Noise problems with Digirig and IC-2730A

I use Digirig Mobile on ic-2730A and connect SP2, microphone RJ45 and computer. Since the analog signal and digital signal share the same ground wire, I can hear a clicking noise from receiver when IC-2730A transmitting. After unplugging the SP2 cable, the noise is disappeared. disappear.

That is a frustrating problem. Does it prevent you from using digital modes, like packet and Vara?

If so, have you considered using ferrite beads on the signal wires and even the power supply leads? Is the antenna far removed from the transceiver? Have you considered using ferrite beads on the feedline to the antenna?

There is a troubleshooting guide: Troubleshooting Digital Modes – digirig

Also congratulations on your DIY digirig, which you presented earlier. I noticed that you use an insulating material for the case:

My Digirig has a metal enclosure. Have you considered a metal case for your Digirig to suppress RFI?

73 Constrainted

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I think this is a problem of design. Not antenna or feed line problem. If i only transmit, the signal is clean. When i plug the RX line between Rig and Digirig, noise will begins.

WSJTX works well. As the noise level is not too high.

OK, that narrows it down. Do ferrite beads on the RX line ( or the other line, too) reduce the noise?

73 Constrainted

Are there consumer radio designs which separate the digital and analog grounds? I don’t think so! Don’t we just jam the digital signals onto an analog voice signal path?

Ah, maybe some designs cut out the hand microphone path when digital/backpanel connection is in use. So I can see a problem with that, OK.

73 Constrainted


I hope you are finding a solution.

Are you using VOX or PTT to transmit? Users here have had success with PTT:

with a solution:

But they do not mention noise. Does this problem persist with battery power? I am sure you will find a way to succeed.

73 Constrainted

Hello. I have an IC2730A and haven’t run into problems with the digirig yet. I use the Icom RJ45 cable in the mic jack which sounds like your setup. If you want me to try something and report back let me know. It caught my eye that you were using speaker 2. I noticed in the manual that SP1 and SP2 behave a little differently. Just a stab in the dark, but if you use SP2 and don’t have the rig set to mute the other band on transmit, is it possible there is some noise in the internal speaker causing the clicking? Anyway if you want me to try something let me know. Good luck.

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I have (a year ago) used a Digirig Mobile V1.9 and an older Icom 2100 which is a lot like the new modern Icom 2730 but only a 2m model.
But it has the same EXT SPEAKER jack for Tx audio and the 8 pin MODULAR mic and PTT line on front.

I got it to work with FLDIGI and with VARA FM with no issues.
Had filters on the USB cable or replaced the one from DigiRig with a better one. It sure sounds like RFI.

I used the RTS pin set “high” to accomplish PTT with my 1990’s Icom 2100.

Be careful with the RX audio via the EXT SPEAKER jack, as the radio’s VOL knob will allow way way too much RX audio to get into the Digirig’s RX mic input on the C-Media sound card.

I can hook mine up again and play with it.
But simple solutions are usually to use REALLY good usb cable from Digirig to computer. The Digirig AUDIO cables and PTT do not carry “digital signals” that you are talking about. The audio from radio to Digirig and from Digirig to radio carry ANALOG signals. And at those frequencies (1500 Hz) are no problem.

I’m wondering if there is something special about the Icom 2730’s PTT circuit. Does it work like earlier Icom VHF rigs by just grounding the PTT pin on the 8 pin modular socket?

Of, as I recall, some fancy Icom VHF rigs used a digital signal for a PTT.
The old RigBlasters had to use a different microphone from the stock one.

But you are pulling the MIC out from the radio, when you plug in the Digirig.
So forger that comment.

Let us know how you solve the problem.

de k3eui barry

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For folks who do not know this about some Icom FM mobile rigs —-

This particular dual-band FM Icom rig (2730) has NO DATA PORT (that 6 pin mini-Din that is so popular). The older 2720 and 2820 radios did have a DATA port. The DATA port is where you pick up RX and TX audio, PTT, and a GND.
On some models you could pick up RX audio with wide-band (9600 baud quality) as well as the normal filtered audio (1200 baud).

That saves Icom some money to eliminate the DATA port.

However, it forces the sound card modes to use the front 8 pin modular RJ45 jack to carry transmit (analog) audio, and PTT and a ground. Then it forces users to pick up receive (analog) audio from the EXT SPEAKER jack (#1 or #2) since this rig has no dedicated “headphone” jack.
But there are TWO EXT speaker jacks - you set up how they function in MENU.

As I recall my DigiRig Mobile V1.9 has WAY to much audio gain in the C-Media’s MIC input (receive audio). So I did “cut the trace” on the Digirig circuit board to enable a 20dB attenuation (there is no RX level knob). I also had to reduce the RX level sensitivity (mic input) with Windows Sound levels.

So be careful, when you plug in the SPKR plug, you MUTE that speaker plug’s audio. I used a simple audio (Y adapter) splitter - one side went to the Digirig audio line and the other side went to an external speaker so I could hear all of the sounds of receive. The rig had no way to monitor your own TX audio (most modern rigs allow that called a MONITOR circuit).

Perhaps the sounds you are hearing come from the rig’s INTERNAL speaker when you transmit. That should not happen (normally).

Try these

  1. Since the 2730 is dual-band, plug the RX audio cable (3.5 mm mono or stereo) into the “other” EXT speaker jack and see what happens.
    You might lower the RX volume (knob on rig) by turning the knob CCW.
    You might “enable” the 20dB of RX attenuation by cutting the board trace.
    You might lower any Windows RECORDING (microphone) audio level to give the C-Media sound card “just enough” audio but don’t starve it.
    As I recall, I lowered the RX audio level in Windows to about 5%.

Are stations hearing your TRANSMIT audio with no distortion?
Or, can you listen to your transmit audio on a second radio or HT?
That is also a good clue about RFI (keep the RF cables far from the USB cable)

What you are describing should NOT happen!
I sense it is because the Icom 2720 has no dedicated DATA port where the levels are mor appropriate for sound card input/output.

PTT method should not affect your TX audio.
Using a COM port and the RTS line for PTT is not that unusual.

de k3eui barry
west chester pa


The 2739 has TWO mic ports. One on the control head, the other on the back panel of the main radio.

Try switching to see what happens?

Sorry, the the main ham companies need a digi port on all mobiles. With WinLink so common, you would think.

Then again, they do not have forums like this to have civil discussion about such matters

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2739? Is this a typo? I thought the discussion is about the IC-2730.
Are you sure that the radio has a mic port on the rear of the radio?
I own the IC2739E and there are two 3.5mm speaker ports.

73, Werner oe9fwv

sorry for the typo on my side: I own the IC-2730E, not the IC-2739 (which does not exist imho)

Werner oe9fwv