Ten Dollar Frequency Counter's - Thread #2

[CJay]

I would be surprised if it could measure the frequency of a keyfob transmitter accurately, I've got a couple of Racal counters here which cannot manage that.

I think it's the modulation scheme used, to encode the bits they turn the carrier on and off which upsets frequency counters unless the gate time is faster than the bit length (which is unlikely).

I think if you get your hands on a cheap PMR446 or FRS handheld radio it'll work just fine and display the transmit frequency.

[JPortici]

I got one! I got one! Nice little thing.
Has anyone  already bothered to do a case with input/power connectors?

[de0508]

Hallo,

i got one and change the hardware, so that there are no more hardware faults.

These are on the ATmega48pa side:
1) missing wire AVcc to +5V and
2) a bias voltage to 2.41V on the T1 input.

On this way i wrote a new firmware, a reciprocal frequency counter.
3) So i must add a wire from T1 input to INT0 input.

Now i can set the MB501L preselector to 1:128 and the max. frequency that i can messured will be round 1.1GHz.

The new firmware will scale the value on LCD automatic.

If some one replace the MB501L with a MC12079 (1:256), the rf frequency counter will reach 2.2GHz, but i thing the both 1N4148 will not work propertly.

For every change of the prescaler value, the new firmware source must be changed on a prescaler define only.

What a nice diy hack..

[tablatronix]

Nice I have one as well and was gonna hack around with it a bit, waiting for my isp programmer to arrive, were you able to pull firmware ( write protected on or off  ? )

Also considering replacing the prescaler with 1/256 would be nice if you can get the firmware to handle it, I also like that this has 3 io built in for adding buttons for additional functions.

What do the current IOs do ? They seems to change scale?

[de0508]

Hello tablatronix,

i don't have check the funtion of the original firmware or want to download it.
The only goal was to write a modify frequency counter my firmware with my call and functionality.

What the Jumper J1-J3 in the original Firmware do, i don't know.

[vk3pb]

Hi

I have a project where I want to use one of these cheap chinese frequency counters to measure the frequency (60-70mhz) of a communications receiver. However the difference is that I want to connect an Arduino to the frequency counter and somehow read the frequency from the frequency counter. Can anyone suggest how this might be doable?
 
cheers Peter

[cdev]

The PIC 8 digit one I have allows you to add or subtract an arbitrary IF from the displayed frequency.  I don't know if its possible to extract the displayed frequency from it easily. There are two 5 pin connections to each of the two banks of 4 digits, which is likely the signal for the display so if you simply sniffed the signal on those pins - knowing what protocol the seven segment displays with decimal points used, that would be it.

Also there is a six pin header which may be labeled "USART" .

[Old Don]

One on Banggood in kit form:  https://www.banggood.com/DIY-Frequency-Tester-1Hz-50MHz-Crystal-Counter-Meter-With-Housing-Kit-p-1063307.html?rmmds=search&cur_warehouse=USA

[chick0n]

I need a cheap small 2.4GHz Counter.

So I ordered a PLJ-0802, its perfect... I even can set IF Offset +- 1GHz....

Except, it can only measure up to 1.1GHz.

It has the MB501 Prescaler, so I thought I can replace it, with the Pin compatible MB506 Prescaler, which goes up to 2.4GHz.

It even has "MB506" Imprinted on PCB.

The MB501 is configured to 1/64, the MB506 Datasheet says it can be configured to 1/64 too. But it seems, it can only scale to 1/128 or 1/256. 

Is it maybe possible to Hack the firmware, to accept 1/128?

[Gyro]

Did you buy the MB506 from ebay or aliexpress? If so, the chances are that it's a re-marked reject part or a fake. The datasheet seems quite clear.

Edit: Or you have a problem with the soldering of the select pins.

[chick0n]

Did you buy the MB506 from ebay or aliexpress? If so, the chances are that it's a re-marked reject part or a fake. The datasheet seems quite clear.

Edit: Or you have a problem with the soldering of the select pins.

https://www.ebay.de/itm/1PCS-FUJITSU-SOP-8-MB506P-G-MB506P-MB506/152444966478

They do work Ok...Execpt i cant configure to 1/64....

Datasheet says:
"It will divide the input
frequency by the modulus of 128 or 256"

Configuration Table in Datasheet:



I attached SW1 and SW2 to VCC.

[Gyro]

Hmm, a European ebay seller normally gives you a better chance of a genuine part. Maybe contact them and tell them it's faulty.

Did you read earlier in the thread (reply #28), it could be that the micro or whatever cannot handle 2.4GHz/64 and is aliasing - from the picture, the prescaler output is going straight into a uC pin.

[chick0n]

Did you read earlier in the thread (reply #28), it could be that the micro or whatever cannot handle 2.4GHz/64 and is aliasing - from the picture, the prescaler output is going straight into a uC pin.

Hmm...thats a possibility...is it possible to Filter the Output?

I will check the MB506 Output with Spectrum Analyzer today...

The counter has PIC16F648A MCU.

[chick0n]

Ok...I checked this crap with analyzer and signal generator...

"MY" MB506 isnt capable of dividing by 64. It looks like, only SW1 Pin is working.

The MCU of the Counter is capable of handling over 40MHz input, and is displaying 2.4GHz at 37.5MHz input.

I will try some other prescalers like MC12034 and MC12079....

[chick0n]

I own another counter with MB506, this one can divide by 64....

So the ones I ordered from Ebay are really fake / defect.... 

[Gyro]

I own another counter with MB506, this one can divide by 64....

So the ones I ordered from Ebay are really fake / defect.... 

Oh well, now you know. I had almost given them the benefit of the doubt myself with the aliasing theory!

It just goes to show that you can't even trust European ebay sellers for such things these days. 

[Datman]

It can work down to a few Hz:
https://www.eevblog.com/forum/projects/ten-dollar-pic-100khz-2-4ghz-frequency-counter/25/