Clearspeech units do NOT keep noise OUT of the first RF stage. They operate as
audio DSP. It is a totally different approach from either the ANC-4 and the MFJ
1025.

I own both the ANC-4 and the MFJ-1025.

These units use a separate noise sensing antenna mounted close to ground. Mine
are about 20 feet long and about 3 inches above the ground.

Both units use analog operational amplifiers to cancel manmade noise BEFORE the
noise enters the receiver [before the first rf amplifier stage].

Operation is easier to describe in terms of two op-amps. Op-amp#1 adjusts the
gain of the input#1 noise to match the noise level and inverts the noise signal.
[-mmnoise#1 @ input#1]

Op-amp#2 has one input from the station antenna that contains signal plus
manmade noise [signal + mmnoise] and the second input from the noise amplifier
[-mmnoise#1] that has inverted noise only. This amplifier algebraically adds the
two signals [eg: signal + mmnoise - mmnoise]. The output of this amplifier has
just signal. The manmade noise has been canceled!!

In my station the ANC-4 is used primarily because it is simpler to use. There
are only two adjustments, noise gain and noise phase.

The MFJ-1025 has three adjustments, noise gain, noise phase and T/R delay [for
QSK type usage]. I don't use QSK so I can't comment on this feature.

Each unit has several push buttons for basic frequency range.

Both units will easily reduce manmade noise, power line noise, switching power
supply noise, noisy power insulators, Computer monitor noise, tv set noise, etc
by 60 to 70 dB. A S9 noise level can be reduced to less than S1 approaching S0.
Both units have a slight reduction in net RF gain of about 1/2 S unit. Either
unit will allow you to copy a S1 signal in the presence of S8 or S9 external
manmade noise [NOT adjacent channel QRM!!][They are VERY broadband noise
amplifiers].

The ANC is physically smaller and has two adjustment and two push switches. The
MFJ has three adjustments. I have not opened the case of either unit so I can't
comment on construction quality.

I bought my MFJ new from HRO. I bought my ANC off eBay. Why two noise
cancellers? I have two HF rigs operating simultaneously in my shack.

The ANC is my favorite because of ease of operation. It is on my IC-756 Pro III
[basic HF rig]. The MFJ-1025 is on my 60 meter dedicated radio.

/s/ DD, W1MCE

Sun Tzu wrote:
There are 2 noise reducing units on the market I am considering for
purchase either one, MFJ-1025 1.5 - 30 MHz Noise Canceling Antenna and the
Timewave ANC-4.

A number of yrs ago I made my one and only purchase of "Mighty Fine Junk"
and have'nt been back since.

So I need some input here. Which unit is better and why.