antentopSince2 July

Ham Spirit
Free Choice



Free Antentop Amateur Open Book
Antentop Album
Antentop Survey




Antentop is FREE e-magazine devoted to Antennas and Amateur Radio an

Special page devoted to

Something about ATU

Custom Search


ANTENTOP- 01- 2004, # 005

Something about ATU



By Igor Grigorov, RK3ZK



What an ATU does?


You should not think that an Antenna Tuning Unit (ATU) is a magic thing to do any antenna work well with your transceiver. At installation between the transmitter and feeder the ATU only does matching of output impedance of your transmitter with input impedance of your antenna - feeder system. It means that ATU allows to the transmitter with output of 50 Ohm to work normally with antenna plus feeder having any input impedance. But probably SWR would be enough high in the feeder. If the ATU is installed between antenna and feeder it does low SWR in feeder and provides good operation for the transmitter. But probably the antenna would work not in good way.


So, an ATU provides safe operation for transmitters end stage, if the ATU is between the transmitter and the feeder, additionally an ATU does low SWR in

feeder, if the ATU is installed between antenna and feeder.


As usual modern transceivers and military equipment have inner ATU that does matching end stage with feeder or antenna. Below we take close look to ATU design.


ATU Design


Fig. 1 shows schematic of a "classical" ATU. Such ATU has:


-        a Matching Unit, that provides the matching of end stage of the transmitter with antenna - feeder system. Matching Unit is the "heart" of any ATU;

-        A SWR mater or HF-bridge, that shows how the matching is done;

Page 40


40 41 42 43 44 45




QRP Transceivers and PA from Accessible Parts IP for QRP Antentop Book Radio Antenna Engineering Book Antentop Printed and e- magazines



Just for Fun:

Map IP Address

Thanks for your time!

Last Updated:

February 23, 2020 21:57

Antentop Home Page

Free Antentop Open Book