About my second question on the different readings of the K3 ATU and the LP-100A. Gosh Darn It -- I knew that. I was not thinking. I had been doing so many different measurements this morning that when that came about (the different readings), I was surprised but it was obviously not a problem. I just repeated the measurement and yes, the raw SWR is 1.73:1 and the K3 Tuned to a flat 1:1 yet the LP-100A is reading the raw SWR.
But, actually that was not my main question. The thing that prompted me to ask send the message was the first question about the fold back on power and if it needs the K3 ATU Tune button to be pressed to reset even though the load is well matched and should not fold back at all.
>
> 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
>>
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