David Cutter wrote:
>
> I have a "QRM Eliminator" by SEM (a UK firm long gone) awaiting repair and
> I
> wondered how best to use this in conjunction with diversity. It is a
> phasing unit requiring another small (probably vertical) antenna to pick
> up
> local QRN, which is theoretically cancelled using its 3 controls. I
> think
> there are other similar products on the market. I'm thinking to combine
> this with another rx antenna which would then feed the rx port of the
> second
> rx on the K3. It needs a little thought.
>
> David
> G3UNA
>
I'm doing something similar. I have a pair of identical Beverages 887' long
at 40 degrees azimuth. They're spaced ~1/8 wl apart and staggered ~1/4 wl.
I'm feeding both to a MFJ-1025 Noise/Signal Phasing box. The forward lobe
is relatively insensitive to phase shifting but you can steer a null to the
rearand sides to reduce QRM or QRN by 20-25 dB from a specific direction. I
use this as one input to my K3 in diversity and either a RX 4SQ or my
transmit antenna for my other diversity antenna. W8JI has a webpage below
with a number of useful mods to the 1025:
http://www.w8ji.com/mfj-1025_1026.htm
The 1025 works reasonably well for this but I'll soon replace it with the
DXE NCC-1 which has a better front end and less internal noise.
73, Bill
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