500mhz freq counter

[edrich]

hi
I am looking for a schematic for a frequencey counter that can read 1-500mhz(atleast)
i would like LED display, but anyother way would help.
it must use minimum amount of components ,and must not be hard to find.I live in south africa, and down here it is quite hard to source components.

thanx

edd
(zr5tux)

 

[John Sorensen]

500 MHz?! Good luck. Whatever will measure that frequency will have to run many times faster. Not bloody likely. Not for a roll-your-own with garden-variety parts.

j.

Reconsider your specification.

Is that supposed to be milli-hertz? That's much easier, then :wink:

 

[edrich]

lets rephrase.
its to mesure RF.
I can get most maxim, PIC, Atmel,FAIRCHILD, TI ,LM(the device prefix),and a few others.
I would think to make something with a freq multiplier?

fanx

 

[Nigel Goodwin]

lets rephrase.
its to mesure RF.
I can get most maxim, PIC, Atmel,FAIRCHILD, TI ,LM(the device prefix),and a few others.
I would think to make something with a freq multiplier?

Try looking on the PICList, there's a link there to an LCD version of the original MicroChip frequency counter application note. This gives an auto-ranging 0-50MHz frequency counter, using a cheap low speed PIC.

You then just need a high speed divide by ten prescaler - this is the usual way a high frequency counter works, and is nice and simple.

 

[edrich]

I as under th impression that a prescaler is only for a small freq band, not wide as what i need.
if I am wrong, could ome one just give me a schmatic of a divide by 10 prescaler?

thanx

edd

 

[Nigel Goodwin]

I as under th impression that a prescaler is only for a small freq band, not wide as what i need.
if I am wrong, could ome one just give me a schmatic of a divide by 10 prescaler?

A prescaler is usually a single chip, it's simply a high speed digital divider chip - it puts out one tenth of the frequency you input to it. I don't know how low they work, it's not something you would bother trying, but it works from below 50MHz to above 500MHz (usually 1.2GHz, from what I remember of them).

It's a standard feature on commercial frequency counters, almost all of them will use a prescaler for the higher ranges - all you need to do is stick one on the input and shift your decimal point.

 

[edrich]

I will se what prescaler chips I can get here in durban.
but I guess this will decrease its accuracy?

and what would one use to make a freq higher?

thanx

 

[Nigel Goodwin]

I will se what prescaler chips I can get here in durban.
but I guess this will decrease its accuracy?

I don't see why? - as I've already mentioned, this is how commercial frequency counters work.

Obviously if your counter was accurate to 1Hz at 50MHz, it would only be accurate to 10Hz at 500MHz - but the percentage of accuracy would be identical.

A company called Plessey used to make popular prescaler chips, but I think they went bust many years ago.

and what would one use to make a freq higher?

Various ways, none of which are frequency insensitive (as a prescaler is).

You can use frequency multiplication, as commonly done in FM transmitters, or PLL techniques - both will only work over a limited range, particularly the frequency multiplier.

 

[k7elp60]

A frequency counter is only as accurate as the time base used to gate the monitor circuits. Plus the extreme right hand digit is generally only accurate to plus or minus 1 digit.
Depending upon your required sensitivity the higher frequencies you may need a preamplifier before the scaler. All the counters I recall for the higher frequencies have a 50 ohm input impedance, therefor parts layout and construction my be critical.

 

[edrich]

thanx
for all the hlp.
I was told that the pic freq counter are fairly accurate


thanx

edd

 

[pike]

Mate if you can get a frequency counter up to sampling speeds good enough for 500mhz i think you would deserve a nobel prize, don't you think???

Seriously though how would it be possible for a PC motherboard be able to generate CPU clockspeeds of 3.4 gigahertz ???

 

[edrich]

I am going to use a prescaler

I am going to use a prescaler, 1-8 and that will do me up to one ghz
I am going to use a freq counter that does up to 125 meg
wil send link later

 

[panic mode]

CPU motherboard doesn't use any signal in 3.4GHz range.
All signals on motherboard are much slower. High speed CPUs
internaly generate higher clock. This has been common practice
since 486DX2 and that's close to 20 years.
DIY counters for gigahertz range are not much of a deal anymore
because of technology advancements.
Just take a look at
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=232884
It's a $2 prescaler chip that runs up to 3GHz.
Simple frequency counter using LCD and microcontroller can be
made for up to some 50MHz. Now if you divide the input signal
10, 100 or 1000 times you should be able to use that frequency counter
to measure much faster signals (10x, 100x, 1000x). Don't take
my word for it, take a look at this:
http://www.qsl.net/n9zia/pre/
There are faster prescalers as well, like Zarlink that works up to 13.5GHz
but I didn't bother to look up pricing:
**broken link removed**
The whole 3GHz frequency counter project could cost as little as $50
(at least for the hardware, don't know how much you value your time).
Since most guys with some electronics knoweledge and internet access
coud do it, I wouldn't consider 500MHz counter project a candidate
for Nobel prize.