In your context the ANT1 circuit was normally terminated, one port in the transmitter, the other in an antenna. That's normal, a load on both ends. ANT2 was NOT normally terminated unless you want to treat the reactive 10 k+ Z termination of the tiny capacitance across the relay as "normal".
If antenna two was actually being used for something while TX on ANT2, there would be something on J43 when not in transmit. If you have a sub RX on the non-TX line, then the crossover means something, as in do I need to close the COR relay. But that now is the same as your ANT1 termination, TX on one end, ANTenna on the other, except RX on one end and antenna on the other. I could say that your method was the one rigged (as in not normal), and was devised to come up with the worst possible reading. I actually USE ANT 2 during TX on ANT 1. That's when you want to know the separation. I don't get readings as bad as yours. 73, Guy. On Sun, Apr 29, 2012 at 5:51 PM, Mike Harris <mike.har...@cwimail.fk> wrote: > I thought it was clear that all I was looking at was a transmit > parameter, that is, what came out of ANT2 when ANT1 was was carrying a > signal. This gives an idea of the coupling across the C/O relay K18 > which selects ANT1 or 2. In this context both ports were terminated. > > I fail to see why I should also have to terminate J43 on the KAT3, it > would in effect doubly terminate the port with one termination before > the wattmeter and one after. Not a satisfactory situation for the > measurement. Naturally, if the Sub RX is connected to J43 that job > would be being done by the input of the RX and readings might be different. > > I have my Sub RX either listening to the same antenna as the Main RX or > to the Aux antenna port. Nothing connected to J43. > > The idea was to see what happens with one of a set of standard set-ups, > not one where the configuration has been rigged to try and maximise a > reading. If there is a real need to absolutely minimise what came out > of, or into, the unused antenna port then by all means terminate J43. > It's yours to do with what you like. > > Regards, > > Mike VP8NO > > On 29/04/2012 17:06, Guy Olinger K2AV wrote: > > You are getting some really worse numbers than I did. > > > > You may have ant2 only terminated on one end of its cable connections, > > which would be really worse on 6 meters than 160. There is one of those > > bitty jacks that needs a cable attached to it and then terminated. It's > > the "other" antenna connection that allows you to listen on whichever of > > ANT1/2 the TX is NOT using. > > > > Out on Core Banks, NC, we were using doublets at right angles on the same > > pole to ANT1 and ANT2, receiving with diversity. There was 30 dB > > separation with the two antennas hanging on the same pole. How much > better > > does it have to be inside the K3? > > > > You need to terminate the internal K3 connection of ANT2 when you make > the > > measurement. Also the shields of both cable connections at both ends > need > > to be grounded as well as terminated. > > > > 73, Guy. > > > > On Sun, Apr 29, 2012 at 9:28 AM, Mike Harris<mike.har...@cwimail.fk> > wrote: > > > >> Interesting. I looked at it from the other direction. With the K3 ANT1 > >> connected to a dummy load and ANT2 connected also to a dummy load via my > >> WM-2 QRP wattmeter. > >> > >> With 100W out at ANT1, out of ANT2 I measured 30mW at 50MHz down to 1mW > >> at 7.1MHz. A range of -30dB to -50dB. 50MHz is not in the WM-2 spec, > >> however, 25mW was measured at 28.2MHz which gives -36dB. > >> > >> There are obviously potential measurement errors there so no one needs > >> to take it as absolute. Perhaps someone with access to precision > >> equipment could also do the test. > >> > >> Regards, > >> > >> Mike VP8NO > >> > >> > >> > >> On 28/04/2012 12:27, Mark - G4AXX wrote: > >>> The isolation between ANT 1 and ANT 2 varies from -76dB at 1.8MHz to > >> -46dB at > >>> 50MHz. > >>> This is measured with a signal generator, using the K3 S-meter, with > ANT > >> 2, > >>> AUX RF and RX ANT IN terminated in 50 Ohms. > >>> > >>> http://elecraft.365791.n2.nabble.com/file/n7509068/ANT1-2_leakage.jpg > >>> > >>> The isolation between AUX RF and ANT 1/2 is>95dB (1-30MHz), rising to > >> -70dB > >>> (52MHz). > >>> This was measured with an N2PK VNA. > >>> > >>> I have tried to dress the unscreened wires from ANT 1& 2 to the ATU > in a > >>> way to minimise coupling, but the coupling is dominated by the > >> capacitance > >>> of relays K18& K19. > >>> > >>> Using ANT1/2 for Diversity reception means the receivers are never > truly > >>> independent. There is likely to be more coupling inside the K3 than can > >>> usually be achieved by physical separation of the antennas. > >>> > >>> Operating Diversity reception with the SUB RX fed from the AUX RF BNC > >> input > >>> is the way to go. > >>> > >>> 73 Mark G4AXX > >> ______________________________________________________________ > >> 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 > ______________________________________________________________ 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
