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 Post subject: fluke 1911a freq counter
PostPosted: Jun Fri 29, 2012 5:29 pm 
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Joined: Mar Sun 15, 2009 6:45 pm
Posts: 27
Location: usa
Hi everyone,
I picked up a Fluke 1911a freq. counter for $35.00. Since i'm new to this hobby. I need a-little guidance for checking this counter to see if it is working correctly. I have a manual on the way. But if this thing isn't working right I want to cut my loses and move on to another counter . I'm sure these things aren't cheap to fix or calibrate .

Thanks for any help you can give me
Wayne


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jun Fri 29, 2012 6:17 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3022
Location: Seattle WA US
If you have the version with built-in NICAD battery pack (called Option-01), you have a problem. Ifso, get rid of it.

--Chuck


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jun Fri 29, 2012 6:37 pm 
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Joined: Mar Sun 15, 2009 6:45 pm
Posts: 27
Location: usa
Chuck,
This unit is 115 volt unit . No option 01 No internal batteries .

Thanks for the quick come back

Wayne


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jun Fri 29, 2012 7:39 pm 
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Joined: Nov Sun 07, 2010 7:16 pm
Posts: 648
Location: Rochester, MI
That's a decent looking counter. What's the problem?

Fluke probably has the manual available on their web site if you need it.


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jun Fri 29, 2012 8:49 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7574
Location: Long Island
The 1911A is a decent counter. It has two input channels, a high impedance "A" input that is good to 125 MHz, and a 50-ohm "B" input. The "B" input is pre-scaled, so it is good from 50 MHz to 250 MHz. It should do just about anything you could possibly want from a counter in antique radio, unless you plan on fixing old television or UHF gear.

With respect to checking it out, the two things you have to look at are, (A) do the inputs still work, or have they been blown by overloading; and (B) how accurate is the time base?

Specifications for input sensitivity are given in the manual, and vary between 15 mV and 35 mV depending on which input and frequency range you're testing. Ideally you'd use a calibrated signal generator and attenuator, or an RF voltmeter, and see if the unit still meets spec in this regard. Without such facilities, one could try to see if you can couple a weak signal from a generator to the "A" input by holding the test leads close without actually touching them. This probably won't work with the "B" input due to its 50-Ohm impedance, so you'd need to connect them together and see how low you can adjust the output of the generator and still get a stable reading.

Verifying the frequency accuracy of a counter is harder to do; ideally this calls for a reference signal that is at least an order of magnitude more accurate than the counter. Lacking that, probably the best thing to do is look for, or build a crystal calibrator. Crystal reference modules from junked PCs and other devices can be had for little or nothing; most of them simply require five volts DC input to produce a reasonably accurate and stable output that can be used to see if the counter is right or not.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jun Sat 30, 2012 3:33 pm 
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Joined: Jun Wed 08, 2011 2:33 am
Posts: 6418
Location: Ohio 45177
Yes, I would have your 1911 checked for accuracy whenever possible. We had two of those at work at one time. At least one of them would change frequency indicted from an audio source based on amplitude of input. Very deceiving. But they were getting pretty old by then. They seemed kinda hard to trigger too. But ours were perhaps "used up" by then. I am sure that the accuracy could be quite sufficient for AM/FM radio repair service.


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jul Mon 02, 2012 11:21 pm 
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Joined: Mar Sun 15, 2009 6:45 pm
Posts: 27
Location: usa
Thanks everyone for the advice. It sound like the unit is worth some time and money to determine if it is working .I believe i will hold off on doing anything until i receive the manual. Hopefully that will give me the needed guidance for it's normal operation.

Thanks again for your time and wisdom
Wayne


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 Post subject: Re: fluke 1911a freq counter
PostPosted: Jul Tue 03, 2012 4:27 am 
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Joined: Mar Mon 17, 2008 5:05 am
Posts: 5172
Location: Ashhurst, New Zealand
Chris108 said:
Quote:
Lacking that, probably the best thing to do is look for, or build a crystal calibrator. Crystal reference modules from junked PCs and other devices can be had for little or nothing; most of them simply require five volts DC input to produce a reasonably accurate and stable output that can be used to see if the counter is right or not.


Hopefully the counter already has a crystal oscillator as its reference frequency, so comparing to another is really chasing your tail - which one is right?

If you have a receiver that will receive WWV/WWVH with SSB at the same frequency as the counter oscillator or it's harmonics, then there is a good method that I use that will get you pretty close. I see that the 1911 has a 10MHz oscillator and spec is 2ppm.

Let us know how you get on.

_________________
Cheers - Martin ZL2MC


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