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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 30th May 2018, 11:59 am   #1
davidgem1406
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Default Black Star Meteor 1000 Counter.

Yesterday I was using my Black Star counter along with a signal generator to check the FM calibration on a Goodmans One Ten tuner/amplifier.

I was using the counter to set the generator frequency, whilst the generator was connected to the aerial input of the tuner.
Also, an AVO meter was connected to a test point in the tuner ( the only meter I had that would do 50uV)

I had a problem with the counter in that it produced a huge amount of radiation that drowned out the oscillator signal.
This radiation/interference was being created by the by the gate frequency, varying the gate frequency would vary the interference, most of which was being picked up by the connecting leads of the AVO meter.
Removing the AVO did not cure the interference, but it reduced to a far lesser level.

I remember, from a long time ago, that I had opened the case to the counter and found it was an all plastic construction without any internal screening.

If possible I would like to add some screening. Using conductive paint or metal foil to coat the inside of the cabinet and grounding it comes to mind.

Has anybody experienced this problem?
Or are there any other ideas as to how this counter can be screened to reduce the radiation it puts out.

I would mention it is not an AC supply driven unit so there is no external grounding available. It uses either batteries or an external DC supply. In this case, it was the external DC supply.

Best regards
Dave
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Old 6th Jun 2018, 8:46 pm   #2
Nymrod121
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Default Re: Black Star Meteor 1000 Counter.

Hello Dave,

As a first move, how about wrapping the entire frequency counter in aluminium foil as a temporary measure to see whether the interference is indeed being radiated through the plastic box? (also: try this with - then without - the Meteor's counting input being in parallel with the signal generator and the tuner-under-test).

From personal experience with frequency counter circuits used on FM tuners, comprehensive screening and robust decoupling of power supply leads (feedthrough capacitors etc.) is essential. I'm recollecting a General Instruments Application Note for the AY-5-8100 that I had a go at building some years ago. The wideband 'shash' it generated was very difficult to cure, especially the frequency readout (a Futaba 5-LT-03 fluorescent display).

I hope this helps.

Best wishes
Guy
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Old 6th Jun 2018, 9:36 pm   #3
ukcol
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Default Re: Black Star Meteor 1000 Counter.

Forgive me if I've missed something obvious but once the generator has warmed up and you have established that it is not drifting, can't you simply turn the counter off?
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Old 7th Jun 2018, 10:05 am   #4
mhennessy
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Default Re: Black Star Meteor 1000 Counter.

In my experience, all counters are noisy, but some counters are noisier than others

Price and brand doesn't seem to be a significant factor. I guess when you've got that many TTL signals bouncing about in there, it's not surprising. Whether the plastic construction makes it worse is an interesting question, but based on my experiences, it might not be a worthwhile exercise given how much leaks out of counters using metal enclosures. Having said that, an awful lot of the counting logic is contained within a single IC, so perhaps it's not as good at creating RF noise as some of the more discrete units out there...

I don't suppose you know of anyone locally who could lend you a different unit? That might give some indication of how yours compares, and whether it's worth trying to improve it...
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Old 13th Jun 2018, 11:19 am   #5
davidgem1406
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Default Re: Black Star Meteor 1000 Counter.

Hello all,

At the moment I have other things on the bench so no room to play with the counter and signal generator.
I have not tried any cures for this problem as yet but will do so as soon as possible.

Yes, I could turn the counter off but I use it to monitor the generator output frequency.
As I mentioned, most of the noise was being picked up by the meter leads, disconnecting them reduced the noise to much lower level.

I do have another counter a Racal 9901 (only does up to 50 Meg) that puts out next to nothing if anything at all.

Will post any results later.

Best wishes
Dave.
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Old 26th Jun 2018, 1:51 pm   #6
davidgem1406
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Default Re: Black Star Meteor 1000 Counter.

In the last day or two, I have had cause to use the counter and signal generator again, to check the FM calibration on another radio.

The setup was exactly as before, but this time there was no sign of the counter causing interference. I can only surmise that the interference maybe arrises with certain radios only and is not general across the board.

I will, however, as time permits, see if I can repeat the problem.

My thanks to all for their input.

Best wishes
Dave.
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Old 26th Jun 2018, 9:28 pm   #7
MotorBikeLes
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Default Re: Black Star Meteor 1000 Counter.

Am FM radio willl suffer more from impulsive interference (commutator motor, digital has of the counter etc if the discriminator is not correctly balanced. Better sets have a trim pot as well as the coil alignment to minimise AM interference.
Les.
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Old 26th Jun 2018, 9:32 pm   #8
MotorBikeLes
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Default Re: Black Star Meteor 1000 Counter.

An FM radio will be much more susceptible to digital hash (your counter) or impulsive interference from say a commutator motor if the FM discriminator is not properly aligned. Better sets have a variable pot as well as the coil to optimise. If your previous set was not correctly aligned ---
Les.
Sorry for duplication, I thought the first one was lost during the slow loading. Not sure if site or my bad connection.

Last edited by MotorBikeLes; 26th Jun 2018 at 9:33 pm. Reason: As above
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Old 26th Jun 2018, 9:35 pm   #9
davidgem1406
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Default Re: Black Star Meteor 1000 Counter.

Hi Les,

Thanks for that information. That is something I did not know, I will tuck that away for future reference.

Dave.
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Old 26th Jun 2018, 10:13 pm   #10
MrBungle
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Default Re: Black Star Meteor 1000 Counter.

I know this thread is old now but... My TTi TF930 is not noisy. Floating, battery powered and same construction.

Use a shielded cable or scope probe and ground it properly and it’ll probably be fine. I usually use a 10x tek probe for my counter. The front end on these is very well isolated from the digital side of things.

Also try it on batteries. If you have an external DC supply it might be a switching supply and actually be the thing generating the noise.
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