Crystal control on the TR7 is independant of the programming matrix., The PTO tunes up and is offset 50 kHz, so finding the right crystal is f + 5.05 - f(MHz). To crystal control to 7.055 MHz, you'd order a crystal for 7.055 + 5.05 - 7 or 5.105 MHz. For bands that are on a .5 MHz boundary, you'd subtract an extra .5 to put the crystal within the 5 to 5.5 MHz range. The above crystal would put you on 3.555 MHz on 80 meters (3.5 + 5.105 - 5.05).
Since crystal control is related to a specific band, you should program the AUX7 as documented above. This is not mandatory.
I do not have specs on the crystal, but an educated guess would be HC/25U, 20 pf, series, fundamental.
