One more comment about measurement methods. Gerald may have gotten the 1 dB figure from my blocking measurements (instead of dynamic range). Onset of blocking, or gain compression, is usually measured at the 1 dB point. I only measure blocking at 100 kHz, as the phase noise of many radios predominates closer in. I also now measure blocking against a 1 uV signal, as this generally keeps the AGC out of the picture. The League may use an S5 signal, but that allows the AGC to counteract the blocking for several dB. I have seen the audio output stay constant, yet the S meter drop from S5 to S4 to S3, etc. as the generator was increased in level while making the blocking measurement. Depending on what S5 is on a given radio, this gives numbers that are hard to compare from radio to radio. Since most radios today, especially with the preamp off, have an AGC threshold around 2 uV or higher, a 1 uV signals seemed like good choice. In the case of the 5000A, since the phase noise, at least on my sample, was flat, I still had problems with the noise at 100 kHz while trying to measure the 1 dB drop in audio for the blocking test, using the old standard RMS volt meter. (HP 3400A with linear dB scale)
The League is now using a spectrum analyzer to measure blocking. Phase noise can be going up, as measured on an RMS meter, but the audio can be going down due to blocking, if observed with a spectrum analyzer. I went to the analyzer method when I measured the 5000A blocking. This will likely be my standard in the future. Even with a 10 Hz bandwidth on the spectrum analyzer, the audio level still wobbles around a bit from sweep to sweep as it integrates the noise and signal. On the subject of Elecraft and Flex, I think it is wonderful that additional US manufacturers are back in the fray, competing with Japan, Inc. 73, Rob Sherwood, NC0B >>> "Gerald Youngblood" <[EMAIL PROTECTED]> 10/6/2007 7:03 pm >>> There are both misconceptions and apples/oranges measurements here. The IMD DR3 numbers quoted by Elecraft are almost certainly measured using the ARRL lab methodology (IP3 Measured at S5). Using the ARRL S5 IP3 test methods, we measure the FLEX-5000 at 100+ dB IMD DR3 at any spacing (including 100 Hz or less). Those are top class numbers at any spacing. Note that Sherwood uses a different measurement technique where IP3 is measured at a 1 dB rise in the noise floor. Sherwood measured the FLEX-5000 at 96 dB at any spacing using his methods. Sherwood's website shows the Elecraft K2 at 80 dB IMD DR3 at 2 kHz and 98 dB at 20 kHz. There is no independent measurement info on the K3. By the way, I have tremendous respect for Elecraft. This is only an effort to clear up some misinformation. 73, Gerald Gerald Youngblood, K5SDR FlexRadio Systems Ph: 512-535-4713 Fax: 512-233-5143 Email: [EMAIL PROTECTED] Web: www.flex-radio.com > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Richard Smith > Sent: Saturday, October 06, 2007 2:58 PM > To: FlexRadio@flex-radio.biz > Subject: [Flexradio] Fw: [Elecraft] Comparison: K3 and SDR 5000A > > I believe there are significant misconceptions here that > should be addressed by someone closer to the Flex Radio > product than myself. As I understand it, there is no need > for a "roofing filter" in the SDR-5000 because of its direct > conversion architecture - the same thing that makes my K2 so > good without a roofing filter. Yet I have now seen shots > taken at the SDR-5000 in several places for its lack of a > roofing filter. Am I ignorant of the facts, or are they? > Also, making the decision to purchase one radio over another > based on a perceived shortfall in the 20 kHz dynamic range > when the close in 2 kHz dynamic range of the SDR-5000 is > superb, and possibly the best in the industry, seems wrong. > > Am I missing something? > > Rich W1EZ > > > ----- Original Message ----- > From: "John A. McCabe" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Saturday, October 06, 2007 2:24 PM > Subject: Re: [Elecraft] Comparison: K3 and SDR 5000A > > > > Hi John, > > > > Although I do not have a 5000, I do have a SDR-1000. > Elecraft and Flex are > > both Good companies that produce great radios. However, I > believe one > > major difference between the K3 and the Flex 5000 will be > in wider space > > dynamic range. The close-in 2Khz dynamic range for the 5000 > I believe was > > measured by Rob Sherwood at 96db which is a good number. > But the 5000 > > does not have roofing filters, so if I am not mistaken, the > 96db IMD > > dynamic range will the same at 2Khz, 5Khz, 10Khz, 20Khz, > and beyond, as > > it is with most sound card based SDR's. To me a 96db > Dynamic range beyond > > 20Khz is not good. I believe that a 96DB dynamic range is > around 40-45db > > over S9, so if my calculations are correct, IMD could be a > problem from a > > 45db over S9 signal 20Khz or more away. That is one of the > reason's why I > > chose the K3 over the 5000. The K3's close in numbers will > be around the > > same is the 5000, but the wider spaced measurements I > expect to be much > > better then the Flex-5000. > > > > > > John, KD8K > > _______________________________________________ > > Elecraft mailing list > > Post to: [EMAIL PROTECTED] > > You must be a subscriber to post to the list. > > Subscriber Info (Addr. Change, sub, unsub etc.): > > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > > Elecraft web page: http://www.elecraft.com > > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > FlexRadio Knowledge Base: http://kb.flex-radio.com/ > FlexRadio Homepage: http://www.flex-radio.com/ > > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
