An S/P DIF-based External DVR for the IC-7800

by David A. Kopacz, KY1V


I am extremely excited about my new IC-7800. What a fantastic radio.

After using it for a few days I thought I would try out the Digital Voice Recorder (DVR) feature. Pretty neat. I can call CQ effortlessly, and I can record what I hear which can be handy when trying to copy a weak signal and get a DX stations call sign. I can play the recorded audio back over the speaker or in headphones as many times as necessary.

What has frustrated me is the fact that I cannot record a station and then play back that recording to them over the air. "Why would I want to do that?", you may ask. For many reasons, however, two that come to mind right away are the fact that I may want to let a station with an audio problem hear exactly what he sounds like, or I may want to play a snippet of audio back to a station that has excellent audio. I am sure you can come up with plenty of your own reasons to want to play back the audio of a station you have recorded.

Well, it cannot be done with Icom's current implementation of the DVR. What a shame!

I do, however, have a solution that produces a high quality playback of the audio recorded of on-air stations. It is actually quite simple to implement and uses a feature of the IC-7800 that is not available on any other radio made.

Your new IC-7800 has two external connections called S/P DIF (Sony / Philips Digital Interconnect Format). These interfaces provide high quality digital audio input and output interfaces to the radio via optical cable.

What do you need? I recommend a Sound Blaster Audigy 2 ZS Platinum or Platinum Pro. Both of these sound cards come with an audio "drive" that provides the S/P DIF optical interfaces to the computer sound card via a Firewire (IEEE-1394) connection. This allows you to send audio from your radio to the sound card and from the sound card back to the radio, with the highest quality currently possible. Are you thinking like me? I just found another feature never before available that helps justify the cost of this radio!

How do you use this new feature? Well, this part is a bit quirky because there is no way to permit the transmitter to allow transmission of both the audio from the microphone and the S/P DIF at the same time, so you have to switch back and forth. Basically, once you hook up the interface, your radio will start sending audio to your computer's sound card (without even using the volume control on the rig - mine is all the way down), and you can use the free software (Creative Wave Studio & Creative Graphic Equalizer) that came with the Audigy sound card to record the incoming audio. To play it back, you simply push the PLAY button on the software and make one menu change to the radio.

The menu item that needs to be changed is as follows:

  1. Press SET

  2. Press ACC

  3. Scroll to DATA OFF MOD

  4. Rotate the main VFO dial to select

  5. MIC, ACC-A, ACC-B to transmit using your microphone

  6. S/PDIF to send the wave recording to the transmitter.

If you leave this menu item up, you can switch back and forth pretty quickly. However, I think it is kind of cheesy, so I am going to ask Laurent (F6DEX), the developer of TRX-Manager, to make a button on his radio interface for the 7800 that will quickly switch back and forth between MIC and S/PDIF modes when not in DATA MODE.

Some other advantages of this method are that you can record entire QSO's, or even record rogue operators whom are causing deliberate interference so you have proof to provide to your radio regulatory agency.

It is nice to be able to have such a quality interface to the radio for recording and playing audio. Great job Icom!


The diagram for connecting the Audigy drive to the Audigy sound card is provided by Creative Labs and is simple to follow.

You could also use a microphone input to the Audigy sound card, and use the graphic equalizer to tailor your audio before it ever gets to the radio. This would permit you to leave the radio set to S/PDIF all the time, and never have to switch back and forth to use the record feature.

I also found that I can plug my Heil Headset directly into the Audigy MIC input and use the Creative Equalizer to tailor my audio when in S/PDIF mode. Switching to MIC mode (via the SET > ACC > MOD DATA OFFmenu) I can switch back and forth between the Heil headset plugged into the Audigy sound card and the Heil boom mike plugged into the radio.

Please note that when using the microphone plugged into the sound card routed to the radio via the S/PDIF interface, you lose access to the speech compressor, but you gain the value of the computer's software to tailor the audio before it reaches the radio.

In addition, I have discovered today that I can use TRX-Manager's TRX-Command window to create two custom commands  and  to switch between MIC input and S/PDIF input with the click of a button. Here are the command codes:

This is very handy, especially when using a microphone connected to the rig and recording stations for on-air playback. You can also use the spare Macro buttons on the main monitoring window for more convenience.I named one MIC and the other SPDIF.

While it would have been much simpler for Icom to permit the playback of recorded audio over the air, I am beginning to think that this method is much more versatile, provides more flexibility and is of much higher quality.

Copyright  2004 D. Kopacz KY1V. All rights reserved.  Last revised: September 25, 2019.
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