Auto Tuner Refuses to Tune, Why?

Automatic antenna tuner of my FT-710 radio has the ability to tune an SWR up to 3:1. But sometimes the radio refuses to even try tuning. Here are the two interesting situations which I found.

What you saw now is the normal operation of the built-in automatic antenna tuner of FT-710. A long press of the ‘TUNE’ button below the power switch activates it. Rattling sound is heard as different combinations of capacitors and inductors are tried using relays to find the best match. In between, ‘HI SWR’ flashes several times and the SWR indicator needle touches infinity several times. Finally it settles down with the best match and gives you an SWR near 1:1 during transmit.

Previous one was on 20m band and this one is on 40m band, both for my multi-band fan dipole which has elements for 40m, 20m and 10m. Same procedure is followed by the radio.

This is what happens when I try to tune 80m band, for which the antenna does not have elements. The radio gives a different tone and shows ‘HI SWR’ indicator. It just refuses to try tuning. That means the SWR is way beyond the tuning range of the auto tuner. We do expect very high SWR on 80m for an antenna with elements starting from 40m only.

Now this is the other extreme. It appears as if the tuner is not working. When I saw this for the first time, I even missed a contact with an extremely strong station because I did not try to call. What I missed was that there was no ‘HI SWR’ indication. Actually the SWR was 1:1 on that frequency and there was no need for the auto tuner to select inductors and capacitors! That is how it appeared as if the auto tuner is not ‘tuning’!