As harmonics are present at the output, a low-pass filter is required.
Good harmonics filters for amateur radio bands can be found at the G-QRP web site, good up to 10 Watts and low insertion loss :
The PCB filter fits in a 80 x 25 x 25 mm enclosure sold by SV1AFN
The filter with 3 x T37-6
The result after tweaking the inductors :
Return loss @ 7050 kHz is 22 dB, SWR = 1.17
