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This atu was made to go with my new rig , The HB-1A. The radio doesn't have a vswr meter so my first thought was to fit one in the radio.Space inside the rig is a little tight to say the least so i decided to make an atu with a vswr indicator fitted instead . This then could be used elswhere when needed as i don't have an atu in the shack so it may come in useful at some time.The atu is the classic T match design and i have 2 switches on the front for atu in and out and one switch for the vswr indicator in/out.
The switch on the top of the unit is the 12 position inductance switch.The front panel houses the 2 capacitors and the 2 switches along with the LED right at the bottom. The 2 switches allows me to use the atu in a number of ways. I can use the atu with or without the vswr indicator in line or i can bypass the atu and just use the indicator .The rear of the unit has the 2 bnc connectors and also a banana socket for any counterpoise i may need. I may decide to fit a 4.1 balun in the unit at a later date but for now it's all i need.
schematic
The caps are 2 polyvaricon caps with a sweep of around 4-142 pf if im not mistaken. The tapped inductor is made from 2 stacked T68-2 toroids with around 22 turns in total tapped every 2 turns and around 4 turns between last 2 taps. The switches are DPDT with wire used standard speaker wire.The vswr indicator is the one in the menu.BELOW is the inductance arrangement .As you can see i have the tapped inductor but after building the atu wasn't sure if i had enough of an inductance sweep so decided to fit an inductor consisting of a T68-2 with 23 turns on that can be switched in and out of line with the tapped inductor
hooked up to my 40m loop the atu found a match on bands 40,30,20 and 15. These were the only bands i have on my K1 which was used to try atu out . I will get the 817 out at a later date and see how i get on with all bands.Next job is to see if i have enough room inside the unit for a 4,1 balun. i will put pics of completed unit on the albums section once all work finished .
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