[Elecraft] Re: KAT3 ATU and SPE Expert 1K-FA Amplifier

[Stewart Baker]

I made some measurements of the isolation between ANT 1 & ANT 2 on 
my K3.

There is little difference between ATU & BYPASS. Unable to do 
50MHz.

1.9MHz 	58.1dB
3.7MHz	51.9dB
5.1MHz	49.2dB
7.0MHz	47.1dB
10MHz		44.7dB
14MHz		42.5dB
18MHz		40.8dB
21MHz		39.2dB
24MHz		37.1dB
28MHz		35.7dB

So on 60m for 100W from ANT 1 there will be 1mW from ANT 2.

73
Stewart G3RXQ 

On Tue, 15 Jul 2008 17:45:19 +0100, Dave G4AON wrote:
> Chris
>
> Is this simply an issue of RF being picked up by the antenna 
connected
> to the output of the linear, which it would see as reverse RF 
whenever
> you transmit directly from your K3 on another antenna?
>
> Also you can measure the RF from ANT2 when transmitting on ANT1 
fairly
> easily... On my K3 with 100 Watts out of  ANT1 I cannot measure 
anything
> from ANT2, with or without the ATU in use. I tested right up to 
50 MHz -
> the lower limit on my power meter is 50 mW.
>
> 73 Dave, G4AON
> K3/100 #80 & Acom 1000
> ----------------------------------
>
> My K3 has the KAT3 ATU fitted and I therefore have the options 
of
> selecting ANT 1 and ANT 2. I use the K3 with the SPE Expert 
1K-FA
> amplifier.
>
> After looking at the diagram showing the switching of the KAT3 
in the
> K3 Owner's manual, am I right in thinking that when transmitting 
(I
> am a CW operator), there should not be any RF on the antenna not
> selected?
>
> I use ANT 1 for all my HF antennas, including 6m, and ANT 2 for 
a
> resonant inverted vee for 60m that I put up yesterday.
>
> The reason I ask the question above is that when I select ANT 2 
(for
> 60m) and transmit, the 1K-FA immediately goes into STANDBY mode
> because of a high SWR.
>
> I am wondering if my KAT3 ATU is working properly? With the KAT3 
in
> BYPASS mode (which is how I have been using it for all my HF
> antennas), the K3 SWR meter gives an SWR of 1:1 on 60m, which it
> should do as the antenna is resonant.
>
> When I switch the ATU to the AUTO position on 60m with the same
> antenna and then tap the ATU TUNE button, the K3 makes a similar
> noise to the K2 ATU I have, but does not display any readings. 
When
> I then transmit, the SWR meter shows maximum SWR and about 40 
watts
> output with the K3 power contrtol set to 100 watts.
>
> I have tested the KAT3 relays using the L1-L8 and C1-C8 and Ct
> settings in the KAT3 CONFIG menu and they appear to be working 
ok.
>
> This is the first time I have needed to use the KAT3 ATU or the 
ANT
> 1/ANT 2 facility since I got the K3.
>
> I would appreciate any advice or suggestions, please.
>
> Thanks and 73 de Chris, G4BUE
>
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