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

Wed Dec 5 02:31:09 EST 2012

Dr Rohde is quite right in this matter.

It is quite pointless to design receivers that have adjacent channel 
suppressions that
are 20 - 30 dB better than the suppression of the transmitters that 
they are supposed to co-exist with.

Even "mediocre" receivers have SSB adjacent channel suppression in the 
order of 70 to 80 dB, which is better than the 55 - 60 dB
suppression that high-grade ISB transmitters can offer.

As a professional designer and systems integrator of HF systems, both 
fixed and mobile, I have had many opportunities to ponder upon the
performance limits of realisable hardware.

Transmitter noise floor and spectral purity are somewhat neglected 
parameters in the HF system planning process, maybe because they are 
difficult to
measure.

In the amateur radio context, I feel that development actually has 
gone in the wrong way. 
The better SSB transmitters of "yesteryear" had better IM performance 
and lower noise floors,
as they used RF inverse feedback and narrowband tuned signal paths.

However, I am in favor of the NPR testing method for receiver 
characterisation, as it can provide an overall figure of merit which is 
composed of both
close-in and far-off adjacent channel behaviour.

This method may have been of even higher importance when the "radiated 
power arms race" still raged among the HF broadcasters.

73/
Karl-Arne
SM0AOM

----Ursprungligt meddelande----
Från: ahmet-m at usa.com
Datum: 2012-12-05 06:16
Till: "Per-Tore Aasestrand"<ptaa at ieee.org>, "PREMIUM-RX"<premium-
rx at mailman.qth.net>
Ärende: Re: [Premium-Rx] Noise Power Ratio Testing of Radio Receivers

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
 aul at 8zo.com > Home Page: http://www.premium-rx.org/ > 
______________________________________________________________ Premium-
Rx mailing list Home: http://mailman.qth.net/mailman/listinfo/premium-rx
 Help Page: http://mailman.qth.net/mmfaq.htm Post: mailto:Premium-
Rx at mailman.qth.net Help Contact eMail: paul at 8zo.com Home Page: http://www.premium-rx.org/

______________________________________________________________
Premium-Rx mailing list
Home: http://mailman.qth.net/mailman/listinfo/premium-rx
Help Page: http://mailman.qth.net/mmfaq.htm
Post: mailto:Premium-Rx at mailman.qth.net
Help Contact eMail:  paul at 8zo.com
Home Page:  http://www.premium-rx.org/