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

[Per-Tore Aasestrand]

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 input
> 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 narrower 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 article 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/
>
>
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