How to Connect a Heil Element

This classic microphone could have a Heil element retrofitted for amateur radio service.

Microphone elements have different frequency response characteristics based on their intended use. Broadcast microphones exhibit the widest possible frequency response to preserve the fidelity of the transmitted audio. By contrast, microphone elements for amateur radio have their response limited to the range of normal speech---300 to 3,000 Hertz---to comply with federal and international bandwidth rules. The Heil HC-4 and HC-5 dynamic microphone elements further accentuate audio response within this range to give the transmitted signal added "punch" that improves readability under poor radio conditions.

Things You'll Need

• Microphone housing
• Screwdriver set
• Soldering iron
• Desoldering braid
• Heil microphone element
• Wire cutters
• 1 microFarad non-polarized capacitor
• Solder
• Microphone amplifier or step-up transformer (if needed)

Instructions

1. Disassemble your factory microphone housing with a screwdriver. Keep track of the screws as you remove them.

2. 

   This desoldering pump is an alternative to the braid.

   Desolder the two wire leads from the existing element, using a soldering iron and desoldering braid. Remove the element, and set it aside.

3. Place the Heil element in the space where the factory element was located. If the factory element had a molded plastic surround, you may need to clip the plastic with wire cutters to make clearance for the new element.

4. 

   Use a grounded soldering iron for this and all electronic work.

   Solder the leads to the two terminals on the Heil element. If the factory element was electret, connect the 1 microFarad capacitor in series with one of the leads.

5. Reassemble the housing, dressing the wires properly to avoid pinching and short circuits.

6. Connect the microphone to your radio, and adjust the microphone gain while transmitting into a dummy load.

Tips & Warnings

• The Heil element can be placed in any microphone housing as long as you wire it so it is electrically compatible with your transmitter.

• Ensure that your transmitter is compatible with a low impedance microphone element. If it is high impedance, you can still use the Heil element, but you may need to add a microphone amplifier or step-up transformer.

References

• ab4oj.com: "Roll Your Own Microphone"; Adam Farson
• ARRL Handbook for Radio Amateurs; American Radio Relay League; 1996

Resources

• Read this Article in Spanish