Resent Due to Reflector Problems
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Bob (K4TAX) said:
"Perhaps we are not being clear in out terminology between AVC and AGC. In
case you thought so, they aren't the same. Today's digital radios don't
have AVC systems so don't expect the AGC system to do what a AVC system
does."
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Bob, as with all kinds of statements about DSP based radios, it really
depends on the release of the firmware.
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Gary Barbour said:
"The V1 firmware contained an AF AGC in addition to the IF AGC.
This resulted in a better leveling of the overall audio but at the cost of
adding to noise levels and effectively canceling the RX EQ functions.
V2 doesn't add leveling to the audio. In places where there is some
impact on the audio levels, like below 150 Hz the V2 version makes it
worse because we run twice the DSP filtering that was in the V1
firmware."
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As you can see from Gary's comment, the V1 Orion code does have an AVC
function. I never really understood Gary's comments about noise - both the
ARRL MDS tests and my recent - less accurate - MDS tests indicated that
the Orion MDS is great, thus noise doesn't seem to be an issue? I don't use
the receive EQ, but I really didn't follow the logic of Gary's comment on
that function either. What I do believe is that the AF AGC (AVC) was very
important in maintaining the right internal signal levels in the Orion to
prevent audio overload and distortion. I can't help but believe that leads
to some ofthe signal distortion heard in the V2 code today.
Anyway, there are a lot of differences between the V2 and V1 code and some
didn't necessarily result in improvement. And, at least the V1 version of
the Orion firmware did have an "AVC." Some other DSP radios may also
have this function.
73, Merle - W0EWM
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