External antenna will not work with KA500, don't even get static in any freq.

someone is using a ham radio near it

How do you have it installed? in a vehicle? or in a building. What power supply configuration are you using? Is it adequately earthed/grounded? What type of antennas do you have? waiting for your info :)

Possible failed amplification unit (may be internal to the radio or may be external somewhere in the car, usually in the trunk or under the rear seats)

then you will need a converter box,there is no analog signal anymore,it was changed to digital,your tv is not hd if you dont even get one channel,you also need a hd antenna,

This problem, really need to be on a bench to test.. FREE at any good cb shop, to tell you what is wrong.... But most times when a freq counter is not working. Either the crystal is bad, poorly soldered, or its not receiving an input signal. Best way to test is to have a second freq counter external inline using coax.. and check the output of the radio and see if it shows correct or wrong. If it is showing correct they you internal freq counter is messed up. and needs to be check for a bad crystal or solder joints. sometimes even the voltage regulators go bad.. If it is showing a wrong freq on external counter then check the radio's crystal and oscillator circuit. this too can be as simple as a cold solder joint. on the solder side check the small surface mount diode near the PLL, next to the PLL shielded covers. It is normally black these come loose often times too. If you need more help feel free to call or text for more help.

I have a unit like that. The antenna appears to be dead. It just searches forever and never finds anything. I use an external antenna that I got from eBay (brand is Gilsson) and it works fine. You just plug it in the external jack (after removing the little rubber plug) and it works even better than the built-in antenna.

http://www.police-scanner.info/police-scanner-frequencies.htm you may need to put in the new freq. # a few months ago most went to new freq. #

if you are receiving stations on the higher frequencies then your radio is the problem and not your antenna or anything else

install external antenna but need more info to be helpful what type of ant on it now and freq of receiver if possible

It sound like one of this radios is out of frequency, basically need service to determ what exactly is wrong. When one of the radios is out of freq, basically mean that the radio is not receiving or transmitting where suppose to.