Jim,
Nice piece of work, and most interesting, thanks for sharing!
--
Thanks and 73's,
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On Tue, 2015-08-11 at 10:12 -0700, Jim Brown wrote:
> On Tue,8/11/2015 8:49 AM, Manfred Mornhinweg wrote:
> > I can't conveniently run my computer from batteries to break any
> > ground loops, because it's a desktop computer.
>
> Ground loops are a fiction, a wrong concept to explain noise coupled in
> unbalanced connections between equipment powered from different sources.
> The REAL cause of hum, buzz, and other noise coupled in this manner is
> leakage currents in the Green wire (safety ground) in the AC mains.
>
> See http://k9yc.com/GroundingAndAudio.pdf
>
> The proper solution is BONDING, not isolation.
>
> I've been measuring IMD of various rigs and amplifiers using an Elecraft
> P3 attached to a K3, sampling at a capacitive tap with the amp/rig
> feeding a big 500W dummy load, and the rig transmitting dits in the
> range of 30 wpm. Because keyed CW is 100% square wave AM of a carrier,
> the harmonics that make up the keying waveform excite IMD in the DUT.
>
> The P3 with the SVGA board is capable of resolution on the order of 2 Hz
> with 80 dB amplitude display. This is 500 times better than the
> frequency resolution of my HP and Rigol spectrum analyzers.They are good
> for looking at harmonics, but useless for looking at CW bandwidth.
>
> Here's an in-progress report on my work. I've used Power Point to show
> it, but this is not a Power Point for a presentation, simply a
> convenient way to display the data and document the test method.
>
> http://k9yc.com/P3_Spectrum_Measurements.pdf
>
> I measured three power amps using a second K3 to drive them -- a Ten Tec
> Titan 425, an Elecraft KPA500, and an ACOM 1010.
>
> 73, Jim K9YC
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