Posted by
Mike Harris on
Apr 29, 2012; 1:28pm
URL: http://elecraft.85.s1.nabble.com/K3-ANT-1-2-isolation-tp7500652p7511081.html
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/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html