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 Post subject: Heathkit IM-4100 Frequency Counter erratic display questions
PostPosted: Aug Sun 11, 2019 12:05 am 
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Location: Minnetonka, MN 55305
I purchased my IM-4100 recently and have not been able to achieve a reliable readout. My only purpose is to check IF frequency from my signal generator when aligning a radio. With power on, set to kHz, mode set to frequency and input attention at 10 my signal generator set to 455 I see fluctuating numbers on the display from 4892 down to 4208 at one second intervals. Unless I'm missing something this unit is defective.?

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 12:46 am 
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GSD wrote:
...... to check IF frequency from my signal generator


What brand of sig gen? Many output non-sinusoidal signals that confuse many frequency counters.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 12:50 am 
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Heathkit IM-4100.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 12:53 am 
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Do you have modulation turned off?
Most freq counters will give erratic results with modulation on.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 12:59 am 
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Tried it both ways. I adapted a small diameter shielded cable for this application. No in-line cap. The readout does respond to changes in the generator output but not synchronized with the output frequency and always bouncing around.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 1:28 am 
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Location: Norfolk, VA
GSD wrote:
Heathkit IM-4100.


?? I asked about your Sig Gen, not the counter. :?

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 1:32 am 
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Joined: Dec Sun 16, 2007 4:59 am
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Yes you did. "Both ways" referred to modulated or not. Apologies for the ambiguity here.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 2:10 am 
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Findm-Keepm wrote:
GSD wrote:
...... to check IF frequency from my signal generator


What brand of sig gen? Many output non-sinusoidal signals that confuse many frequency counters.



Didya miss this? I was asking what is the make and model of your signal generator? Many signal generators have proven themselves to be of questionable output that drives frequency counters crazy. Non-sinusoidal outputs are common on many low-end generators, and no amount of waveshaping by the counter's input circuitry is gonna correct for that.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 3:51 am 
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Oh man! I'm not hitting on cylinders here. My GENERATOR is part of the B&K 960 Transistor Analyst device. Yikes!

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Aug Sun 11, 2019 4:18 am 
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Set the attenuator to 1 and try again.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Sat 07, 2019 4:59 am 
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Location: Minnetonka, MN 55305
This just in: I took my Heathkit counter to the Pavek Museum where Karl using a reliable generator confirmed that the frequency counter is working perfectly. Thanks for all the help.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Sat 07, 2019 5:10 am 
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The two possibilities as I see it are either insufficient signal level into the counter, or the omission of a coupling capacitor. The input of most counters is direct coupled and for measuring signals you need to block dc.

A counter that is driven marginally will count some of the time but not all, since its signal threshold isn't solidly exceeded. In extreme cases you may need a preamplifier.

What is the sensitivity specification for the counter, and how much signal are you feeding to it? Most counters will work with around 50 mV signal but that's marginal. If the counter has a level control, turn it slowly to try to find the sweet spot.


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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Sat 07, 2019 10:16 am 
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GSD wrote:
Oh man! I'm not hitting on cylinders here. My GENERATOR is part of the B&K 960 Transistor Analyst device. Yikes!

Transistor radio analyst.

Allow me to suggest getting an actual general-purpose signal generator.

More on the possible causes of strange readings....even the better generators do not always have sine-wave outputs. They depend on harmonics to get the higher frequencies. I run a PACO E-200C with a Heath IM-4100 counter, and I routinely get a frequency reading that is 2x the actual generator output.....not a problem, as long as the reading is stable.

Further, the fact that the generator uses harmonics allows me to accurately measure up to 100MHz or so for FM work. In the PACO generator, 100MHz is the 4th harmonic, so the counter only has to deal with 25MHz.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Sat 07, 2019 12:35 pm 
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Location: Long Island NY
The Heathkit IM-4100 is a simple and very robust counter with decent sensitivity and performance. You'd be surprised how many of them are still in use. However there is one weakness, and that is the white Burndy IC sockets inside many of them. The plastic outgasses and contaminates the contacts, then you get erratic behavior which can be confirmed to be the counter and not the signal source.

If your unit is acting up and has the white IC sockets, take each IC out of its socket, clean the pins with a little DeOxIt on a cotton swap, then put it back. If that doesn't work you're in for some deeper troubleshooting, but 90% of the time a good cleaning of the IC pins is all you need to do.

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Sun 08, 2019 4:38 am 
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Joined: Dec Sun 16, 2007 4:59 am
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Location: Minnetonka, MN 55305
The suggestion that I should use a dedicated signal generator proved to be perfect. I have owned a Heathkit Ig-42 generator for many years. I concluded, years ago, that it didn't work. I took the generator to the Pavek to test it as well. I was using a Heathkit probe with a proper Amphenol connector BUT, it is not the correct probe for the IG-42. Instead, it appears to be for a signal tracer with a diode in the circuit that, of course, blocked the signal from the generator.

The generator works perfectly and as suggested, it has sufficient output to drive the counter properly. The generator has an attenuator range selector that is x1, 10, 100, 1K, 10K. We assumed that the highest output was at x1 but it is 10K. Odd.

Both units work perfectly AND the IG-42 analog scale is dead on. Amazing. Thanks for all the help as always!

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 Post subject: Re: Heathkit IM-4100 Frequency Counter erratic display quest
PostPosted: Sep Mon 09, 2019 3:05 am 
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Joined: Dec Sun 16, 2007 4:59 am
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Location: Minnetonka, MN 55305
Here is an image of the Heathkit Signal Generator that works with the IM-4100 Counter


Attachments:
rsz_101_0937.jpg
rsz_101_0937.jpg [ 240.87 KiB | Viewed 344 times ]

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