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are class e rigs wide?




 
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N2DTS
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« Reply #25 on: November 10, 2009, 10:10:12 AM »

And that is exactly what goes on with this fellow, who sometimes then turns things up to drive them away, ranting and raving about those damm ssb guys....

I dont have a problem if a guy wants to run a real wide signal, in the daytime, if he can find an open 25 KHz or so, but to do it at prime time, and cause problems for 2 other AM qso's and 2 other ssb qso's....

I just wonder if something is wrong with the radio, or its being over modulated, or its just no cut of the high frequency audio.

If you run a 32V3 at 100 watts, I dont think you need to worry about excessive bandwidth, as the signal wont be very strong. But running a high power rig takes some responsibility I think, limiting the negitive modulation and the high frequency stuff.
Most people seem to do that quite well.
If you are going to spend thousands of dollars on audio processing equipment, maybe get something to check the transmitted signal?

Brett






I really get a charge out of guys 20 KHz wide complaining about SSB signals 5 KHz away.
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« Reply #26 on: November 10, 2009, 10:34:34 AM »

A while back there was another thread pertaining to bandwidth and I think Don, KYV, wrote an great description as how to correctly measure the same. As in any industry, there are accepted standards, with specific details as how the measurement is performed. Radio, not being my ball of wax, leaves me to believe some of us don't have that standard tatooed inside our eyelids, nor have the proper equipment for the measurement.

73's
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« Reply #27 on: November 10, 2009, 10:44:46 AM »

  Generally, with a decent , selective reciever that is operating properly..if you hear a fellow who is S9 when his carrier centered in your pass band and you are still hearing  him spitting and sputtering 10 KC up the band, while stronger stations (S-9+30)in his round table are not being heard.. It may be reasonable to suspect he is a bit wider than the stronger stations  (?)


YES!!  (Especially if everyone is runnning similar transmitted AUDIO bandwidths and the stronger signal is NOT splattering)

Comparing many signals with the offender is a great way to get a feel for what is happening. But in general, you will need to use a front end attenuator to standardize all signals so that they are the same strength when compared.

Before giving out bandwidth reports to anyone on AM, it pays to spend some time listening in the AM broadcash band and seeing just how your receiver handles these stations, weak and strong. Since most AM BC stations are generally clean at +- 5KC, this is a good standard to train yourself.

Also listen to many ssb stations to get a good idea how they should spread out. I find the cleanest ssb stations are usually above 3900 and in groups of low key type conversations. These guys seem to tune up their amps correctly. The widest ssb signals are found (lately) in the DX window 3786-3800 as many try to squeeze the last watt out... Grin  The extended ssb guys are usually clean, but there are exceptions. You can hear the clean wispy sound as their signals tail off when tuned across - not grungy splatter. Since most ssb QSO's are spaced/channelized  3kc apart, the ones that are operating and not complaining are usually clean. Most ssb rigs use 2.4kc filters (or less) so they have a built-in standard which AM does not have.

If a spectrum analyzer is not available, I sometimes will simply listen to my own signal in another receiver. Put a 18" clip lead off the back of the receiver and adjust it's length (rolled up) until your signal is S9 +40. Then as you talk, tune up and down the band to see what the crud sounds like and looks like on the S-meter.  If the receiver is not leaking in RF and is not being overloaded, it will tell you the story.  I consider the point when your side crud is down at least 40db to be the point of "reasonable" roll-off.

T
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« Reply #28 on: November 10, 2009, 10:56:24 AM »

Too many generalities here. What does wide mean - exactly. Give me some real numbers or a mask. Just because you can hear (whatever that means) a station up the band does not necessarily mean they are wide.

I've heard a lot of complaining from some who purposely chose to operate only 5 kHz from another strong AM signal/QSO and then complain about splatter. Such an approach is hardly being reasonable.

That said, there are some who are very wide, either on purpose of out of ignorance (neither is acceptable) and they think they are doing AM a favor by "cleaning out the Window."  There is no window and they are cleaning nothing but are making a ton of enemies (on which they seem to thrive).
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« Reply #29 on: November 10, 2009, 11:08:28 AM »

I agree on the receiver limitations, on a poor receiver, there is really no way to tell if the signal is really wide.
But a spectrum analyzer does not have those problems, nor does the flex 5000.

Brett





Uh.... a qualified NO to both.  As Steve said, "what's too wide?"- that's the first question.  Next, if you don't understand the limitations and functions of either piece of gear, you're not gonna get meaningful measurements.

I could use a spectrum analyzer to "prove" your signal is a megahertz wide.

Neither one is a panacea.
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« Reply #30 on: November 10, 2009, 11:24:32 AM »

That said, there are some who are very wide, either on purpose of out of ignorance (neither is acceptable) and they think they are doing AM a favor by "cleaning out the Window."  There is no window and they are cleaning nothing but are making a ton of enemies (on which they seem to thrive).


Yes, the "Us and Them" mentality does lots of damage to AM.  A modern ssb receiver can operate very close below an AM station on 75M and barely know the AMer is there cuz of the opposite side suppression of his ssb receiver. However, the AMer complains cuz he is hearing both sidebands in a wider bandwidth. Losing battle. Beating up on the ssb guys only makes it worse.

Commercial AM broadcash stations use 10kc spacing between stations.  7-8 kc is a reasonable spacing between ham AM stations, though the ssb crowd will come in MUCH closer and not even know they are interfering with the AM QSO.  Tough problem, indeed.

T
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« Reply #31 on: November 10, 2009, 12:01:05 PM »

I had a problem years ago, with reports that my signal was splattering on voice peaks.  A quick glance at the scope showed a normal looking pattern, but upon closer investigation, I could see "hair" growing on the positive voice peaks.  Apparently something in the modulator was ringing or going into parasitic oscillation.  I tried several things at low level and with the driver stage, with no effect.  Then, while browsing in some old Radio handbooks, I noticed a circuit showing a class B modulator that had a 100Ω resistor in each plate lead.

I looked in my junk box and found a couple of what looked to be about 20-watt, composition resistors at somewhere between 50 and 100 ohms (I'll have to measure them with the ohmmeter next time I think about it).  I connected them between the plate leads and the plate caps of the modulator tubes, and sure enough, the "hair" was gone and I didn't get any more splatter reports.

I have seen suggestions that tube type modulators be cross neutralised just like a push-pull rf stage.  Never tried it, but it might be a worthwhile experiment.

A class D or E rig, tube type rig and a pulse duration modulator all have one thing in common: garbage in, garbage out.  The splatter and distortion could be occurring somewhere early in the audio chain at frequencies that transformers in the later stages of a tube type rig would filter out due to their limited frequency response, but that a perfectly linear modulated stage with near zero distortion and response from DC to daylight would pass unimpeded.

Something that many hammy hambone types are apparently not aware of is that the apparent bandwidth on the dial of the receiver as you tune across as signal is the sum of the bandwidth of the transmitted signal and the passband of the receiver.  An unmodulated carrier with zero bandwidth will be audible across 3 kHz of dial display when receiving with a 3 kHz SSB filter in the receiver.  A SSB signal will be audible across about 6 kHz.  A 7 kHz wide AM  signal will be audible across 10 kHz of dial space.  Add the slope at the edges of the i.f. bandpass filter and the signals will appear even wider.

I once got a chuckle when a slopbucketeer with a terribly crappy, raspy, distorted sounding signal called me to complain that there was something wrong with my transmitter; I had a "wide" carrier.  He  could hear the heterodyne squeal almost 3 kHz away from my frequency!

Also, if your spurious distortion products are reduced to 40 dB down outside the normal passband, that is considered a clean signal according to good engineering practice, meets FCC specifications and exceeds the specs of many commercially manufactured rigs, especially older ones.  But if you are coming in at 60 dB over S9, that means your distortion products are still coming in at 20 dB over S9.  If the noise floor happens to be very quiet, even at S9 signal strength the -40 dB products may be audible outside the normal passband.
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« Reply #32 on: November 10, 2009, 12:39:12 PM »

That said, there are some who are very wide, either on purpose of out of ignorance (neither is acceptable) and they think they are doing AM a favor by "cleaning out the Window."  There is no window and they are cleaning nothing but are making a ton of enemies (on which they seem to thrive).


Yes, the "Us and Them" mentality does lots of damage to AM.  A modern ssb receiver can operate very close below an AM station on 75M and barely know the AMer is there cuz of the opposite side suppression of his ssb receiver. However, the AMer complains cuz he is hearing both sidebands in a wider bandwidth. Losing battle. Beating up on the ssb guys only makes it worse.

Commercial AM broadcash stations use 10kc spacing between stations.  7-8 kc is a reasonable spacing between ham AM stations, though the ssb crowd will come in MUCH closer and not even know they are interfering with the AM QSO.  Tough problem, indeed.

T

Maybe what we really need is some regulation by bandwidth. I think there was some talk about this in the past.
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« Reply #33 on: November 10, 2009, 12:42:02 PM »

Or not. Most of this discussion has centered around not knowing how to measure bandwidth. Having a rule that cannot be enforced is useless.


That said, there are some who are very wide, either on purpose of out of ignorance (neither is acceptable) and they think they are doing AM a favor by "cleaning out the Window."  There is no window and they are cleaning nothing but are making a ton of enemies (on which they seem to thrive).


Yes, the "Us and Them" mentality does lots of damage to AM.  A modern ssb receiver can operate very close below an AM station on 75M and barely know the AMer is there cuz of the opposite side suppression of his ssb receiver. However, the AMer complains cuz he is hearing both sidebands in a wider bandwidth. Losing battle. Beating up on the ssb guys only makes it worse.

Commercial AM broadcash stations use 10kc spacing between stations.  7-8 kc is a reasonable spacing between ham AM stations, though the ssb crowd will come in MUCH closer and not even know they are interfering with the AM QSO.  Tough problem, indeed.

T

Maybe what we really need is some regulation by bandwidth. I think there was some talk about this in the past.
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« Reply #34 on: November 10, 2009, 01:24:06 PM »

I had a problem years ago, with reports that my signal was splattering on voice peaks.  A quick glance at the scope showed a normal looking pattern, but upon closer investigation, I could see "hair" growing on the positive voice peaks.  Apparently something in the modulator was ringing or going into parasitic oscillation.  I tried several things at low level and with the driver stage, with no effect.  Then, while browsing in some old Radio handbooks, I noticed a circuit showing a class B modulator that had a 100Ω resistor in each plate lead.

I looked in my junk box and found a couple of what looked to be about 20-watt, composition resistors at somewhere between 50 and 100 ohms (I'll have to measure them with the ohmmeter next time I think about it).  I connected them between the plate leads and the plate caps of the modulator tubes, and sure enough, the "hair" was gone and I didn't get any more splatter reports.

I have seen suggestions that tube type modulators be cross neutralised just like a push-pull rf stage.  Never tried it, but it might be a worthwhile experiment.


It may also be good practice to put a 1000 ohm resistor in series with each modulator tube grid. This is commonly done with class A or AB1 push-pull audio power amplifiers to reduce the possibility of parasitic oscillations in the output stage.

I don't think you would want to do this in a class AB2 or class B modulator stage, however. You want to keep the impedance between the audio driver stage and the modulator grids as low as possible, to keep the driver regulation high as the modulator tube grids are driven positive.

73,

Bruce
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« Reply #35 on: November 10, 2009, 01:55:26 PM »

Brett:

There are some very good comments and technical information here. I'll offer my thoughts...

As one who is experienced with both tube transmitters and Class E, I feel when operated correctly the class E transmitters are naturally capable of passing wider and cleaner audio than a typical tube rig (say an un-modified Valiant which passes audio only to about 3-4kc for a total occupied bandwidth of up to 8kc). Tube rigs often have limited power bandwidth that creates a drooping occupied bandwidth as the measured frequency is increased from the carrier.

The PDM modulators on Class E rigs tend to be flat with full power bandwidth and have a high frequency limit as based by the PDM filter. Most of these are set at 8-12kc and drop fast (12-24db/octave) and thus have an occupied bandwidth of up to 24kc. Mine starts diving at 8kc, and I also have a low level 36db/octave brick wall filter set at 6kc at the end of my air chain. In result and also due to previous audio processing, I have a good amount of RMS audio power occupying a 12kc RF bandwidth, but nothing outside of that as it is generally better than 40db down.

A few Class E folks use a linear modulator that has no inherent bandwidth limitation. Thus the vocal sibilance is the frequency limiting component.

As usual, when examining a signal one has to keep a keen eye out for receiver overload or the noise blanker adding it's own artifacts.

Hope this helps.

73,
Dan
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« Reply #36 on: November 10, 2009, 02:18:57 PM »


I could use a spectrum analyzer to "prove" your signal is a megahertz wide.


Hi John

Just a quick question from my own curiosity and lack of knowledge. Hey this is a part time hobby and I have no formal radio education other then that needed to get an Advanced in 68!

The station I was observing on the SDR-IQ was in QSO with several other AMers on 3885. With the waterfall display I could see horizontal voice peaks out about 25 KHZ either side. I could tune down using a narrow filter setting and hear splatter from those peaks way down the band.

I am very impressed with the filtering on the SDR so "I presumed" what I heard was true. I should also note that when the other stations were on they occupied a very small piece of the spectrum.

There was an AM QSO on 3890 that was able to continue and I could filter out the 3885 QSO until the wide signal came on

So the question is; Am I truly seeing a wide splattering signal or to your point, am I "proving" something that is not correct?

To another posters point, if I remembered the stations call I would PM him and let him know. But I do not. I do hear him a lot on 75. Hopefully it was inadvertent.

73

Carl
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« Reply #37 on: November 10, 2009, 02:47:42 PM »

Carl,

Where were the off freq. signals relative to the noise floor on your SDR?
I can see horizontal, freq. spikes even as far out as 50 kc from the carriers of  typical AM operators in a quiet part of the band on my QS1R, say the 3733 crowd.

Also how much contrast are you using on your waterfall display? At high 'beta' everything shows up.  normal 'beta' not much except the signals down 40dbv or so from the carrier.

But I will say that some very strong ham signals (-40dbv carriers at my location) show freq. spikes many kHz's farther out and  harder than much stonger, clean BC signals (-10dbv) down.  For whatever reason, some ham signals are far dirtier or simply don't have high pass filtering.  

Hard limiting without filtering, of course, generates approximate square waves with sidebands tapering off into the aether  Grin
I think a lot of guys overprocess signals and try to put  'smilie' roll-off characteristics on the air.  (Hi bass, low mid's, hi treble)
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« Reply #38 on: November 10, 2009, 02:52:07 PM »

What's a "horizontal frequency spike"?
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« Reply #39 on: November 10, 2009, 02:58:51 PM »

Ans.: -that which shows up perpendicular to the time axis on the waterfall display.
..."What, don't you respect Wilsiz'ms?  Grin

See all the little squiggles ?  right and left of the CW sig's.


* 20M CW SS contest 08 11 09.JPG (168.72 KB, 904x710 - viewed 979 times.)
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« Reply #40 on: November 10, 2009, 03:06:20 PM »

..uh, er, in this case most are from lightning strikes somewhere outta the picture, but dirty AM looks similar , they just disappear right and left of the carrier.  I'll have to snap a better AM example.
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« Reply #41 on: November 10, 2009, 03:08:23 PM »

Ans.: -that which shows up perpendicular to the time axis on the waterfall display.
..."What, don't you respect Wilsiz'ms?  Grin

See all the little squiggles ?  right and left of the CW sig's.


Ah... should have guessed...

I never use a waterfall display....   Smiley

Much more usefull info in the normal spectrum display.
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« Reply #42 on: November 10, 2009, 03:16:24 PM »

What I was seeing was there, and not any fault of the receiver.
Other signals were just as strong and were narrow.

Using the flex 5000 which is the 3rd receiver on the sherwood list:

http://www.sherweng.com/table.html

The top receivers are all very close in specs.

I had an sdr-iq in the past, its good if a bit clunky to use, and yes, at any reasonable signal level, what you see is what you have, not something the receiver is generating.

If the signal is weak and/or far away, you might not see much, but if its 20 over, you see it quite clearly on most sdr receivers, and hear it in other receivers.

Brett








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« Reply #43 on: November 10, 2009, 06:07:12 PM »


A few randomized thoughts...

Anyone can run almost any rig and make a mess on the band.

The filters in a given PDM modulator are usually analog filters. IF said filter is say a second order filter at 5kHz. (-3dB point) and the signal is 40dB over S9, then there is an audio component at 10kHz away that is only 24dB down from 40dB over, or 16dB over S9! If someone is listening at 10kHz away to an S9 QSO, I would expect that they would think they're hearing major splatter. Obviously, in the case of the use of an even higher order filter, there would be less energy out there... A 4th order filter would get you 48dB at 10kHz...

Let's all not forget that AM is + and - the audio bandwidth.

Also, I have a really slick little +/-4.5kHz Murata ceramic filter in the IF of my 440S, and it really does let me listen to an AM QSO that is only 5kHz  separated with relative ease.  It sounds pretty good. Also in the SSB mode I usually have very little difficulty copying an SSB QSO that is within about 2-3KHz of the carrier of a strong AM QSO... it's not quite so easy using my R-388 (yet... until I mod the filter scheme)

               _-_-bear

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« Reply #44 on: November 10, 2009, 06:24:15 PM »

It used to be very common to have a big roundtable on 40 meters on 7285, 7290, and 7295, without problems.
That was before the days of broadcast rigs and class E rigs.
I was just listening to 3 seperate qso's on 3874, 3880 and 3885, and they were not causing me any problems with a 5.2 or 6 KHz filter.
Modern sdr stuff is brick wall filters, sort of like the old mechanical filters were, only much better.
Most of the other (non sdr) modern gear is not as good, but good enough for close ssb.

Brett

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« Reply #45 on: November 10, 2009, 06:40:44 PM »

I have a friend with a SDR rx who has told me that some of the grungy signals he sees come from hams operating ssb with exciters driving solid state amps.  IIRC they are frequently Icom exciters driving either Ameritron s.s. amps or the PW1, and there has been a problem with the fancy Yaesu 9000 rig but that may have been a single case or something Yaesu fixed.  

There are spectrum analyzers and spectrum analyzers.  Rigs like the Icoms with "fish finders" are not spectrum analyzers.  Ditto for the older CRT panadaptor station accessories--these are intended to find signals--that's about it.  

My impression is that the participants here work hard to insure our modulation is below 100% negative, audio is ~ 5 Kc or less, and are properly loaded and linear and you all set a good example for me.  I also think that "clean" should apply to everyone regardless of carrier power.    

Brett, in going back through the posts I am trying to figure out what you want--you generated an interesting discussion but it seems that since you started using your SDR receiver you have found some station that bothers you.   Until you can identify this station I don't think anyone can help you.   The best course of action is to probably send the operator a very diplomatic and tactful message about his signal if you hear him again.  If it is or were me putting out the garbage that is something I would appreciate and seriously investigate.  Whomever it is, he may blow you off.  Then you can either accept grunge signals as a fact of ham life, or do something?  ...not sure what but whatever you do, make sure you have your act together  Wink  Personally, I always want to hear from competent hams with accurate measuring devices.  Some yahoo with a fish finder is another matter. Cheesy    

<<<It used to be very common to have a big roundtable on 40 meters on 7285, 7290, and 7295, without problems.
That was before the days of broadcast rigs and class E rigs.>>>

I have a hunch that on this, you are probably going to have to live with the status quo if you want to be a happy ham  Grin 


All the best and 73

Rob
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« Reply #46 on: November 10, 2009, 07:41:45 PM »

Quote
It used to be very common to have a big roundtable on 40 meters on 7285, 7290, and 7295, without problems.

It used to be common that those QSO interfered with each other greatly and reduced the ability to enjoy good AM audio, in my experience. Five kilohertz is way too close. Even if all the participants in both QSOs had rigs that produced ZERO energy a mere 3 kHz from their carriers, there would still be 1 kHz of overlap.


Quote
Also, I have a really slick little +/-4.5kHz Murata ceramic filter in the IF of my 440S, and it really does let me listen to an AM QSO that is only 5kHz  separated with relative ease.

How so? If you are 4.5 kHz from your center frequency, you are only 500 Hz from carrier the other AM signal 5 kHz away. This would be well into the audio/sideband. Or it is the filter only 4.5 kHz wide total (+/- 2.25 kHz).

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« Reply #47 on: November 10, 2009, 08:23:34 PM »

The measurement of occupied bandwidth is standardized by the ITU under SM.328 and actually two methods are acceptable:

x dB and the 99% Power methods

For the x dB method the total signal power is used as a reference and the and the high and low spectral sides are found where the envelope is x dB down. x is typically 26 dB for common modulations like AM. The occupied bandwidth is the difference between the high and low - 26 dB points.

For the 99% Power method, typically a digital method is used to divide the signal envelope in to bins. Starting outside the sidebands, bins are subtracted one by one from the upper and lower sides of the envelope until only 99% of the power remains. Essentially 0.5% of each sideband power is removed. The occupied BW is the difference between the last two bins that were removed to reach 99%.

A fancy Agilent spectrum analyzer would be able to do both of these automatically. 

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« Reply #48 on: November 10, 2009, 08:34:40 PM »

Well, the reason I brought it up was to try to figure out if it was something in the typical class E rig, the way it was being run, if you did not get the filters right what would happen, etc.
I have heard you can get parasitics in them that wipe out fets...

As the weather cools off, there is less motorcycle and yard stuff, and my ham radio activity picks up.
The flex, being very interesting, also has me listening and actualy operating much more than I normaly would be.

Plus, it does not hurt for people to think about what they are doing, and how they might do better.

As far as getting close, with a good receiver, I really dont have a problem with 5kc spacings with 90% of the AM signals on the band, I guess the high end stuff rolls off some, to a low enough level where it is not noticable.
Right now there is an ssb group on 3890 that is 2.7 Khz wide, and an AM signal on 3885.407 and in 5.2 KHz passband set, I dont hear the ssb guys at all. There is also a strong AM signal on 3880 and I get some low artifacts that dont bother the signal on 3885.407 much at all.
If all I had was a 6 or 8 kc filter, it might be more of a problem, but I dont remember it being much of a problem on 40 in the old days....
Now some people back then used to take out half the band, Irb comes to mind...I could always tell when he was on...

Brett


 
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« Reply #49 on: November 10, 2009, 08:42:00 PM »

What's a "horizontal frequency spike"?

Here is an example of what I was referring to. It is an AM broadcast signal on 840 KHZ. Note the voice peaks either side of the carrier (red line) extending out about 5 KHZ.

The station the other night had the same peaks, at about the same strength extending about 25 KHZ either side of the carrier

Also interesting in this pic to see the data stream on WCBS 880

Carl
WA1KPD


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Carl

"Okay, gang are you ready to play radio? Are you ready to shuffle off the mortal coil of mediocrity? I am if you are." Shepherd
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