[RTTY] RadioShack transformer IMD

[Joe Subich, W4TV]

 > I was expecting a higher IMD reading with the transformer inserted
 > between the input and output of the soundcard as compared to the
 > straight-through cable. What am I missing?

You're not missing anything ... you will not see any increase in IMD
(or harmonic generation) as long as the signal level stays in the
linear area of the transformer's B-H curve (generally stay out of
saturation) ... if the transformer is well designed.

73,

    ... Joe, W4TV


On 5/15/2012 4:11 PM, Don Hill AA5AU wrote:
> I bought a RadioShack "Ground Loop Isolator" today and decided to test the IMD of the transformers (there are two in the device).
>
> I used Digipan in its IMD measurement mode and looped the output of my soundcard directly back into the input with a
> straight-through cable. Playing with the output and input levels, the typical IMD measurement in Digipan was about -61 to -58. I
> then inserted one of the transformers of the RadioShack device and the IMD did not change. I played with the levels and was able to
> put the transformer into saturation and could see the signal in the display, but with every level tested, and regardless of
> frequency (used 1kHz, 2kHz&  3kHz) when the level was below saturation there was no difference whether or not the transformer was in
> line.
>
> I was expecting a higher IMD reading with the transformer inserted between the input and output of the soundcard as compared to the
> straight-through cable. What am I missing?
>
> 73, Don AA5AU
> http://www.aa5au.com
> http://www.rttycontesting.com
>
>
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