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 Post subject: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sun 12, 2021 6:30 pm 
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Joined: Apr Fri 30, 2021 1:17 am
Posts: 22
Finished re-capping my SX-110 last night. Aligned this morning. Works fine but when I turn on the noise blanker it seems kind of garbled.

Any thoughts?

Thx!

Greg.


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 Post subject: Re: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sun 12, 2021 7:38 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 287
Location: Kingwood, Texas
It’s not a noise blanker. It’s a noise limiter. When switched in, the clipping action will add a certain amount of distortion to the audio. Unless the distortion is truly excessive, it’s probably normal.

Darrell


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 Post subject: Re: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sun 12, 2021 8:16 pm 
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Thanks. That make sense.

I appreciate the reply!

Greg.


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 Post subject: Re: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sun 12, 2021 8:28 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 8068
The diode clipper type ANL circuits work well for keeping lightning crashes from deafening you but they definitely aren't like the more recent noise blankers.

ANL circuits were called automatic because once turned on they clip anything above a certain level above the AM carrier, that level was determined by circuit components and more sophisticated ones have a control to set where the limiting occurs.

Noise blankers silence the receiver for a tiny fraction of time (for the duration of the noise impulse) usually by biasing a mixer or IF stage into standby and the noise impulse is picked off early in the receiver before it is widened by the high selectivity filter(s) in the receiver.

Both have their place and some receivers have both noise limiters and blankers. Limiters can cause annoying distortion when they also clip desired audio peaks while blankers degrade the strong signal performance of receivers, some rather extremely. Limiters work very well for lighting static and can be beneficial for some forms of powerline noise where the distortion is a useful tradeoff but blankers are usually better equipped for impulse type noise like powerline and ignition noise but not as useful for noise which would require a very long and obtrusive blanking period (as is typical with lightning static).

My military RAK and RAL regenerative receivers use a clipper tube in what they designate as an AVC system. This "AVC" tube clips all audio beyond the selected level and the manual wisely warns that it is not to be used for voice signals, it is there to protect the operators ears from being "blasted" when operating CW. Distortion is understandably extreme when using this sort of clipper circuit as a volume control/limiter.

Rodger WQ9E


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 Post subject: Re: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sun 12, 2021 8:34 pm 
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Joined: Apr Fri 30, 2021 1:17 am
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Great explaination!

Thanks.

I appreciate the reply!

Greg.


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 Post subject: Re: Hallicrafters SX-110 seems noisy with noise filter on.
PostPosted: Sep Sat 18, 2021 4:28 am 
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Joined: May Wed 20, 2020 1:33 am
Posts: 408
Location: Rockford, IL
Like the "Lamb Silencer" of the SX-28 :-)

rsingl wrote:
The diode clipper type ANL circuits work well for keeping lightning crashes from deafening you but they definitely aren't like the more recent noise blankers.

ANL circuits were called automatic because once turned on they clip anything above a certain level above the AM carrier, that level was determined by circuit components and more sophisticated ones have a control to set where the limiting occurs.

Noise blankers silence the receiver for a tiny fraction of time (for the duration of the noise impulse) usually by biasing a mixer or IF stage into standby and the noise impulse is picked off early in the receiver before it is widened by the high selectivity filter(s) in the receiver.

Both have their place and some receivers have both noise limiters and blankers. Limiters can cause annoying distortion when they also clip desired audio peaks while blankers degrade the strong signal performance of receivers, some rather extremely. Limiters work very well for lighting static and can be beneficial for some forms of powerline noise where the distortion is a useful tradeoff but blankers are usually better equipped for impulse type noise like powerline and ignition noise but not as useful for noise which would require a very long and obtrusive blanking period (as is typical with lightning static).

My military RAK and RAL regenerative receivers use a clipper tube in what they designate as an AVC system. This "AVC" tube clips all audio beyond the selected level and the manual wisely warns that it is not to be used for voice signals, it is there to protect the operators ears from being "blasted" when operating CW. Distortion is understandably extreme when using this sort of clipper circuit as a volume control/limiter.

Rodger WQ9E


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