S-Match© experiment

PA1PRD's endfed tuner

More info about the S-Match© can be found at the website of PA0FRI

I always wanted to experiment with this design to feed my horizontal loop. Since the system works with a simple transformer the radio is not physically connected with the antenna and that's one of the things I like of this design. Other advantages claimed are better balance compared to a T-Match with 1:4 balun and a higher antennacurrent into the antenna. So, I aquired a homemade matcher from PA1PRD Erik at a sale from our radioclub. It is a very simple endfed tuner which he used for a 80/40m wire hanging in the air below a kite. Both coil and capacitor are homemade. Just perfect for my little project. I dismantled the whole thing and made some improvements on the capacitor.

Measuring everything I was already afraid I would have too less capacity (140pF), but for just a experiment it's not a problem. I don't bother you all with the technical aspects of building this whole antennatuner but in the end it cost me a "few" hours. What was more important to me were the results. I wanted to verify the claims given. At first I measured the current behind my Palstar AT2K which is a T-match with built in 1:4 balun. Transmitting with 40W FM I measured about 0,8A on one side and 3,4A on the other side  of the open line with my clamp meter.

Nice?

I connected the S-Match© and with the help of my MFJ-259B I found a nice 50Ohm match on 30m. Oh yes, with 40W input I measured again and found a high current of 300A on one side and 80A on the other end. This couldn't be true. Besides that, the radio kept transmitting even when I switched PTT off. Not good. I decided to listen how receive was and it was not that good.

Transformer

Switched back to my vertical and had a lot of signals from stations all over the band. So I thought I made a fault constructing the antennatuner. Then suddenly it occured to me that I connected the wrong ladderline (have 2 coming into the shack remember). I was matching a piece of about a meter ladderline and the tuner could still get a 50Ohm match!!! Wow!. Now, I connected the right ladderline which connected the loop to the tuner. But the disaster already happened. I probabely forgot to switch off the MFJ-259B and the high radiation from the unshielded tuner and high antennacurrents probabely fried the very sensitive diodes inside. Stupid me!

Anyway I wanted to continue the experiment to I decided to connect a SWR meter to tune the S-match©. Now I measured transmitting with 40W FM a current of 34A on one side and 2,8A on the other side. Still a big difference between both sides of the ladderline, could be a loop cannot be balanced just like a dipole with 2 exactly same lengths? But it is significant more compared to the output of the Palsar T-match tuner. It was relatively easy to find a good match though, only not above 14 MHz as the capacitor probabely hasn't got enough capacity. I consider the experiment as successful and learned interesting things already.

Unfortenately I damaged my MFJ-259B analyzer  during the experiment and so I searched on internet how to repair the thing. That didn't look easy to me as the diodes are SMD types. Thinking about my escapades repairing the IC-706 and modifying the FT-817 I decided to find someone that repairs these things. I found radioamateurshop.nl which is not really a shop although it is in the name. It is a repairservice for hamradio equipment. So I already shipped the analyzer and hope it will be repaired soon.