scope pattern

[K1JJ]

Notice there is a BIG gap between a readability 3 or 4.

3 -- Readable with considerable difficulty
4 -- Readable with practically no difficulty


When an S-meter is properly calibrated and the RST "ear" guidelines are followed for reports, most hams are disappointed when they hear their reports.  Getting a 4X5 is really a good report, but many guys would start looking outside to see if their antenna was still up...

When receiving a report, it is important to also listen to the reports given to other stations, so we can see how we compare with the average station.  If we're running QRO and the station is giving everyone a 5X5 and you get a 5X8, that's a good thang. If he's giving everyone a S9+20 and you get a 5X8, that's a bad thang...

Relativity is what it's all about with reports.

Another thang: The most important thing hams want to know is, "How loud is my signal compared to others?"  We should always watch the meter carefully and as a service give out exact meter readings. The biggest waste of time is to hear someone say we are 59+++ or just 59.  If hams weren't interested in reports, they'd be on Skype. Most hams are naturally a competitive lot.

T

[KB2WIG]

When i was moobilin a lot, I'd work SSB. I  made the mistake of giving someone a report in a corntest... Your S4 to S5....  "Well which one is it!?"  I guess I was insulting him.

 I'll start giving out S10's.  That oughta make 'em happy.

klc

[w5omr]

I'll start giving out S10's.  That oughta make 'em happy.

Too often these days, I hear signal reports of "you're S-9 to S-10"...

huh?

[Steve - K4HX]

Signal reports are largely useless, no matter how "accurate." What does S9 mean if the noise level is S8? A good report would always include the signal referenced to the noise. And as Tom noted, some comparison to other signals from a similar location provides context.

[w5omr]

Steve, I'm gonna be back in San Antonio the 12th of March for the weekend.  I'm looking to fire the rig up and do some operating.  Hopefully we won't be in full-force Spring-time thunderstorm season.

When and Where do you typically operate so I have a better chance of finding you on the air, rather than shot-gunning the whole damn band trying to find a decent AM QSO?

[Steve - K4HX]

3870-3885 kHz
3700-3725 kHz

[W7SOE]

Can someone clue me into how to tell if the modulation is out of phase by looking at the scope?

73

Rich

[k4kyv]

Look for the voice peaks with the greater amplitude above and below the edge of the pattern for the unmodulated carrier.  They should go in the positive direction, not in the negative.

[Steve - K4HX]

Phase is not correct term, even though it is widely used. It is audio polarity.

Look at the three waveforms below. The first is with the audio polarity set for maximum positive peak modulation. The positive peaks extend well beyond 100 percent - entirely due to the asymmetry of my voice (no limiting used), as shown in the second waveform, which is the audio straight out of the microphone. Note the large amount of asymmetry.

Now look at the third waveform. This is the same audio as in the first two waveforms but with the polarity flipped. Notice that now with 100 percent modulation on the negative peaks, the positive peaks do not even reach 100 percent (about 80 percent). This is the undesired setting for the audio polarity.

[W7SOE]

Thanks guys, I see it!  (I think)

So this has only to do with the nature of our asymmetric voice?  We "connect" the part of the modulator that drives the RF up (positive peaks, away from baseline) with the part of our audio that is asymmetrically large.

Do I have that right?

Man, I bet my JVII is backwards, can't wait to check.   


Rich

[Steve - K4HX]

You got it!

[KX5JT]

What if one tube is a bit stronger than the other?  Brandon gave me that tip.  Put it in the position that makes higher positive peaks.

[W7SOE]

Steve, BTW, thank you very much for those scope shots.

Rich

[Steve - K4HX]

You're welcome.

[Steve - K4HX]

Some more good info on this at the link.

http://www.arrl.org/files/file/Technology/tis/info/pdf/5405037.pdf

[W7SOE]

I tried to determine what the "phase"  (Would polarity be a better word?) was on the JVII.  Very difficult to find a definitive answer.  Just using my voice makes it hard because I can get various patterns depending on my volume and tone.  i did not see a definite difference in the positive peaks either way.........

Rich

[WA1GFZ]

Everyone has a different voice you might be more balanced than some of the nuts out there

[Steve - K4HX]

Connect your mic directly to your scope. This will tell you if your voice is asymmetric or not.

I tried to determine what the "phase"  (Would polarity be a better word?) was on the JVII.  Very difficult to find a definitive answer.  Just using my voice makes it hard because I can get various patterns depending on my volume and tone.  i did not see a definite difference in the positive peaks either way.........

Rich

[W7SOE]

Everyone has a different voice you might be more balanced than some of the nuts out there

Being balanced has never been my strong suit!

[W2VW]

If your Viking cuts off the lows there may not be a whole lot of difference.
Low grid current can limit the positive peaks too.

[w5omr]

If your Viking cuts off the lows there may not be a whole lot of difference.
Low grid current can limit the positive peaks too.

I may have to re-think my advice then, of tuning a rig such as a viking II.  I've been suggesting that to tune the rig, put it in CW position (no key, or key down), and tune the oscillator/buffer circuit as shown by the book, and then adjust the grid drive to show 7.5mA of current.  Then, switch the meter to the plate position, quickly dip the final, and then make your loading adjustments (if needed) to bring it to ~180mA (saving 40mA from the suggested 220mA for a little 'breathing room' on the modulation transformer secondary, and slightly higher impedance in the final - 3.3k vs 2.7k) then reduce the grid drive, until you see the final plate current -just- start to drop.  bring it back, and leave it there.

I think think that would reduce the grid drive enough on a pair of 6146's to make any noticeable difference, but I could be mistaken.

[KX5JT]

I reversed polarity on my condensor by putting it into a different preamp with a "phase reversal" button.  The negative peaks are gone and the positives are higher.

I reversed the leads on the D-104 and got the same results.

Apparently my voice is backwards.  Thanks everybody for the help!

[Steve - K4HX]

Just leave it at 7.5 mA from the start to finish.

If your Viking cuts off the lows there may not be a whole lot of difference.
Low grid current can limit the positive peaks too.

I may have to re-think my advice then, of tuning a rig such as a viking II.  I've been suggesting that to tune the rig, put it in CW position (no key, or key down), and tune the oscillator/buffer circuit as shown by the book, and then adjust the grid drive to show 7.5mA of current.  Then, switch the meter to the plate position, quickly dip the final, and then make your loading adjustments (if needed) to bring it to ~180mA (saving 40mA from the suggested 220mA for a little 'breathing room' on the modulation transformer secondary, and slightly higher impedance in the final - 3.3k vs 2.7k) then reduce the grid drive, until you see the final plate current -just- start to drop.  bring it back, and leave it there.

I think think that would reduce the grid drive enough on a pair of 6146's to make any noticeable difference, but I could be mistaken.

[WD8BIL]

The mod transformer rolls off below 250 CPS like a rock down a well.

[KX5JT]

I noticed on my Viking II when I pumped in sine waves, that 250 Hz started to distort before hitting 100%.  Up to 8Khz was fine... I didn't test higher, maybe I should.