G'day My pleasure.

Travel adjust. This allows you to increase or decrease the maximum servo movement. Say you have a model and you have set it up with the supplied hardware and you simply cannot get enough rudder travel. This happened to me with a small electric glider. So I then used the travel adjust to get 150% of the normal movement and this was enough to fly the model.

Another example might be when setting up a throttle connection you find that the throttle is fully open but there is still some servo movement to go and the push rod is being bent. This is not good as the servo is stalled and drawing more current than necessary. So you use the travel adjust to decrease the servo throw to avoid the stall. If you find you have to use large amounts of travel adjust, it is generally best to try to correct the problem mechanically first and use the travel adjust for small adjustments.

Sub Trim. I find that when I build a model, put the servos in and set things up that the servos do not always end up a the Zero position ie, the horn may not quite be at right angles to the servo when the radio is set at the middle of its travel. You can then use the sub trim to zero the servo and then mechanically zero the elevator or aileron and then fine adjust with the sub trim.

Have fun. You are right. The books that come with radios rarely tell you examples of how to use the functions they provide.

I really like the features on the computer radios these days. Even the low cost ones like the DX6 and Hitec Optic 6 have some very nice features which make setting models up and flying them far easier than in the "good old days". But, don't rely on the features to fix problems with servo and pushrod adjustments. Get them as close to right as you can with mechanical adjustments and then use the electronics to fine adjust things.

Cheers

Mike in Oz