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Author Topic: New Video: Simple way to use your oscilloscope as a station monitor  (Read 2372 times)
W2AEW
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« on: December 28, 2012, 01:26:54 PM »

This video shows a very simply way to couple a small portion of your transmitted signal into an oscilloscope to monitor the RF envelope of your transmitter.

http://www.youtube.com/watch?v=2D83xp3H5Bo

If you like this video, consider subscribing to my YouTube channel:
http://www.youtube.com/w2aew
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AC5UP
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« Reply #1 on: December 28, 2012, 07:08:09 PM »

'Scuze me while I nitpick:   At 1:20 in to the video you refer to using an SO-239 to BNC female adapter.............. then show a PL-259 to BNC female adapter

There was a thread here a while back about the proper nomenclature for such adapters, and although it's true the adapter you used will convert an SO-239 jack to a BNC female jack, the adapter itself has a PL-259 on one end.   Wink
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W2AEW
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« Reply #2 on: December 28, 2012, 07:46:34 PM »

'Scuze me while I nitpick:   At 1:20 in to the video you refer to using an SO-239 to BNC female adapter.............. then show a PL-259 to BNC female adapter

There was a thread here a while back about the proper nomenclature for such adapters, and although it's true the adapter you used will convert an SO-239 jack to a BNC female jack, the adapter itself has a PL-259 on one end.   Wink

Oops!  Good catch! I did a couple of takes on the video, and in some of them I talk about "converting the SO-239 to a BNC".  Oh well, sometimes my brain and my mouth do two different things!    Tongue
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WB2WIK
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« Reply #3 on: December 28, 2012, 07:59:58 PM »

Comment from the Peanut Gallery:

Ignoring the 30-second commercial advert (!), the main video is over five minutes long to discuss what can be very well discussed, disclosed and addressed in about 90 seconds.  The "preamble" discussion is, IMO, not relevant at all and I'd omit all of it.

Then, I do this stuff for TV shows where every second is money spent, so we try not to waste seconds. Wink

I think the intent is terrific, it just takes much more time than necessary to convey the information required.

Perhaps it should be mentioned that a "100% perfect" looking RF envelope can contain an enormous amount of distortion.  I've gone through the exercise with my own scopes: If I purposely introduce a 10% distorted modulation signal to a perfect transmitter, it produces 10% distortion of the output signal, and on the scope, it looks absolutely perfect. Wink
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K8AXW
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« Reply #4 on: December 28, 2012, 08:24:03 PM »

WIK:  What you say is true but since he's suggesting a procedure that could result in destruction of the scope input, it's no doubt prudent to keep repeating himself to help prevent this. 

No matter how much you hope, you will always have someone to screw the pooch out of shear stupidity or a mental lapse. 

I think in comes down to checking your signal without having to build up an adaptor or attenuator this will do it.  Personally I'd rather build the adaptor to CMA!  I'm always doing something stupid!
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W2AEW
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« Reply #5 on: December 28, 2012, 08:35:26 PM »

Comment from the Peanut Gallery:

<snip>
I think the intent is terrific, it just takes much more time than necessary to convey the information required.
<snip>


Steve, I think this comment applies to nearly all of my videos!  I certainly appreciate your constructive advice.  I need to learn to 'get to the point already!'

Definitely good points regarding being able to 'see' distortion, or rather not being able to see it!
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AC5UP
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« Reply #6 on: December 29, 2012, 06:50:03 AM »

If you can stand one more comment...

I need to learn to 'get to the point already!'

Yeah, you do tend to repeat yourself. A cue sheet (outline) of talking points might be helpful while preserving the spontaneity of the narration. Or, if you  were me, you'd voice the piece as Porky Pig for the sake of novelty. At least you'd know how to end it... BeDe, BeDe, That's All Folks!

http://upload.wikimedia.org/wikipedia/commons/7/76/Mel_Blanc_4-15-05.JPG

Now that I got that out, one thing you might consider is a few words about what you're looking for on the 'scope. No flat topping on peaks, good symmetry above & below the base line, and with the mic gain turned down a near absence of carrier indicating the internal SSB carrier balance adjustment is good, etc. It also wouldn't hurt to show us what an AM envelope looks like compared to SSB as a bonus moment of infotainment.

If anything, the video proves that 'Scopes really are cool..........!
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W5DXP
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« Reply #7 on: December 29, 2012, 07:20:28 AM »

I think this comment applies to nearly all of my videos!

You are not alone. Most of the investment, health, and survival videos are so long I never make it through them.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K0JEG
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« Reply #8 on: December 29, 2012, 10:52:04 AM »

you could also connect a probe to the tap of an SWR meter too. You'd also get the benefit of a known tap value (with some research) for better measurements.
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AA4HA
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« Reply #9 on: December 29, 2012, 07:48:43 PM »

This video shows a very simply way to couple a small portion of your transmitted signal into an oscilloscope to monitor the RF envelope of your transmitter.

I watched your PSK31 video as well. If you want to try a "silly scope trick" feed your computer audio into your B channel and you might be able to do an A-B function with your scope and see the differences between input A and input B. If things are nice and sinusoidal (and phased correctly) there should be a straight line. If you overdrive you will see the resultant difference on the A-B trace. (some scopes allow you to invert one of the inputs)

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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
W2AEW
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« Reply #10 on: December 29, 2012, 09:32:55 PM »

I watched your PSK31 video as well. If you want to try a "silly scope trick" feed your computer audio into your B channel and you might be able to do an A-B function with your scope and see the differences between input A and input B. If things are nice and sinusoidal (and phased correctly) there should be a straight line. If you overdrive you will see the resultant difference on the A-B trace. (some scopes allow you to invert one of the inputs)

I like the idea of adding the baseband audio signal to the scope for visual comparison.  However, I don't think the subtraction will work since one of the signals is at RF and the other is the AF baseband signal.  They won't null, even if perfectly aligned.
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http://www.youtube.com/w2aew
WB2WIK
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« Reply #11 on: December 30, 2012, 01:31:52 PM »

I've been told by life-career teachers that repetition is key to success in teaching.

The only teachers I've ever had who I liked, admired, appreciated and actually taught me anything were the ones who never repeated anything.  If I don't get it the first time I hear it, I'm not likely to get it the tenth time, either. Wink

I'd try seriously to avoid repetition; maybe others don't feel this way, but it tends to turn me off entirely and change the channel (so to speak).

Best teacher I ever had was a pretty new teacher who spent all his time getting the students to talk, instead of him.  He also didn't use the prescribed books, and taught mostly from the top of his head.  He was an unbelievable, "real" teacher. 

Because he was new and not tenured and refused to use the books he was supposed to use, he lasted only two years in the system and quit teaching.  He went on to found a chain of book stores and became a millionaire by the time he was about 35. Smiley

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