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Simple ATU

Posted: Mon Mar 31, 2025 3:33 pm
by Andrew (grayhat)
Covers all bands from 80m up w/o any band switching, for QRP it can be built using polyvaricons, in effect the hard to find parts are the twin air variable capacitors

full informations here

https://www.pa0fri.com/ATU/FRImatch/FRImatcheng.htm

and here is a nice version

http://dl4cs.de/funktechnik/ant/fri-match/en.htm

this ATU is easy to turn into a remote one since there's no band switching it's just a matter of using stepper motors or R/C servos to turn the variable capacitors plus a couple of relays for the hi/lo Z switching and for the ATU bypass (see second link above)

Re: Simple ATU

Posted: Tue Apr 01, 2025 7:47 pm
by Andrew (grayhat)
also see

https://www.hamradiosecrets.com/homebre ... tuner.html

although the links at previous post carry all the needed infos

Re: Simple ATU

Posted: Fri Apr 04, 2025 7:04 pm
by KL7MJ
Andrew (grayhat) wrote: Mon Mar 31, 2025 3:33 pm ... there's no band switching ...
I was just reading through W6SAI's antenna book, and he has a Z-match that switches in additional capacitance that allows a tuner to cover 160 - 10m!
I have a ZM-2 (Z-match) as well as some small pi and T-match tuners, and I think the Z-match is the most flexible in terms of frequency coverage.

Re: Simple ATU

Posted: Fri Apr 04, 2025 8:43 pm
by k8zfj
I agree about the z match. Have built several blt+ that worked just as well if not better than an em-2

Re: Simple ATU

Posted: Fri Apr 04, 2025 8:44 pm
by k8zfj
I agree about the z match. Have built several blt+ that worked just as well if not better than an em-2

Re: Simple ATU

Posted: Fri Apr 04, 2025 9:26 pm
by Andrew (grayhat)
The Fri-Match is derived fron the Z-match, full story here

https://www.pa0fri.com/ATU/FRImatch/FRImatcheng.htm

:)