How to use a Frequency Meter - UK Vintage Radio Repair and Restoration Discussion Forum

wireless_paul · 9th Jul 2003, 12:53 pm

Can someone give me an idea of how to use a Frequency Counter. I have a Racal 9520 with nixi tubes.
Also why does it give a frequency readout when connected to some Signal Generators but refuses to give a readout when connected to other Signal Generators.
Paul

Duke_Nukem · 9th Jul 2003, 1:04 pm

The signal generators that don't seem to drive the meter probably aren't giving out enough volts of signal.

Don't know the Racal 9520 but things to check might be the input impeadance which I guess could have a 50 ohm input or something - which wont help if driving from a 600 ohm sig gen output.

Other possibilies are there may be some switches to do with filtering and these could also cause a lack of readings e.g. if there is a " high frequency " switch then the counter may only detect waveforms with " fast " edges.

TTFN,
Jon

peter_scott · 9th Jul 2003, 7:39 pm

Check that you have the input threshold in the right
place. If you are supplying it from a pulse generator then
the signal may be all above ground and with a ground
input threshold the counter may not see any transitions.

Peter.

jim_beacon · 11th Jul 2003, 10:30 pm

A lot of older frequency counters require levels in the volt range to trigger them reliably, many older sig gens (Marconi TF2002, TF2015, TF2016 etc) have a high level output intended to drive a counter - by the way, when not in use, the high level output should have a cap over it to prevent RF leakage.

Jim.

wireless_paul · 12th Jul 2003, 1:14 pm

Is there any way to increase (amplify) the output from a signal generator so as to be able to use an older frequency counter (I do like the nixi tubes!!).
Paul

jim_beacon · 12th Jul 2003, 7:26 pm

Hi Paul,

If the generaor will trigger the counter with its maximum output, then use an external attenuator, if not, there are a number of wideband amplifier chips on the market which will do the job, or if you are working at fairly low frequencies, a simple op-amp buffer.

Jim.

PS. make sure you have the generators modulation switched off when you try to measure frequency, otherwise it will never give an accureate output.

9th Jul 2003, 12:53 pm	#1
wireless_paul Hexode Join Date: Mar 2003 Location: World Heritage Village of Saltaire, Shipley, West Riding of Yorkshire. Posts: 324	How to use a Frequency Meter Can someone give me an idea of how to use a Frequency Counter. I have a Racal 9520 with nixi tubes. Also why does it give a frequency readout when connected to some Signal Generators but refuses to give a readout when connected to other Signal Generators. Paul

9th Jul 2003, 1:04 pm	#2
Duke_Nukem Octode Join Date: Jan 2003 Location: Birmingham, West Midlands, UK. Posts: 1,268	Re: How to use a Frequency Meter The signal generators that don't seem to drive the meter probably aren't giving out enough volts of signal. Don't know the Racal 9520 but things to check might be the input impeadance which I guess could have a 50 ohm input or something - which wont help if driving from a 600 ohm sig gen output. Other possibilies are there may be some switches to do with filtering and these could also cause a lack of readings e.g. if there is a " high frequency " switch then the counter may only detect waveforms with " fast " edges. TTFN, Jon

9th Jul 2003, 7:39 pm	#3
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: How to use a Frequency Meter Check that you have the input threshold in the right place. If you are supplying it from a pulse generator then the signal may be all above ground and with a ground input threshold the counter may not see any transitions. Peter. __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

11th Jul 2003, 10:30 pm	#4
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: How to use a Frequency Meter A lot of older frequency counters require levels in the volt range to trigger them reliably, many older sig gens (Marconi TF2002, TF2015, TF2016 etc) have a high level output intended to drive a counter - by the way, when not in use, the high level output should have a cap over it to prevent RF leakage. Jim.

12th Jul 2003, 1:14 pm	#5
wireless_paul Hexode Join Date: Mar 2003 Location: World Heritage Village of Saltaire, Shipley, West Riding of Yorkshire. Posts: 324	Re: How to use a Frequency Meter Is there any way to increase (amplify) the output from a signal generator so as to be able to use an older frequency counter (I do like the nixi tubes!!). Paul

12th Jul 2003, 7:26 pm	#6
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: How to use a Frequency Meter Hi Paul, If the generaor will trigger the counter with its maximum output, then use an external attenuator, if not, there are a number of wideband amplifier chips on the market which will do the job, or if you are working at fairly low frequencies, a simple op-amp buffer. Jim. PS. make sure you have the generators modulation switched off when you try to measure frequency, otherwise it will never give an accureate output.