# Digirig and ICOM IC-2820

**URL:** <https://forum.digirig.net/t/digirig-and-icom-ic-2820/4607>\
**Category:** Uncategorized\
**Tags:** icom-ic-2820h\
**Created:** [October 12, 2024, 9:13pm UTC](https://forum.digirig.net/t/digirig-and-icom-ic-2820/4607 "2024-10-12T21:13:52Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![K3euibarry](https://forum.digirig.net/user_avatar/forum.digirig.net/k3euibarry/32/906_2.png) [@K3euibarry](https://forum.digirig.net/u/K3euibarry)\
**Post date:** [October 12, 2024, 9:13pm UTC](https://forum.digirig.net/t/digirig-and-icom-ic-2820/4607/1 "2024-10-12T21:13:52Z")

</div>

**DigiRig V1.9 sound card and Icom 2820 dual-band FM radio**

**Note: the DigiRig has a COM port thus the PTT function can be over the COM port using the RTS or DTR pins for SEND.**

**This makes it an ideal sound card for any of the “linked modes” (VARA FM) via Winlink Express or VAR AC applications.**

**I just hooked up my 3 yr old DigiRig V1.9 to a 10 yr old Icom 2820 (dual band FM rig with DATA jack 6 pin MINI DIN)**

**The DigiRig RADIO cable (4 pin, TRRS) hooks up to the Icom 2820’s 6 pin MINI DIN plug, but this cable has the RX audio on Pin 4 (9600 baud).**

**This is RECEIVE audio. From pin 4 the receive audio is wide-bandwidth and FLAT, often called the 9600 baud cable (grey/green color)**

**The other 3 wires in this cable are for TX audio and a PTT and ground.**

**This is the RADIO cable, not the SERIAL cable.**

**There is nothing plugged into the SERIAL cable socket at this time.**

**This is NOT the optional Digirig cable that picks up RX audio on PIN 5 (1200 baud, filtered, and narrow bandwidth).**

**Either RX cable should work fine, but PIN 4 is Wide-Bandwidth (6 kHz) and PIN 5 is narrow-bandwidth (3 kHz - filtered like speaker audio)**

**Unless I were trying to run VARA FM “wide” this cable to pick up RX audio on PIN 4 would be required.**

**Tx audio is hooked up to PIN 1 (the only TX audio input on the MINI DIN port.**

**But the ICOM 2820’s MENU is set to transmit via 1200 baud (pre-emphasized and filtered) similar to the rig’s mic jack.**

**I did have the option to set the Radio’s TX audio also to wide-band 9600 baud (with no audio filter)**

**but for now, the TX audio is set to narrow bandwidth option (1200 baud).**

**On most FM mobile radios the MENU SETUP determines the TX audio path.**

**NOTE: Tx is by PTT on the COM port (set to 9600 baud, 8 bit, 1 stop bit, no parity checking)**

**Thus, this setup does NOT rely on VOX for PTT (send) like a SignaLink.**

**SignaLinks are MONO only (left channel) and the PTT is a bit finicky with VOX and DELAY (hang-time).**

**However - the DigiRig is very small size and has no knobs to adjust TX audio, RX audio.**

**You do the levels adjusting in the software settings, and in the Windows settings.**

**MY Windows 10 levels**

**Tx audio = Speaker out audio level is set to -22 dB (10%)**

**This would have been less attenuation if I had set the radio to TRANSMIT at 9600 baud.**

**Fldigi Tx attenuator is set to -8 dB for the RF spectrum set to amplitude carrier = amplitude 1st sideband for MOD INDEX of 1.5**

**Thus, the DEVIATION is equal to: MOD INDEX x AUDIO freq = 1.5 x 1.5 kHz = 2.25 kHz deviation (about ideal)**

**Here is the RF spectrum centered on VFO = 145.690 MHz, showing that the amplitude carrier = amplitude 1st sidebands**

**Recorded by a RSP duo (hardware) and RSP Spectrum Analyzer (software) shown below.**

**NOTE: no PL tone sent on simplex, so each multiple “sideband” is 1.5 kHz from the RF carrier on 145.690 MHz**

**This is very different spectrum compared to AM or SSB.**

**If you try this on a repeater frequency with a PL tone, the spectrum looks much more complex, so adjust TX level with NO PL tone.**

**note: since I am transmitting at 1200 baud, the higher pitch sounds will have a greater deviation (just like human audio with a microphone).**

**It does not seem to cause any problems (my experience) with receiving stations set up for 1200 or 9600 receive audio.**

**Ideally - you might want all stations on a 2m FM net to be set up for 1200 baud (filtered) or all stations to be set up for 9600 baud (unfiltered) but**

**with the narrow bandwidth FLDIGI modes on FM radios like MFSK, OLIVIA, THOR, Cont, AFSK RTTY, or even VARA narrow ==\> it does not seem to matter.**

**Almost all of these modes require a bandwidth of less than 2.5 kHz, centered at 1500 Hz.**

 ![image](https://forum.digirig.net/uploads/default/original/2X/1/1900e581f9d39f2602145097136f8a5bf4077edb.jpeg)

Here is the resulting **RX AUDIO** (received on Pin 4 with flat audio or 9600 baud, wide 6 kHz bandwidth)

but only recorded up to 2500 Hz.

The amplitude is fairly constant over the audio range 500 - 2500 Hz (where Fldigi operates on most modes)

de k3eui barry

 ![image](https://forum.digirig.net/uploads/default/original/2X/5/512ffa0bb664d811e195b26dc97bfe2e071f64ae.jpeg)