Thursday, November 10, 2016

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.

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.

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 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.


Photon said...

Very interesting! I like the S-Match! Shame about the analyser, but all will be well in the end...

PE4BAS, Bas said...

I just tested it to see if it worked. Till now no contacts were made. I probabely will try that another time. The design and construction are very simple. Wish I knew this before I bought that expensive Palstar 10 years ago. I imagine what I will know in the future ;-). 73, Bas

Bert, PA1B said...

Hallo Bas, het is zeker niet leuk als er iets mis gaat. Maar wat er gebeurd is, schept een nieuw perspectief en/of nieuwe ervaring. Laat je niet ontmoedigen, maar neem de tijd om een nieuwe stap te zetten. Succes, 73, Bert

Hans said...

Hoi Bas, leuk dat experiment met de S match/ L-tuner.
Je zou zelfs nog in de spoel aftakkingen kunnen maken voor nog nauwkeurige afstel. Maar erg leuk om daar mee te experimenteren en ook zelf te maken. Alleen jammer dat je MJF-analyzer hiervoor de geest moest geven. Ongeluk zit in een klein hoekje. Niks aan te doen. Ik hoop dat de kosten zullen meevallen.
73 Hans, PE1BVQ

PE4BAS, Bas said...

Hallo Bert, ja achteraf had ik voorzichtiger moeten zijn. Maar ja, je stelt dingen op, je verwacht wat, je wilt foto's maken voor het blog. In m'n hoofd was ik al een verhaald aan het schrijven. Beter is om eerst het experiment rustig te doen. Maar ja....ondertussen kreeg ik bericht dat de analyzer weer klaar is en ben ik bezig om de S-match alweer te verbeteren. 73, Bas

PE4BAS, Bas said...

Hallo Hans, voor de kosten van de reparatie koop ik geen nieuwe. Natuurlijk is het zonde geld en had ik beter moeten opletten. Maar wat gebeurd is, is gebeurd. Terugdraaien kan niet. Ik wil nu een schuif maken over de spoel. Met aftakkingen en een schakelaar vind ik helemaal niks. 73, Bas

Peter pa4o said...

Gebruik hier ook een Smatch en kan de open lijn aansluiten of op de afstemC of op de spoel. Beide gaat perfect. Kosten waren beneden de 10euro. Mooi dat je mfj weer klaar is Bas, was wel even schrikken..

PE4BAS, Bas said...

Hallo Peter, ik weet dat jij er goede resultaten mee boekt. Ben wel nieuwsgierig hoe jij dat doet met die aansluiting aan C of L. Moet het maar eens bekijken. 73, Bas