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 Post subject: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 1:32 am 
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hi, I am new to a lot of this and wondering if I can figure out 50% modulation with analog scope? Scope is at 5 volts/div in picture.

Setup with scope says to set the 'level' at mid position I guess that isi 50%?

I cal at 20v pp for most settings (manual) & at mid level little less than 10v pp. so close to 2.5v with 50% deviation or half of 10v? thanks trying to understand.


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ECIFG_40600.face.jpg
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ECI_50%modulation.jpg [ 714.25 KiB | Viewed 371 times ]

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Last edited by ttx450cap on Oct Sat 17, 2020 1:40 am, edited 3 times in total.
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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 1:36 am 
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instructions


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 1:39 am 
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How to calculate modulation percentage:

http://rfcec.com/RFCEC/Section-3%20-%20 ... le%20K4RFE).pdf


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 1:58 am 
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bob91343 wrote:
How to calculate modulation percentage:

http://rfcec.com/RFCEC/Section-3%20-%20 ... le%20K4RFE).pdf


get error on link? maybe shorter link - simplify http://rfcec.com? thks

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 2:05 am 
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Sorry it wasn't a good link. But the info is widely available.

"http://rfcec.com/RFCEC/Section-3%20-%20Fundamentals%20of%20RF%20Communication-Electronics/33%20-%20TRANSCEIVER/Transceiver%20-%20Amplitude%20Modulation%20Percent%20of%20Modulation%20(By%20Larry%20E.%20Gugle%20K4RFE).pdf"

Eliminate the quotes. The system truncates the link if I don't add them.


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 2:18 am 
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bob91343 wrote:
Sorry it wasn't a good link. But the info is widely available.

"http://rfcec.com/RFCEC/Section-3%20-%20Fundamentals%20of%20RF%20Communication-Electronics/33%20-%20TRANSCEIVER/Transceiver%20-%20Amplitude%20Modulation%20Percent%20of%20Modulation%20(By%20Larry%20E.%20Gugle%20K4RFE).pdf"

Eliminate the quotes. The system truncates the link if I don't add them.


thks will try and pull out only the key words and try

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 17, 2020 3:26 am 
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No, just highlight the link but only the part inside the quote marks and you will have it.


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Mon 19, 2020 10:56 pm 
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ttx450cap wrote:
bob91343 wrote:
Sorry it wasn't a good link. But the info is widely available.

"http://rfcec.com/RFCEC/Section-3%20-%20Fundamentals%20of%20RF%20Communication-Electronics/33%20-%20TRANSCEIVER/Transceiver%20-%20Amplitude%20Modulation%20Percent%20of%20Modulation%20(By%20Larry%20E.%20Gugle%20K4RFE).pdf"

Eliminate the quotes. The system truncates the link if I don't add them.


thks will try and pull out only the key words and try


you got me and Da........... between bad eyes and clicking the link I got error :( removed the quotes and it work, thanks for the kick. I wont say I built websites & have cis degree :oops: along with admin work. thks...

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Wed 21, 2020 1:26 am 
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bob91343 wrote:
No, just highlight the link but only the part inside the quote marks and you will have it.


I think I am about where I can be w/o a reference. Need to get a dig scope to help verify my thinking someday..

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Wed 21, 2020 3:38 am 
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ttx450cap wrote:
hi, I am new to a lot of this and wondering if I can figure out 50% modulation with analog scope? Scope is at 5 volts/div in picture.
Image

There are some tricks to getting a good stable trigger on a modulated RF signal. You won't be able to determine the modulation level very easily until you can get good stable triggering.

One approach is to adjust the trigger level to near the peak of the modulation, in other words, way above zero, until the trigger level is so high that the scope doesn't trigger any more, then back off a little.

Another approach is to rely on some of the modulation coming through at audio frequencies (i.e. feedthrough from the modulation signal), and so set the trigger to "HF Reject" and hope there's enough audio coming through to trigger on. Your scope doesn't give you this option.

A third and very good approach is to apply the AF modulation signal (not the modulated RF, just the signal that's modulating the RF) to the external trigger input and set the trigger to EXT.

A different approach is to skip trying to get a stable trigger of the modulated RF, and instead set up the scope for a trapezoidal waveform. You can read about it in just about any edition of the ARRL Handbook. Here's a couple of web links, too:
https://www.tpub.com/neets/book21/90a.htm
http://rfcafe.com/references/radio-news ... o-news.htm

By the way, what was your scope triggering on? In the photo, it looks like the trigger selector was set to EXT rather than CH1.

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Wed 21, 2020 11:41 pm 
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stevebyan wrote:
ttx450cap wrote:
hi, I am new to a lot of this and wondering if I can figure out 50% modulation with analog scope? Scope is at 5 volts/div in picture.
Image

There are some tricks to getting a good stable trigger on a modulated RF signal. You won't be able to determine the modulation level very easily until you can get good stable triggering.

One approach is to adjust the trigger level to near the peak of the modulation, in other words, way above zero, until the trigger level is so high that the scope doesn't trigger any more, then back off a little.

Another approach is to rely on some of the modulation coming through at audio frequencies (i.e. feedthrough from the modulation signal), and so set the trigger to "HF Reject" and hope there's enough audio coming through to trigger on. Your scope doesn't give you this option.

A third and very good approach is to apply the AF modulation signal (not the modulated RF, just the signal that's modulating the RF) to the external trigger input and set the trigger to EXT.

A different approach is to skip trying to get a stable trigger of the modulated RF, and instead set up the scope for a trapezoidal waveform. You can read about it in just about any edition of the ARRL Handbook. Here's a couple of web links, too:
https://www.tpub.com/neets/book21/90a.htm
http://rfcafe.com/references/radio-news ... o-news.htm

By the way, what was your scope triggering on? In the photo, it looks like the trigger selector was set to EXT rather than CH1.


thks.. I was/am trying to cal my eci transistorized 80s function generator. wanting to understand how to cal 50% mod on the scope if possible at those settings. Dont have much RF experience. Math is what I could work with.. might not be that simple.

Someday if I get a dig scope I might not further learn to read a scope. need both. :)

2v/div, dc in pict. sine wave not very rounded

p.s. set up as previous described..


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eci_1k_s_no_mod.jpg [ 675.29 KiB | Viewed 218 times ]
eci_1k_50%_mod.jpg
eci_1k_50%_mod.jpg [ 697.09 KiB | Viewed 218 times ]

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Thu 22, 2020 12:51 am 
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Slow down the sweep to something closer to the period of the audio modulation. It’s hard to tell, but I think the photos are showing a few cycles of the RF carrier, with a low level of modulation, only about 30%. That might just be an artifact of the triggering, though. Slow the sweep down until we can see a few cycles of the audio modulation. That’s where the triggering gets tricky, you might need to hook up the external trigger or go to X-Y mode and look at the trapezoid.

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Thu 22, 2020 11:47 pm 
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stevebyan wrote:
Slow down the sweep to something closer to the period of the audio modulation. It’s hard to tell, but I think the photos are showing a few cycles of the RF carrier, with a low level of modulation, only about 30%. That might just be an artifact of the triggering, though. Slow the sweep down until we can see a few cycles of the audio modulation. That’s where the triggering gets tricky, you might need to hook up the external trigger or go to X-Y mode and look at the trapezoid.


will this work? 2vdiv - mid level gen set
how do you fig out 50% mod? is it just linear math? thks


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Fri 23, 2020 1:52 am 
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ttx450cap wrote:
will this work? 2vdiv - mid level gen set
how do you fig out 50% mod? is it just linear math? thks

Do you have a manual for your scope? In the photo, you have both X and Y inputs set to be CH1.

Does your function generator have a separate output of the modulating signal? If it doesn’t, you can’t easily make a trapezoidal display of the signal.

If it does, then set the Y Mode, on the left-hand side, to CH2. Then disconnect the main function generator output from VH1 and instead connect it to CH2, so it will be the Y axis signal. Then connect the modulating signal output of the function generator to the CH1 input of the scope. Adjust the VOLTS/DIV knobs until the whole trapezoid fits within the scope screen.

As for calculating the percentage of modulation, did you read either of the links I previously posted? I can’t explain it any better than the links do. The RFcafe link has a picture that summarizes the calculation:
Image

Read the links and then come back with specific questions if there is something you don’t understand.

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Fri 23, 2020 10:31 pm 
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stevebyan wrote:
ttx450cap wrote:
will this work? 2vdiv - mid level gen set
how do you fig out 50% mod? is it just linear math? thks

Do you have a manual for your scope? In the photo, you have both X and Y inputs set to be CH1.
Quote:
no, but I see there's is a manual for the Iwatsu SS-5702 that is close or the same, been only looking at service manual.. hate online print.


Does your function generator have a separate output of the modulating signal? If it doesn’t, you can’t easily make a trapezoidal display of the signal.
Quote:
yes, just for 1Hz out, doing the the setup for cal., I needed to use the High output as in screen-shoot-cal manual?/quote]

If it does, then set the Y Mode, on the left-hand side, to CH2. Then disconnect the main function generator output from VH1 and instead connect it to CH2, so it will be the Y axis signal. Then connect the modulating signal output of the function generator to the CH1 input of the scope. Adjust the VOLTS/DIV knobs until the whole trapezoid fits within the scope screen.
Quote:
willl try


As for calculating the percentage of modulation, did you read either of the links I previously posted? I can’t explain it any better than the links do. The RFcafe link has a picture that summarizes the calculation:
Image

Read the links and then come back with specific questions if there is something you don’t understand.
Quote:
as specific as I can be-cheers cannot even see the photo?

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Last edited by ttx450cap on Oct Fri 23, 2020 10:57 pm, edited 1 time in total.

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Fri 23, 2020 10:55 pm 
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manual shows only half pages,,, again.. this is a good link

bad link https://www.ece.rice.edu/~jdw/data_sheets/ss5702.pdf

good link for me anyway - https://elektrotanya.com/iwatsu_ss-5702 ... nload.html

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Fri 23, 2020 11:38 pm 
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my scope needs two inputs for x-y no? when I use my octopus box I use two feeds?

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Fri 23, 2020 11:52 pm 
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stevebyan wrote:
ttx450cap wrote:
will this work? 2vdiv - mid level gen set
how do you fig out 50% mod? is it just linear math? thks


Read the links and then come back with specific questions if there is something you don’t understand.


is this what you are asking? took this pict yesterday before the x-y picts above.. slowed the sweep down, believe its in 2vdiv.. thks


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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 24, 2020 4:07 am 
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ttx450cap wrote:
my scope needs two inputs for x-y no? when I use my octopus box I use two feeds?

Well, your scope photos show an XY display with only one signal, so no, your scope can do XY with only one input. That’s not very useful, though, because it will always just show a 45 degree line.

But yes, in general you want two different inputs for XY mode.

stevebyan wrote:
... set the Y Mode, on the left-hand side, to CH2. Then disconnect the main function generator output from CH1 and instead connect it to CH2, so it will be the Y axis signal. Then connect the modulating signal output of the function generator to the CH1 input of the scope. Adjust the VOLTS/DIV knobs until the whole trapezoid fits within the scope screen.

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 Post subject: Re: ECI fuction gen 40600 cal question
PostPosted: Oct Sat 24, 2020 4:10 am 
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ttx450cap wrote:
is this what you are asking? took this pict yesterday before the x-y picts above.. slowed the sweep down, believe its in 2vdiv.

Yes, that’s what I meant when I asked you to slow down the sweep.

The drawing I posted tells you exactly how to calculate the percentage modulation from that scope display.

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