Aliexpress frequency counters

[Terry Bites]

Am I going mad?
Well, madder.

I run a small community repair shed on Saturdays and we were looking for a cheap counter.
Here's what I dont get; many Aliexpress frequency counters have a 13MHz reference output. Not 10MHz. WTF
So, does anyone know why this is and what use is there for 13MHz?
Not that I'd use it as a reference anyway.

[rvalente]

Old HPs 53xxx piles up on Ebay, they're just great! 75 to $100, Worth considering!

[mikeselectricstuff]

Surplus ex-cellular oscillators maybe

[Terry Bites]

Cheapskates!

I've decided not to mod all my old gear to use 13MHz.
us South London geezers are far too stubborn for all that old malarkey.

[PCB.Wiz]

Here's what I dont get; many Aliexpress frequency counters have a 13MHz reference output. Not 10MHz. WTF
So, does anyone know why this is and what use is there for 13MHz

26MHz TCXO and VCTCXO are cheap and easily available to 0.5ppm.
This will be /2 to give 50% duty cycle.
 
You should try to find a Reciprocal Frequency Counter, but I’m not sure what Ali names those.

[Conrad Hoffman]

An HP5334B can usually be had for cheap. If it doesn't already have one, you can install an ovenized oscillator. They're 100 MHz, so if you need more you probably need a different model, probably not a reciprocal. At one time Optoelectronics and Startek made tons of inexpensive counters for hams, but those days are gone. Now Opto only has a couple fairly expensive ones and I think Startek is gone entirely. Should still be many on eBay.

Then, of course, you need a GPS oscillator like Leo Bodnar to calibrate it!

[mawyatt]

Agree, 13MHz makes no sense at all!!

Stay away from that (and a lot of other similar AliX) stuff!!

Next thing you know, they'll start with things that display in dBwtf units

We should all know that 2 awe-shits = -6dBwtf 

Best

[amyk]

Surplus ex-cellular oscillators maybe

Bingo.

https://en.wikipedia.org/wiki/Crystal_oscillator_frequencies

13.000  GSM/UMTS     Commonly used as a reference clock for GSM and UMTS handsets. (13 MHz is exactly 48 times the GSM bit rate). Commonly available as TCXO and OCXO.

[Haenk]

On the other hand, that would suggest these might be not that bad as a frequency counter. 

[PCB.Wiz]

Agree, 13MHz makes no sense at all!!
Stay away from that (and a lot of other similar AliX) stuff!!

AliExpress is ok, when used with care.

An example is this 8 digit Frequency counter module,

https://www.aliexpress.com/item/1005008284489840.html
based on this work

https://www.zl2pd.com/files/PLJ-8LED_Manual_Translation_EN.pdf

It uses a PIC16F648A+2.4GHz prescaler + 2.5 ppm VC-TCXO.
It gives one price/performance point.
The little PIC has no capture modes in async counting modes, so it uses a simple gate-time counter, but the 1Hz LSB may be fine for many uses.

[Datman]

https://www.eevblog.com/forum/projects/ten-dollar-pic-100khz-2-4ghz-frequency-counter/msg2265540/#msg2265540
They are very good for the price. If you want more, search for a used Racal-Dana 1992 or similar.
https://www.ebay.it/itm/326603416586

[PCB.Wiz]

https://www.eevblog.com/forum/projects/ten-dollar-pic-100khz-2-4ghz-frequency-counter/msg2265540/#msg2265540
They are very good for the price.

Yes, a good price/performance point.

Further up from Alixpress are the 'big-box counters'

https://www.aliexpress.com/item/1005008463767841.html
but the shipping is expensive, and it is not clear if they have reciprocal resolution ?

but you may get more for less, if you go more modern with a DDS Generator/Frequency Counter, as the included counter has quite good resolution.

https://www.aliexpress.com/item/33042950680.html  Character LCD 0.01Hz resolution

https://www.aliexpress.com/item/1005009065662711.html  TFT LCD 

Or, you can go the project way, and this RP2040 one is well documented.

https://www.eevblog.com/forum/projects/pico-frequency-counter-using-rp2040/

A RP2350 version of that should give better performance.  I've not seen one yet ?

[alex843]

Surplus ex-cellular oscillators maybe

13 MHz is used in GSM base stations which makes sense in that application:

* 13 MHz/48 = 270.83 kHz which is the GSM Air Interface bit rate/symbol rate.
* 13 MHz/65 = 200 kHz, the GSM radio channel spacing.

[5U4GB]

AliExpress is ok, when used with care.

Also a great source of stuff that's good-enough and where you don't fuss too much about the loss if someone uses it to, for example, check whether the mains frequency is exactly 50Hz.

[mino-fm]

Am I going mad?
Well, madder.

I run a small community repair shed on Saturdays and we were looking for a cheap counter.
Here's what I dont get; many Aliexpress frequency counters have a 13MHz reference output. Not 10MHz. WTF
So, does anyone know why this is and what use is there for 13MHz?
Not that I'd use it as a reference anyway.

This one uses Vref = 12 MHz https://www.eevblog.com/forum/projects/pico-frequency-counter-using-rp2040/msg4151122/#msg4151122
:-)

[bingo600]

I have one of those Ali 2.7GHz counters that uses 13MHz - It has an Atmega inside.

I had a few Pletronics 26MHz OCXO's in the drawer , and an AC74 .....
Runs quite stable now.

[dobsonr741]

Why 13 MHz?
Because 26 MHz TCXOs are everywhere—thanks to cellphones. GSM, LTE, GPS… all tick to 26 MHz. And when Chinese makers whip up gadgets from bargain-bin parts, guess what crystal fell off the truck? Yep. Divide by two, call it 13 MHz.

[Haenk]

Why 13 MHz?
Because 26 MHz TCXOs are everywhere—thanks to cellphones. GSM, LTE, GPS… all tick to 26 MHz. And when Chinese makers whip up gadgets from bargain-bin parts, guess what crystal fell off the truck? Yep. Divide by two, call it 13 MHz.

An that's bad, because?
On the one hand suggesting to buy decade old gear, on the other hand refusing the re-use of precision parts. OK, they crystals certainly or most likely *are* reused and not declared as such. But I would guess these cheap chinese instruments are as precise as those old HP units, even with ovenized crystals.