Connecting the Astatic D-104 to the National NCX-5

I enjoy tinkering with and operating vintage equipment. One recent project has been a National NCX-5. Been hoping to put it on 80M in AM mode. I had not been able to get reliable audio out of this radio and started to suspect the Microphone.  I had been using an old Turner 454C.

I also have an Astatic D-104 microphone and wanted to use it with the NCX-5. However, the NCX-5 takes a standard stereo 1/4 inch plug for the microphone.  My D-104 has a 5 pin CB-type connector.

I thought about re-wiring the D-104, but instead decided to leave it intact. I thought it would be more interesting to build an adapter cable.  This meant understanding the wiring on both ends.

I was able to get the manual to the NCX-5 on the Bama site. It showed how to wire up the 1/4 inch stereo jack.

The D-104 on the T-UG8 stand was a little trickier.  There were multiple connections to contend with.  Fortunately, the bottom of the microphone had a schematic.

A little time with the Ohm Meter and I was able to figure out the pins on the Mic plug. Notice that the switch is in the "R" position.

The pins on the D-104 were as follows.

Pin	Color	Purpose
1	White	Microphone
2	Open	Open
3	Black	PTT Switch
4	Shield	Ground / Mic Ground
5	Red	PTT Switch

I was able to match up the pins and solder the cable appropriately.  Since the NCX-5 uses the same common for the switch and the mic ground, I ran both the Black wire and the Shied to the shield/ground on the National.  Here's what I soldered up.

Pin	Color	Purpose		Connected To
1	White	Microphone	->	Mic/Middle
2	Open	Open
3	Black	PTT Switch	->	Ground/Base
4	Shield	Ground	->	Ground/Base
5	Red	PTT Switch	->	PTT/ Tip End

Here's the completed cable.

I soldered up the cable and tested things out.  PTT worked great and the radio appeared to be putting out clean audio in my tests.  Next step is some on the air tests and AM QSO's.