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Reviews Categories | Filters, Audio: (DSP and others) | MFJ-784B Help

Reviews Summary for MFJ-784B
MFJ-784B Reviews: 32 Average rating: 4.4/5 MSRP: $249.95
Description: DSP Noise Filter
Product is in production.
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K1FPV Rating: 5/5 Aug 23, 2006 09:45 Send this review to a friend
Good for the Price  Time owned: more than 12 months
I purchased my 784B nearly 5 years ago to use with my old IC-740. The IC-740 is a terific transceiver but being nearly 25 years old, lacked some of the noise reduction features and audio selectivity features of more modern transceivers. Well, the MFJ-784B took a good receiver and made it much better. For the price it is excellent.

It isn't as good as a Timewave DSP-599zx, but is also nearly half the price. It does show some signs of aliasing when the noise reduction is employed, but doesn't introduce enough distortion to be objectionable. If you don't have the $$$ for the Timewave, I highly recommend the MFJ-784B.
KG0WX Rating: 5/5 Apr 18, 2006 05:52 Send this review to a friend
For an audio DSP, works amazingly good!  Time owned: 0 to 3 months
I've operated several dsp's:

Radio Shack
TS2000X Kenwood
BHI ltd (FT-817)
FT-857D Yaesu
K2 DSP Elecraft

All of the above, yes, including the Elecraft, suffered from a "watery" sound when pushed too far. Most had skirt slopes around 20-25 degrees off of vertical. The best slope angles were achieved with the K2 DSP.

Well, I've moved on and now have a TS-850SAT so I went looking for an outboard DSP for it. Found this one (a 784 non "B") for $75.

Man, I keep upgrading station equipment! This thing even beats the Elecraft DSP! No watery sound unless you REALLY push things. Now the K2 DSP had gain controls for each DSP mode which is very nice (I had mine set to +1.5db) but the MFJ-784 has AGC (even better idea). The AGC is a set it and forget it feature, once you get your input and output volume set right (read the manual hi).

Now onto the filters - There are so many tweaks on this thing it's not funny. Still, unlike the K2, it's pretty intuitive - getting lost in sub menus is not easy when there are no menus! Knobs rule!

Here is how I set up my 10 custom programmable modes:

1) CW mode, 700hz width, 500hz center
2) CW mode, 500hz width, 500hz center
3) CW mode, 300hz width, 500hz center
4) CW mode, 150hz width, 500hz center
5) CW mode, 75hz width, 500hz center
6) SSB mode, 2200hz width, 1250hz center
7) SSB mode, 1800hz width, 1250hz center
8) SSB mode, 1400hz width, 1250hz center
9) SSB mode, 1050hz width, 1250hz center
10)LR/HR wide open with 75% noise blanker

#10 is neat for SSTV - the knob position is the same (10) for SSTV/Fax/WeFax or for custom filter #10. So, when working SSTV, hit 1 button to change from voice quality to SSTV mode.

BTW MFJ likes to call this DSP a "Brick Wall" DSP. well, a few minutes with Spectrogam will make you think....."yep, that's a brick wall"!

I'll tell ya, each of the DSP's I've owned has further impressed me with it's performance. With each I thought I had reached the best. The MFJ-784 beats 'em all.

I really hate to admit that but it's the truth. this DSP is better than any I've tried (including the Elecraft DSP).

PY2FWA Rating: 5/5 May 12, 2005 11:56 Send this review to a friend
FB Job  Time owned: 0 to 3 months
I bought the MFJ784B today and i very happy with it, With my TS-450S and FT-840 (both without any filter)the signal with this DSP filter was excellent, very station on 40Mts band i can't hear whitout the filter, fantastic.
K2PGB Rating: 5/5 Mar 27, 2005 14:53 Send this review to a friend
Near Perfect  Time owned: 3 to 6 months
Have 500 cycle filters in both a TS-680s and TS-140S and also use a TS-830S. The filter works great on CW and SSB. Could not be more satisfied.
K8AC Rating: 5/5 Feb 22, 2005 06:42 Send this review to a friend
Gets the job done  Time owned: more than 12 months
I've used the 784B for a couple of seasons now on 160 meter CW. My requirement was to be able to dig the weak ones out of the noise better. The secret is to use the filter with AGC ON, CW mode, and tunable filters knobs properly set. No need for a very sharp bandwidth as set by the B/W control. The filter often makes the difference between barely discerning the signal and 100% copy. I've used Timewave 599zx and DSP 9 filters and neither came close to the MFJ for weak signal CW. The auto notch also works well on SSB (better than Timewave) and you'll hear less artifacts in the resulting audio.

Note that this filter is large in comparison to the competition.
K2JF Rating: 5/5 Aug 26, 2004 18:18 Send this review to a friend
Where'd the noise go?  Time owned: 0 to 3 months
I live in the middle of Manhattan and have tried everything to deal with this S8 noise level. I thought it was power line noise, but now think it's ol' QRN - atmospheric noise. Anyway, I got this 784B only a week ago and really love this piece of equipment. It takes that noise right out to where I can listen now without thinking I'm sitting in the bottom of Niagra Falls anymore.
I find that setting the filter to SSB, even though I primarily operate CW helps in the quality of the audio. The noise reduction and AGC are incredible and with just a little experimentation it's easy to find the best combination of settings to make for good listening.
I've bought and sold all manner of gear lately but this one is staying right here.
KB3JLZ Rating: 5/5 Feb 26, 2004 11:32 Send this review to a friend
Pretty darn good!  Time owned: 0 to 3 months
Have had the unit for almost three months. Wow! I am also on of those that other than the setup, just puts the instruction manual in the file cabinet. Dont! Keep it handy to see what the knobs and buttons really do. I agree with other reviewers that a spectrum analyzer (software one will work!) is really usefull in setting/seeing what the filters do. A great example is the waterfall display in PSK31/other digital modes. WOW! I was working 15m PSK31 and used the unit to clean up/wipe out a bunch of QRO PSK people. Brick-walled everything except the weak signal I was hunting after. RTTY modes was impressive as well. SSB mode helps alot too. The auto notch just wipes out the on freq tuners dead! Mind you this box isnt going to solve all your noisy band problems but if you have an older rig that dosent have DSP (like my 757gx) this guy will work some lesser wonders for you.

Really like it!
AF4KK Rating: 4/5 Jan 28, 2004 14:46 Send this review to a friend
Great (not so little) unit!  Time owned: more than 12 months
I've been using my MFJ 784B since 1996 and it's been a fine unit. My favorite functions are the programmable filters (they can get quite NARROW!), the built-in SSTV filter and the very-adjustable noise-reduction function. The amp built into the unit also reduces stress on your radio's audio output section. My only gripe is its (sort of) large size but that's a minor issue. Well done, MFJ!!
XE1UFO Rating: 5/5 Sep 4, 2003 18:40 Send this review to a friend
Really great!!  Time owned: more than 12 months
I used this unit with the following rigs:
--Atlas 210X (with only 2.7 Khz built-in filter)
--Kenwood TS180S with double in-line 1.8 Khz filters
--Kenwood TS140S with single 2.4 Khz filter
--Alinco DX70, with 2.4 Khz filter.

I espescially enjoyed using it on 160, 80 and 40 meters for digging signals out of the noise. It DID take a little work to learn, but very well-worth the trouble. It of course does its greatest difference on radios with the widest built-in filtering. On 40 meters it is great for knocking out the broadcasters.
PY5CL Rating: 4/5 Jul 16, 2003 19:46 Send this review to a friend
It Works  Time owned: more than 12 months
I was not able to adjust filters until I started using it with an audio spectrum software, now I know how much filter to apply
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