Re: [TenTec] Tx IMD and Purity

[george fritkin]

What is the issue?  Nobody can even hear -30 distortion products.   If you are running digital, you should not be using high power where distortion products could be a problem.  No need to ramp up product costs for fancy numbers.

George, W6GF
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[george fritkin]

Distortion products have nothing to do with dynamic range of hearing. If you can hear products -60 DOWN from main signal, you have super human hearing. I am basing my info on years of designing audio stuff

George, W6GF
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[Jim Brown-10]

On 7/2/2013 11:10 AM, george fritkin wrote:
> Nobody can even hear -30 distortion products.

WRONG!  30 dB down from 1.5kW is 1.5 watts.  If that 1.5 watts is your
neighbor a few miles away, he's 30 dB over S9 and the trash is on top of
the S9 station you're trying to copy, you damn well WILL hear it, and
you'll be thinking about putting pins in his coax if he doesn't clean it
up.

While I agree that AUDIO distortion IN THE PASSBAND at 30dB down does
not matter, the SPLATTER it produces matters a LOT.  And that's for ham
radio.  If you're listening to acoustic music and you're not deaf, you
CAN hear some kinds of distortion products in the -60dB range, depending
on the nature of the distortion.

73, Jim K9YC
Fellow, Audio Engineering Society
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[N8MSA]

And 1.5 watts, through a decent antenna system, now becomes the equivalent of a nice QRP station - covering up that DX station, when propagation is right, that you were trying to work. Those of you with P3s shave probably already seen it in your waterfalls - "walls of noise" up to 9/10 kHz wide. Those that haven't should; it's a real eye-opener.


Mike Alexander - N8MSA

[hidden email]

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: [hidden email]
Sent: Tuesday, July 2, 2013 3:06:36 PM
Subject: Re: [Elecraft] [TenTec] Tx IMD and Purity

On 7/2/2013 11:10 AM, george fritkin wrote:
> Nobody can even hear -30 distortion products.

WRONG! 30 dB down from 1.5kW is 1.5 watts. If that 1.5 watts is your
neighbor a few miles away, he's 30 dB over S9 and the trash is on top of
the S9 station you're trying to copy, you damn well WILL hear it, and
you'll be thinking about putting pins in his coax if he doesn't clean it
up.

While I agree that AUDIO distortion IN THE PASSBAND at 30dB down does
not matter, the SPLATTER it produces matters a LOT. And that's for ham
radio. If you're listening to acoustic music and you're not deaf, you
CAN hear some kinds of distortion products in the -60dB range, depending
on the nature of the distortion.

73, Jim K9YC
Fellow, Audio Engineering Society
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Please help support this email list: http://www.qsl.net/donate.html 
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