On Tue, 18 Nov 2003, Bill Tippett wrote:
> Jason, please don't take my comments the wrong way, I'm only
> trying to explain a commonly misunderstood point.
I love the Jupiter - I think i'd love the Orion even more if I had one.
Definitely not taken the wrong way!! I feel jubilant to have a Jupiter
'cause I know that it's the best rig out there short of an Orion.
[campy dialog on]
> I've gotten some questions to the effect that "My XXXXX radio has no
> problems eliminating a very strong signal just a few kHz away, why is
> Orion any better?" The answer to this is that intermodulation
> distortion (IMD) products are caused by TWO or more very strong signals
> within the receiver's roofing filter. These signals mix together and
> cause phantom signals (IMD products) that will appear in your passband
> and sound like "bleeps and bloops" on CW or simply noise for wideband
> signals (like SSB). Most radios will easily handle ONE very strong
> signal within their roofing filter, but the IMD problems come when there
> are TWO or more, and this is why IMDDR3 is very important to contesters
> and DX'ers who want to hear weak signals closely surrounded by many
> strong signals.
That's a very good description - now I want an Orion even more! Argh!
> Does this mean it is a bad receiver? Not at all. But just
> don't expect it to perform like an Orion if W1AW AND ANOTHER S9++ signal
> happen to come within +/- 7.5 kHz of your listening frequency. I hope
> this helps explain what this IMD business is all about and why it is
> mainly of concern to contesters and DX'ers (especially us low-band
> types).
This explains a lot. I hope this kind of information makes it to the
TenTec site and other places so that more people will be aware of this.
I don't think this topic has been brought up with the clarity which you
provided.
thanks,
Jason
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