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Phase Shifter in Noise Canceller and ReView MFJ-1025/26 + e.t.c
Some time i understood what i need Noise Phase Canceller, may be as MFJ-1025/1036 or others.....Ham`s who work on Low Band of HF know what in some time need to kill noise from one directional. I many time ago looking very good article DL2KQ Igor, who introduse good analog of Noise and Interference Canceler MFJ-1025/1026.
Anchor links about Noise Canceller
< http://dl2kq.de/ant/3-15.htm DL2KQ Igor
Schematic by PA0SIM ( used analog of Capacitive Goniometer as Phase Shifter)
< Good and Interesting info about different Noise cancellers by Martin G8JNJ + good schematic Antenna Canceller (PDF)
Many Noise cancellers has a some problem (especially which has simple circuits of Phase Shifters)
1. The phase shift circuits do not provide a full 180 or 360 degree shift.
2. The phase shift circuit introduces big amplitude variations (10 to 20dB or more) if you turn phase shift.
This means that you have three and more knob for controls which all interact quite badly with each other making it a nightmare to setup quickly.
In simple circuits used RC phase shifter - "turn Phase Shift - change Amplitude" (is not bad circuits - it work good, but tuning for killing noise is not simple)
So more better circuits can be use transformer couplers (as Antenna Canceller) or goniometer circuits as old RDF (Radio Direct Finding systems)
Inductive Goniometer (Rotating Transformer) I use this circuit (Phase Shifter 0..360 degr):
This circuits can be use Capacitive Goniometer (PA0SIM) (but need rare Differential Capacitor)