Recently John, M1BAI, successfully transmitted ATV pictures to John, G0API, on 13cms. G0API, using a 40 ele Yagi just a few feet off the ground, gave a P5 report. John 'API recorded some of the QSO, so I borrowed the tape and made a copy from which I've grabbed a couple of still pictures. These are off screen so do not fully represent the quality of pictures received. Also, M1BAI told me that he has not yet added pre-emphasis to his TX.Here are the received pictures.
|Computer generated test card.
|The 13cms Transmitter.
On left hand side of the box is the G1MFG TX board
Just visible at the top right is a 5v regulator for the PA, in thermal contact with the big aluminium plate on the back. Above it is a PA/driver sequencer
At the bottom right is the 1W GH Engineering PA.
A cooling airflow is provided by the little fan and the strategically placed exhaust tube.
This is the Yagi that John ('BAI) has built from scratch. The TX box (shown in the picture above) is bolted to the end of the 'U' bolt antenna clamp threads (partly visible at the bottom right).
The boom is square section aluminium tube (10mm?). White plastic standoff insulators, cut from B & Q stock, are passed through clearance holes in the top surface of the boom and screwed to the bottom of the boom. The aluminium rod elements are a jam fit in the standoffs. Inside the black plastic box is the reflector also a folded dipole fed via a semi-rigid coax balun.