http://elecraft.85.s1.nabble.com/K3-ANT-1-2-isolation-tp7500652p7512137.html
unterminated. Maybe it is the electronic equivalent of a Persian rug.
> 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<
[hidden email]> 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<
[hidden email]>
>> 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
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