And, interestingly, Rob Sherwood agrees with you (If I can presume to speak for him, based on my reading his commentary.. he'll probably weigh in) He comments on the problem of making decisions on numbers that actually have fairly high uncertainty.
Ok, I will weigh in. The numbers gives one the option to rule out some equipment that may not meet your operating habits. I am not going to want to buy a radio with a close-in IMD DR3 in the low 60s if I want to operate CW contests. If what I do is rag chew with a few friends in the middle of the week on SSB, it probably doesn't matter what rig is in my shack. The rig I want for my main operating position is certainly going do be different from what I want in my car where size may be the most important factor. The League has said that some hams will pick a rig because it is 2 dB better than another product. Unfortunately they fostered this concept by publishing numbers to tenths of a dB. Noise floor is easy to measure, yet if you did a test on a radio every hour for 24 hours, you would get different numbers by 1 or 2 dB as it warmed up over that long a time. Don't get lost in the minutia. I put a big emphasis on how a radio sounds during extended operation. That requires a lot of listening, and pages of write-up, which is not going to appear in a table on the web. A review in Passport to Worldband Radio, an SWL publication, goes into all sorts of Pros and Cons for every model, and looks at inband audio distortion, AGC operation, ergonomics, etc. One would hope that reviews in Amateur publications, which have pages of space to allocate, would be filled with this kind of detail. Unfortunately that rarely happens, but often is full of unsupportable off-the-cuff comments. What good is a review that says X radio puts out 2.2 watts of audio at 10% distortion? A totally messed up audio chain could pass that test. Who in their right mind would want to listen to 10% distortion? The ear/brain has an astounding ability to hear in-band distortion that is 60 dB down or more. If voice or CW notes have distortion products that go out to 10 kHz, the radio will be very fatiguing to those of us who have not suffered hearing loss from age or high-noise environments. An AGC that exaggerates every little click, tick and pop drives me nuts, and I now have developed a lab test to evaluate at least part of this problem. Some of the more recent equipment will be re-evaluated in this respect, and data added to my web site over time. Some newer DSP radios perform very poorly in QRN, yet our Amateur publications have either completely missed this problem, or are afraid to touch it. There is a valid concern that a radio can be made to pass a test that is not valid or no longer valid. When the League made IMD DR3 tests in the 70s at 20 kHz only, it was generally valid for the architectures of that time. Then the up-conversion, multi-IF radios came along and the 20 kHz test became incomplete. In 1977 I started publishing close-in data at 2 kHz since it tested a radio more like a contest pileup. It took the League 20 years to add 5-kHz data, and even longer to include 2 kHz data. Is 2 kHz testing some magic number? No, but data taken at less than 1 kHz becomes rather theoretical. Unless the OEMs really start cleaning up the key click problem, and reducing phase noise even more, it is going to be hard to work a 1 uV signal when they guy 1 kHz away is 70 dB stronger. Key click sidebands and transmitted phase noise will likely overwhelm the weak signal, even if the receiver is "perfect". When the Flex 5000A was going to come down the pike, I was loaned an SDR-1000 before the 5000A was available, so I could get my feet wet in the concept and the software. The 5000A was only in my lab for a couple weeks, with very early software. Initially I was very concerned that classic tests would be invalid or at least incomplete in evaluating the 5000A's performance. Surprisingly I did not find that to be the case. The normal numbers are excellent, and those who have used it in contests in the last few months have found it performs quite well. If the numbers are good, and the radio flunks contest 101, then obviously the tests are no good. There is something to be said for testing a radio with wideband noise, with a notch in the passband, and looking for the integrated power to fill in the notch with distortion products. Maybe a European publication could tackle that idea since 40 meter broadcast signal level is such an issue on that side of the pond. What it really comes down to is whether the operator enjoys using the rig. A radio with menus many levels deep may be intuitive to some, and an enigma to others. I may want to reach up and turn a knob, and others like to click a mouse. Neither is right or wrong. Now we have new approaches from US OEMs that are offering different ways to provide top-notch performance. What more could we ask for? 73, Rob Sherwood, NC0B _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
