Monday, February 22, 2021

S-match - Palstar AT1KM with 1:1 balun efficiency/balance comparisation

  First of all, don't expect a very scientific comparisation here. I haven't got calibrated equipment. It is just a practical comparisation between the S-match antennatuner I previously converted from a MFJ-948 and the Palstar AT1KM with homemade 1:1 current balun for the low bands. Personally I think it is not a fair comparisation since the components in the S-match are inferior compared to the components used in the Palstar. However, I was just curious...



Measurement was made with 50W input. Output current was measured with my homemade RF current meter.

             Palstar                            S-Match

Band%Left%Right %Left%Right
806060
4535
602530
3010
405040
4030
305045
4030
2080      70
7060
174545
4030
157070
7060

Not surprisingly the S-match does not perform as good as the Palstar with 1:1 balun. I think this is because of the used components in the tuners. The Palstar has bigger capacitors and a huge variable coil. The S-match has small capacitors with a switchable coil, this coil is made of wire that is only 1/4 of the size the Palstar coil is made of. Besides that the S-match has a lot of additional wiring because it is a converted T-match and components are not in the ideal place. However, the S-match is advertised as doing a great job in balancing, in this it does a good job....but the Palstar T-match design with 1:1 balun outside the tuner does at least the same job in balancing.

My conclusion is that if you want to use a doublet as your antenna and think you need a special (balanced) tuner for it to feed the open line this is simply not necessary. If you have a simple T-match tuner or even a automatic tuner that has enough capacity, with a good 1:1 current balun outside the tuner it will do the job.

Past experiments:


4 comments:

  1. Nice kit and interesting results non the less. 73 have fun de Simon M0YKS

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    Replies
    1. Tnx Simon, it is a interesting comparisation. In the end the S-match conversion would not have been needed. A simple quality 1:1 current balun at the output had done the trick just as well. 73, Bas

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  2. Thanks Bas. Very interesting work. Two points that I think also relevant: (1) the MFJ is considerably cheaper than the Palstar and (2) it is considerably lighter. Even if the MFJ had proved to be not so good, the price and/or weight issue could, itself, tip the 'balance' (bad joke!)

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    Replies
    1. True John, it is not a fair comparisation. On the other hand I alsop wanted to show that you don't need a special tuner to feed a doublet or open line.
      By the way I doubt you'll notice the difference on air. As a sidenote this is not very scientific, it's a practical test. This is the outcome but it could be that measuring the RF current has nothing to say about the effeciency of both tuners. Unfortunately I haven't got the knowledge of everything. Any comments on this topic are most welcome. 73, Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas