Testing the ATU-100

After weeks of rain, today we had a nice sunny day, so time to get out to a local park and set up my KX3, with the internal ATU disabled, and test the ATU-100 (See my report on building it here).

I set up my favourite SOTA antenna, a 9.15m endfed with 4m CP, and a 9:1 UNUN, coax 3.5m RG-58. The antenna was sloping from abt. 5m to 1m above ground as you can see in the picture.

The KX3 tunes this antenna without any problems from 80m to 6m, SWR = 1 everywhere, but of course, the efficiency will vary considerably.  

I tried to tune the antenna with the ATU-100 on all bands from 80m to 6m.
I double checked the SWR with a Hansen SWR3S SWR/PWR meter, since the SWR meter in the KX3 is rather coarse to get a good reading.

At first, the ATU wouldn't work in AUTO mode, so I set it to MANUAL, and then got it tuning by pressing the red TUNE button each time I changed bands.
Here the results.

The small differences in measured SWR are acceptable I think.
SWR is measured on a different spot along the transmission line, and there may be a slight loss in the connecting cable.

Next, I put the tuner back in AUTO mode, and did a few band changes ... and believe it or not, it worked like a charm !

I went back to 40m ==> 1.21 , then to 20m ==> 1.05, then 15m ==> 1.17, then 10m ==> 1.16, and back to 40m ==> again 1.21, all within a few seconds of transmitting, and without touching any button.

During the whole afternoon, the average current consumption was 30 to 40 mA. And I could not hear the strange noises as reported on the SOTA Reflector by Ed, DD5LP.

[Note: the laptop case contains my 4-band 50W amplifier (the so called Chinese DIY Kits 70W Amp), LiPo battery,  another ATU  (an LDG Z100) and the Hansen SWR meter]

Ok, time for another test, QRP !

I intended to use this tuner for my QCX rigs (40m and 20m models), but for this test I just put the KX3 at 5W.

But now comes the disappointment: the ATU-100 as built does not tune with only 5W.

I have to study the manual and some websites, I may have to put a few more windings on the Tandem Match to increase its sensitivty.

So nothing else to do than tune up with 15W, and then reduce the power to 5W QRP.

The sun was still shining, so I tried to make a few QSO's. Unfortunately, no SOTA stations in Europe were spotted. Here the log of what I worked, and powers used.

* The bad report I got from EI7JN was because I had put the ATU in AUTO mode again, and halfway each transmission it started retuning, but then stopped at a bad SWR, and as a result the KX3 folded back to only 5W. Even when tuning manually then, it was difficult to get a good tuning, since the KX3 refused to put out more than 5W. 

By 17:30 local time, I was getting cold and it was time to go home ...

CONCLUSION

From these short tests, I could conclude the following:

Does it work ?
Yes, sometimes, if you're lucky, and if you have more than 10W, so as it is, it's not suited useful for QRP.

Is it reliable ?
Hmmm, I would have to do some more testing. I don't think I would trust it as my only option.
For SOTA, I will rely on the tuner in the KX3 for sure. And for the QCX rigs, i will probably stick to the tuned antenna's I was using before (link dipole, half wave endfed or ground plane vertical).

So all in all, a nice little tuner, and it can fulfill some purposes ... but don't expect more from it than what you paid for ...
If I find better results after more testing, I'll let you all know.

73,

Luc ON7DQ