This week I did some succesful experiments with the 23 cm FM ATV transmitter with ALPS VCO. The transmitter provides about 30 mW to an 23 cm PA which delivers 1...2 Watts at 1.2 GHz. One of the tranmissions shows my testpicture at the PI6ZTM repeater:
I did not include PLL circuitry in the design. The circuit is straight forward:
The video branch contains: CCIR-filter, VCO ALPS 1679C and MMIC MSA-0886.
August 12, I was able to test the audio part (7.02 / 7.2 MHz oscillator). It worked, but there was some 50/100 Hz hum. Also I found that results were better when the 7 MHz signal was injected just after the 50 k potmeter.
The VCO can be tuned from 1100...1350 MHz.
At this moment, the experimental circuit is soldered on unetched PCB.
23 cm ATV transmitter
The ATV transmitter is connected to the Power Amplifier (design PA0VRE):
2 Watt PA with BFQ68 and BFQ136
The PA delivers its output signal to a homemade biquad antenna, connected with about 8 meters RG6U coaxial cable (75 ohms).
To my surprise the transmitter is very frequency stable. No PLL circuit required !