G3SEK wrote:
>The problem with any two or three fixed tones is that the test signal
>doesn't explore all possible weaknesses of the power supplies. Although
>it's an improvement to add a third, lower tone which modulates the other
>pair, that doesn't solve the whole problem.
>Speech has the advantage of being realistic, and by using something like
>a .WAV file it is now possible to create a speech test signal that will
>be bit-for-bit identical wherever and whenever it is used.
If there ever will be a voting for a "standard speech" test for amplifier
IMD, I would vote
for one single word; the name of a certain village in UK:
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch
Here you can find the pronounciation instructions and the .WAV to be
standardized:
http://www.nwi.co.uk/llanfair/say.htm
http://www.nwi.co.uk/llanfair/soundfiles/llandad4.wav
Sorry for wasting the bandwidth but I simply could not resist!
Now trying to be serious....
I think that testing the amplifiers also with real speech signals is a
good idea. With modern spectrum analyzers (such as HP 8563E) the
resolution bandwidth is no problem. Video averaging and peak hold
will show both sides of the coin; average and peak "splatter".
A standard .WAV may be a bit difficult to agree on.
I my memory serves me right either HP or Rohde & Schwarz
had "Artificial Voice Generator" in the analog era! I think it was for
audio system (telephone?) crosstalk measurements. Did not find
it on the current HP and R&S catalogs....
By the way. What exactly are the standard tone separation
in two-tone tests and tone separations and relative tone levels in
three-tone tests for HF/VHF (HAM) linear amplifiers?
73,
Ilkka OH3NJC (ilkka.kontola@nmp.nokia.com, oh3njc@sral.fi)
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