http://elecraft.85.s1.nabble.com/OE3HKL-s-Measurements-tp7639931p7639966.html
> Correction:
> The sentence:
> "However, the improvement from using the preamp shows up only if the
> preselector handles large signals at least as well as the rx itself."
> Should be replaced by:
> "However, the improvement from using the preselector shows up only if the
> preselector handles large signals at least as well as the rx itself."
>
> 73,
> Erik K7TV
>
> -----Original Message-----
> From:
[hidden email] <
[hidden email]> On
> Behalf Of Erik Basilier
> Sent: Friday, April 06, 2018 8:28 PM
> To:
[hidden email]
> Subject: Re: [Elecraft] OE3HKL's Measurements
>
> Since I do read German, here is my quick attempt to translate the section
> ("Fazit") where the author summarizes his findings about testing methods and
> receiver performance:
>
> "No IP3 value can be derived from the results of this measurement technique
> using broadband pulses with a crystal-based notch filter. However, the
> results do show the resistance to interference generated from summation of a
> broadband interfering spectrum, which seems crucial to me when it comes to
> evaluating the interference handling of an SDR with the ADC at the front.
> In any case, the listed signal levels (for +10 dB (S+N)/N) provides a very
> good way to compare the relative performance of the tested receivers; the
> higher the listed signal level (dBm), the better the better the performance
> in handling strong signals.
> Roofing filter quality can be observed by proper selection of pulse
> frequency for close-in measurement (use e.g. 2 kHz). This is in contrast to
> what can be done with two-signal testing (even using many different
> frequencies).
> In particular, the pulsing measurement technique illustrates how the use of
> a preselector influences receive performance. Earlier one could only rely on
> subjective impresisons in practical use. Our results show that use of a
> preselector always makes sense, even when used with the very best
> receivers!!! Even with the RX-OE3HKL receiver design which by itself can
> handle levels that are up to 26 dB higher, improvements up to 9 dB from the
> preselector are seen. Notable is the performance of the IC-751A with
> preselector and roofing filter: Results are almost as good as those of my
> own receiver design. However, in contrast to the situation when using the
> 2-signal method of testing, when using the pulse signal, without the
> preselector, the roofing filter doesn't yield much improvement. Apparently
> the reason is that the broadband signal quickly overloads the front end
> circuits. Without using the broadband pulse signal it would not be possible
> to reconcile lab measurements with real-world reception results seen when
> using the 2x120m V-antenna! However, the improvement from using the preamp
> shows up only if the preselector handles large signals at least as well as
> the rx itself.
> The K3 is by far the best of the commercial units, and without having to be
> modified. This result is confirmed by practical experience in reception
> testing using the 120m-V-beam during a contest. Results improved by another
> 2-4 dB after a firmware update was performed (see the red corrections).
> The IC-7300 clearly performs more poorly than the analog radios with roofing
> filters, in practical reception as well as in lab measurement. When the
> preselector is added, it partly outperforms the FT-1000 Field with
> preselector and roofing filter. Based on this result, I conclude that an SDR
> with the ADC in the front end, when used with good antennas and in the
> presence of sftong signals, should if possible only be used in combination
> with a preselector.
> I would like to establish that the here described test setup with its
> broadband discrete signal is a better proxy for real-world interference
> signals than is the stochastic noise signal used in Noise Power Ratio
> testing. Furthermore, by varying the pulse frequency, one can vary the
> intensity of the interference in a way that is clearly quantified by
> observing spectrum analyzer output. In contrast, the noise level in NPR
> measurement is defined by the high ratio of peak value to rms (10 to 11). In
> this scenario t would likely take very expensive equipment to perform
> measurements with sufficient accuracy for comparison purposes.
> I would also like to mention that NPR measurements at 3dB (S+N)/N will not
> be sufficient to take into account the effect of higher-order IM products.
> To achieve that, one must increase input levels to the point that a further
> increase of 1 dB will lead to a 3 dB increase at the output (3rd order).
> This is what it takes to get results from the NPR method to agree with
> results from the pulse signal method."
>
> My apologies in advance to OE3HKL for any misinterpretation I might have
> made.
>
> 73,
> Erik K7TV
>
>
> -----Original Message-----
> From:
[hidden email] <
[hidden email]> On
> Behalf Of Erik Basilier
> Sent: Friday, April 06, 2018 5:06 PM
> To: 'Bob DeHaney' <
[hidden email]>;
[hidden email]
> Subject: Re: [Elecraft] OE3HKL's Measurements
>
> The German website describes how this om has developed his capabilities over
> the years, based on his specific circumstances and needs. This has resulted
> in a measurement technique with arguable advantages, achieved with a
> homebrew, very specialized test setup, implemented for the 40m band. While
> the author apparently had access to some lab-quality test equipment for
> testing his home-brew test equipment, it appears to me that it would be much
> more expensive to implement his receiver testing setup using only a
> combination of off-the-shelf lab test equipment, if that is even practically
> doable.
> I haven't read everything on the website, but for those who find the German
> confusing, the following is my summary overview of some of the site content.
> He put up a huge horizontal V antenna that picks up high signal voltages
> from BC signals etc, so rx overload and even damage is a concern.
> His latest home-built rx is good, but he still looks for improvements, and
> he focuses on preselectors as a possible way to improve performance.
> Preselectors don't seem very popular these days, but the author makes a case
> that at least for his extreme conditions, they can contribute in a
> meaningful way to how strong, nearby interfering signals can be handled.
> This turns out to be the case for his homebrew rx and also several
> commercial rigs, including the K3. The K3 of course has its roofing filter
> as standard equipment. The IC-751 and an FT-1000 Field have both been
> modified to add roofing filters that are not part of the original design.
> The IC-7300 which places its ADC at the front end, cannot be so modified due
> to its basic architecture, and is tested as manufactured.
> To test for unwanted response to nearby strong signals the author used 3
> types of test setups: IP3 (two input frequencies), continuous noise spectrum
> (measuring Noise Power Ratio) , and the broadband spectrum carefully
> generated by pulses, which varies with pulse frequency. The latter method is
> considered the best, and most similar to real band conditions, and
> applicable to all the tested receivers (the IP3 method makes no sense for
> the IC-7300 type architecture).
> The pulse generator setup has a notch filter that keeps the pulse spectrum
> out of the rx passband, which is set to 500 Hz. When the power of the pulses
> is cranked up, the rx does respond eventually, but the higher the pulse
> power tolerated, the better the rx. The table presented shows "tolerated"
> (in some sense) pulse power in dBm for the different receivers with and
> without use of the homebrew preselector, which always helps.
>
> 73,
> Erik K7TV
>
> -----Original Message-----
> From:
[hidden email] <
[hidden email]> On
> Behalf Of Bob DeHaney
> Sent: Friday, April 06, 2018 12:52 PM
> To:
[hidden email]
> Subject: [Elecraft] OE3HKL's Measurements
>
>
> You are correct Breitband means Wide Band in English. Only his home-built
> receiver is better than the K3 measurements
>
> Vy 73 de Bob DJ0RD/WU5T
>
>
> ---
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