Why? A 736 doesn't have 6 meters.
The AH-4 will tune continuously from 1 Mhz through 60 Mhz with a caveat or two. The minimum length for 160 meter operation is about 45 to 50 feet if the unit has an adequate ground. On 75 meters the minimum length is about 25 feet again with an adequate ground. From 40 on up 8 to 9 feet is required.
The listed range is 5 to 5000 ohm, but in reality it is about 6.5 ohms to about 3500. While it will match high impedance loads up to 5000 ohms, the input SWR climbs because the output capacitors are fixed between 3500 and 5000 ohms.
Obviously, on certain frequencies using certain lengths, the coupler will not match as the antenna is too close to an exact half wave and the input impedance is out of the range of the tuner.