Sorry Geoff. My setup is fairly basic but I believe quite adequate. I use two +10dBm low noise xtal oscillators operated within the 40m band. The output of each is attenuated 20dB before combining via a Minicircuits SCP-2-1. Thereafter the signals pass through an 8MHz LPF to a step attenuator. The SCP-2-1 provides around 33dB port to port isolation at 7MHz. Isolation between the oscillator output stages is therefore around 73dB.
73 Bob, 5B4AGN On 12 December 2010 10:04, Guy Olinger K2AV <olin...@bellsouth.net> wrote: > Thank you, Bob. > > But you have robbed Geoff of his favorite whipping boy. We will have > to take Geoff out to a pub and help him drown his sorrows. > > What was your setup? > > 73, Guy > > On Sat, Dec 11, 2010 at 11:11 PM, Bob Henderson <b...@5b4agn.net> wrote: > > Bottom posted for context. > > > > Geoff GM4ESD wrote > > > > "If I had a K3, before I changed the HAGC threshold my *first* > > measurement would be to look at the output of the SA612 mixer (with a > > spectrum analyser) while introducing two or more very close spaced > > signals into the antenna port, so that these signals do get through > > the roofer - as in a pileup. The objective, of course, would be to > > obtain an acceptably clean output from the mixer with non intrusive > > products over a wide range of input levels. IMHO the higher the > > HAGC's threshold can be the better, provided its control is tight > > enough when activated to protect all what follows." > > > > > > I made within DSP b/w IMD measurements on my K3 and comparable > > measurements on my K2. These were included in a post dated 5 December > > but you may have missed it. > > > > The following measurements relate to K3 S/N 4904 on 7MHz with 2.7kHz > > roofing filter and 2.7kHz DSP b/w. Default slow AGC was selected. > > The table shows input level at the K3 antenna connector for > > each of two carriers spaced 500Hz. At each input level, the level of > > the strongest IMD product observed at the AF output using an HP8568B is > recorded > > alongside. > > > > -73dBm Better than -55dBc (Input S9) > > -63dBm -55dBc > > -53dBm -50dBc > > -42dBm -45dBc > > -33dBm -42dBc > > -23dBm -37dBc (Input S9+50) > > > > These figures are good and IMHO entirely acceptable. Some older > > transceivers would struggle to provide -35dBc at S9. > > > > I made a similar set of measurements with my old K2 S/N 997 > > > > -73dBm -50dBc > > -63dBm -48dBc > > -53dBm -45dBc > > -43dBm -48dBc > > -33dBm -45dBc > > -23dBm -15dBc > > > > Broadly speaking the K3 is as good or better than the K2, which is > > itself good. It is possible later mods to the K2 may have made it even > > better. The most recent mods to my K2 were carried out over 5 years ago. > > > > 73 Bob, 5B4AGN > > ______________________________________________________________ > > 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 > > > > ______________________________________________________________ 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
