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Old 13th Dec 2014, 3:47 pm   #1
jim_jobe
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Default 1-500MHz frequency counter

I've just bought one of those 1-500MHz frequency counters on ebay for £7.59 and it looks to be just the job but I don't recognise the small coax socket at the interface. Has anyone else bought one who can advise me on this please?
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Old 13th Dec 2014, 3:53 pm   #2
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Default Re: 1-500MHz frequency counter

Which one?

I'm suspecting it will be a "SMA" connector - as used on mobile phones and wireless-routers.
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Old 13th Dec 2014, 4:49 pm   #3
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Default Re: 1-500MHz frequency counter

If it is the one that Google popped up searching for
Quote:
frequency counters on ebay for £7.59
It is indeed an SMA.
 
Old 13th Dec 2014, 6:25 pm   #4
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Default Re: 1-500MHz frequency counter

Thanks guys. I've ordered an SMA male to male connector with 1.5m of coax in between so I'll cut one of the males off and attach a suitable probe. It was not knowing what to call it that was the problem as is often the case.
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Old 13th Dec 2014, 6:53 pm   #5
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Default Re: 1-500MHz frequency counter

Good grief, the SMA torque spanner will cost far more that the counter

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Old 13th Dec 2014, 9:42 pm   #6
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Default Re: 1-500MHz frequency counter

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the SMA torque spanner will cost far more that the counter
Taking this as is, just nip it up all will be well.

I do like the SMA, a small (large ish) connector that is common and therefore cheap, very good for internal stuff.
 
Old 14th Dec 2014, 12:18 am   #7
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Default Re: 1-500MHz frequency counter

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Originally Posted by Bazz4CQJ View Post
Good grief, the SMA torque spanner will cost far more that the counter
I thought just finger tight would suffice??
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Old 14th Dec 2014, 2:09 am   #8
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Default Re: 1-500MHz frequency counter

Yes, tongue in cheek, though I have seen torque spanners used on SMA. I thought my 99MHz counter was good value at £15, but that was some time ago. Has yours been supplied with any guidance on the usable input level; too little or too much can upset them.

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Old 14th Dec 2014, 11:59 am   #9
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Default Re: 1-500MHz frequency counter

No Bazz, no info at all. I was thinking of adding a zener to the input but need to know what the max is.
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Old 15th Dec 2014, 12:56 pm   #10
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Default Re: 1-500MHz frequency counter

Have you any advice at all on what the max input voltage is likely to be Bazz? I have an old RS counter that will take inputs up into the hundreds of volts depending on frequency so I will only be using the new one for low level transistor circuits; checking oscillator frequencies, etc. I've trawled the net but surprisingly can find no info on this, considering the thousands that have been sold. There isn't even a manufacturer's logo on it!
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Old 15th Dec 2014, 1:29 pm   #11
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Default Re: 1-500MHz frequency counter

These look quite good and I'm thinking of getting one myself as I don't have one and my 'friend' decided to sell his for next to nothing without offering it to me first!

Shall I risk it or wait for yours to arrive so you can report on how good it is - probably risk it.

I think I noticed one with an even higher resolution for something like £24. Maybe not the same frequency range.
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Old 15th Dec 2014, 2:02 pm   #12
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Default Re: 1-500MHz frequency counter

I've just given it a try with a 10MHz crystal oscillator and it shows that as 10.0016MHz but I don't know how accurate the oscillator frequency is (It's just a 7490 divider unit).
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Old 16th Dec 2014, 8:49 am   #13
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Default Re: 1-500MHz frequency counter

Quote:
Originally Posted by jim_jobe View Post
I don't know how accurate the oscillator frequency is
Beat it against a 10 MHz source (WWV) using a shortwave receiver. If it's just a loose HC49/U XTAL the accuracy will be low.

It's odd to have an SMA connector as a test socket. A BNC is much more convenient and way more common.

Tjerk, 9ZZ
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Old 16th Dec 2014, 6:15 pm   #14
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Default Re: 1-500MHz frequency counter

Cheers Tjerk,
Yes, I'm going to do that. I'm just waiting for the male connector and coax to arrive. I'll report back when i've done that.
Many thanks
Jim
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Old 17th Dec 2014, 3:46 pm   #15
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Default Re: 1-500MHz frequency counter

I've got one on order - worth a punt at that price!
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Old 17th Dec 2014, 4:45 pm   #16
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Default Re: 1-500MHz frequency counter

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Originally Posted by PE9ZZ_JO22KI View Post
It's odd to have an SMA connector as a test socket.
Not these days, a BNC would put too much stress on a small PCB, let alone taking a lot more space.
 
Old 17th Dec 2014, 5:02 pm   #17
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Default Re: 1-500MHz frequency counter

I disagree. I use SMA connectors a lot and it's a hassle to tighten the nut. Not a problem for (semi-)permanent connections. But the twist'n'lock bayonet of the BNC ("Bayonet Navy Connector") beats this over and over again, hands down. Usually I'm not going over 4 GHz, the limit for BNC.

Tjerk, 9ZZ
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Old 17th Dec 2014, 6:04 pm   #18
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Default Re: 1-500MHz frequency counter

Quote:
Originally Posted by PE9ZZ_JO22KI View Post
"Bayonet Navy Connector"
I think it's actually "Bayonet Neill–Concelman" - see here

Hugh
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Old 17th Dec 2014, 6:12 pm   #19
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Default Re: 1-500MHz frequency counter

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Originally Posted by jim_jobe View Post
Have you any advice at all on what the max input voltage is likely to be Bazz? !
I think the advice given with the pair I have is to set the level between 50-150mV. The reason that I raised the question is that I did overload one and had to send it back to get it fixed. Of course, yours may be different.

I did ask the question previously on the forum about affective ways of protecting the input but don't recall any exceptional suggestions. A pair of Schottkies side by side may be a basic approach. Something more elaborate would probably be nice in terms of keeping the input impedance high .

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Old 17th Dec 2014, 6:19 pm   #20
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Default Re: 1-500MHz frequency counter

It is quite sensitive Bazz. I've just hooked it up to this little oscillator I put together to test RF Germanium transistors (It goes from 8 to 20 MHz) and it worked quite nicely when connected to the 6-turn green coupling coil. As I said earlier I don't intend using it with high amplitude RF.
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