G8MNY TECH 27.08.19 05:35l 79 Lines 3539 Bytes #365 (0) @ WW
BID : 19077_GB7CIP
Subj: Antenna Noise Canceller No 4
Path: OK0NBR IR2UBX IW0QNL JH4XSY JE7YGF GB7CIP
Sent: 190827/0831Z @:GB7CIP.#32.GBR.EURO #:19077 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW

By G8MNY (Updated Jun 19)
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A few years ago I bought one of these HF RF noise cancellers by JPS (Timewave make the same item).

It works by null steering principle of using a 2nd noise pick up aerial & phase changing it signal & level, to exactly cancel the main aerial noise. The principle is quite different to the digital signal processing used in the BHI NES LS or modern SDR rigs. Sometimes I also use my rigs tunable inpulse Noise Blanker, to remove very spiky ignition like noise too if the adjacent chanels are free of strong signals. The 3 methods used together can make a really good shack noise reduction system.

.-------------------------------. .-------------------------------.
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\\ //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\\
││ /~\ Freq /~\ ││ ││ /~\ /~\ 12V Noise ││ ││ _ Phase │( )│ Range │( )│ ││ ││ │ o │ │ o │ Power Antenna ││ ││ (_) o (_) \_/ (_) \_/ ││ ││ \_/ \_/ (·) (o) ││ ││Power Phase Gain ││ ││ Ant Radio ││ └└─────────────────────────────────┘┘ └└─────────────────────────────────┘┘
FRONT REAR

The unit has Auto Tx RF sensor, & quickly switches to through Tx mode when up to 100W of RF is detected. And it is in through mode when switch off.

Three press buttons select "Power On", "Phase Range" & "Freq Range", 2 pots are then carefully used to get a deep noise null (20 to 30dB), if the noise is coming from a single direction!

MODIFIED POLAR DIAGRAM _
___ ___ · ''· Noise
/ \│/ \ \│ \ Nulled
Noise ( x ) ) Out
\___/│\___/ /│ / Heart
Dipole Paturn ·_..· Paturn

For the noise aerial, I use an external 20ft of wire (not the optional tele- scopic rod) not near the Tx/Rx aerial.

Wire \│/ --- 30ft----- \│/Main Other
Noise │ │Tx/Rx Aerial
Ant │ _____ __ ___ │ \│/
││ANC-4│ │PA│ │ATU├─┘ │
└┤_____├─┤__├─┤___├───────────┘
12V │
│ ______ ___ __/
└┤HF RIG├───┤BHI├─┤LS│
12V│ +NB │ 12V~~~ ~~\
~~~~~~
A noise aerial that is too close, will pick up the same phase, & nulling will remove the noise & all wanted signals too! Also on Tx too much RF up the Noise ant port will cause failure of the 100R protection resistor. (Mounted on PCB storks in case!) So do take an internal picture, just in case U need to replace a burnt R in yours!

IN USE
I found that you soon get used to the ANC-4 pot settings, which will alter depending on the ATU settings & aerial used. As the RF null signals in front of the HF Rx, the affects are real. And further rig DSP or post rig BHI DSP noise processing will complement the overall noise reduction, without much wanted signal degradation.

With 2 noise sources e.g. mains 100Hz Buzz (sounds like fried eggs, & seen on a Scope displaying AF & timbase locked to mains) that are on different mains phases, from 2 neighbours, I get better Rx results with a different "Other" Aerial on Rx, so I switch the ATU & re-tweak the ANC-4 for best null, but still Tx on the main aerial.



See my Tech Bul on "BHI Noise Eliminating DSP LS.

Y don't U send an interesting bul?

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