 MHz Band Connection

Connect the 3.5 MHz expansion coil and adjust telescopic element length without a short plug.

7 to 50 MHz Band Connection

Connect telescopic element directly to base coil. Use short plug for 7 MHz band and higher frequencies.

Frequency Tuning Adjustments

Adjust telescopic element length for tuning frequency. Lower frequency by stretching, increase by shrinking.

Counterpoise Connection

Connect a counterpoise wire (e.g., polyvinyl chloride insulated wire) to the R-shaped terminal for better communication.

Performance and Troubleshooting

SWR Check and Tuning

Check SWR by adjusting telescopic length, counterpoise length, and wire arrangement. Use an antenna tuner if needed.

Environmental Factors

SWR may vary based on grounding and installation position. Antenna tuner is recommended for low frequency bands.

Operational Considerations

Product is for amateur radio only. Stop use if abnormal phenomena occur. Check connector fit and avoid continuous output.

Overview

1. Function Description
2. Important Technical Specifications
3. Usage Features
4. Maintenance Features

The COMET HFJ-350M is a portable telescopic antenna designed for multi-band HF to 50 MHz amateur radio communication. Its compact, 3-division structure makes it highly convenient for transport and field operations.

Function Description:

The HFJ-350M operates as a 1/4 λ base loading type antenna, covering a wide range of frequencies from 3.5 MHz to 50 MHz across nine bands. Frequency adjustment is primarily achieved by altering the length of the telescopic element and, for most bands (excluding 3.5 MHz and 7 MHz), by using a short plug to select specific loading coil taps. For 3.5 MHz, an additional expansion coil is used, and the frequency is adjusted solely by the telescopic element's length. The antenna requires capacitive coupling with a grounding system or a counterpoise for optimal performance.

Important Technical Specifications:

• Model: HFJ-350M
• Frequency Bands: 3.5 / 7 / 10 / 14 / 18 / 21 / 24 / 28 / 50 MHz (9-Bands)
• Antenna Type: 1/4 λ base loading type
• Max. Input Power:
  • 75W (SSB) for 3.5 MHz
  • 100W (SSB) for 7 - 50 MHz
• Impedance: 50Ω
• Length:
  • Minimum: 370mm
  • Maximum: 1665mm
• Weight: Approximately 260g (including 3.5MHz expansion coil)
• Antenna Connector: M-P (PL-259)
• Counterpoise Compatibility: Round-shape solderless terminal compatible with stranded wire up to 3.5 sq [AWG12].

Usage Features:

• Portability: The 3-division structure allows for easy disassembly and transport.
• Multi-band Operation: Covers nine popular HF and 50 MHz amateur bands.
• Frequency Adjustment:
  • 3.5 MHz Band: Connect the 3.5 MHz expansion coil to the base coil, then the telescopic element. Adjust frequency by changing the telescopic element's length. No short plug is used.
  • 7 MHz Band: Connect the telescopic element directly to the base coil. Adjust frequency by changing the telescopic element's length. No short plug is used.
  • 10 MHz to 50 MHz Bands (excluding 7 MHz): Connect the telescopic element directly to the base coil. Use a short plug to select the desired band by connecting it between "Term. 0 (Common)" and the specific terminal for the band (e.g., Term. 1 for 10 MHz, Term. 2 for 14/18 MHz, Term. 3 for 18/21/24 MHz, Term. 4 for 28 MHz, Term. 5 for 50 MHz). Fine-tune frequency by adjusting the telescopic element's length.
• Telescopic Element Adjustment: Stretching the rod element lowers the tuning frequency, while shrinking it increases the tuning frequency. Adjustments should be made from the upper narrow part of the element.
• Counterpoise Requirement: Requires a counterpoise (e.g., polyvinyl chloride insulated wire) connected to the provided solderless terminal. The length of the counterpoise is critical for optimal VSWR and varies with the operating frequency and environment. Recommended standard lengths are 20m for 3.5 MHz and 12m for 7 MHz, but longer lines may be necessary depending on conditions.
• VSWR Checking: Due to the narrow tuning band of loading coil-shortened antennas, an antenna analyzer (such as CAA-500Mark II) is recommended to find the tuning frequency. If VSWR characteristics are poor, especially in low frequency bands, an antenna tuner (e.g., COMET CAT-300) may be required.
• Installation: The antenna should be installed as vertically as possible for best communication. Avoid placing it near other antennas, buildings, or obstacles, as this can degrade SWR and shift resonance frequency.
• Not for Mobile Use: This product is explicitly not suitable for vehicle mounting or use while driving.

Maintenance Features:

• Careful Handling: When installing, removing, or adjusting the antenna, avoid opening your eyes at the rod's end.
• Heat Precaution: Do not touch the antenna during or immediately after transmission, as it may be hot and cause burns.
• Secure Connections: Ensure all fixing screws are tightened firmly to prevent accidents.
• Obstacle Awareness: When extending the rod, always be mindful of overhead obstacles.
• Moisture Protection: The antenna is not waterproof. Do not use it outdoors when wet, and ensure it is completely dry before use.
• Physical Damage: If the telescopic element is bent, it cannot be repaired. Handle it carefully to prevent damage.
• SWR Degradation: Continuous output can cause element heat and SWR deterioration. Reduce output power or increase the output interval if this occurs.
• Unauthorized Modifications: Repairs and modifications by the customer are not recommended as they may cause damage.
• Troubleshooting: If any abnormal phenomena occur during use, stop immediately and check the antenna status and connector fit.

The HFJ-350M is designed exclusively for amateur radio communication.

Comet Antenna HFJ-350M Specifications