Watts on the bench #8 – FT817 DSP installation

I bought my FT817 from Strictly Ham back in March 2012 and it was stock standard when I got it. Fresh out of the box, just as it was built.

I was, and still am, happy with how this little radio performs and I am still amazed at the great QSOs I have using only 5 Watts or less.

Recently I have fitted a whip to the front of my car and I have been using the FT817 whilst mobile. The low output power hasn’t been a bother to me as I have mainly been working SOTA activators who are also using low power but the noise the radio was picking up from the car was annoying.

When out in the country, far from power lines and other sources of interference, when heading downhill with no acceleration, the S meter would drop to S 1. As soon as I accelerated to climb the next hill the noise would rise to S 8 and any weak stations underneath would be lost.

Ribbon cable connector at back of radio

The noise was being radiated by the engine and was present when I was running from the internal battery in the radio or from the car’s battery.

The solution to this was to fit the bhi DSP Noise Eliminating Module from W4RT.

I ordered online and it arrived about four week later.

The little module came with printed instruction which I had already downloaded and read.

Location of C1338 – needs to be removed
Input and output wires attached

The instruction were easy enough to follow for someone who has the experience with electronic circuits. This is not something I would suggest for a first up project.

All up it took about two hours to install.

I had two minor problems with the installation.

  • The button would jam against the top panel as it was being pushed over slightly when I was attaching the cover. This took a little bit of adjustment of the Z bracket and PCB to get a position where it was good.
  • The beep level was too loud and I had to take the radio apart to adjust it after assembly.

Once fitted, and set to level 3 or 4, the vehicle noise is all but gone. It still shows on the S meter but at least now I can drive and listen to weak signals without losing them each time I accelerate.

Holes marked for drilling
Keyboard in position – held in place with Z bracket

DSP module in position – held by double sided tape



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