Using a Heathkit HD-15 phone patch as a DVK interface  

Basically the sound card audio is fed into the line input of the patch unit. The mic audio is taken from one of the outputs. Since the HD-15 has both 600-ohm and Hi-Z outputs, it will work with new radios and older types alike. So far, I have tried this interface on the Kenwood TS-180S, Icom IC-451A, IC-751 and Yaesu FT-221 radios. In order to use the interface with the station mic and logging software, you will want to add some impedance matching to the sound card output and switching of the audio and PTT line. If you don't mind modifying the HD-15, you can put everything inside the box.



Audio from the sound card (8-ohm) is fed through an impedance matching transformer into the line input (600-ohm). This interface allows the audio level to be monitored on the VU meter and the TX mic gain can be adjusted using the front panel control. The sound card volume can be adjusted to match the station mic level when the 'Trans gain' control is mid range. The sensitivity of the VU meter can be increased if necessary by reducing R1 (3600-ohm), which is connected between S1-A to S2-4. The VU meter allows you to set all your wave files to the same level. After recording your files, play each one into the DVK interface and reset the volume of each accordingly.

A small control relay switches the audio between the station mic and the DVK. The newer radios power the mic (8V) from the front panel connector. Unfortunately this power source is current limited to a few mA, so you can't 'steal' the voltage to drive a relay for example. Just the same, don't forget the 2ufd dc blocking capacitor. Use the 600-ohm audio for new radios and the Hi-Z audio for older radios using a high impedance microphone. Needless to say, shielded audio cables are used for all mic connections. I used one of the RCA phono jacks for the mic output to the radio.

Another small control relay switches the PTT line. The control line from the pc interface (ground on TX) can be connected at the SPKR terminal for example. The wire going to this terminal can be removed. While not necessary when using a RIGblaster interfaced to the logger, a bypass switch should to be wired in series with the pc interface line to drop the PTT control, if you hit the wrong F-key for example. Connection to the radio's PTT line can be made via the other RCA phono jack. I used a single DPDT relay to switch both the audio and the PTT line.

I connected to the 8-ohm speaker output of my sound card since the level of the line output was not high enough to drive the DVK interface. There is more than enough audio available. If you want to add an 8-ohm audio attenuator to make the volume adjustment less sensitive, attach a T-pad at the line terminals going into the 8-ohm/1K-ohm transformer. 10dB T-pad: 2 x 4.3-ohm series resistors and a 5.6-ohm shunt resistor to ground. 20dB T-pad: 2 x 6.8-ohm series resistors and the shunt resistor is 1.5-ohms.


   Using a Kenwood PC-1A phone patch as a DVK interface  

The sound card audio is fed into the line input of the patch unit. The mic audio is taken from the normal audio output. The PC-1A was made for TS-520/820/930 series radios with high impedance mic inputs. You will want to add some impedance matching at the interface audio input and some switching to use the interface with your Kenwood station mic and the logging software. If you don't mind modifying the patch unit, you can put everything inside the box.



Audio from the sound card (8-ohm) is fed through an impedance matching transformer into the line input (600-ohm). The transformer can be connected to the line terminals inside the box. The sound card volume is adjusted to the same level as the station mic when the 'TX Gain' control is mid range.

The PC-1A has a front panel mic connector for the station mike and a cabled output line, so the mic cable wiring may only require a connector change. A small control relay is wired in place of S1-2 and switches the audio between the station mic and the DVK audio. Shielded audio cables are already used for the mic connections, so keep your relay wiring as short as possible. Another small relay is wired into the PTT line at Pin-2 of each mic connector to switch the PTT line. The pc board construction makes adding the relay modifications slightly harder than the open wiring of a Heathkit HD-15. Since the mic connections and DVK audio are available on the top of the pc board, removing the board is not necessary. A single minature DPDT relay could be used to switch both functions.

The PTT control line from the pc interface (ground on TX) can be connected to the RX IN terminals for example. The wires that are connected to those terminals can be removed. While not necessary when using a RIGblaster interfaced to the logger, a bypass switch should to be wired in series with the pc interface line to drop the PTT control, if you hit the wrong F-key for example.



Do [ right mouse, Back ] or click your browser's [ BACK ] button to return.