Motorola HMN3596A

Mikrofon do radiotelefonów Motorola:

Zastąpiony przez Motorola PMMN4090A.

Modyfikacje

Changes required to improve the audio quality

Refer to Visio Drawing for component references. (HMN3596A xxx.vsd)

C2 [10n] is increased to 0.22 μF
R2 [560 ohms] has a 22 Ω placed in parallel across it. (See bottom photo)
The rubber funnel also made the audio sound somewhat nasal
To improve the acoustical properties of the microphone perform the following: The rubber funnel is squashed flat (that is, rather like squashing the protective rubber ring around the lens of a camera). The FET capsule is removed from the PCB. Solder two short insulated wires of about 3 cm long to the capsule. The capsule is then pressed into the squashed funnel. Mount the capsule now in its rubber ring into the microphone case ensuring that the capsule face sits directly behind the microphone grill. Now feed the two wires through the PCB. Once the PCB is in the correct position, solder the wires. See photo right.
This modification can also be performed on the GMN6146C too.

All these hand microphones have a monitor/hook switch facility built in. When the mic is resting in its hook, a contact is made between the ring and button on the rear of the mic. [Therefore, the set will only respond to a selective call. When off hook, the set can go into nonselective reception mode.] This is a programmable option within the set.
Be aware that if the mic. line (Pin 5) is momentarily shorted to common (pin 4), the set powers down. If shorted again, the set will power up again. (Just in case you think you have blown the set up!)
There are three types of hand microphones suitable for this radio: GMN6146C, HMN1056D and HMN3596A. Only the last type is suitable for electrical modification because it uses discrete as well as SMD components. The HMN1056D cannot be opened without damaging it and the GMN6146C uses only SMD components, which makes it difficult to modify.
The GMN6122A can be used, but needs similar modifications and a RJ45 plug to be fitted.