Re: LF: Re: Mains QRM blanker by PA0LQ

["Dick Rollema" <d.w.rollema@freeler.nl>]

To All from PA0SE

Dave, G3YMC wrote:


> The noise canceller which Steve
> GW4ALG designed is derived from Harry PA0LQ's version
> with ideas from other sources - this can be found in the RSGB Low
> Frequency
> Experimenter's Handbook and on Steve's site
> (http://www.alg.demon.co.uk/radio/136/intro.htm).
> Steve's unit does exactly the same as Harry's - picks up the offending
> mains
> interference with a seperate small antenna and nulls it from the wanted
> signals.

PA0LQ's noise blanker derives the blanking signal from the mains. It is
different from the system described in the LF Handbook.

In my announcement on the reflector I said that PA0LQ used the blanker to
eliminate interference from fluorescent tubes. But that is not the case.
My aging memory failed me, for which I apologize.
But the blanker is very effective on noise from light dimmers and other
pulse shaped interference with mains frequency. When driven by 
pulses from a separate receiver tuned to 100 kHz the blanker could
possibly also be used to fight LORAN interference, but this has not been
tried by PA0LQ. 

The description and circuit diagram of PA0LQ's noise blanker and
non-ringing 30 Hz wide audio filter are now available in English. I will
send it to you by direct e-mail when requested.  

73, Dick, PA0SE