[Elecraft] Using 2nd Rx to reduce noise

[Bill Tippett]

On Tue, Jan 26, 2010 at 12:09 PM, Vic K2VCO <vic at rakefet.com> wrote:

> Bill W4ZV wrote:
>
>>
>> Mike Keller wrote:
>>
>>> Has anyone found a way to use phase cancel external noise heard in the
>>> main Rx using the second Rx and a "noise antenna"
>>>
>>>
>> Not internally, but you don't need the KRX3 to do that.   You can use an
>> external device such as the DXE NCC-1, MFJ-1025/1026 or Timewave ANC-4 (in
>> order of effectiveness based on personal experience with all 3).  Noise
>> canceling works best if the noise is a point source, although it can
>> sometimes help reduce noise from a general direction (such as lightning
>> QRN).
>>
>>
>> http://www.dxengineering.com/Parts.asp?ID=1227&PLID=215&SecID=114&DeptID=12&PartNo=DXE-NCC-1
>> http://www.mfjenterprises.com/Product.php?productid=MFJ-1025
>> http://www.timewave.com/support/ANC-4/anc4.html
>>
>
> If you have the KXV3 (the so-called 'transverter interface' which is much
> more than that) you can simply connect the noise canceller between the RX IN
> and RX OUT. This enables you to avoid using the kludgy relay in the device
> for t-r switching.
>

The KXV3 does make it easier to connect the main antenna, but you may still
need to protect the noise antenna input which is not routed through the
KXV3.

>
> Bill, is that in order of increasing or decreasing effectiveness?
>

Most effective is the DXE NCC-1 (also MUCH more expensive).  The MFJ-1025
works reasonably well, especially if you do W8JI's mods below,

http://www.w8ji.com/mfj-1025_1026.htm

...but it's more critical to adjust, has a higher internal noise floor and
less robust front end.  Some have had good luck with the ANC-4 but I
personally did not.

To do noise canceling internally to the K3, you would need a convenient way
to adjust both amplitude and phase.  Although amplitude can be done with RF
Gain and ATT/PRE, there is presently no adjustment for phase.  For ease of
use both amplitude and phase adjustments should be large knobs which the
K3's ergonomics preclude.  For example the easiest to use NCC-1 is nearly
the same size as a K3 itself! (4.25" X 9.5" X 9.5")

73,  Bill  W4ZV