[ICOM] Contest performance of Pro III?

[Bill Tippett]

W1NR wrote:
 >There is nothing that filters can do for you if someone is putting
large amounts of RF energy on top of the signal you are trying to hear.

         While true, this is not the complete picture.  A receiver
can generate its own internal noise within the passband due to
interfering signals which are outside the passband.  This can
happen in many ways:

1.  IMD products are generated when two external signals (both
of which may be outside the passband) mix to create internal
(to the receiver) signals within the passband.  IMD dynamic
range is the metric for this problem.

2.  Internal phase noise which is generated by the receiver's
own synthesizer.  This sounds like white noise and effectively
raises the noise floor of the receiver.

3.  In-band IMD which is the result of signals within the
receiver's passband being distorted by the receiver itself.

         For a good understanding of these issues, there are
several good articles:

"QST Product Reviews -- In Depth, In English" by KC1SX (who
actually does ARRL's Product Tests)
http://www.arrl.org/tis/info/pdf/0408032.pdf

"The DX Prowess of HF Receivers" by SP7HT
http://www.arrl.org/tis/info/pdf/020910qex036.pdf

"Radios Used in a Contest Environment" by Rob Sherwood NC0B
of Sherwood Engineering at the 2004 Dayton Hamvention
http://www.sherweng.com/presentation.html

...and a follow-up Receiver Performance White Paper by Sherwood:
http://www.sherweng.com/images/MeasurementAccuracy&SampleVariation.pdf

Tom Rauch W8JI on Receiver Performance
http://www.w8ji.com/receivers.htm

                                 73,  Bill  W4ZV