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Author Topic: Antenna tuner for random wire/longwire  (Read 2664 times)

Offline joczo

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Antenna tuner for random wire/longwire
« on: May 20, 2017, 1333 UTC »
Hi guys,I'm coming with a pretty noob question.Sorry asking it here,but you are nice guys,maybe you could help  ;D
I messed up my antenna tuner which I had until a couple weeks ago.So I started to make another one,with bigger coil and variable capacitor,because the other one didn't really handle 100W.
I tried out a couple schematics,but it didn't work very well,it couldn't handle my 30meter long random/longwire antenna.
First I tried this one,but it only worked for longer wavelenghts than the antenna(40 and 80m): http://homebrewradio.tripod.com/sitebuildercontent/sitebuilderpictures/tuner001.jpg
After I tried this,but also didn't work really well.It did something on the upper bands,but couldn't get the SWR down to 1.0 on none of the bands.
So finally,my question is,can you suggest an antenna tuner schematic that works from 10 thru 80meters?I don't need nothing fancy,just to do it's job.
One more thing,I only have 1 variable capacitor right now,and my coil has about 22 turns,it would be great to make one with these components.
Thank you very much!  :D

Offline ThaDood

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Re: Antenna tuner for random wire/longwire
« Reply #1 on: May 20, 2017, 1430 UTC »
Well, for a schematic of the tried and true MFJ-941D tuner, scroll down to page 4,    http://www.tgc-ares.org/mfj-941d.pdf      Actually, you can make this tuner better than MFJ with delron insulative washers and not using "rivets to aluminum" on the chassis. I've improved my 941D tuners by soldering GND braids from circuit board GND to daisy chaining the outer SO-239 connectors. You can tune just about anything from 160M to 30MHz. I mainly use mine to make-up the lack of auto tuning on the newer 60M band. Many older auto tuners, and rigs that have the built-in auto tuner just won't do do it, but my MFJ-941D manual tuner works great there. I haven't tried it on 30M, but it should work great. Best of luck!!!!!
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Offline Josh

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Re: Antenna tuner for random wire/longwire
« Reply #2 on: May 20, 2017, 1735 UTC »
Also for messing around on 160, it can help if you replace any toroid wrapped wire with teflon insulated wire, they can arch over in certain instances operating near/on 160m and it doesn't take much wire to do the job so it's cheap to do. Also if not using a built in balun it might help to disconnect it from the circuit as it may be active at all time, check schematic for details. I have an old mfj tuner that would emit a plasma on the wall behind the tuner from the balun terminals, indicating a very high potential, removing the balun eliminated the plasma display.
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