Wednesday, May 16, 2012

HF antenna tuner

 This box is laying in the shack for so long that I almost had forgotten it.
At some point I had an FC-102 antenna tuner that worked great on my "piece of aluminum tube" vertical antenna, then I decide to part with it because I didn't had the matching FT-102 transceiver and I could easily built another antenna tuner. I regret that decision, I have now the FT-102 but not the FC-102....

The swr meter built in the box is a Daiwa cross needle and the rf caption is of the bridge type. works nice.

The variable caps were an ofter from a friend, although not in perfect state they do work, I will improve the shaft electrical connection to the vanes, it's a little loose and I don't want intermittent operation. The coil was bought at some hamfest thinking in this build.

Mechanical work is just a pain if you don't have patient and shop full of  materials.
 The shaft isolator/coupler is just a little piece of plastic hose, not the best solution but for now it's enough.

Schematic is a simple T-match, the coil connections were made by testing, for each band, with the antenna analyzer, for best match but the coil material is not easy to solder so I will probably replace it, see last image. I added a parallel 56pF cap to left tuning cap to extend range, In the future will put a switch in and out of circuit.

It can match my 18Mhz band dipole to any band between 1.8Mhz and 29Mhz.

Now I am building a new coil to replace the present one. Just need to get some wire....

Of course the can will be's just a fixture for the coil winging.

Have fun!

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