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are class e rigs wide?




 
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N2DTS
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« Reply #75 on: November 11, 2009, 05:12:38 PM »

Here are some more shots of the AM band, I am not 'doing' anything with the flex, it just shows you the spectrum, you cant do anything but change the amaount of freq you look at.

There are plenty of signals that have something off one sideband, others that look normal, etc.

Brett


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« Reply #76 on: November 11, 2009, 05:14:11 PM »

another one


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K5UJ
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« Reply #77 on: November 11, 2009, 05:15:34 PM »

Quote
Maybe I will have to come out with a box that has switchable high slope 5, 7.5 & 10kHz LP filters that can go inline with the mic, or inline at line level? Anyone think this is of interest??

What I'm doing now, is running a behringer 1124 parametric eq as a bandpass filter.  it has a cut of -48 dB on each of left and right channel.  I cascade them.  

there are a few problems with this though.  1.  It's a behringer, i.e. hard to figure instructions and user interface.  2.  I think it adds a bit of A to D-D to A distortion.  3.  As a parametric eq. to work it you have to be versed in the audio world lingo of octaves and all that which I admit I do not really understand.   I had to get an initial setup from a friend to get started, from which I made a few alterations.  

But once it is setup, you can have cutoff presets in different memories and simply dial in your rolloff.  

There's probably a better solution in a nice sounding gentle roll off  passive filter however, that can be switched in and out.

Rob
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N2DTS
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« Reply #78 on: November 11, 2009, 05:26:52 PM »

I used a 20 band analog graphic equalizer in the past, the vx2000 ($100.00) does it now.
You can pick up eq's used for about $50.00, small rack mont units...


Brett

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« Reply #79 on: November 11, 2009, 05:46:25 PM »


Rob,

The modern Behringer stuff is big  bang for the buck, and if it does 48db/oct is FB.
Cascading standard analog filters can lead to wierdness in the passband, but that's another story for another day...


The octave thing is merely a doubling of frequency. Or halving of frequency.

1000Hz center freq, one octave up = 2.0kHz one octave down = 500Hz. simple enough...

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« Reply #80 on: November 11, 2009, 06:00:06 PM »

  My neighbor has 2 class E rigs . The 100 watt rig is 20 inches wide, the 400 watt rig is only 19 inches wide. Go figger ?
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« Reply #81 on: November 11, 2009, 06:10:53 PM »

Time to interject a bit of technical reality  Wink

First, class E transmitters are not wider than any other transmitter type.  I have run transformerless modulators constructed from tubes, and the audio performance is identical to my class E rigs.  The absolute widest signal that I have heard on 75 meters within the past couple of years is, in fact, coming from a valient.  This can be backed up by Bruce, who has observed the same station.  No names - the guy is a good guy, and once made aware of the issue, is now actively correcting the problem.

Second, the bandwidth of any pulse width modulator is generally NOT limited in the output filter, but rather is limited in the INPUT filter (anti-aliasing).  You CAN limit it in both places, but is HAS to be limited in the input filter first otherwise there is a good possibility of high frequency distortion.

Third, unless we know how many DB down from the carrier the sidebands are, we don't "really" know the bandwidth of any given signal.  I've heard "wide" sidebands, but when I moved the receiver up to the carrier, I find the sidebands were 70dB or more down where I was listening (about 10kHz away).  I'm not sure that qualifies as wide.  And, I have to add the width of my IF in there, which means I was really listening to more like 5kHz away and not 10....

4th, the flattened triangle of the power bandwidth curve can be created with any good transmitter.  It simply means the station in question has a very high power bandwidth capability, and does not imply wide, simply flat.  The fact that the sides were triangle shaped indicates some type of roll off was in use.  Easily created by a good audio processor, and I have heard lots of them.

All that being said, this is not a class E thing.  Old Irb was PLENTY wide with his DX100  Cool

Regards,

Steve
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« Reply #82 on: November 11, 2009, 06:19:45 PM »

Steve,
Thank you..........a little common sense.
Bill 
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« Reply #83 on: November 11, 2009, 06:27:08 PM »

After that fresh air I'd like to suggest we all stop using terms like wide and narrow.

We should also stop throwing bandwidth numbers around as if they were absolute. The AM community is better than this.

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« Reply #84 on: November 11, 2009, 07:56:18 PM »

Ok, so how would you have me put that someone is taking out 2 qso's on each side of his 20+ KHz (wide) signal?
If three people are in a round table, at roughly the same signal strength, and two look to be about 6 Khz wide, and not interfering with other qso's, and the other guy is as above, how would YOU put it?

The question I started with was basicly could something be wrong with a class e rig (or rather the pdm modulator) or is it the operator?

I am suspecting because it can pass 15KHz audio, it is passing 15 KHz audio and at high levels...

Brett

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W2PFY
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« Reply #85 on: November 11, 2009, 08:16:36 PM »

Now broadcast rigs are also suspect.  Where will it end?
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« Reply #86 on: November 11, 2009, 08:29:52 PM »

  My neighbor has 2 class E rigs . The 100 watt rig is 20 inches wide, the 400 watt rig is only 19 inches wide. Go figger ?

Well shaooot, my little ole K7DYY Sr is 300 watts and only 6 inches wide.

Tongue

Rich
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« Reply #87 on: November 11, 2009, 08:30:19 PM »

Bear,  yeah I think perhaps cascading analog filts does some phase shifting problem--the behringers are DSP but just using one channel to get 48 dB cut is probably plenty.  My pal nearby calls me Overkill -- well deserved label.  

Steve -- great to have you weigh in -- tnx

Brett, I did some thinking about your observation of some bc stations having asymmetric sidebands and I stupidly didn't think of this earlier--if you are taking instant snap shots of spectrum of course you will see this.   When you look at say, 80 kHz chunk of the AM bc band, or enough to get a plot of 7 or 8 stations, you have to sample for several seconds.  Are you doing that?  If you are getting an instantaneous look, you are going to see good plots for locals coming in on ground wave but due to uneven arrival, lack of rx diversity reception and selective fading, the skywave stations will show that unevenness between upper and lower sidebands.   It's just normal skywave--nothing wrong or amiss.   Your flex radio panadapter is like other pieces of analytical equipment--takes time to get the hang of it.  I suggest you spend a few months fooling around with it.

73

Rob
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« Reply #88 on: November 11, 2009, 08:48:55 PM »

With over 30 years in network broadcast and audio I can only refer to a VERY wise man who once said (regarding bandwidth):


"I don't understand why some people like to limit other peoples activity, or
choices.
It seems to me like there is very little important communication going on in
ham radio, so why stress the narrow bandwidth? Would it block some critical
or important communication?

Ham radio just seems like a bunch of people who enjoy fooling with radio
equipment, so why not just let them fool with it?


What about operating on an empty band, the operator still must (by law)
sound like a cheap cell phone?


There are other modes much narrower than ssb, why not not ban ssb as wasting
spectrum?


People should try to get along, I dislike contests, they can take over and
ruin a band, I am not fond of RTTY, or slow scan TV, or ssb, or many other
things other hams do, but the last thing I would want to do is restrict
something that others find enjoyable. "

Hmmmm..

73 to all the FINE sounding signals just "fooling" with Ham radio..


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« Reply #89 on: November 11, 2009, 08:59:37 PM »

Ok, so how would you have me put that someone is taking out 2 qso's on each side of his 20+ KHz (wide) signal?
If three people are in a round table, at roughly the same signal strength, and two look to be about 6 Khz wide, and not interfering with other qso's, and the other guy is as above, how would YOU put it?

The question I started with was basicly could something be wrong with a class e rig (or rather the pdm modulator) or is it the operator?

I am suspecting because it can pass 15KHz audio, it is passing 15 KHz audio and at high levels...

Brett

First thing would be to contact the person, tell him what you observe and how you observe it. I've had some bloopers on the air like an arcing grid tank. A report from a concerned fellow ham was welcome.

The point of my post is bandwidth numbers are thrown around by hams as if they were finite values like counting bricks.

This ISN'T QRZ.

This group used to collectively teach much better than the average amateur radio clusters I've encountered. There are lots of people digesting every post on this site. We are still doing well but some things need attention.

Reducing bandwidth to absolutes isn't accurate. This group collectively knows better than to ignore roll-off.

You posted "look at this crap" with a garden variety common IBOC AM broadcast signal which has been commonplace for several years. FCC says it is perfectly fine. I'm with you. It ruins AM BC DX. Who is right? The broadcaster who's signal you are looking at is broadcasting within CFR. They are in the right.

The whole reason AM users hang out in the ghetto is they are aware of friction with other fone modes. Otherwise they could set their bandwidth to sound like a warmed over ricebox on AM and live with lesser quality than a good current ssb system.

A constructive continuation of this thread would be how to view an acceptable AM signal verses a defective one on your equipment. This would include measurement errors found with experience and measures to mitigate them.  

Apologies to grammar police et al.

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« Reply #90 on: November 11, 2009, 09:12:16 PM »

Quote
The question I started with was basicly could something be wrong with a class e rig (or rather the pdm modulator) or is it the operator?

I am suspecting because it can pass 15KHz audio, it is passing 15 KHz audio and at high levels...

It is not a classE thing, so don't single out classE equipment.

Most likely the operator, just as in SSBer's who don't know how to properly equalize, errr, adjust an equalizer for a SSB signal, or who "over equalize" thinking boost is always better than cut. People who fail to educate themselves in audio chains and RF really should not touch anything but the VFO, IMHO.

Phil - AC0OB

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« Reply #91 on: November 11, 2009, 11:08:05 PM »

What's a "horizontal frequency spike"?

First off I don't have a dog in the fight about class E. If it makes nice sounding AM I am all fer it.

My problem is what I heard and saw the other night. I am just trying to understand it.
Here is a shot tonight of a CBer that had a wide signal. He was not particularity strong but you could hear him up and down  about 50KHZ from his center freq. he is only S4 so it is not a strong signal.

So this is what I meant by a horizontal frequency spike. As he yells into the mike you can see the horizontal effect. You can also see the sig rise up on a fair amount of the spectrum.

He was bragging about running an old Yeasu into a HB amp putting out 500 Bird Watts on peaks.

I saw the same type of sig that night on 75 and just wonder did I really see a sig that was that wide or is my equipment fooling me?

Thanks

Carl
/KPD




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« Reply #92 on: November 11, 2009, 11:48:30 PM »

Carl,
That's splatter....

As you can see, I use mostly the panadapter...

Hard to tell how significant a signal is, just by a change in background color....

Better to say "The transmitter seems to be putting out a lot of energy at 25khz away from the carrier...."  than to say it's "wide"...     Grin

Check out WBCQ from just a few minutes ago.........

If we just look at the waterfall display, some would say that  it's over 50kc wide....
In reality, it's about 8kc.


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« Reply #93 on: November 12, 2009, 01:02:44 AM »

Ok, so how would you have me put that someone is taking out 2 qso's on each side of his 20+ KHz (wide) signal?
If three people are in a round table, at roughly the same signal strength, and two look to be about 6 Khz wide, and not interfering with other qso's, and the other guy is as above, how would YOU put it?

The question I started with was basicly could something be wrong with a class e rig (or rather the pdm modulator) or is it the operator?

I am suspecting because it can pass 15KHz audio, it is passing 15 KHz audio and at high levels...

Brett



What design was involved?  At least with my designs, they all have filters that start rolling the audio off above 5kHz or so.
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« Reply #94 on: November 12, 2009, 08:42:11 AM »

Hmm - SDR panadapters are not calibrated Spectrum Analyzers maybe?
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« Reply #95 on: November 12, 2009, 09:08:58 AM »

OK-FINE................ I guess it's about time I chime in on this one.

A "wide signal", music, art, beauty, and sexual perversion all have one thing in common.
It is only in the eyes of the beholder.

When you refer to a "WIDE" signal are you referring to a clean high fidelity signal, or a dirty transmitter spewing "artifacts" all over the band. Any one of us out there pretty much knows what an AM signal should sound like, and how much bandwwidth it SHOULD take up. this is pretty much common sense and good operating practice.

Like Dave and others have said: "I dont want to sound like a cheap cell phone!" But, by the same token, if I'm putting out an unusually wide signal, I would expect someone in the AM community to let me know so I can check it out. Also I also had a problem tossing "artifacts" all over the band one night. I was kind of sleepy and not watching the scope, come to find out I had a porcelain insulator supporting the tank coil arced through and with carbon tracks that was causing the problem on mod peaks. thanks to someone telling me I had "artifacts" I headed a possibly larger problem off at the pass.

The issue of AM bandwidth has always been the subject of heated discussions and lots of pissing and moaning. It always gets some people's feathers ruffeled. Any wide bandwidth caused by dirty, defective or improperly adjusted transmitters should not be tollerated. However, the bandwidth required to put out a CLEAN, good sounding signal should be a non issue. I will always accept constructive criticism from someone that I consider to know what they are talking about. As far as the SSB crowd goes, they would piss and moan about our bandwidth if it was 100Hz! ! !

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« Reply #96 on: November 12, 2009, 09:49:51 AM »

  My neighbor has 2 class E rigs . The 100 watt rig is 20 inches wide, the 400 watt rig is only 19 inches wide. Go figger ?

Well shaooot, my little ole K7DYY Sr is 300 watts and only 6 inches wide.

Tongue

Rich
Yep, I had one of those too. I bought it after seeing how WIDE my neighbor's Class E rigs were .

   Some people seem think wider is better. Not sure I agree .
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« Reply #97 on: November 12, 2009, 10:54:13 AM »

Fun thread and gettin' wider, oops, er ah "longer."

I believe I was the first to define 'horizontal frequency spikes,'  Grin

-Great technical (or lack thereof) of measurement discussions.

'Excessive' or 'dirty' bandwidth kind of reminds me of  one of the US Supreme Court judge's opinion in relating to porn,
"I know it when I see it."

Well, "I know it when I hear it" too.

Check out these two local BC stations.
Which one is using the old plate modulated BTA?
Which is complying with the restricted modern standard?
Which sounds like crap?  Well, believe it or not, you actually have to listen to the audio.


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« Reply #98 on: November 12, 2009, 11:07:34 AM »

That was what I was asking about, if the pdm modulator could have a problem, or if it was just the case of passing 15 KHz audio.

I think its kind of rude to run that bandwidth at nite on a crowded band and take out 4 other qso's, I dont have a problem if someone wants to go 30 KHz wide in the daytime or when there is lots of room.

It makes no difference to me, as I cant hear anything above about 3500 hz anyway.


But I have no idea if it was the audio, or something wrong with the rig.

I would like to look at signals and see what happens when you overmodulate a class E rig, and what the signal looks like when it passes a lot of 10 KHz and above stuff.

I would GUESS just passing a lot of high end would not look like a squashed triangle, but more like normal modulation with less in the sidebands, but also dont know what 150% positive modulation with lots of highs looks like. Can you do that on a class E rig?

Brett


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« Reply #99 on: November 12, 2009, 11:19:04 AM »

Quote
Check out these two local BC stations.
Which one is using the old plate modulated BTA?
Which is complying with the restricted modern standard?
Which sounds like crap?  Well, believe it or not, you actually have to listen to the audio.

This sounds like the old, "What's My Line" TV program.

I would guess the Country station is using plate modulation while the "local" station is using an IBOC mask.

Phil - AC0OB
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