Phil,
The LP-100A (or any external SWR/power measurement device) is not
accurate when you are using the KAT3 (K3 internal ATU) since it is
on the *output* of the tuner and not the *input*.
A tuner *DOES NOT CHANGE THE SWR BETWEEN THE TUNER AND ANTENNA* it
only changes the SWR seen by any device looking at the *input* of
the tuner. With the KAT3 the *input* to the tuner is "inside* the
K3.
73,
... Joe, W4TV
On 4/23/2012 3:17 PM, Phil Hystad wrote:
> I am trying to learn the behavior of the K3 ATU Tune. I am switching between
> two loads. One is dummy load with SWR of about 1.1. The other is a mismatch
> on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A
> meter). I am attempting to use the ATU Tune button to bring this unmatched
> SWR load into a match of 1.5 or under.
>
> So, I am getting strange results. I can use my external AT1KM tuner to bring
> this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the
> 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the
> LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode
> where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and
> read out the 4.9 SWR. At this point, it looks like I get a fold back on
> power of about 50 percent (operating at 10 watts so fold back to 5 watts I
> guess). The next thing I do is switch the AT1KM tuner back into service
> without changing anything. When I key down I am getting SWR of 1:1 on the
> LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune
> button, it quickly tunes and the power is back to full power (or, 10 watts).
>
> So, my question --- If the K3 folds back power due to high SWR then is it
> required to hit the tune button to reset power when you now have a matched
> load, 1:1 in this case?
>
> I hope I have explained the situation, it is a little involved in set up but
> I ran across this accidentally while measuring some different antenna loads.
>
> Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the
> tune button for one of my antennas (in this case different from above
> scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on
> the SWR display which I figure is either 1:1 or close to it. But, I have an
> LP-100A sitting on the output of my K-line (I have a KPA500 in there but it
> is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1.
> Who do I believe? The LP-100A was calibrated at the factory (not a kit).
>
> Thanks,
>
> 73, phil, K7PEH
>
> ______________________________________________________________
> 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
