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Reviews For: MFJ-720 Deluxe Super CW Filter

Category: Filters, Audio: (DSP and others)

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Review Summary For : MFJ-720 Deluxe Super CW Filter
Reviews: 1MSRP: $44.95 in 1981
Description:
The MFJ Deluxe Super CW Filter gives an incredibly narrow 80 Hz bandwidth and extremely steep skirts with no ringing for razor sharp selectivity. It will pull CW signals out of interference in any ham radio band. You simply plug the kit into your radio phone jack to drive phones or between audio stages for full speaker operation. You can select three bandwidths: 80, 110, 180 Hz. Noise is down at least 60 dB one octave from center frequency for 80 Hz bandwidth. Center frequency is 750 Hz. The kit's 8 poles active IC filtering uses low Q cascaded stages. Stops ringing. No impedance matching needed. No insertion loss.
Product is not in production
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# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0015
KB2HSH Rating: 2021-11-09
Nearly identical to the CWF-2 Time Owned: 3 to 6 months.
As summer began to wind down, the Lancaster Hamfest took place at the Transit Drive-In...just northeast of Buffalo NY. Passing by the tables, I stumbled upon a basket case MFJ-720 Deluxe filter that had clearly seen better days. As an avid collector of early MFJ gear, I couldn't pass it up...at $3, if I couldn't make it work, the old school Ten-Tec box was worth $3. The original owner/owners, took the "golden screwdriver" to the 720...and botched it quite badly.

Upon examination, the 720 is almost 100% similar to MFJ's older CWF-2, with the exception of an RCA in and out Jack on the rear apron. This is different from the CWF that has 1/4" mono on the front and screw terminals on the back. The 720 has the 1/4 jack, as well as the RCAs.

The filter has the same 80/110/180 Hz filtering capabilities, centered at 750Hz.

The one thing that I did notice is that, unlike the CWF-2 that can happily run off of a 9v battery for weeks at a time, the 720 needs a bit more amperage to make it happy. Perhaps this is why the 720 has a coaxial power jack on the rear apron. When given the correct power, the 720 plays happily.

Coupled with the MFJ Cub 9340 that I picked up, the filter makes the little 2 watt transceiver play like a big radio. Signals seem to pop out of the noise at the 110 and 80 Hz settings.

Despite being older...and by older, we're talking a design that is almost 50 years old, it is a filter/design that works quite a bit better than older filters, like the Autek QF1, and even the newer Radio Shack DSP40. This is why I have these MFJ filters on my FT-817, my Atlas 215, and my Atlas 180...even though that filter is the SBF-2, a SSB filter with wider bandwidths specifically for sideband.

Best of all...typical trips to ebay can turn these up cheaply.