Marker  generator !!! - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: July 06, 2013, 07:16:29 am
content: Hello,I have an analogue scope, and Id like to put 1 kHz markers along the trace, when I need then is this possible, I wondered if there's a marker generator circuit anywhere, so any help would be most appreciated .Paul

author: Bored@Work
author_rank: Super Contributor
timestamp: July 06, 2013, 07:57:57 am
content: There are different things of what people call a marker generator. If you want what I think you want, then for that type of marke ryou need a (triggerable) 1 kHz pulse generator. Almost any kind of pulse generator would do, depending on what precision and accuracy you want.Then you have two issues:1) How to synchronize the marker generator's phase with the signal you want to measureThis really depends on what you want do. E.g. do you need synchronisation at all? If yes, and if your oscilloscope has a trigger-out you could use that to start a 1 kHz pulse train from your marker generator. This requires your marker generator can be triggered. Add a bit of adjustable time delay and you can position the marker signal's phase relative to the signal you measure.If you instead want to have a marker in a sweep then your marker generator would have to be triggered on the sweep control signal, often a sawtooth signal, instead of the oscilloscope's trigger-out.The most simple way I know to add a kind of trigger circuit to a generator is to kind of fake it. You use a contentiously running oscillator at a frequency much larger than the marker frequency you want. You run that high frequency through a resettable divider. The trigger signal goes to the reset input of the divider. You get some phase jitter and glitches at the output, but it might be good enough for your purpose. Oh, and you need to have some pulse forming at the output of the divider.2) How to couple the marker generator output into the oscilloscopeIf your oscilloscope has a Z input you use the marker generator output to blank or intensify the signal at the marker position. Alternatively, if you have a two-channel oscilloscope you could just display the marker signal on channel two. If that is not possible you could mix the input signal and the marker signal. If that is not possible you could open your oscilloscope and add a Z-input or blanking input.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: July 06, 2013, 08:04:56 am
content: A marker generator often comprises of a crystal oscillator (at say 1, 2, 4, 5 or 10 MHz) and IC frequency dividers to divide it down to the desired frequency. A frequency counter or HF radio receiver tuned to WWV on 5 or 10 MHz can be used to align.This is a clever circuit that gets down to 10kHz with a single chip and 6.4 MHz crystal. Another IC would allow 1 kHz.http://www.qsl.net/pa2ohh/fmarker.htmHere's a similar one that goes down to 5 kHz.http://www.norcalqrp.org/files/NorCal_QRP_Club_VE3DNL_Marker_Generator_A.pdf

author: Unknown
author_rank: Unknown
timestamp: July 06, 2013, 08:49:50 am
content: Ok I may need to explain in more detail what I'm attempting to do, I want it as a guide to set up I F filters , so say I had 5 markers on the scope all at 1 kHz apart, so I could setup the peak of the filter on the centre one then use the others to set up the shape, that's my idea, maybe I'm going about it the wrong, I've had a look on the scope can't see a Z, just channels 1+2 & X. I have a correction to make, looking at the manual it says "Z mod" situated on the rear panel and connected to a isolating capacitor to the grid of the CRT. a positive going signal is necessary to intensify the trace with 10v amplitude providing a good contrast. A negative going signal of similar amplitude will blank the trace ? OK

author: woodchips
author_rank: Frequent Contributor
timestamp: July 06, 2013, 09:07:11 am
content: Don't forget that the scope has time, not frequency, on the X axis. Can have markers 1ms apart but not 1kHz. Looks like a spectrum analyser is what you are needing. If using a function generator to sweep the frequency then a monostable on the ramp voltage controlling the frequency will give a blip. That could brighten the trace, or put a spike on the unused Y channel.

author: Unknown
author_rank: Unknown
timestamp: July 06, 2013, 09:11:27 am
content: Quote from: woodchips on July 06, 2013, 09:07:11 amI have a correction to make, looking at the manual it says "Z mod" situated on the rear panel and connected to a isolating capacitor to the grid of the CRT. a positive going signal is necessary to intensify the trace with 10v amplitude providing a good contrast. A negative going signal of similar amplitude will blank the trace ? OK

author: Bored@Work
author_rank: Super Contributor
timestamp: July 06, 2013, 09:44:44 am
content: Quote from: woodchips on July 06, 2013, 09:07:11 amf=1/t, so wanting to have 1 kHz markers is not a problem at all.However, it appears that he wants to have markers in a sweep, soQuote from: Bored@Work on July 06, 2013, 07:57:57 am

author: Unknown
author_rank: Unknown
timestamp: July 14, 2013, 03:24:22 pm
content: Quote from: vk3yedotcom on July 06, 2013, 08:04:56 amThank you for your help I built the sucker ,I put a fixed cap in to get it working variable one on the way, really happy with it, this is on the 5khz tap

author: w2aew
author_rank: Super Contributor
timestamp: July 14, 2013, 08:35:58 pm
content: Quote from: Telequipment on July 06, 2013, 09:11:27 amThere's a video for that! Here's an example of creating an intensified 'marker' on the trace using the z-axis to modulate the intensity.

author: Unknown
author_rank: Unknown
timestamp: July 15, 2013, 05:57:52 am
content: Thank you Alan I will watch it this evening