[Lowfer] Poor man's mw/lw wideband noise reduction

[Dave Brown]

An LF oriented phasing system of this type was originally described by 
the late ZL2BBJ in the ZL amateur radio journal 'Break-In' in October 
1996.  Another version built by George, ZL3PN was published in the 
November 1996 issue.
The October 1998 LF column in Break-In described yet another version 
built by the late ZL3VN. These all differ from the VK5BR version (AR, 
2000)  that Scott referenced, primarily in the use of discrete 
bipolars or FETs, rather than op-amps.  I can arrange copies for those 
interested.
73
Dave, ZL3FJ

----- Original Message ----- 
From: "Scott Tilley" <sthed475 at telus.net>
To: "Discussion of the Lowfer (US, European, &amp;UK) and MedFer 
bands" <lowfer at mailman.qth.net>
Sent: Sunday, January 11, 2009 8:33 AM
Subject: Re: [Lowfer] Poor man's mw/lw wideband noise reduction


> HI Paul
>
> A method  used here done with a small 'noise' antenna and my LF 
> 'sense'
> antenna and then mixing the two RF signals together produces 
> excellent
> results and even allowed me to work the Yukon from within the City 
> of
> Vancouver...  Normally a phase shifting network is used on the noise
> signal to allow one to first adjust the phase of the noise signal 
> 180
> degrees of the received noise on the sense antenna.  Once you have
> adjusted the phase then the amplitude of the two RF signals is 
> adjusted
> such that the offending signal is canceled.  This is really an 
> iterative
> thing as each back and forth adjustment further improves the 
> canceling.
>
> I use such a device on 2200m to deal with my one neighbour's light
> dimmer.   It also works (very well I might add) on any signals you
> receive on both antennas so it can be used to cancel local NDBs for
> example so you you can hear the DX ones on the same frequency...
>
> See here for a design I modified for 2200m.  It works well in the 
> lowfer
> band to 600m as described...
>
> http://users.tpg.com.au/users/ldbutler/LFNoiseCancel.htm
>
> Also see
> http://www.alg.myzen.co.uk/radio/136/pre_sel.htm
>
> 73 Scott
> VE7TIL
>
>
> PAUL DAULTON wrote:
>>
>> I found an article in Elektor magazine feb 2005, which can be
>> downloaded from Elektors's site, about
>>
>> a noise reduction method.
>>
>>
>>
>> Basically two receivers are used.The loudspeaker outputs of the two
>> radios are connected in phase while
>>
>> the speaker in the second rec is disconnected. With the second
>> receiver tuned a little higher or lower than
>>
>> the main one the speaker of the main receiver is fed with the
>> difference between the two signals. External
>>
>> antennas should be connected in parallel. Using the volume 
>> adjustment
>> on the second radio a setting can be
>>
>> found that should result in a reduction of noise.
>>
>>
>>
>> Sounds good I am trying to figure out how to apply to Argo 
>> connections.
>>
>>
>>
>> Any comments?
>>
>>
>>
>> Paul K5wms
>>
>> ------------------------------------------------------------------------
>>
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