Manager


Manager - NA4M
Manager Notes

Reviews For: MFJ-784B

Category: Filters, Audio: (DSP and others)

eMail Subscription

Registered users are allowed to subscribe to specific review topics and receive eMail notifications when new reviews are posted.
Review Summary For : MFJ-784B
Reviews: 33MSRP: 249.95
Description:
DSP Noise Filter
Product is in production
More Info: http://www.mfjenterprises.com/products.php?prodid=MFJ-784B
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00334.3
PY5CL Rating: 2003-07-16
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
W7TUT Rating: 2003-03-04
Works great, easy to use Time Owned: 0 to 3 months.
Am using it on a Yaesu FT-840 which had little
or no filtering. Works great. Narrowed up
SSB signals, reduced background noise and
didn't reduce received signal. Also eliminated
some feedback I was getting during xmit into my
external Kenwood speaker.
K6LDX Rating: 2003-02-21
Good for QRM Time Owned: more than 12 months.
I used the MFJ784B for two years with my (non-DSP) FT840 and found it did a good job (for an AF filter) on QRM - took a little learning but was basically easy to use. It was less effective on QRN or local RF noise (AC lines, etc.).

I sold it with the FT840 when I upgraded to an (IF) DSP-equipped rig. Now I wish I had kept it as it has some flexibilities that my new rig's DSP doesn't have!

If your rig has DSP, it probably isn't worth buying unless you find a used one cheap. If you're using a non-DSP rig and have limited filters available, its worth considering.
G0NVD Rating: 2003-01-04
Big box little use Time Owned: 0 to 3 months.
I found this unit of very little use compared to the JPS NIR-10 . it seemed to reduce not only the noise but also the signal being received. Shame as I love all other MFJ products I have.
AF8X Rating: 2002-10-01
Hmmmm Time Owned: 0 to 3 months.
I attached the MFJ-784B to my Kenwood TS50 and was surprised at the signals it brought up that were inaudible without it. I use the settings I programed into it, but if you are trying to adjust the settings while a station is calling CQ, you may spend too much time adjusting and tweaking and lose the contact. It's best to use programed settings or go without at least until you've made the contact.
K2PJT Rating: 2002-08-12
Performance varies with receiver Time Owned: 6 to 12 months.
I use both the MFJ 784B and the W9GR units for CW. The MFJ seems to work best with my R390A and the W9GR seems to work best with my Oakhills 100A tranceiver. I give the edge to the MFJ unit because of the flexability in tuning audio bandwidth and frequency. It is also much less prone to AC hum with generic power supplies.
NZ5L Rating: 2002-03-29
works like magic Time Owned: 0 to 3 months.
I recently acquired this unit thru eBay. I do a lot of CW and my IC-718 isn't equipped with any IF filters. This was a cinch to hook up, as the cables were included, and thanks to the "fast start" pages of the manual I was off and running in about 10 minutes. I often have high noise levels here (NE PA) and QRM is endemic everywhere, but the 784 makes a very dramatic improvement in copyability, almost like magic. This is a very good CW filter and I recommend it for any CW op, esoecially those using older rigs or lacking an IF filter.
NI0C Rating: 2001-12-10
Good programming features Time Owned: more than 12 months.
I use my MFJ-984B 100 percent of the time with my TS-850s. Even though my Kenwood has
a 1.8 Khz SSB filter and cascaded 270/250 Hz CW filters, I still need the additional selectivity
and noise rejection provided by the MFJ audio DSP. I set up several of the programmable filters
so that they are centered on the CW tone frequency of the TS-850s (my tone preference is 650 Hertz.) I programmed the bandwidths for 250 Hz, 200 Hz, 150 Hz, and 100 Hz. Then I set up four other filters the same way centered around an alternate CW tone of 700 Hertz. This leaves two other selectable filters which I programmed for SSB settings to accomodate different voices.

Once programmed this way (and it doesn't take too much effort to program), I find I almost never
use any of the manual settings. Also, since I live in a high noise area, I keep the NR turned on with about a 40% setting on the level control. I routinely copy stations I otherwise couldn't without this unit.
KG6AMW Rating: 2001-08-07
Does The Job Time Owned: more than 12 months.
This is a good filter. I generally don?t care for DSP filters because they promise more than they can deliver, but the MFJ unit does seem to work well.

Physical Layout Front and Back Panels
Power, 10-16 vdc @.5 amp
Headphone plug in 1/4 inch
Speaker out, capable
AGC button, gain control
Program button, memory and CW spotting tone
Memory button
Filter switch, 10 settings
Tunable filter left side, adjusts frequency
Tunable filter right side, adjusts bandwidth
Manual notch filter button
Auto notch filter button
Noise reduction, knob adjustable
Volume control, knob adjustable
Speaker button
DSP function button
Power button

The unit has 10 filter settings which include, CW, SSB, RTTY,
Packet, Amtor, Pactor, SSTV/Fax and 3 general bandwidth options.

The DSP units offers 3 general functions.

Band-pass
The band-pass feature is good. Given your mode of operation, you select and adjust band-pass sufficiently to limit nearby tone or voice interference. It works well for the most part
but does take practice and the realization that some S9 signals will have some blow by or ringing.

Notch Filtering
This unit offers both automatic and manual notch filtering. The automatic notch and manual notch effectively eliminate nearby tones. The manual notch in some ways is much more interesting. Once you get the hang of it, you can use this
notch to lessen strong general noises.

Noise Reduction
The noise reduction feature is generally OK, it won?t help you dig out a really weak signal. Rather, it is used on moderately weak and stronger signals to give the listener a quiet zone to hear the sender thus limit fatigue.

As I said in the beginning I?m not a fan of DSP but the MFJ 784B unit is good enough for me give it 5. To get the most out of this unit, requires that you read the instruction manual which can be a bit demanding. Read it and think on it and you
get it. The basic thing to remember is to select your filter setting and use the tunable filter knobs. The left one centers the frequency and right one adjusts the bandwidth. Everything else is just pushing buttons.
EA5OM Rating: 2001-01-30
Good DSP Time Owned: more than 12 months.
I have the mfj-784b from one year and using it without problem. The auto-noch is cappable of eliminate automatically 2 (or 3? heterodines) at same time. The manual noch is compatible with the automatic mode and is really impressive. The variable bandwith works very well.
In cw mode i like the variable center and also variable bandwith with pot. resistor. No button-fixed mode here! they are memory positions, also predefinied digital modes, noise reduction, etc etc. all runs very well. This hardware dsp remember in most to Brian k6sti VERY GOOD program.
purchased to local contest club. Any years ago...
I used also the Timewave DSP 59 plus but...i sold this unit and changed for the mfj.
An for all users: HAVE YO READ THE INSTRUCTION MANUAL? hummm 73 dx hi hi!