Batboard

i have a question for the board. i am researching the connection of a MFJ434 voice id'er with a maxtrac mic jack.
several emails to mfj provided a response from one of their techs of, i think the maxtrac pinout is compatible with yaesu, but he wasnt sure.


batlabs site shows maxtrac pin 5 is mic 6 is ptt and pins 3 for hook and 4 is ground

MFJs manual for the 434 shows connections for Mic,mic ground,ptt and ptt ground

has anyone had experience wiring up a cable for a maxtrac to the 434?
is anything special to be included in the wiring, such as extra resistors...etc?

ive wired up audio cables for mfj tnc's to various ham radios without problem, just never done a maxtrac mic project before

i would appreciate any help, thanks

Very simple and easy to interface.

When looking into the front of the radio, pin 1 is the one at the top, closest the volume control.

There's +8VDC on the MIC Audio line to power the preamp inside Motorola microphones. You'll need a 10uF 16V cap in series with the audio line, positive towards the radio. The MFJ unit might already have one. You'll need an audio level of around 250mVAC. Hopefully the MFJ unit has an adjustment pot. The "nominal" impedance of the MIC Audio input is 600 ohms.

PTT rests around +5V. Just ground it to cause the transmitter to key up. A dry relay contact or an open collector transistor works fine.

There's only one ground pin; use it for both MIC Audio and PTT.

You only need to worry about the HOOK line if you want the radio to use carrier or coded squelch. There may be a setting in the programming software to ignore this line and act as if it's always grounded. When ungrounded the radio will be in carrier squelch mode.

Bob M.

2.2 uF 25 volt capacitor + towards the radio. Best to also add a 2.7 K resistor in series to better match the mic input.

80 to 120 mV is the proper input to the mic.