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Reviews For: Radio Shack DSP 40

Category: Filters, Audio: (DSP and others)

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Review Summary For : Radio Shack DSP 40
Reviews: 40MSRP: 39.95
Description:
Noise reduction system / with built in speaker.
Product is in production
More Info: http://www.radioshack.com
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00403.5
N2MDV Rating: 2019-04-29
Good for taking out tune-up HET's. Time Owned: more than 12 months.
Bought at a local Hamfest in 1998 from a Radio Shack dealer letting this go for only $5.00! Couldn't turn that down. At 1st, I wasn't at all impressed, and glad that I only paid $5.00 for it. Then, I'd gotten to see its advantage. On SSB, when you're listening to a great QSO and someone has to tune-up right on that FREQ, kick that DSP ON and that HET whistle just disappears. NICE!!!!! Today, I have Kenwood rigs with that BC (Beat Cancel), button that does the same thing. But, for my SSB rigs that don't have that, this little outboard DSP is still a nice addition to have.
KI6R Rating: 2019-01-18
CW Bandpass Tested Time Owned: 0 to 3 months.
I tested the CW bandwidth in the narrow setting:
-3dB at 600 and 908 Hz, center about 750 Hz.
-3dB bandwidth of 308 Hz.
-6dB at 579 and 928 Hz, -6dB bandwidth 349 Hz.
It would make a reasonable CW filter for a receiver that lacks narrow filtering. The AF output must not be connected to a speaker that has either the +/- connected to DC power supply common. A speaker isolated from ground/common must be used.
AA7BI Rating: 2018-07-20
Audio Technician's View Time Owned: N.A.
As a professsional studio finalizer for CD issuance, I thought I'd chime in and try to help a little. Many people posting here clearly do not understand how to operate this inexpensive gizmo and are missing out. So here is my perspective:

There are three settings: NR, SSB and CW.

NR simply means "Noise Reduction" and features three levels of Low-Pass Filters, each one cutting more highs, but retaining all the bass. This setting effectively blocks heterodynes and some static. Use with AM or FM.

SSB is for sideband and gives three bandpass filter setting that are increasingly narrow, cutting both bass and treble. Likewise, heterodynes and static are reduced.

CW is for morse and has three settings that become so narrow and sharp it almost has that tin-can effect. It reduces static, but not heterodynes (otherwise you'd receive no code).Pick the setting that works for you.

INPUT level into the device is crucial, or it simply won't impress anyone. Once the Noise Reduction button is pressed your rig's volume level must be adjusted so the green light just flickers. Then set the DSP 40's volume control to a comfortable listening level. Now you're operating correctly.

As this unit works in the final audio stage of your rig, it will not sound as clean as a new rig with DSP in the IF. It is most assuredly just an aftermarket add-on. But as these units sell for between $5 and $25 at Flea Markets, you will get a lot of performance for very little money. Some rigs which only have audio output to headphones will really benefit from the DSP 40 as it is a powered speaker as well. It brings older rigs to life and makes receive much more enjoyable with less noise.

A well-kept secret...Hope this helps...

73 de Bob

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Earlier 5-star review posted by AA7BI on 2012-03-17

Can't even remember how long I've had mine, but it must be 15 years or more. I sold the first. Big mistake. Got my Radio Shack dealer to hold the next one for me prepaid.

I use mine with a TS-140S and an HW-8. You can't do better for getting a quick and narrow filter for CW. Improvements on SSB are notable while blocking any stray CW signals or AM carriers in the phone band. Atmospheric noise and tones are diminished considerably.

Tried it mobile but found it didn't help as much as I would have liked. It, like the more expensive DSP gizmos, does not fix everything. But it sure is a shot in the arm for older radios.

OK, so here is where the big guns come to brag about how much they can afford to spend. I can only afford this, and cent for cent, it performs very admirably. In fact, it helps filter out the heterodynes from the big gun QRM.

73 de AA7BI/VE5
NA5XX Rating: 2016-03-06
Decent Cheap DSP Time Owned: 6 to 12 months.
I am using this DSP mobile with an IC-706. Worked well to filter our adjacent channels during the weekend DX contest. Not excellent DSP, but when you can pick on up for about $15 it is worth it.
IZ7FMM Rating: 2016-01-30
Good for CW only Time Owned: 0 to 3 months.
Basically this filter works good just as bandwidth filter: excellent filtering on CW, so&so on SSB.
Noise reduction does'n work in any mode.
For CW use with vintage radio it's a very good toy, and you can spare lot of money using this one instead of expancive internal christal roofing filters.
N1HWQ Rating: 2015-04-14
Helpful for SWLing Time Owned: more than 12 months.
I had one of these little units hiding in the bottom drawer of my nightstand for over 20 years. I had forgotten all about it until I stumbled upon this thread. So I hooked it up to the Sony 7600 shortwave radio on my nightstand and was pleasantly surprised by the results. By turning on DSP and using SSB mode I was able to eliminate about 40 percent of the background noise. Not bad.

I originally bought this device for use in my car with a 10 meter mobile radio years ago. As I recall it wasn't particularly good at eliminating alternator noise while driving. But for casual shortwave listening I'd give it a thumbs up. Every little bit helps.
KD4OBQ Rating: 2014-09-22
Great bang for the buck Time Owned: more than 12 months.
I have owned one of these since they first came out in the mid 90's. For CW they are wonderful but SSB not so good. I paid full price for mine and peddled it at the next hamfest. A year or so later when they were blowing them out I bought 20 of them for $5 each and doubled my money at hamfests ($10) I did manage to keep one and a few years later got into QRP. Great difference on a HW-7 or 8 and several other rigs through the years. It is no Timewave or JPS but neither was the price. Great unit for CW.

KD4OBQ
W4KYR Rating: 2013-12-18
It did nothing to help electrical buzz Time Owned: 0 to 3 months.

I bought this in the mid 1990's when Radio Shack was selling them. I thought it was supposed to help with electrical noise reduction. It seemed to have no effect on helping to reduce the ongoing electrical buzz that appeared nightly in my apartment building.

I can't vouch on how well it worked to clean up CW signals as that is not what I bought it for. But for noise reduction of electrical buzz on the shortwave bands, it did nothing of the sort. I ended up returning to Radio Shack to get my money back.

If you want this to get maybe more clearer CW, it might work. But if you have line interference on the shortwave bands. The only thing this will do is to lighten your wallet some. Steer clear of this.
WA7ZYQ Rating: 2013-12-17
It is decent for what it does Time Owned: more than 12 months.
This is not the piece of crap that some portray it as, nor is it a wondrous object. It does okay for what it costs.

What it does not do is have any noise reduction, per se. See the QST review and Radio Shack's admission of that. What it does do is seem to reduce noise because of its dsp filtering.

It is a handy little audio amp, and a filter and it will boost the signals of some of the radios that it is used with. It is not a qrp device, but can be used with some qrp rigs which are lacking in audio output.

These were not expensive devices, so moderate your expectations and you will not be disappointed. I give it 3 stars because it does most of what it says it does and it does it reasonably well for what it costs. I've had mine since I bought it new from Radio Shack and I haven't seen any reason to get rid of it so far.
W5LZ Rating: 2013-12-17
Good - but. Time Owned: more than 12 months.
I've had more than one of them over the years. You have to keep in mind that this model was one of the first ones out some 30 (?) years ago. It wasn't the -best- at the time but it was available at a lower cost. Is it comparable to later models of DSP filtering? Not hardly, but what do you expect from older models of -anything- much less DSP filters. So depending on what you compare the thing to, call it a '4' or a '3', sort of.
- Paul