> Does a transmitter with poor 3rd order IMD therefore have any noticeable
> distortion in the voice quality due to the speech intermod products within
> the audio bandwidth?
Why would it have audible distortion? The garbage being measured is already
20-30dB down, is outside the passband of the receiver fileters, and the
receive detector and audio system already has IM products. Not only that,
many locations have high noise levels masking IMD that can be heard in quiet
locations.
There is also a BIG difference between off-frequency products and distortion
that you can hear inside the passband. The same is true for keyclicks. What
you hear inside the passband is not related to actual bandwidth.
This is why information is generally not reliable when we ask random
operators how we sound, or if our rigs are clicking or splattering.
> >Ironically, the most meaningful test of IMD performance for SSB is also
> >the simplest - just tune away from the signal, using a good receiver
> >that isn't being overloaded, and notice how far away you have to go
> >before the splatter dies away into the noise.
>
> Using the (meaningful) receiver method, I have heard terrible, very wide,
> signals transmitted from "high end" transceivers, and excellent, no
> splatter, signals from the so called "cheap" transceivers!
If you look at measured performance, price has little to do with results.
Look at close-spaced receiver tests at:
http://www.w8ji.com/receiver_tests.htm
The cheap (old technology) K2 receiver which isn't especially well-designed
equals or beats all of the receivers on that page. If you listen to sound
files on the keyclick page, you'll see top of the line radios have terrible
clicks. Price has nothing to do with quality.
73 Tom
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