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pay attention to how low they go if it matters to you.i have a cheap chinese counter that goes upto 2.4GHz and is very accurate - cost me about €10 but it wont go down into the 2digit KHz area.so i cant use it to check 32.768KHz "clock crystals" that often feed PLL's
If you're a beginner you probably should start with just a cheap simple counter. Counters vary in price from £10 to £thousands.The general features to look out for are:1. As stj says, the low end frequency.2. Does it allow an external 10MHz reference?3. Is it a reciprocal counter - that is does it count period using its own oscillator which gives much more accurate results for low frequencies.4. Does it have some sort of interpolation (so it can measure down to less than a whole cycle of its own clock).5. Can it do back-to-back or continuous measurements or is there a gap between them.6. Does it do time measurement between channels (start on channel A and stop on B for instance).7. Does it have a computer interface (USB/ethernet are more useful than GPIB which requires expensive controllers/cables - RS232 is OK but probably requires an adapter).8. Does it do things like time stamping and line fitting to points (only in the more expensive counters so probably not worth worrying about).9. How good is its own internal oscillator? (Not that important if you can use an external reference such as a GPSDO or just a good OCXO off ebay.)Counters with 4. & 5. are the more expensive ones. 4. is often given as one shot resolution (in the range 25psecs to 250psecs or so for counters with interpolation).You can have 5. without 4., as in the TTi counters which are reciprocal and can take back to back measurements but don't have interpolation.Then there are user interface issues such as is the display easy to use/backlit and is there a battery option if you get into ham radio and want to have it portable.
I have a cheap chinese counter that goes upto 2.4GHz and is very accurate - cost me about €10 but it wont go down into the 2digit KHz area, so i cant use it to check 32.768KHz "clock crystals" that often feed PLL's