[TenTec] ARRL Reviews

[jrhallas at optonline.net]

Folks, 

To get the definitive  information on this topic, please go to  www.arrl.org/forum. Look for the “Technology”
category and then scroll down to “Equipment Testing.” Look for the three
postings from ARRL Lab Manager Ed Hare.

 Regards, Joel

 Joel R. Hallas, W1ZRTechnical Editor, QST

ARRL,
the national association for Amateur Radio™

----- Original Message -----From: Bill Tippett Date: Thursday, September 1, 2011 8:37 amSubject: Re: [TenTec] ARRL ReviewsTo: tentec at contesting.comCc: hans at pa1hr.nl> W3ULS wrote:> > >With the changes ARRL has made in reporting IMD3 for > receivers, all you have> to do is subtract 8-10 dB to get very close to Rob Sherwood's > findings. No> biggie.> >         The actual IMD difference is ~12 dB which is the > difference > in noise bandwidth between 3 Hz (spectrum analyzer) and 50 Hz > (approximate BW of the human ear) using [10 log(BW1/BW2)] or > 12.2 > dB.  I'm afraid it IS a biggie if someone looks at PA1HR's > unfootnoted listing and concludes the FT-5000 is head and > shoulders > above other rigs.  It is not, as can be seen in Sherwood's > table.  It > simply has the benefit of being tested using *new* methodology > versus > other rigs using the *old* methodology, and there is not even > any > indication of when the measurement methodology was changed!> >         One of the major benefits of any published test data is > comparability, and ARRL's older data (I'm not sure of the exact > date > of the methodology change) is definitely not directly comparable > to > current data.  Unfortunately I believe Peter Hart of RSGB's > RadComm > is now using the same IMD measurement methodology so his data is > also > not comparable over time.> > >IMHO, Sherwood and his work are admirable, even irreplaceable. > Yet I think> he is overly critical of the ARRL and its lab procedures, given > the fact of> the ARRL's large overhead that must be paid for and the good > work they do> overall. They beat the FCC in the U.S. Court of Appeals for the > District of> Columbia, for example, which is no small accomplishment. So I > can live with> a little less rigor in the testing area as long as Rob Sherwood > (and Peter> Hart) are around to offer their opinions.> >         I'm certainly not critical of everything ARRL does for > us.  However when published comparisons are made of their data > without so much as a footnote detailing the differences in > measurement methodologies, then criticism may be justified.  The > average person reading these comparison listings may be > seriously > misled if they simply take them at face value.  I'm copying this > to > PA1HR so hopefully Hans will consider footnoting the differences > in > measurement methodologies, and perhaps Joel W1ZR will tell us > exactly > when ARRL's methodology changed.> >                                         73,  Bill  W4ZV > > _______________________________________________> TenTec mailing list> TenTec at contesting.com> http://lists.contesting.com/mailman/listinfo/tentec>