BHI DSP NOISE REDUCTION BOARD

Just received one of the BHI DSP Noise Reduction boards.

This one has a 3 watt audio amp on board.
So it will drive speakers directly.

Built it on some plexi, couldn't lay my hands on a bit of PCB here at the /2 QTH <grrrr>.
It will take speaker level input, as supplied. Running it out of the phone jack. Tried it
on several receivers. Have made no board level adjustments, running it as it arrived so far.

It's set for 8 levels of suppression. You can set it for 4.
A close look at the chart in one of the manuals shows a curious set of relationships.
As the level of suppression increases the noise suppression seems to plateau, while the
suppression of "tone" increases...

Another thing I noticed is that the clips online, both from the mfr and users (youtoobe) appear to show the unit working better than the one I have here. Generally speaking voices sounded clearer and better on the online clips. Interestingly, some of those clips show the unit completely eliminating music on a foreign broadcast SW. I could not duplicate these results

The higher levels of suppression do not appear to be useful so far. The result is a rather "ringy" audio that is reminiscent of the way a ring modulator sounds.

There is a slight delay imparted by the unit, when played in tandem with the main speaker, it appears as a moderate but not intolerable echo - same with monitoring transmitted audio, does not make you stutter. That's good.

The "no processing" position seems to run the DSP anyhow, and the HF noise is somewhat attenuated compared to straight through, which is the "power off" position where the signal runs through a relay, input connected to output. In most situations this is not all bad.

The scheme of switching the DSP levels by pushing a button multiple times and listening to a beep was concerning before I had the unit running. The idea of trying to pick the just right level at any given time and having to scroll through 8 positions did not seem like it would work. But, as it turns out it seems like there are actually only two, maybe three positions that are useful.

I have found so far that position 2 of 8 is a good one. So, since it remembers where you left it, you can just power on, and hit the "select" button to toggle the unit between no DSP action and level 2 DSP action, or hit the power off and go straight through.

This works out nicely.

The /2 QTH being in the city of Albany NY has a pretty good, although not all that bad ambient noise level. It runs daytime between ~S6 and sometimes (on occasion, and I then get worried if it will ever come down) as much as 20 over. The average is with the needle more or less straight up in the middle of the scale. Luckily, most signals are above that noise floor. At night things are usually much calmer. Which is very good.

So, here's what I found. Since the BHI module has its own amp, I plugged in a "full range" 8 inch paper cone driver and set the input up with a long coax cable and phone plug on the end. I tried the BHI with the TS-440, R-388 and the new SX-28.

One of the things that happens when you have a pretty good background "white noise" is that a strong station will quiet everything, and then when they unkey the white noise rushes back at you. Even with the RF gain lowered, if you need to hear weaker stations, that noise is going to come back as the AGC releases.

The BHI does a very good job of "hushing" that background. Not totally gone, but reduced sufficiently so as to make the sound of the idle receiver not the sound of a noise generator with the volume jacked up, filling the shack.

It does also do well with making it easier in many cases to hear stations that would otherwise - no matter what other knobs on these radios that were fiddled - be rather in the noise less in the noise. Sometimes it does make the difference in being able to hear a station near the noise floor.

In a QSO with strong stations, I'd turn it off. In conditions less than wonderful, turn it on.

If this thing was priced at about half it would be a solid SLAM DUNK purchase. They'd probably sell a whole lot more of them too - but that would cut the margin down to almost non-profit I suppose. But, my calculation on this was that there's no benefit to having gear that does cost $$ and not being able to hear what you want to hear! So, if this board did what it was advertised to do, it would be worth the price. And, so I think it is worth it. The BHI does get rid of a whole lot of hash noise that I do not enjoy coming forth from the speakers, and it also does a reasonably good job on cleaning up difficult signals enough of the time to be a real plus.

Keep in mind that this unit has a bandwith limit set at 4300Hz. But since the idea is to eliminate high frequency hash, it's not much of a problem. I think of it as just another filter, another tool to use.

Btw, I ordered this one from Gigaparts, not the W4 who also sells them - he might be fine once he gets relocated, I don't know.

_-_-bear

PS. this board works far better than the "noise reduction" on SDR Console - if you've used that. I do not have experience with the DSP functions on the Anan or the Flex series to compare with.