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Author Topic: The NRSC filter and Ham radio  (Read 16379 times)
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WB4AIO
WB4AIO
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Better fidelity means better communication.


WWW
« Reply #25 on: March 05, 2011, 05:05:40 PM »

Kevin:

The Maxim filter I built is very steep and it's phase shift is small for most of the passband, rising quickly as the cutoff is reached. I take a cheaper and dirtier way out for the overshoots. I put the filter after all processing. I add a negative clipping diode after this filter to grab the little HF-based overshoots at the expense of a very slight amount of harmonic based splatter. I then do it again-add another filter and then a diode to reduce the events. Cheap dirty and it works. Not as good as phase shift correction as Orban and others do.



Very clever! Thanks for the data sheet link.


Quote
WWCR-uses an Orban HF 9105A. This box is louder and carefully adds more distortion than a 9100A. When adjusted well (listen to the BBC or some VoA), it is very effective with little trade-off. When the knobs are cranked as on WWCR, it is awful. I owned a 9100A and 9105A for a while and know the sonic signatures of them.

73,
Dan
W1DAN


Interesting. Someone needs to gently advise WWCR that 25 per cent. distortion and audio that sounds like it's in a persistent selective fade doth not a large listener base beget. WBCQ is so much more listenable; night and day!

There's an AMer in 9-land, W9AD, that I heard using an Omnia One on 75 meters, and he has it adjusted beautifully. It doesn't sound particularly processed -- the audio has a delightful low end and tons of clean presence, and it's heavily modulated without sounding strained at all.


All the best,


Kevin, WB4AIO.
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« Reply #26 on: March 05, 2011, 07:36:51 PM »

Kevin:

I heard W9AD and he sounds good!

As you know digital processing takes advantage of delays that get around the "capacitor style" detector overshoot in processing. This, along with digital distortion cancelation makes for loud and clean audio. However for ham radio, you cannot really heat the soldering iron to modify these boxes as you can do with the old analog boxes.

As far as WWCR and other bad sounding SW broadcasting, I guess they make their own bed!

73,
Dan
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WA3VJB
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« Reply #27 on: March 05, 2011, 09:16:19 PM »

There's an AMer in 9-land, W9AD, that I heard using an Omnia One on 75 meters, and he has it adjusted beautifully. It doesn't sound particularly processed -- the audio has a delightful low end and tons of clean presence, and it's heavily modulated without sounding strained at all.

http://www.qsl.net/wa3vjb/7285-W9AD.mp3
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