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7.296 USB next to 7.290 AM




 
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Author Topic: 7.296 USB next to 7.290 AM  (Read 4538 times)
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KA3EKH
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« on: November 12, 2018, 09:33:00 AM »

So this past weekend I was part of a field exercise, Able Archer 83 and as part of this set up operated my GRC-106 on 7.296 USB. Going to assume that being 6 Kc above the AM channel at 2.290 and running USB there would be no issue with anyone operating AM down at 7.290 given a good AM response don’t see there sidebands extending more than four or five Kc above and below the carrier and my operations up at 7.296 being upper side band only and limited to 3.2 Kc extend from 7.296 to 7.299.3, have no issues confirming that I am on frequency and find the 700 cycle buffer enough for not extending beyond 7.300.
This does not take into account people running old radios with super wide band IF stages but going to assume that just about any receiver produced in the past fifty years will have an IF stage that can allow these two operation to coexist without issues. When someone is running Am on 7.290 I do not hear anything listening to 7.296 USB except maybe once in a while some low level noise may appear but it in no way interferes with our operations up on 7.296, also not that although it is 40 meters and LSB is the accepted mode for SSB on forty with surplus military equipment much of it only operates on USB only so that’s another reason to hang out near the edge of the band so we don’t have to hear people telling us about being on the wrong side band.
Will be interested to see what some of the “hard core” AMers have to say about this line of thought.

Ray F/KA3EKH

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KA0HCP
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« Reply #1 on: November 12, 2018, 05:20:14 PM »

Your post seems to ramble a bit...

I disagree with your thinking that 6kc's is enough separation for AM & SSB.  Even with an IC-7600 with all it's excellent filters, I find that nearby USB signals cause problems with my listening to AM.  For anyone using older receivers the interference is even greater.

I'm not sure what other points you are trying to make.  I don't understand why 7296kc is important.  bill.
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KA3EKH
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« Reply #2 on: November 13, 2018, 08:50:26 AM »

People who use surplus military equipment tend to think in terms of channels, and with a lot of the equipment being limited to USB only we are somewhat limited to operating just within certain sub bands or locations, channel 3 on 60 meters is real popular for example.
Turns out now that many of us are looking at 7.296 being there is rarely anything going on up that close to the band edge. The Midwest Military Radio Collectors group have established a net up there on Saturday mornings. Although that net is mostly USB it also runs AM first Saturday of each month. This last weekend I was doing a field operation in Davidsonville Md. 7.296 was a primary contact frequency during the event.
I went down and checked 7.29 before operating on 7.296 for anyone operating and the one time there was an AM station on I did not operate, but the question is just how much space do we provide to any station from the center of their carrier to your carrier?
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WB2EMS
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« Reply #3 on: November 13, 2018, 10:46:19 AM »

I often hear and operate AM on 7295. On a busy weekend I hear groups on 80, 85,90 and 95 depending on the hour and conditions. As we get into winter conditions I think you'll find that frequency may be busy a fair bit. Perhaps lower in the band would be less crowded. Some of the older rigs are operating Crystal controlled and can't easily move.
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« Reply #4 on: November 13, 2018, 10:52:36 AM »

it really does depend on the receiver. My SX-28 gets messed with by close SSB, but the R390A easily adjusts to remove it. At least the GRC-106 has decade tuning and very sharp response on transmit and receive so that one knows almost exactly where the bandwidth is. For a time there was a guy making a replacement filter for USB/LSB for that set. It goes in the receive audio module and one can use the fsk position on the function switch or some other existing hole to install a switch for it such as reference in or whichever.
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« Reply #5 on: November 13, 2018, 05:35:56 PM »

When I hear USB on 7296 I will try to make contact.......TNX   Steve
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« Reply #6 on: November 14, 2018, 01:03:14 PM »

Quote
Will be interested to see what some of the “hard core” AMers have to say about this line of thought.

Well if 40 opens up this winter and people start using 7.290 & 7.295 or 7.293 on a regular basis, you will have no problem having people telling you what they think on ssb at the high end of 40. You'll probably be a popular as someone driving a buss at high speed on a city sidewalk. It won't have any effect on me since I won't be operating there this winter and I personally can't complain since it on a first come basis and is legal to do so. But you did ask Grin Grin  It would probably work great at night. I wonder if this will encourage other ssb people to operate the upper area without regard to a gentleman's agreement that someone said is in place?
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KA3EKH
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« Reply #7 on: November 15, 2018, 10:03:41 AM »

Think maybe the bigger question here is bandwidth and what’s expected. As pointed out in the second response I do tend to ramble on and perhaps have an issue expressing what I am saying.
This is somewhat how I see it. If you have a AM QSO on 7.290 and we assume a “communications grade” bandwidth of three or four Kc that puts that channel out 4 Kc each side of the carrier including sidebands, or 7.286 (LSB) out to 7.294 (USB) at 5 Kc you’re hitting 7.285 to 7.295 I would like to assume that not very many of the AM operators are pushing response beyond 5 or 6 Kc although I think many feel they are.  SSB operators are almost all limited by response of their filters to between 3 to 4 Kc and in the case of what I am talking about with this small group of military radio users we are all limited to USB only so at 7.296 we occupy 7.296 to 7.299/7.3
Some receivers are worse than others, perhaps some of the worst are the old Military receivers from WW2 that some people are still using. Things like BC-348 receivers are by nature maybe 20 Kc wide or more. But most Ham radios of post war design have tighter pass bands in the IF, unless you’re dealing with bottom end SWL receivers any real Ham receiver had some form of filtering built in. I am going to assume that any receiver with 6 to 8 Kc filter would not have an issue with channel spacing this close but can see that a 8 Kc filter will perhaps experience some interference from the adjacent side band.
Maybe at the end of all of this I have two questions.
First, what is the most common IF filtering that most AMers are running? Is it 6 Kc, 8Kc or something as wide as 16 Kc? When I run AM I am almost always receiving using  4 or 8 Kc filters.
Second, what is the expected transmitted bandwidth? Not many stock Ham transmitters are good out to 10 Kc and very little information is carried above 3.5 Kc or so. I maintain a couple AM Broadcast stations and years ago we changed our processing to limit response above 5 Kc from the FCC limit of 10 Kc and for commercial 5 Kw broadcast stations 5 Kc frequency response is adequate, just how much more beyond 5 Kc is required in Ham radio?
Don’t get me wrong, I am not trying to tell people what to do or how much bandwidth they can have but just want to get a feel of what people expect.
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« Reply #8 on: November 15, 2018, 11:28:42 AM »

Think maybe the bigger question here is bandwidth...

This is somewhat how I see it. If you have a AM QSO on 7.290 and we assume a “communications grade” bandwidth...

I don't know what you mean by “communications grade” bandwidth since you did not define it. In fact, I do not think there is a set definition. One can assume what you will but in AM we attempt to reproduce a natural sounding voice with good articulation. In fact, I use some pre-emphasis to cut through the noise and it is very effective.

There is NO comparison between restricted SSB audio and AM.

First, what is the most common IF filtering that most AMers are running? Is it 6 Kc, 8Kc or something as wide as 16 Kc? When I run AM I am almost always receiving using  4 or 8 Kc filters.

See above. We AMer's prefer not to reproduce restricted SSB sounding audio.

Second, what is the expected transmitted bandwidth? Not many stock Ham transmitters are good out to 10 Kc and very little information is carried above 3.5 Kc or so.

Who says?

Many of the older converted AM broadcast transmitters can reproduce audio out to at least 12.5 kHz. I ran proof of performance tests in the '60's where the tube transmitters were good out to 15khz.

Some of the HeathKit and EF Johnson transmitters are probably good to 5kHz unmodified but AMer's modify them them for a flatter audio response and better articulation.

I maintain a couple AM Broadcast stations and years ago we changed our processing to limit response above 5 Kc from the FCC limit of 10 Kc and for commercial 5 Kw broadcast stations 5 Kc frequency response is adequate, just how much more beyond 5 Kc is required in Ham radio?
Don’t get me wrong, I am not trying to tell people what to do or how much bandwidth they can have but just want to get a feel of what people expect.

That's unfortunate. For Sports/News/Talk format that may be sufficient, but not for a station broadcasting music. If you want muddy audio and complaints from listeners, set your audio to start rolling off at 4.5kHz. That limitation was started by some conglomerates who had no interest in keeping AM viable.

In fact, for our stations, we reproduce audio up to at least 7.5kHz.

See my other comments here: http://amfone.net/Amforum/index.php?topic=44341.0

Where the AM operator sets his audio response is up to him. If there are no receivable and adjacent QSO's, one may set his audio to reproduce up to 7.5kHz audio. If there are say adjacent QSO's on each side, he may choose to rolloff at 4.5kHz to 5kHz. 


What to expect from AM operators? Articulate, natural sounding audio with a bandwidth sufficient to achieve that sound.


Phil
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Steve - K4HX
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« Reply #9 on: December 09, 2018, 10:08:06 PM »

Something to consider.

https://amwindow.org/tech/htm/ambw.html
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« Reply #10 on: December 13, 2018, 01:19:53 AM »

So this past weekend I was part of a field exercise,

I have a solution: decaf!
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MikeKE0ZUinkcmo
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« Reply #11 on: January 24, 2019, 07:24:13 AM »

I don't understand why it seems so important to some, to squeeze operations into an group of frequencies where its known that considerable activity, typically with much less capable equipment, takes place.   Then, attempt to place blame for said resulting interference onto those being interfered with.  Unfortunately, a modern, well used, tactic!!

The phone band is at least a couple hundred KC wide, and I'm sure a Narrow "communications grade group" could find another 3-4 KC wide slot to park with nowhere the risk of interfering with other nearby "communications grade" capable users.
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« Reply #12 on: January 24, 2019, 09:28:17 AM »

What I've found over the years often those complaining the most about QRM don't seem to know how to use their VFO.
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« Reply #13 on: January 24, 2019, 01:48:43 PM »

What I've found over the years often those complaining the most about QRM don't seem to know how to use their VFO.

Isn't THAT the truth. What was it we used to say to the AMers who stuck in the imaginary 75m AM Window after the phone expansion? Break the grease loose on that VFO and move around. 

To Ray's original question or dilemma: 7.285-95 has long been an AM hangout on 40m. Since AM is typically a wider mode than single side band, it stands to reason that AM receivers will be broader and more susceptible to interference from adjacent activity regardless of mode. Trying to put a number on it would assume equal equipment and conditions for all.

And to Mike's point - there is more than ample space on 40, 75/80 and elsewhere to operate. I disagree with the narrow-minded approach that says "We AMers just use these few frequencies, you SSB guys have the rest of the band". I believe I'm allowed to operate AM in any portion of the band where phone is allowed and my license privileges allow. Listen first, then go for it.

That said - I avoid places like DX windows, the AWA group and other known areas of specific activity. If I was operating SSB, I wouldn't select a section of the band known for AM activity. I'll skip my 'nets' rant today.  Wink

These days the bands are like a ghost town much of the time. Folks would do well to move around more, including and maybe especially AMers. Unlike a decade or three back, there really is no excuse beyond sudden band condition changes for interference problems.

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« Reply #14 on: January 28, 2019, 01:51:21 AM »

"communications grade" can mean almost anything depending on the authors of the book or document, all of whom may be well-respected. There are no possible targets that will meet every radio communication situation.
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« Reply #15 on: February 12, 2019, 02:13:02 PM »

We use 7293 and 7295 here on the west coast.

--Shane
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