The AM Forum

ran across this DSP noise reduction board by accident on yoohootube. It had escaped my scan, apparently it's been around for a while. Looks like it has some utility and merit. But I could NOT find anyone using it for ham AM. Heard a few examples of SWL AM... looks like it kills that pesky noise rather nicely.

Problem is that on yoohootoobe, everyone is using little teeny tiny speakers - hard to know what it might sound like with somewhat better, wider bandwidth speakers...

Anyone got experience with it?

https://www.bhi-ltd.com/noise-cancelling/pcb-modules-low-level-audio/ (https://www.bhi-ltd.com/noise-cancelling/pcb-modules-low-level-audio/)

                              _-_-bear

anyone see or hear of it?

think I am going to drop one into my TS-440, and if it works ok, maybe get the general purpose one and set it up on the headphones out of various boatanchor receivers feeding a small power amp.


                            _-_-

I hate to promote anything other than a real boatanchor radio here, but I found that my Tecsun PL660 with its sync detector feature does amazing things. It allows me to hear the USB or LSB of an AM signal and by narrowing the bandwidth of the radio, does a nice job to clean up a QSO in battle conditions.
Full range audio going through those noise reducer circuits, speakers, etc etc give weird effects if you switch in too much processing.

Fred

I have the NEDSP1062-KBD module built into a Yaseu SP-8 speaker which after installing this module and packing the speaker with speaker foam I use it for a general communications speaker.  The module is a large help on SSB and CW and I would say is marginal on AM.

I use the BHI Neim1031 outboard with my R390A, and it works great. Listen to the attached file of N5AEA on 40 the other night. After several seconds, I switch the DSP noise reduction in -- dramatic. Then I switch it out, and then back in -- I am very pleased with this little unit, and it really does help readability in noisy conditions.

Doug

Impressive. I do hear some artifacts and there is some hollowness, but on a noisy signal it's a big improvement.

I'm a not-a-fan of those little 3" paper cone speakers.

And, for radio usage, not-a-fan of "hifi" speakers either.

Prefer "old school" 8" and up paper cones loaded into an appropriate cabinet, with absorption on
the back side. I find that gives a very very good natural sound and doesn't make the noise
prominent while not dropping off the ~5-6kc highs either.

So, I'll be interested to see how the little inboard module fares on AM fone.
There are *definitely* times when I'd like to NOT hear the background band/rfi noise, especially when
a big signal unkeys, or a weaker station is riding the noise floor...

We'll see how it fares in this set up... I ordered one from the USA "distributor".

                   _-_-

[quote...especially when a big signal unkeys,...[/quote]

Squelch can take care of this problem. If you are worried about pw types being squelched out, use a smart squelch circuit.

http://www.repeater-builder.com/projects/jpl-vox-sq/ssb-squelch.html

It's an interesting idea.
The site cited shows a "vox" circuit, but I presume it could be used as a squelch?

But a typical "hard squelch" does not sound good. The TS-440 has one built in. NG.
What's needed, IF one wants to use such a thing would be some "conditioning" of the
control line to change the slopes of the on/off and to not cutoff the audio entirely.
I'd want some sort of level reduction so that the receiver does not sound totally dead.
More like AGC/ALC action, but keyed off the voice... for AM it might work keyed
off a carrier... but then I'd worry about missing low S-meter level stations.

...but heck, that's more or less the
function that the DSP board does, and it has adjustable dB levels of "filter" action, which scrub
white noise entirely.