Sven Karlsson wrote:
yes, they are sensitive. On the other hand switching up- and downconverting DC/DC converters are common in this area, so we should be able to solve these problems.Hi Holger,the low costs for the PCBs (about 10-20EUR at quantities of 10-20pcs.) won't justify the higher effort of a 'universal' PCB design.I would like to disagree. I have some experience in running electronics projects (have run more than 20 major projects both as a hobby and professionally). I have learnt the hard way that generalism is a good thing indeed and it really pays of in these kinds of small projects. In my experience, the major problem here is to make things actually work properly since we are dealing with (microwave) radio electronics. Tuners tend to be very picky with noise in the ground and power supplies. In most cases, if not all, you will have to use proper ground and power planes (possibly multiple ground/power planes) and very good voltage regulation. This applies even to monolithitic tuners/front-ends, at least the ones I've seen. From your schematics it looks like you are going to use switchregulators to generate all voltages. I would suggest to make sure that the front-end _really_ can handle the noise on the power input. You might need to use linear regulators on some of the more sensitive power rails.
In the MAX??? datasheets you'll find the noise curves - IIRC they are about an order of magnitude smaller than the noise level acceptable at the tuner supply inputs.
The Microtune 7072DTF, just for the reason that we can get them easier than other ones.And by the way, what front-ends are you going to use?
Holger
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