Tuesday, June 21, 2016

West Mountain Radio CLRdsp Noise Reduction

I have been chasing DX on HF non stop since the day I passed my Tech exam. My style is using headphones and I usually turn off the AGC and ride the RF Gain knob. I did noticed that after chasing DX for long periods my ears would start ringing really bad and nonstop . My radio does have a few features to help with noise but it's nothing special. I don't even thinks it's adaptive. What works on one station or band is not going to work on the next. I find myself constantly redoing the settings while moving up and down the dial.

A good friend of mine (Mike-KC0BRA) who I chase DX with everyday was also having the same issues as me (ringing ears). He picked up a 2nd hand Heil DSP speaker. He sent some before and after video's of the DSP speaker and I was blown away by how well it worked. .I know not all DSP are the same but I needed something to knock out the noise and hiss. I spent a few hours reading reviews for all the different models on eHam and spent even more time watching YouTube videos. The model I picked up was a West Mountain Radio CLRdsp.
The CLRdsp is extremely easy to setup. You have two options to feed audio from your rig to the CLRdsp. You can use either the headphones jack or the speaker out jack on the rig. I opted to go with the speaker out to feed into the CLRdsp and plug my external speakers directly into the CLRdsp. Everything you need to be up and running is included in the box.The CLRdsp removes almost all hiss and white noise. It made a tremendous difference allowing me to dig out really weak DX stations that would otherwise be lost in the noise.
What sold me was the fact that the CLRdsp will adapt to what it hears automatically. I don't need to fiddle around with my rigs Contour and DSP settings as I did before I purchased this unit. SSB voice is a complete pleasure to listen to. It really made a huge difference in the 450d receive audio. If you have a basic HF rig like I do and you love chasing DX ....Do yourself a favor and get this DSP. You will wonder how you listened to the bands without it.

What I personally like:
Proven design (This might be v3 or v4 of the CLRdsp line)
Built like a tank.
Simple setup & very easy to use
Removes almost all the high pitched annoying hiss on HF
Adapts almost real-time to what it hears even with heavy fading.
No need to constantly dial it in.
Fantastic SSB clarity.
Really does pull out the weak stations burred in the noise.

What I don't like:
Slight delay in the audio loop if you want to monitor your audio out signal with headphones.
It's not cheap.

Brian-K6BRN posted the best way to get the CLRdsp up and running with minimal fuss. This is from his E-Ham review. I emailed Brian asking for permission to repost it here. Please follow what Brian outlined. Getting the CLRdsp "loaded" is not covered anywhere in the manual or online.

My first discovery was that it’s VERY important to properly “load” the CLRdsp input level (i.e. A/D converter).

If the input level is too low, noise reduction is less effective and DSP artifacts, i.e. “the underwater voice” effect, are pronounced. Too high and the CLRdsp begins to clip (and distort) audio, indicated by the normally green CLIP led on the front panel flickering red. In most cases, best results were obtained by:

1. Setting the noise reduction knob fully counter-clockwise (i.e. to minimum)
2. Turning up the rig’s volume control until the CLRdsp CLIP led just begins to flicker red
3. Backing the rig’s volume off slightly to eliminate the red flicker, then
4. Setting noise reduction to the desired level.

This loading adjustment is actually fast and easy, but is NOT detailed anywhere in the very short and inadequate CLRdsp manual. The loading level should be adjusted whenever the noise or signal level changes dramatically – i.e. when changing bands or when a new and powerful signal booms in. The right rig volume setting is also affected by the level of noise reduction set on the CLRdsp; lower levels of noise reduction will cause the CLIP led to light at lower rig volume levels – higher levels of noise reduction seem to allow higher levels of loading. So some “fiddling” can help optimize results.

My next discovery was how (well) the TONE control worked in combination with my rig’s IF Shift control. When the IF shift is adjusted to avoid strong adjacent signals, audio tonal balance changes, emphasizing either the bass or treble elements of speech. This can be very annoying. The CLRdsp’s TONE control really helped to restore tonal balance and I found myself using this control in combination with very slight tweaks to the TS-440SAT’s IF Shift even when there was no interference, simply to achieve improved audio quality.

The CLRdsp put out plenty of audio into every 8 and 4 ohm speaker I tried, and its own integrated volume control is very convenient. It had significantly more “punch” than the TS-440SAT had by itself. I finally settled on a very old Bose 201 speaker I saved from the scrap heap – it was not a very good AV speaker, but it made a great match to the CLRdsp as a rig speaker. I also used the CLRdsp with headphones with very good results. The CLRdsp has a separate headphone output jack that mutes the speaker output when in use and it can be set to accept either stereo of mono headphones, using an internal jumper.

The CLRdsp requires from five to 30 seconds to fully adapt to the noise and interference environment – and it continues to adapt as long as it is on. Each time the level of DSP noise reduction is manually adjusted, its best to pause for a while to see how the DSP filters settle in to the new level. During the settling period, the noise/interference level may be higher and there may be more voice distortion than when it reaches a (somewhat) “steady state”.

Once the CLRdsp was connected and adjusted as described above, I used it on 20, 40 and 80 meter SSB with great results. Background static was usually heavily suppressed (sometimes eliminated) with minimal impact on voice quality, and interfering tones were simply gone. My noisy TS-440SAT receiver became very quiet and pleasant to listen to – remarkable. Most interesting, the CLRdsp sometimes helped me pull SSB voice signals out of the noise, when I could not do so by (my) ear alone. In these cases, correct input level setting to the CLRdsp unit seemed more critical – I had to “fiddle” with it a bit.

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