[TenTec] Further Orion Sub Receiver -- Some results

[Ron Castro]

Grant:

What do you see at 100% modulation?  I have noticed a fair bit of distortion 
on AM on the O2, even on ground-wave commercial broadcast signals, and have 
reported this to TT.  I don't hear it at lower levels of modulation, and 
it's most noticeable on peaks, particularly on voice.  Sounds like 
flat-topping of some sort.

Ron N6AHA


----- Original Message ----- 
From: "Grant Youngman" <nq5t at comcast.net>
To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
Sent: Friday, March 17, 2006 1:39 PM
Subject: Re: [TenTec] Further Orion Sub Receiver -- Some results


>> One of those, in particular, is that (approximated to the 2nd
>> harmonic), distortion in a square law detector is actually
>> lower when a steady state AM signal is tuned to remove most
>> of one sideband than when the carrier is centered in the
>> passband.  ... Blah blah
>
> Actually, that's not correct.  Lankford adjusted the square law equations 
> to
> the case of diode (half-wave detector) multiplying by the Fourier series 
> for
> half-wave rectification.
>
> Some preliminary tests done at 7 Khz with a 1000 Hz AM signal modulated at
> 50% on the Orion II subreceiver does indeed show some increase in 2nd 
> order
> harmonic distortion when the passband is shifted.
>
> Generator 8640B at 7 Mhz; modulated 50% at 1 Khz.
>
> BW: 6000 Hz, PBT:  0 No discernable 2nd harmonic
>
> Following are the 2nd order products relative to the fundamental for 
> various
> settings of PBT.  Total AUDIO bandwidth is 5000 Hz at 2K shift and 5500 Hz
> at 2500 shift.
>
>    PBT
> - 2000 Hz:  -45dB
> - 2500 Hz:  -33dB
> + 2000 Hz:  -33dB
> + 2500 Hz:  -34dB
>
> The largest of these (-33dB) represents 0.05% harmonic distortion.  A
> relatively small number.  3rd order products were visible but well below 
> 2nd
> order, and I didn't take the reading.
>
> Grant/NQ5T
>
>
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