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write your own review of the Radio Shack DSP 40.
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ELJAY
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Rating: 3/5
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Dec 1, 2007 15:43
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Limited but useful
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Time owned: more than 12 months
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I got mine from a Radio Shack surplus store for $10 so perhaps my opinion is bolstered by the relatively good value.
The DSP 40 is of limited use. It's not a good noise blanker. In fact, it can sometimes exaggerate certain types of noise, turning a mildly unpleasant buzz into an unbearably harsh rasp.
What it is good for is reducing hum and nearly eliminating whine.
This can be useful when detuning a broadcast station a few Hz to clarify voices. Often when using this trick whine increases. The DSP 40 can help minimize this whine. It takes a few moments and sometimes some fiddling with the controls is necessary, so experiment with switching between NR and SSB settings, as well as between Narrow, Med and Wide.
It can also be useful for minimizing some noise and adjacent chatter when listening to hams on SSB. In my area (North Central Texas) some local hams (Texas, Oklahoma, etc.) on the 75-80 meter bands are a bit inconsiderate. They either crank up their signals beyond reason until they splatter 10 kHz in both directions with distortion that would embarrass some CBers, or simply haven't calibrated their rig and antenna properly. The Narrow and Med settings can help screen out unwanted chatter from adjacent frequencies.
There's no rule regarding whether to use NR or SSB. Sometimes NR works better on sidebands; sometimes SSB works better on broadcasts.
CW is useful when I'm in the mood to eavesdrop. My CW vocabulary is pre-school level and limited to "de", "73" and "SOS", tho' sometimes I can recognize someone's fist. The CW mode combined with the Medium setting makes it easy to mic the speaker (I get too much noise using the Line Out port to my PC's sound card) and get a clear enough sound to copy the signal and decode it with software. Might be useful with RTTY and other data, never tried it.
It works best when not overloaded, so don't feed too much volume into it. If the green light is steady or flickers regularly, reduce the input volume. Use the volume knob on the DSP 40 to set a comfortable listening level. This will help minimize crackling and whine better than feeding too much into the unit.
The built in speaker for the DSP 40 is pretty awful, tinny and harsh. I've hooked up a nice Radio Shack Optimus XTS 3 cube, one of those solid little speakers with fake wood trim. Sounds really good, mellow but clear.
Don't expect miracles, don't expect it to work with all noises, whines, hums, chirps, beeps, boops and burps. It's definitely *not* a noise blanker, so forget about the "NR" label. But it is useful within limits and worth a few bucks.
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KD7UAK
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Rating: 2/5
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Nov 23, 2007 18:54
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Maybe OK for the price, but...
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Time owned: 3 to 6 months
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I picked up a unit at a local hamfest last summer for $10. For that price I can't really complain. This item is primarily useful as an audio filter, as its noise-reduction capability is so marginal as to be next to useless.
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VR2XMQ
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Rating: 4/5
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Jun 23, 2007 06:23
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What do you expect for $25
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Time owned: more than 12 months
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Honestly what do expect for a $25 DSP filter? In fact it does its job quite well for SSB and CW. Can't complain. The NR mode is not so hot though.
Mine is connected to a Kenwood TS-60 50Mhz transceiver and then to an external speaker permanently. Nice handly size.
Steve, VR2XMQ
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AA5TE
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Rating: 5/5
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Oct 19, 2006 07:17
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Good filter, low price
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Time owned: more than 12 months
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I've had nothing but positive experiences with this filter since 1995 (I think that's when it was made). I've owned two of these, and they are a very good substitute for crystal CW filters if you can't afford them. You can find one of these online or at hamfests for around $25. I've also done the increased audio output modification. I have had trouble with RF getting into the thing, but location, grounding and shielding all help. I have no choice to rate this a 5 based on price and what it does.
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W6RQ
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Rating: 4/5
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Jul 16, 2006 17:19
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works good on CW
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Time owned: more than 12 months
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Does a remarkably good job as a poor man's CW filter. Works good with my Yaesu FT-897D.
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KB5DBR
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Rating: 4/5
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Apr 15, 2006 20:10
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Good for what you pay
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Time owned: 6 to 12 months
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This little filter does just what it was claimed to do. Nothing more. It isn't a big dollar accessory and dosen't perform like one. I have been using one on my FRG-7700 for about a year now and find it helps with weak signal stuff. I do a lot of NDB DXing and find the DSP40 useful in CW mode on weak signals. It's no TimeWave but it isn't priced like one either. IF you don't have the bucks for a big name filter, this little puppie may give you a little help and a little relief on you bilfold.
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NA4IT
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Rating: 4/5
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Jan 9, 2005 21:23
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Good add on for the price!
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Time owned: 6 to 12 months
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I bought one of these at a hamfest sans the cables to try on a Yaesu FT-840. It does very well, and I have since upgraded to a Yaesu FT-900 and use it with it also. A Motorola mobile speaker plugged into it helps bring out the audio. I have found the headphone jack to be weak audio, but useable.
I did the increased audio power mod on mine, and it also helped. I have also found if you get RF into it from 10M-20M, make sure you are running shielded speaker wires from the rig to the DSP to the speaker, and also run shielded on the 12V line. A split ferrite with the 12V line wound 3 times in it helps also. Might have to try moving the bead from one end to the other on the 12V line.
DSP box does well with the notch filtering out the "tuners" and also the narrow settings on SSB and NR help on noisey bands.
Great little add on unit for rigs without good filters!
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NE0P
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Rating: 3/5
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Nov 9, 2004 22:03
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Works ok for the price
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Time owned: 3 to 6 months
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I had one of these filters for awhile, because the price was too good to pass up. I found that the NR works a little, not as good as others. The bandwidth control works pretty good on CW, not too well on SSB. Overall, a decent bandpass filter for CW if you can find it for under $20. If you need something for SSB, there are better options out there.
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KA8KH0
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Rating: 4/5
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Nov 9, 2004 18:03
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Not bad...but...
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Time owned: more than 12 months
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I bought two of these units some time ago for use in my HF packet node setup. (The rigs I was using at the time had no built-in noise blankers.)
That's one thing the DSP40 does well - blanks noise. The unit isn't bad overall and is usually able to improve readability of whatever audio signal you feed through it. A few more bandwidth and mode options would have been nice, however. Still - in many cases, it's better than having no filter at all.
Be sure to verify input-connector polarity; IIRC the tip and sleeve are inverted with respect to "normal" signal and ground.
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