are class e rigs wide?

[N2DTS]

Here is timtron (2 min ago).

[KD6VXI]

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.  

All the best and 73

Rob
K5UJ

Icom DSP based radios have a grunginess sound you can pick out of a pileup, almost.

If it's a clear night on 75 meters, you can hear the Icom's on 80...

On a serious note, Icom's with DSP generate a sound that is ALL their own.  They do make decent AM, though.


--Shane

[N2DTS]

I had a pro 3, cant say I was impressed on rx or tx, but it was simple to use, the band scope was better than anything else besides sdr stuff.
The auto notch gizmo worked fantastic.

Brett

[K5UJ]

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

Pretty interesting.  That's probably WHAS Louisville on 840.  Guess they're analog at night.  The CBS owned stations are all doing digital day/night.  I think the mask is analog out 10 khz then 5 khz for the IBOC digital on each side of carrier.  So WCBS would go down to 865.  The CBS stations here on 670 and 780 do the same thing.   I'm only 10 miles from the 670 tx site so it wrecks my reception of WSM on 650.   WGN on 720 quit IBOC (the rumour is they didn't want to pay the Ibiquity fee) and are now supremely all beautiful sounding analog.  A great receiver audio evaluation tool.  Tuning across them reminds one of the way AM used to be (and ought to be).  

[N2DTS]

Here is wgn in south jersey 10 over s 9.
it looks like something is off to the side of the main signal...

[N2DTS]

Look at this crap!

[WBear2GCR]

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.

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).

It's "9kHz" - ok, sometimes I have to tune slightly off to one side, but the filter works nicely... the rest of the IF selectivity of the 440S is still in play as well... a +/-2.25 filter is too narrow to listen comfortably imho. I got a few filters from Murata and test listened to them for the best balance between wide and narrow, this one won. I can probably scare up the model # and you can check my math and the filter, send me a PM?

 

[K5UJ]

Look at this crap!

610 is a class B channel IIRC i.e. used by regional 5 kw stations like WMT over in Iowa--the one you are seeing is probably over near you in the East.   yeah that's the IBOC response, you have your analog out 10 khz then the digital for 5 more khz.

if you listen on a wide enough analog rx you'll here the digital coming though like bacon sizzling.  makes my superadio unuseable in wide setting. 

re the 720 plot I note that there are one or two other stations there exhibiting assymetric sidebands--notice WLW on 700 has a lot below carrier not much above for example.  I don't know how to operate a flex receiver so can't say what's happening there.

[N2DTS]

On some signals, there is not much modulation, and there is some sort of digital stuff off to one side, on some signals its on the upper sideband, on others its on the lower sideband.
The big 610 signal has a much wider audio, and those two big digital things, not all the signals look like that, some still look like normal AM signals...

If I tune in the signals off to the side and narrow down the passband, say of the 720 signal, it does sound like bacon fry.

Do some signals transmit AM stereo? In digital?
Where does the station id info ride? Some car radios came up with info when you tuned them in...

Brett

[ke7trp]

Interesting Talk here.. 

Alot of people want HiFi AM.  Thats what we strive for and I think I alot of people get carriered away.  One of my AM friends wants MAX bandwidth with the best tone.  His radio is 25KC wide on AM.  I have measured him. He sounds wonderfull but I keep telling him that its pointless because most of the people that are listening to him are on RXers that cant go that wide. I listen about 10KC wide most of the time but when its rough out, I go down to 5KC.  Sure, some fidelity goes away but thats the price you pay when the band is rough.

So.. what is optimal for transmit?  5kc? 6? 8?   What in your opinion is the least amount of bandwidth you can run to have HiFi AM?

My new Transmitter has to be limited in the audio rack.  It will pass 20 to 15K. 

[W2XR]

Interesting Talk here..  

Alot of people want HiFi AM.  Thats what we strive for and I think I alot of people get carriered away.  One of my AM friends wants MAX bandwidth with the best tone.  His radio is 25KC wide on AM.  I have measured him. He sounds wonderfull but I keep telling him that its pointless because most of the people that are listening to him are on RXers that cant go that wide. I listen about 10KC wide most of the time but when its rough out, I go down to 5KC.  Sure, some fidelity goes away but thats the price you pay when the band is rough.

So.. what is optimal for transmit?  5kc? 6? 8?   What in your opinion is the least amount of bandwidth you can run to have HiFi AM?

My new Transmitter has to be limited in the audio rack.  It will pass 20 to 15K.  

My opinion is that it is technically pointless to allow an amateur radio AM transmitter to pass high frequencies in excess of 5 to 8 Khz.; this would of course represent a channel bandwidth of 10 to 16 Khz.  The human voice has very little energy much above 4 Khz, and we cannot legally transmit music, which would require the audio frequency response be out to at least 10 Khz for decent reproduction.

The more important point is, I believe, the shaping of the transmitted audio response to make the audio as high-fidelity (or "bright" sounding, to use a somewhat overworked adjective with regard to the high frequencies) as possible, while minimizing the total occupied bandwidth. The AM broadcast community began doing this in the late 1980s with their adoption of the NRSC preemphasis curve, to compensate in large part for the very poor IF characteristics of AM car radios and the like.  Personally, I think the NRSC boost  vs. frequency curve is too benign for my tastes and for the IF passband characteristics of most AM receivers, but it does represent a good starting point. An excellent treatise on this very subject was written by the truly great audio engineer Bob Orban; you can access it by going to the Orban website and look for the tab for Bob's technical white papers.

This whole thing with high-fidelity transmission of AM is an imperfect science, due to issues of poor SNR and dynamic range because of atmospheric noise, receivers with non-standard IF passband characteristics, non-standard frequency equalization and frequency tailoring at the transmitter end of the link, etc. Don't get me wrong; I enjoy transmitting the best sounding signal I can with the equipment I have available, but I really do realize the limitations of what I am trying to attempt, much to my dismay!

Just my 2 cents worth!

73,

Bruce

[w3jn]

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.

Brett

Brett, you absolutely cannot assume this.  While it may very well be the station splattering, there are other possibilities here as well.

"Horizontal spikes" were mentioned above.  In my experience using high-end Agilent analyzers, this is a classic case of ADC overload, DSP windowing limitations, and/or mixer non-linearities.  In the former case, a strong signal is overloading the ADC and causing low-level artifacts that spread across the sampling bin.  The culprit could very well be a signal or signals well out of the frequency span you're looking at.  

Even if the ADC isn't overloading, the method of windowing used in the software affects how faithfully an input signal(s) is/are displayed.  The "window" is the function applied to the Fourier transform of the signal (i.e. the time domain component of the sample) to attenuate the edges of the time record.  This is done because the FFT of complex signals will end up with leakage across the time record bins (blocks of time-domain sample points) - consider this to be analogous to smearing of the frequency spectrum you're looking at (does this look familiar in the context of the horizontal lines you're seeing?).  

Various window functions provide better frequency resolution at the expense of dynamic range, and vice versa.  A rectangular window has the worst performance in this respect, providing perhaps -40 dB of signal leakage between bins.  What this means is a signal (that perhaps you're not even seeing on the pan display) is leaking thru all the bins and this shows up as a horizontal line.  Windowing is explained in the SDR-5000 manual, but it does not explain succinctly how this manifests itself on the display.

I cut my teeth on the HP 89441A vector signal analyzer which is not all that different, fundamentally, from the SDR-5000.  Its manual contains the best explanation I've seen of all the factors affecting signal analysis using DSP methods.  Chapters 18 and 19, although having some 89400-specific discussions, provide an outstanding tutorial on this subject.  The manual (about 4 MB) can be found here:  http://cp.literature.agilent.com/litweb/pdf/89400-90038.pdf

Next, consider that the SDR-5000 hardware has no narrow-band filtering.  The bandpass filter and low pass filter after the mixer all have relatively wideband responses and, as they are L/C filters, will roll off gradually as opposed to the relative "brick wall" nature of a crystal filter or DSP filter.  You then must consider that when you hook the radio to an effective antenna, the *total* power contained within the response of the filter can be considerable.  The mixer in the SDR-5000 essentially is an array of high-speed flip-flops, providing the necessary I/Q outputs for the DSPs (as I recall this mixer was the subject of a QEX article some time back).  While its performance is certainly impressive like any mixer it's not perfect, and we cannot discount that a strong out-of-band signal (or a whole lot of medium-strength signals) can cause low-level artifacts.

The bottom line here is this:  while the SDR-5000 certainly exhibits good performance in a number of areas, it -like any receiver - isn't perfect.   Because spectrogram displays like the SDR-5000 allow you to see very low level stuff very clearly (those horizontal lines would never be noticed if you didn't have the spectrogram display) - which one cannot see on a swept spectrum analyzer - it lends itself to providing evidence (true or not) that someone is too wide.

They may or may not be; the fellows under discussion could well have issues with their transmitters and be splattering horribly.  Indeed spectrograms can be the best tool out there to quickly identify the source of a dirty signal.  But you can *never*, in the presence of other signals, state with certainty that what you're seeing isn't being generated in the receiver.  

All of this reinforces the fact that regulation-by-bandwidth is even *less* than worthless because of all the misunderstandings about bandwidth measurement.   Just because something is seen on a spectrogram display doesn't mean the station is "too wide" - stuff 40 dB down from the carrier (although easily seen on a spectrogram) is NOT necessarily proof of a "too wide" signal.

[Steve - WB3HUZ]

Cool. I have a 9 kc filter in my 51J-4 and found it to be a rather good compromise between fidelity and selectivity. If a strong AM station is only 5 kHz away, I'm usually switching to the 6 kHz filter or QSYing. 

Post the part numbers when you get a chance. Those 455k units are probably useful in many receivers.

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.

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).

It's "9kHz" - ok, sometimes I have to tune slightly off to one side, but the filter works nicely... the rest of the IF selectivity of the 440S is still in play as well... a +/-2.25 filter is too narrow to listen comfortably imho. I got a few filters from Murata and test listened to them for the best balance between wide and narrow, this one won. I can probably scare up the model # and you can check my math and the filter, send me a PM?

 

[WA1GFZ]

The Flex has an IF of 10 KHz or 11KHz if I remember. You will get responses every multiple of the IF.
This problem was eliminated when the mixer was deleted in the Perseus, QSR1 and HPSDR Receivers.

[KD6VXI]

Interesting Talk here.. 

Alot of people want HiFi AM.  Thats what we strive for and I think I alot of people get carriered away.  One of my AM friends wants MAX bandwidth with the best tone.  His radio is 25KC wide on AM.  I have measured him. He sounds wonderfull but I keep telling him that its pointless because most of the people that are listening to him are on RXers that cant go that wide. I listen about 10KC wide most of the time but when its rough out, I go down to 5KC.  Sure, some fidelity goes away but thats the price you pay when the band is rough.

So.. what is optimal for transmit?  5kc? 6? 8?   What in your opinion is the least amount of bandwidth you can run to have HiFi AM?

My new Transmitter has to be limited in the audio rack.  It will pass 20 to 15K. 

I'm currently using a Class A series modulator in a 25 watt AM TX here.  Passes audio BEAUTIFULLY to 100K and beyond.  I've sent a 50khz tone FM modulated (I injected it via the audio processing software in the PC) and was able to actually send two seperate audio channels out.

Of course, 50 kc away, people wouldn't be too happy   So all of my testing was dummy load only.  After playing with this test, I learned to put am audio low pass filter in line, and as one of the last things in the chain.

I've also found that NB settings can wreak HAVOC with AM and Hi Fi.  I'd get people telling me how horrible the radio sounded, I'd talk them into disabling or otherwise getting rid of the noise blanker, and WOW, YOU SOUND BEAUTIFUL!


--Shane

[DMOD]

Do some signals transmit AM stereo?

There used to be a a stereo AM analog method called C-QUAM which transmitted AM Stereo, which in my opinion sounded better than DRM or the current digital IBOC (Inband-Buzz-On-Channel) krap.

The main problem for analog AM stereo was the limited bandwidth of the IF and RF stages of current receivers, and nightime propagation.

Starting about 1981, companies such as Sprague and Sony started developing wide-band receivers that had wide and narrow band capabilities. The wide band bandpass was over 19kHz at -3dB down.

I contracted with a number of stations in the Midwest in which we installed AM exciters (mostly BE exciters) in currrent transmitters at the time, and the AM stereo was superb on the right receiver.

If interested in AM Stereo, there is a site that discusses the history of AM Stereo:

http://www.amstereoradio.com/

Phil - AC0OB

[flintstone mop]

hello All,
I wanted to quote Bruce, but this website is optimized for firefox and a long reply or a long quote makes the entire display in a reply jump up and down while typing. Gary's explanation....anyway

The bandwidth issue for A.M. has soley been from the manufacture of inferior equipment to the general listening public for A.M. broadcast. Poor/cheap engineering of auto and home radios the last few years, and now the implementation of IBOC that forces narrow I.F. bandwidth to filter out the digital garbage.
I don't understand why we are trying to to force 20-20kc of audio through any transmitter for the transmission of the human voice. Very nice high end and a natural sound of the letter H or S is perfectly audible with a bandwidth of 7kc. To obtain that F.M. sound is not very neighborily, especially if the transmitter/exciter/linear cannot handle the extra audio without distortion.  


Fred

[WBear2GCR]

Current AM Broadcast audio sounds like doogiepoopie to me with the 5kc bandwidth limitation.

I have no idea if that is due to the way that the stations have their processing set up ior if (as I suspect) the 5kc bandwidth limitation just doesn't sound very good for broadcast audio - even for "talk" programs.

Good example is that the local (multiple translators across New England and NY) WAMC simulcasts on 1400 AM (daytimer, down to nil watts during the nite) and flipping from AM to FM in the car is so very night and day... the audio on the AMer sounds pretty similar to most of the other AM (like WGY) stations in this market...  who put the wool sweater  and socks over the mics??

But that has little to do with the way AM amateur radio stations ought to be set up.

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??

                       _-_-bear


PS. did I mention I am always right? 

[K5UJ]

station ID is encoded in the IBOC part of the signal (In Band on Channel, a protocol developed by Ibiquity)

The 30 khz plot is  spreading out from carrier, 10 KHz audio then 5 KHz digital.  
sort of like this:
                           |
                 _    __ |__    _
                | |__ /--|--\__| |


You don't always get that but I have seen other flex displays where it is consistent so I suspect you are doing something with yours that you are not aware of because I can pretty much guarantee you, these commercial stations are not transmitting drastically asymmetric side bands.   Yes, not all AMs are running IBOC so you will find many that are analog only.   Some switch it off at night and run it in the daytime when co channel QRM via skywave is not an issue.  I don't think any AM stereo is going on anymore but don't hold me to that.  

re bandwidth--at night I try to limit myself to 4 KHz with a baseband filter that has a 96 dB cut; in the day I open thing up a bit more but sometimes at night I forget to switch in the filter.  The other night a W2 I was working said he could not understand me because of the lack of highs in my audio due to storm QRN and asked me to boost them so I obliged by bypassing the filter for him.

Last time I swept my rig it was flat from around 20 Hz up to 10 KHz which is what you want but that doesn't mean you tx that wide; you just have a flat response and faithful reproduction of the frequencies you do transmit.  This is not to difficult with modern s.s. rigs like my 1000MP -- the challenge is gg to be when I start running the HT20 and try to get that flat from (I hope) 40 or 50 Hz up to 5 KHz.  DeYellifiying it right?    Or just running it stock with a Hi Z xtal mic and getting that nice crisp punch.

Consumer AM receivers have been rolling off audio lower and lower over the years--car radios now start rolling off at 2 to 3 KHz.  This is an attempt to compensate for the higher noise levels found on AM these days coming from the usual suspects.  A couple years ago Clear Channel announced they were going to start cutting analog audio at 5 KHz--don't know if they did it or not but A.  so much AM is "talk" radio now and B. consumer recievers mostly don't hear above 4 KHz so if they had done that it would have probably been mostly unnoticed.

We have a local station that programs music of your life in full 10 KHz nrsc mask audio and if you have a decent rx, like a modded prod. detector feed to a hi fi audio tube amp driving big speaker it sounds very good.   most listeners don't have this. 


73

Rob
K5UJ  

[flintstone mop]

YES! DEMOD,
I remember hearing that beautiful stereo in a GM Diesel the company owned. The stereo separation was unbelievable and the overall sound was great. It was a station skipping into the Washington DC area, while I was working one night.

FRED

[ke7trp]

Another thought:

  If you taylor your audio to sound Great at 15KC wide on AM, Then a guy listens to you at 5KC, You tend to sound horrible.  Alot of AMers dont get this.  If you taylor your Audio to sound great in a smaller bandwidth such as 6 or 7KC, You tend to sound good at those lower bandwidths.  The next time you hear someone that is real HiFi and wide on the band, Narrow down and you will see the effect.  It changes the guy on the valiant or DX100 little.



Clark

[KD6VXI]

I don't think any AM stereo is going on anymore but don't hold me to that.  

73

Rob
K5UJ  

A friend in the Broadcash Engineering industry was actually bringing up a country station in Bakersfield a couple years ago.  I was interested in using some C-Quam stuff, and he has the test equipment to get a station set up CORRECTLY.

Last I heard, it was all still sitting on the bench at that project.  The owners of the station decided Bakersfield, Ca didn't need ANOTHER AM station.  Supposedly it's all sitting ready to go, towers and all.

So, I think their just might still be a demand for SOME C-Quam.  It could ALSO be that this station HAD all the stuff, and was bringing it (back) online when they had an ownership change.

--Shane

[K5UJ]

Another thought:

  If you taylor your audio to sound Great at 15KC wide on AM, Then a guy listens to you at 5KC, You tend to sound horrible.  Alot of AMers dont get this.  If you taylor your Audio to sound great in a smaller bandwidth such as 6 or 7KC, You tend to sound good at those lower bandwidths.  The next time you hear someone that is real HiFi and wide on the band, Narrow down and you will see the effect.  It changes the guy on the valiant or DX100 little.



Clark

Clark,

I've noticed that effect also but it is not produced only by txing wide bandwidth.  It is due to the op's inability to eq his audio correctly.   If you tx a flat audio plot i.e. a roll up to around 150 hz then a flat line across and roll off at about 4 KHz or 5 or 6 whatever, a ham's audio will sound FB in a 6, 8, 10 or 12 KHz passband.  

What causes the lousy audio from a wide sig in a narrow p/b rx is when the op gets the idea that the way to eq his audio is to boost the lows and highs and attenuate the midrange.  I started out doing that because I was told that was the thing to do.  Where this came from I don't know but somehow the notion that eq sliders should look like a big smile got started.   But if an op eqs watching a time delay spectral audio display and tests by monitoring himself on narrow and wide passbands he can have it both ways.  

73

rob

[ke7trp]

I agree.  I run 20 to 20K through the TX, Then I plot it on a recievers output to the laptop.  You can really see your audio this way.  I have attempted to get mine nice and flat.

CLark

[DMOD]

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??

Bear,

You could design your own or start with Steve's anti-aliasing filter as a template:

http://www.classeradio.com/easy_e_pwm_alternate_filters.pdf

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??

We have one here as well, KMRY, and the audio on the SuperRadio in Wide Band mode sounds great.

Phil - AC0OB