The phase noise on the original Icom IC-751 (not the "A" versions) was so bad that it was banned from our multi-transmitter field day site. Seems it took out a number of bands when transmitting-.
Gene K1NR On Sat, 20 Nov 2010 12:48:53 -0800 "John, KI6WX" <ki...@pacbell.net> wrote: > The ARRL is aware of this issue. This problem was > discussed in my 1988 > articles on phase noise in QST (March & April issues). > The article notes > that a high phase noise transmitter degrades the > performance of a low phase > noise receiver to that of the transmitter. This article > started the ARRL > making composite transmit noise measurements. > > A strong signal (>S9+50dB) from a transmitter with > broadband -130 dBc > composite noise in a 500 Hz bandwidth reduces the > receiver's blocking > dynamic range to 103 dB. Most top notch receivers show a > blocking dynamic > range of around 140 dB. In this case, the dynamic range > is reduced because > the noise floor is increased. > > I don't think most hams are aware of the problem. If you > have a nearby ham > running high power and your receiver doesn't work well > when they are > transmitting, you just assume that the signal is too > strong for your > receiver. > > This problem is like splatter or key clicks. It doesn't > impact the owner of > the transmitter, but instead degrades the receiving > environment of those who > live near them. There is little incentive for the owner > of the high > composite noise transmitter to improve their equipment. > > -John > KI6WX > > > > > The FTDX500 wouldn't be the only one, if a -130 dBc > composite noise > > number defines failure. If you have access to QST > reviews, compare: > > > > Flex 5000 > > FT-2000 > > Orion II > > IC-7700 > > K3 > > > > all of which plot tx composite noise at 100 or 200 W > out to 1 Mhz. You > > can draw your own conclusions, but the FTDX5000 > apparently isn't > > exceptional in that regard. The Flex is no better than > -120 dBc out > > to 1 MHz, the FT-2000 is slightly worse than the > FTDX-5000, and the > > Orion II is no better than -130 dBc out to 100 kHz. The > Icom rigs seem > > to do a little better. The K3 performance indeed far > surpasses the > > others. I could find no comment on these numbers in the > reviews. > > > > Bob NW8L > > > > > Why is this not sent to the Editor and Technical > Editor or QST as > > > well as the lead test engineer at the ARRL lab? What > was their > > > response? > > > > > > If the radio's transmitted phase noise is that bad, > Yaesu should be > > > forced to recall all units currently in the field. > > > > > > > > > 73, > > > > > > ... Joe, W4TV > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html --------------------------------------------------------------------- Web mail provided by NuNet, Inc. The Premier National provider. http://www.nni.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
