> At Ep of 1500 in AB1 3rd/5th is -30/35. However at 2000V
> it slips to -23/27.
> This is a 2 tone measurement which disagrees with Toms
> claim of Eimac using
> a single tone. Maybe they swing both ways (;
Hi Carl,
I actually said (about a dozen times).......
"Eimac uses two tone IM referenced against a single tone of
the test. The ARRL uses IM referenced against PEP."
I assumed people know a two tone test is a two tone test
with two tones, and only the reference point changes. I
assumed people know that a two tone IM test referenced to
one tone of the two tones is a standard measurement method,
which results in 6dB less favorable numbers than a two-tone
test referenced to one tone of two tones.
For example (excuse my repeating it) a tube with -35dB one
tone in a two tone test (Eimac's method) is actually -41dB
using the ARRL method referenced against PEP.
The problem is everyone in the industry in the USA always
used IM referenced against a single tone in two-tone tests
and then around the time of the KWM-380 a few people changed
to dB below PEP. This makes a 6dB discrepancy in the
results.
A modern radio with -32dB PEP tone IM3 actually is the same
as -26dB IM referenced against one tone of the two. THEY ARE
BOTH TWO TONE TESTS.
73 Tom
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