There is also another way, and this involves cubic feet of money. Well; not that bad. For a couple of hundred bucks, you can get a Rubidium oscillator, which comes in different freqs. The 10mhz unit can be used as a standard to align any freq counter with, can be had from eBay, and is accurate within +/- 1hz. Couple of the guys on this forum have and use them on their own freq counters. I use one that I got from eBay.
To be sure that the freq counter you have is of decent quality, it should have TCXO for its own internal freq standard. But even they need to be checked against the 10mhz WWV station or a Rubidium oscillator to be sure that is in dead on freq. It is best to always let your freq counter warm up for at least 30 minutes in a warm room before you use it, otherwise it will not be stable on freq.
To be sure that the freq counter you have is of decent quality, it should have TCXO for its own internal freq standard. But even they need to be checked against the 10mhz WWV station or a Rubidium oscillator to be sure that is in dead on freq. It is best to always let your freq counter warm up for at least 30 minutes in a warm room before you use it, otherwise it will not be stable on freq.