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

Wed Dec 5 03:25:05 EST 2012

Hi,

I doubt that Dr. Rhode was involved in the E 1800 design. This receiver was
made by Telefunken and Rhode was with the competitor Rhode & Schwarz.

A rather 'odd' comment that he made ...

73es,

Per-Tore

On 5 December 2012 06:16, Ahmet G. <ahmet-m at usa.com> wrote:

>
> 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 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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