[Premium-Rx] Noise Power Ratio Testing of Radio Receivers

[Ahmet G.]

Last summer I was speaking with Dr. Ulrich Rohde about the E1800. I asked him what he thinks about this receiver as i believe he was involved.

 One striking comment by him was " I now believe that the limiting factor in a receiver's performance is the transmitter's noise figure and it
 all comes down to how clean the transmitted signal is".
 Hope to spend some more time with him and ask him more questions the next time.

 Regards
 Ahmet Gundes

 Hi, Such a " a barrage of frequencies and input levels" were in fact successfully used by Telefunken to test, among others, the E 1800 series of HF receivers. Such a test demonstrated clearly the good large signal handling capabilities of these receivers. Regards, Per-Tore On 4 December 2012 00:05, Michael O'Beirne <michaelob666 at ntlworld.com>wrote: > > Dear Adam > > Many thanks for all that. > > Perhaps it is also time to re-visit the famous embargoed article by Sosin, > Marconi's Chief Scientist in the Marconi house mag, Point-to-Point > Communication in or about 1972 in which he tried to devise a method of > testing hi-grade receivers using an all-embracing formula (which frankly I > never understood) that took in IP3, front end preselection, reciprocal > mixing effects and much more to try to establish a "failure factor" - ie > the factor by which the receiver fell short of the perfect receiver. > > As I recall, mathematically he appplied a barrage of frequencies and inpu
 t > levels to the receiver to simulate the live mass of signals that appear on > a profesional aerial and derived how the receiver would react to such an > environment rather than the somewhat unreal standard two-signal IP2 and > IP3 test. His analysis demonstrated the continued value of traditional LC > preselectors, albeit that in his time, and still now, tracking preselectors > werw and are a very costly way of doing things. > > In a related sort of way there is also a debate as to what input levels > should be applied to an IP3 test to establish a valid test. > > I personally distrust searching for an IP3 product at the miniscule MDS > (3dB s+n/n). At best one should be measuring this with a true RMS > voltmeter, but how many of us have one? In contrast, going for a 10dB > s+n/n ratio should be more accurate since most average reading voltmeters > will be ok. > > But even then, the levels are unlikely to be "teasing" the switching > diodes in the half-octave filters and 
 elsewhere. And the levels can be > high. Even on my small Wellbrook Loop feeding a spectrum analyser, levels > well in excess of 10mV are to be expected from the usual broadcasters and > they are miles and miles away from me. I dread to think what would happen > if I had a kW down the road. > > 73s > Michael > G8MOB > > ----- Original Message ----- From: "Adam Farson" <farson at shaw.ca> > To: <premium-rx at mailman.qth.net> > Sent: Monday, December 03, 2012 5:46 PM > Subject: [Premium-Rx] Noise Power Ratio Testing of Radio Receivers > > > For the past 3 years, I have been researching the possibilities of using > noise-power ratio (NPR) testing - a test method long employed in the > telecom > industry - as an alternate performance-evaluation technique for HF, MF and > LF receivers. In this test, a noise-band containing a deep, narrow notch is > applied at a fairly high power level to the DUT input. The DUT is tuned to > the centre of the notch, and an IF bandwidth somewhat narrowe
 r than that at > the bottom of the notch is selected. NPR is the ratio of the noise power in > the notch to that in a bandwidth equal to that of the IF well outside the > notch. > > The incident noise provokes active and passive IMD, and reciprocal mixing, > in the DUT. These effects appear as added noise which appears in the DUT's > IF channel. The NPR test emulates a band packed with very strong signals. > Thus, it is felt that this test is a better method for assessing receiver > performance under these extreme conditions than a narrow-band (e.g. > 2-signal) test. > > For several months, John KE5QAP, who is also a list member, and I have been > collaborating on this project. John adds that has tried all the traditional > tests: IMD, second and third order, phase noise, blocking, MDS and so > on. Still, the question is open as to which ones are the most important. > The NPR test gives one number that combines many of these tests in a > meaningful way. > > I have had an art
 icle on NPR testing of HF receivers published in RSGB > RadCom, December 2012, pp. 42-45. In addition, there is a relevant paper on > my website, which incorporates test results for a number of transceivers > and > receivers: > > http://www.ab4oj.com/test/**docs/npr_test.pdf<http://www.ab4oj.com/test/docs/npr_test.pdf> > > http://www.ab4oj.com/test/**main.html#NPR<http://www.ab4oj.com/test/main.html#NPR> > > Recent presentation at the North Shore ARC, North Vancouver, BC: > > http://www.nsarc.ca/hf/npr.pdf > > Best 73, > Adam, VA7OJ/AB4OJ > North Vancouver, BC, Canada > http://www.ab4oj.com/ > > > ______________________________**______________________________**__ > Premium-Rx mailing list > Home: http://mailman.qth.net/**mailman/listinfo/premium-rx<http://mailman.qth.net/mailman/listinfo/premium-rx> > Help Page: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm> > Post: mailto:Premium-Rx at mailman.qth.**net <Premium-Rx at mailman.qth.net> > Help Contact eMail: p
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