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G8MNY > TECHNI 16.12.25 11:08z 80 Lines 3698 Bytes #180 (0) @ WW
BID : 47324_GB7CIP
Read: GUEST
Subj: Antenna Noise Canceller No 4
Path: SR1BSZ<OK0NBR<OK2PEN<CX2SA<F3KT<F3KT<GB7CIP
Sent: 251216/0800Z @:GB7CIP.#32.GBR.EURO #:47324 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jun 23)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
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 and
phase changing its signal and level, to exactly cancel the main aerial's 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 impulse
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.
.-------------------------------. .-------------------------------.
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\\ //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\\
³³ /~\ Freq /~\ ³³ ³³ /~\ /~\ 12V Noise ³³
³³ _ Phase ³( )³ Range ³( )³ ³³ ³³ ³ o ³ ³ o ³ Power Antenna ³³
³³ (_) o (_) \_/ (_) \_/ ³³ ³³ \_/ \_/ (ú) (o) ³³
³³Power Phase Gain ³³ ³³ Ant Radio ³³
ÀÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙÙ ÀÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙÙ
FRONT REAR
The unit has Auto Tx RF sensor, and quickly switches to through Tx mode when
10W to 100W max 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 _
___ ___ ú ''ú Noise
/ \³/ \ \³ \ Nulled
Noise ( x ) > ) Out
\___/³\___/ /³ / Heart
Dipole Paturn ú_..ú 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 \³/ <---->30ft-----> \³/Main Other Rx
Noise ³ ³Tx/Rx Aerial
Ant ³ _____ __ ___ ³ \³/
³³ANC-4³ ³PA³ ³ATUÃÄÙ ³
À´_____ÃÄ´__ÃÄÄ´___ÃÄÄÄÄÄÄÄÄÄÄÄÄÙ
12V ³ ³Ptt
³ ____³_ ___ __/
À´HF RIGÃÄÄÄ´BHIÃÄ´LS³
12V³ +NB ³ 12V~~~ ~~\
~~~~~~
A noise aerial that is too close, will pick up the same phase, and nulling will
remove the noise and 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 and switch settings, which will
alter depending on the ATU settings and 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, and seen on
a Scope displaying AF and timebase 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 and re-tweak the ANC-4 for best null, but
still Tx on the main aerial. On some bands it is possible to null out local
QRM, but can add too much other noises to be useful.
See my Tech Bul on "BHI Noise Eliminating DSP LS.
Y don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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