A Digital Voice Recorder/Keyer Controller for the IC-756Pro II

by Larry Handwerger N2LH


Larry N2LH using the DVR Controller during the ARRL SS Phone Contest.
Fig. 1. Larry N2LH  using the DVR Controller during ARRL SS

This page describes the IC-756Pro II Remote DVR/Keyer Controller designed and built by Larry, N2LH, with the following features:

  1. Four pushbutton switches (S1 through S4) for remote memory selection.

  2. A PTT / XMIT selector switch (S6).

  3. A PTT pushbutton switch (S5).

  4. An RCA jack for a foot switch (J3).

  5. A microphone input jack (J1) Note: Larry uses the HC-5 headset.

  6. A 0.47 µF blocking capacitor (C1) in series with the MIC HOT line, to keep the +5V DC off the Heil element.

Schematic of DVR/Keyer Controller. Copyright N2LH.
Figure 2. Schematic of DVR/Keyer Controller.

 

Reference

Description
C1 0.47 µF 50V ceramic
J1 3mm mono jack
J3 RCA jack

R1

 1.5K 0.25W 5% metal-film

R2

 1.5K 0.25W 5% metal-film
R3 2.2K 0.25W 5% metal-film
R4 4.7K 0.25W 5% metal-film
S1, S2, S3, S4, S5  SPST non-locking pushbutton switch
S6 SPDT toggle switch (On-Off-On)
Table 1. Component List.

Construction: As will be seen from the pictures, the DVR/Keyer Controller is built into a Radio Shack® utility box. A die-cast aluminum box is also suitable. All the required parts should be available at your local Radio Shack store.

The 0.47 µF (4700 pF) blocking capacitor is used to block the phantom +5VDC on pin 1 of  the MIC connector. (Refer to IC-756Pro II User Manual, p. 9).This capacitor was purchased via mail order from an electronics parts supplier; Radio Shack did not stock it. A higher value (0.68 to 1.0 µF) is also usable, and may be in stock at Radio Shack.

I used a plastic utility box, as I wanted to separate ('float') the microphone and PTT grounds;  the microphone  jack is not insulated from the the box. Because of that, I used a small piece of shielding braid taken from RG-174U coax to put over the microphone hot and ground leads. I soldered this shielding to the ground of the cable which plugs into into the IC-756Pro2 MIC socket. The braid is covered with heat-shrink tubing. I was concerned about RF getting into the microphone input.

If a metal box is used, the microphone jack should be insulated from the box to isolate the MIC ground.

Operation: Please refer to the IC-756Pro II User Manual,  p. 73, "External Keypad" for menu setting information and operating instructions.

External view of DVR/Keyer Controller.
Figure 3. Exterior view of DVR/Keyer Controller.

 

Internal view of DVR/Keyer Controller.
Figure 4. Interior view of DVR/Keyer Controller. 

Contents copyright © 2002 Larry Handwerger N2LH (including all images). All rights reserved. 
Page created by A. Farson VA7OJ/AB4OJ. Last updated 06/16/18