GHz prescaler

In the 1.2 GHz input stage (February 1985) for the microprocessor- controlled frequency counter, we used an SB8755 prescaler in the IC7pos- ition. This IC, which divides the 100...1200 MHz signal at input C by 512, is perfect for the purpose, but is rather expensive. Just recently, another prescaler, which is much cheaper and more sensitive, has come onto the market: the U665B from Telefunken. The U665B is a +1024 prescaler with integral pre-amplifier. Its sensitivity is better than 10 mVrmsfor frequencies between 80 MHz and 900 MHz. It is fully usable up to 1200 MHz, but its sensitivity drops to about 30...40 mVrmsat that frequency. To fit the U665B onto the PCB, first remove existing IC7, IC8, and P3. No other components should be removed because, although they may look superfluous, they are needed for the interconnection between the compo- nent and track sides of the board. The new IC is fitted so that its pin 1 coincides with pin 8 of the previous IC7. Next, solder capacitors ...