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

Reviews Summary for MFJ-784B
MFJ-784B Reviews: 30 Average rating: 4.4/5 MSRP: $249.95
Description: DSP Noise Filter
Product is in production.
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KB1VKY Rating: 5/5 Sep 7, 2011 10:36 Send this review to a friend
works great if you do not follow the directions  Time owned: more than 12 months
i have had the mfj 784b for a while now and was ready to give it up. i then decided to play around with it and for go what the directions had told me to do. I use SSB, and AM mode mostly. i found when i set the filter knob to LR/HR and put the low filter knob counter clock wise to approximately 8 oclock and the high filter knob around 12 oclock plus or minus either way. i have the noise reduction "ON" and the knob at approximately 2 oclock. the AGC is set to "OFF". i found the mfj 784b WORKED GREAT. i also found the knobs are very sensitive. if i move them just a hair it makes a big change in the sound of the stations i am trying to bring in. i can now use this filter to tune in distance stations quickly. i also found the "2BP" setting to work almost as well. the "SSB" setting does not work well at all.
my advise to anyone who owns this item and found it does not work for them. forget the directions and play with all the preset set filter settings no matter what mode you are in.
AE5J Rating: 5/5 Sep 4, 2011 17:39 Send this review to a friend
Excellent  Time owned: 3 to 6 months
After using the 784B for some months now, I felt some review might be helpful to someone. First off, this is not something to twiddle with while you are working a contest. However, I found acceptable settings for SSB and CW that offer tremendous benefit.

It is ideal for weak signal DX work. I work primarily CW for this and it is absolutely amazing how it can bring an almost unreadable signal up to full copy. Don't tweak it, just find a good setting with a weak signal, tune without DSP engaged, then punch it on. Quiet, easy, armchair copy.

Use it the same way for SSB. Anyone who works 75m SSB knows how hard it can be to hear through the static and crashes. The 784B takes them out.

I agree that audio is not the best place for DSP, and if you feel that IF DSP is the only way to go, just get out your checkbook. I also use the 784B with an FT-450D (which has IF DSP) and I will state without question that it can be of great benefit. Of course, if you have a rig that has no IF DSP you have two choices: audio DSP or none at all. For the price, the 784B makes a big difference.

I shopped around a good deal before buying the MFJ. You can hear what a good audio DSP can accomplish on the W4RT web site. They have some short audio recordings of audio DSP in and out that give you a good idea of how well they work. The 784B works every bit as well as the bhi system.

By the way. Those who work digital modes using interfaces such as the SignaLink USB with an integral sound card should realize that you have no way to interpose any audio filters when using them. But, many digital modes already utilize their own software audio filtering.

M1JJK Rating: 1/5 Mar 24, 2011 15:19 Send this review to a friend
Poor!!  Time owned: 6 to 12 months
Hello everyone,
I'm going to upset some people with what follows. I don't like the MFJ-784B, I have had two of these and their performance was poor. For contesting and DX their hopeless, by the time you've messed about with the controls you've missed it. I have found that the IF Shift / Bandpass Tuning combined with filters much better and faster at getting rid of unwanted QRN/M. I am not a CW person so maybe its great with narrow modes. Even when I did have the time to mess about with the settings I wasn't that impressed with the results. You are better off investing in a good Inrad / Collins filter/s. After all DSP at the audio stage is a bit late and limited. If you really must have one, and who knows you may love it, get one off ebay or somewhere similar or better still try and borrow one, DON'T pay new price.
And no I wasn't stupid enough to buy a second unit, I was looking after a fellow ham's equipment while he was working abroad.
KA3DNR Rating: 5/5 Sep 20, 2009 11:08 Send this review to a friend
It Works...On Newest Rigs too..  Time owned: more than 12 months
Hello Folks,

I was about to put mine on eBay, thinking it wasn't going to help my new Yaesu FT 450. I was wrong. It definitely does help with the noise, and my CW work. It is well worth it, even to use for the newer rigs.


VE4AMN Rating: 5/5 Jan 22, 2009 14:40 Send this review to a friend
Decent unit  Time owned: more than 12 months
I have had this unit a while and only recently pressed it into service. I added a 12 position switch and RCA jacks (yes 12) so that I can switch in all my receivers. I will add another switch to change speakers.

Overall it works well. I use it with my boat anchors and even over top of the FT-1000mp which has good dsp already. It improves readability a lot, and functions as advertised. I like the programmable options and is has a good internal amp that drives external speakers well.

This unit has been around a while, but it is a sound unit and will make older rigs receive much better.
PD0RTL Rating: 5/5 Feb 11, 2008 06:12 Send this review to a friend
Exelent  Time owned: 0 to 3 months
Got this device now 1 weak.
SSB super clear.
CW super clear.
QRM ???? what was that ??? *g*
RTTY Clear decode.
Exelant device..
DU1MGA Rating: 4/5 Dec 15, 2007 05:08 Send this review to a friend
The 784B is really a must have.  Time owned: more than 12 months

When I was lieving HRO in Woodbridge, one of my good friends there give me as a good-bye present an MFJ-784B. It look like a normal present, BUT he know exact what he give me!!. I'm using my mobil-rig an ALINCO DX-70 as my home rig. This rig has good filters but no fancy thinks like dsp etc. Working with this unit not only remember me to my friend but also know how precise he know the function of this mfj. It brings me back to the old day's where is was so importand to have good feeling in the fingers (0V2 etc.) This mfj is working really excellent. Sometime I grap signals out of the noisefloor I otherweise never was able to hear. To make it short, it is a very good extra to the hamradio-station, if you have the right fingers to tune it hi.
Again thanks to my very good viend and ex collegue how was so wise to give me this pearl of an equipment.

vy 73 de DU1MGA (W3WAZ)
Erwin, Tagaytay, Philippines
OE3SGU Rating: 5/5 Oct 1, 2006 12:14 Send this review to a friend
Ok for the price  Time owned: more than 12 months
I had one of these for some years with my FT-990. I mainly used it for the digital modes and it is really nice for that. For CW and SSB there are maybe better - but more expensive - choices. If you can catch one for a decent price, go for it. It is a nice and handy addition to the shack.
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).

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