On Sat, 26 Aug 2006 17:15:09 -0400, Dave wrote:

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.




you use an antenna thats 20 ft long would that be a dipole?
3 inches off the ground?? no kidding, any idea why so low?
what kind of wire do you use to connect the noise unit to the antenna?

would you say the units eliminate the noise equally as well?
or does one seem to be better than the other?


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