AM Modulation Image

[w3khg]

While speaking into the microphone this is what my scope is showing. How does this modulation look? My audio reports have been excellent. No issues.

[steve_qix]

Where does the unmodulated carrier show on the display?

[w3khg]

Where does the unmodulated carrier show on the display?

[DMOD]

it would be more instructive if we could see the output of the speech amplifier on one channel and the RF waveform on another.

What transmitter - and is it solid state or vacuum tube.

[w3khg]

it would be more instructive if we could see the output of the speech amplifier on one channel and the RF waveform on another.

What transmitter - and is it solid state or vacuum tube.

Yes it would but that's the best I could do. It is vacuum tube. Johnson Viking Valiant.

[w3khg]

Can I determine anything from this?

e.g. Are there too many high's compared to the overall signal?
What should a proper modulated signal look like?
Can someone put an image showing the elements in a properly modulated signal.

Can not locate any images of this doing a search on Bing.com/images

[KB2WIG]

Take your pic.


https://www.google.com/search?q=amplitude+modulation+scope+image&client=ms-android-samsung&prmd=ivn&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiV8q6izdjmAhVGB50JHWOEDBEQ_AUoAXoECBAQAQ&biw=640&bih=288&dpr=3

W2AEW is a Textronix engineer with some very informative videos on youtube.

https://www.youtube.com/watch?v=y4Zt_LJX1Tc

You may find the ARRL Hanfbooks from the early ' 60s helpfull.

Good luck,

KLC

[w3khg]

The AM waveform looks more like a SSB signal!!

[K8DI]

From the rest of the picture, it looks like you're dealing with an older, simpler, scope, that you can't do dual traces on to compare the audio to the rf like so many of those pictures on google show.  One thing you should be able to do, though and gets mentioned here from time to time, and you'll also find in older references, is to display the modulation "trapezoid" or "triangle". 

See
https://www.testandmeasurementtips.com/analog-and-digital-modulation-and-modulation-measurements/
and
http://www.rfcafe.com/references/radio-news/oscilloscope-transmistter-checking-october-1945-radio-news.htm
for more info.


Ed

[w3khg]

From the rest of the picture, it looks like you're dealing with an older, simpler, scope, that you can't do dual traces on to compare the audio to the rf like so many of those pictures on google show.  One thing you should be able to do, though and gets mentioned here from time to time, and you'll also find in older references, is to display the modulation "trapezoid" or "triangle". 

See
https://www.testandmeasurementtips.com/analog-and-digital-modulation-and-modulation-measurements/
and
http://www.rfcafe.com/references/radio-news/oscilloscope-transmistter-checking-october-1945-radio-news.htm
for more info.


Ed

Hello Ed
The scope is the Heathkit HO-10. Perhaps I should purchase the modulation monitor from REA.
Thanks for the heads up.

[kb3ouk]

A scope isn't really going to tell you much about the audio response of the transmitter. You can see if you're fully modulating and that's about it, at least when just looking at the waveform like that. The REA monitor really isn't going to give you any more information. The best tool I've found so far for checking audio bandwidth and response is an SDR waterfall display. Find a clear frequency, pull up a websdr online that you can put a decent signal into, and watch the waterfall as you talk. You'll be able to visually see the audio bandwidth in the waterfall, the brighter areas are what is the strongest.

[KA0HCP]

http://amfone.net/ECSound/
Go to the "East Coast Sound" section of the forum.  Read K1JJ's articles on Sweeping Your Rig, Frequency Response, Receiver Tone Test, etc.
Drink deep. This is the starting point for audio improvements.

While speaking into the microphone this is what my scope is showing. How does this modulation look? My audio reports have been excellent. No issues.