[TenTec] One complicated radio!

[Bill Tippett <btippett@alum.mit.edu>]

W8JI wrote:
>          Yes.  I believe it may be due to the IMDDR3 performance not
> creating internal distortion products within the passband.  Whatever
> the reason, it was noticeably different than my experience with the MP
> in the same contest, same band, the previous 4 years.

>I'm a little puzzled by that. Most of the IM we hear is from transmitters,
not generated in receivers.

        Tom, I'm referring to IMD products generated in the receiver's 
passband.
These sound like "bleeps and bloops" on CW, and are phantom signals created
within the receiver due to non-linearities.  On SSB, I'm not sure what they
sound like, but since we are mixing two strong wideband signals, my guess
is the IMD products sound like wideband noise or possibly splatter.  I'm
honestly not sure why Orion's SSB passband sounded quieter than a MP, but it
was very striking to me.  I'm just speculating it may have been due to the
excellent RX IMDDR3 performance of the Orion.  If we can clearly hear these
products on CW, why would we NOT hear them on SSB as increased passband noise?
Please explain why you don't think we would hear them on SSB.

>I just don't see how that difference ties into IM3 performance. In order to
improve IM3 performance, we'd have to fix the transmitters first wouldn't
we? Or am I missing something?? What roofing filter do you use Bill?

        In the contest I always used the 1800 Hz filter but varied DSP BW 
from a normal
setting of 2000 down to <1700 under heavy QRM.  I also found adjusting PBT 
+150 and
RX EQ -10 dB helped improve the readability with narrow bandwidths.

        Leaving on an Anniversary trip with my XYL in an hour, so I may 
not be able
to respond to anything for a few days.

                                                Happy Thanksgiving All!

                                                Bill  W4ZV


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