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G8MNY > TECH 12.10.24 08:12l 80 Lines 3677 Bytes #999 (0) @ WW
BID : 17722_GB7CIP
Read: GUEST
Subj: Antenna Noise Canceller No 4
Path: IZ3LSV<I0OJJ<GB7CIP
Sent: 241012/0707Z @:GB7CIP.#32.GBR.EURO #:17722 [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 & phase
changing its signal & 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, & 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, & 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 & switch 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. 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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