DPD now available on Icom IC-7610. Just done it!

[KX4QC]

DPD (Digital Pre-Distortion) is signal preprocessing before the transmitter power amp, to remove much IMD from the final signal. Often available on professional and commercial transmitters. Comes standard on the new IC-7760, and can be easily added with the newest free firmware upgrade from Icom. So, how to do, and does it make a difference?

First make sure the IC-7610 is firmware upgraded 1.2x to 1.3x . Do it now, carefully. Pay attention to the instructions from Icom, particularly the dire warnings. I suggest backing up your settings as well, though if all goes well, they should remain intact.

Now download the Icom 1.42 upgrade package and unzip it to reveal the 7610_142.dat file. Copy the .dat to the 7610 folder of a SD card or thumbdrive formatted by the IC-7610. This new upgrade adds DPD and improves menus and IQ handling to external SDR software, so very much recommended.

Return the SD or USB drive to the IC-7610. and select the Menu option SD CARD or USB Flash Drive option, then Firmware Update. Read the cautionary notice, and if unsure, do not proceed. Otherwise, just follow the prompts given by the IC-7610. The process will take about 2 minutes, during which the power must never be interrupted to the IC-7610. (If your electric supply is unreliable, consider using battery power, starting with a really full battery.)

When the upgrade process is complete, the IC-7610 will restart itself. Verify that your settings are intact, and you are like me, back them up again.

Go to Menu then OTHERS and Information then VERSION to make sure that your upgrade has been successful, namely:

Main CPU: 1.42
Sub CPU: 1.06
Front CPU: 1.01
FRGA: 1.12

All good? Let's press on with setting up the new DPD.

DPD Setup

The new DPD setup menu is at Menu, SET, DPD Adjustment. Open it to see options, IC-7610 Single Adjustment, IC-PW2 Linked Adjustment (200V), and IC-PW2 Linked Adjustment (100V). The first is for a barefoot IC-7610, and the other two are for using the new Icom PW2 linear amp. I don't own an amp, so I chose the first. (What to do if your amp is not a PW2? I don't yet know, but if you find out first, post the answer here.)

Open the Adjustment screen. Make sure you are connected to a Dummy Antenna capable of handling full power on all bands. Now use the arrow keys on the Adjustment screen to highlight each of the listed bands, and select ADJUST. The IC-7610 will now apply test signals and self-setup for the cleanest transmitted signal on each band. Oddly, there is no "done" button, so when all bands have been completed, exit the completed process with the EXIT button on the lower edge of the IC-7610. Now to try it out!

Does DPD make a discernable difference?

First bear in mind that DPD is to improve transmitted IMD, so a single tone such as CW or FT8 is not improved. (If this seems strange, look up what IMD is all about, and it should be clear.) So select a favorite SSB band and enjoy a QSO with your trusted friend. An honest report will compliment you on your excellent audio compared with before, assuming you know otherwise how to optimize tome and level settings.

Can you disable DPD after it's set up? Yes, but I can't really think why one would want to do without an improvement embraced by professional and broadcast engineers. You'd go to the DPD Adjustment menu and select the CLR ALL option. Undone!

If you like remote operation of the IC-7610, know that Icom has a free new revision of the RS-BA1v2 software that now includes control of DPD. You still need to purchase the original RS-BA1v2 package, and then apply the free upgrade to the installed package.

There's more info at Acom's website, including free newly updated manuals.

There's some background info at Digital Pre-Distortion on the IC-7610 at https://www.qsl.net/on7eq/projects/dpd-ic-7610.htm .