Ever one to have to take a screwdriver to something cheap to see how they have done it I have done it again this time to a GY560 frequency counter. The factory is kicking these out at 1000+ units a month apparently.
The specs say:
- Frequency step : 200K (digital radio signal), 1K, 100Hz.
- Testing distance : UHF : 8m, VHF : 5m.
- Testing range : 50 MHz ~ 2.4 GHz
- Antenna : pulling out antenna
- Battery : 9V 6F22
- Auto power off time : 1 mins. (except for the digital signal gear)
- Operation : the only one button with all functions.
And I can confirm with playing it really does work 50MHz to 2.4HGz.
It sort of scans constantly (once turned on) until there is a strong signal, locks on and shows the frequency and the signal strength. It auto shuts down after about 60 secs if nothing happens.
The uPC inside is an AVR Atmega8, they tried to hide that by a sticker but yu can still 'just' read the codes. Some of the smd IC are pretty standard and I found a 74HC00, 74HC393 both seem to be performing a divide/count function maybe? an LM358. Some are a little rarer MB506 High frequency pre-scalr, uPC 1667G which I have no idea what it is maybe a pre-amp of some sort maybe?
There is a A 7805 regulator, 4 discrete diodes, an inductor, electrolytic and a resistor, there is a nice little compact 2x8 LCD too, a 4MHz crystal, small trimmer capacitor and a handful of C and R SMD of course.
I managed to keep it working at 8V (I connected a variable supply to it.).
I'd say it operates more like a VHF/UHF field strength meter than a frequency counter, did pick up signals from my WiFi, 6m, 4m, 2m and 70cm. Also a car remote 433MHz and remote door bell 434MHz.
This was the household telephone.
The case comes off, 4 screws, the PCB is hld in place with 4 motherboard riser type hex stand offs that the other 4 screws attach to, the switch is a tiny push to make, and there is a PP3 battery connector and a tiny little whip antenna.
For £7.20 and £5.50 Post bargain really.
I found this schematic which seems to match up with my probing about.
I'll put up some more images of the guts hanging out :-)
The guts of the Yaege FC1, that Paul (see comments) asked about, note the 3.7V 1000mAH battery, you use a mini B USB cable to recharge it!Don't do that from the laptop !!!
The specification manual from mine.
You 'could' add a tunable front end band pass filter.