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Author Topic: How much space (kHz) is enough on SSB?  (Read 3849 times)
KJ6TJX
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« on: March 21, 2012, 09:52:13 AM »

OK... disclaimer first... new to hobby in December and just getting HF feet wet. 

I recently put up a 10 meter dipole connected to an HTX-10.  Even with "poor" conditions late yesterday, there was a fair amount of traffic which surprised (and excited) me.  One particular station in Ohio (I'm northern CA) was hitting me at an S7, had a decent pile up, and never heard me.  No real surprise with the limited power of rig and conditions.  So, I thought... move up and call CQ and see what happens.  I moved up 10kHz and called for a couple minutes and didn't get a response.

How far should I move up in order to avoid interfering, but hope to interest someone seeing/hearing the activity in the general vicinity?  I'm assuming moving up, say 4kHz, would be more productive to call CQ than 10kHz where there isn't activity (and assuming nobody listening).  Moving up 2.5 is probably marginal and could cause QRM or at least irritation.  What's good ops protocol?

Thanks,
Jon - KJ6TJX
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WB2WIK
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« Reply #1 on: March 21, 2012, 09:55:46 AM »

For SSB:

On an uncrowded band, a clear frequency 10 kHz from activity you can hear is a really good idea.  No reason to get closer.

On a very crowded band, I generally use 4-5 kHz away from typical signals, or 6-7 kHz away from very strong ones.

Being up or down 10 kHz from "activity" on 10 meters does not place you in the middle of nowhere, it's only 10 kHz.  Most everyone tunes around a lot more than that.  Many hams use rigs have spectrum displays covering 100 kHz or more of the band per sweep, so if a new signal pops up that the display can capture, they'll know you're there as soon as you transmit, even if they're not tuned to you.



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K1WJ
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« Reply #2 on: March 21, 2012, 10:24:36 AM »

5khz is standard in my operations

Any station using more than 4-5khz bandwidth is a disservice to the hobby in general.

A few of the stations are ridiculous - with hi-fi ssb & high power useage - Not good practice.

73 K1WJ David
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KA5N
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Posts: 4380




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« Reply #3 on: March 21, 2012, 10:31:34 AM »

Well you don't have the greatest antenna,  A dipole up 15 or 20 feet is not great with only
5 or 10 watts.  However I have worked many countries with simple and even indoor antennas
with 3-5 watts.  
You will have better luck answering other stations rather than calling CQ yourself.  As you
gain experience you will learn when to call and when not.  
Instead of low elevation dipoles, try using slopers which are dipoles with one end higher than
the other.  These tend to favor the direction of  the lower end.  You can easily set up two or
three favoring different directions.  Verticals get out better than low dipoles.  They are simple
and need a good ground plane.  Using an elevated vertical with a ground plane of four or more
elevated radials makes a good antenna for 10 meters (or 15, or 17, or 20).
Good Luck, things will get better as you get operating time under your belt.
Allen
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W8JX
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« Reply #4 on: March 21, 2012, 02:16:22 PM »

I use at least 3 khz. Unless you have a rig with a loose/wide front end this is usually enough. If you use a much wider spread you will have trouble finding a hole. At 3 khz I can tune them out completely unless they have a broad signal or splatter. 
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N4NYY
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« Reply #5 on: March 21, 2012, 02:54:38 PM »

Quote
On an uncrowded band, a clear frequency 10 kHz from activity you can hear is a really good idea.  No reason to get closer.

On a very crowded band, I generally use 4-5 kHz away from typical signals, or 6-7 kHz away from very strong ones.

That is a pretty good guide. The bare minimum should be 3 KHz. But 5K is nice and 10K is better. Of course, if it is Field Day, then you are lucky to find a 1 KHz width.
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N4CR
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« Reply #6 on: March 21, 2012, 04:26:22 PM »

If two stations on 3 khz adjacent frequencies are both transmitting within their bandwidth and have good enough filtering to only hear their 3 khz segment then 3 khz is enough. But there's a lot of times when that is not the case. For example, when conditions are excellent or you are in close proximity to a station their signal can 'blow past' your filters and you will get interference from them regardless of the bandwidth.

If you go look at the Sherwood Engineering receiver tests, this one of the tests that separates the great rigs from the average ones.

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

Take a look at the difference between the Dynamic Range for both Wide Spaced and Narrow Spaced (narrow spaced is what I referred to in the first paragraph) and compare the figures for the top rigs and the ones farther down the list.

So, part of the answer lies in how good the equipment is on both ends for both parties in the part of the band in question.

It's pretty common on 75 meters at night to have conversations spaced every 3 khz and if everyone's running standard rigs it pretty much works out ok nearly all the time. As soon as someone comes on one of those slots with an ESSB rig, they blow over the next frequency and the adjacent guys get to listen to buckshot from the wide station. It's one of the reasons that people get uptight over ESSB stations. If ESSB stations gather on a frequency where 5 khz spacing is expected they are just fine and not making other stations angry for not adhering to the 3 khz maximum bandwidth that has been standard since the inception of SSB communications.

Additionally, an over driven amplifier can easily be heard over a 20 khz spectrum slot. And you'll find people 1000 miles away or more coming to your frequency and letting you know you are splattering.

To answer your question in a historical perspective, 3 khz is a minimum separation because we expect normal SSB communications to stay within a 3khz spectrum.

If there's a contest on, forget all of what I just said. You'll find stations overlapping each other in significant ways that make normal communication nearly impossible.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
W8JX
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« Reply #7 on: March 21, 2012, 06:26:30 PM »

If two stations on 3 khz adjacent frequencies are both transmitting within their bandwidth and have good enough filtering to only hear their 3 khz segment then 3 khz is enough. But there's a lot of times when that is not the case. For example, when conditions are excellent or you are in close proximity to a station their signal can 'blow past' your filters and you will get interference from them regardless of the bandwidth.

This seems to be more of a problem with modern entry level immature IF DSP rigs that lack skirt sharpness and selectivity/rejection. In the real world we can rarely have the luxury of 5 khz or more spacing and sometimes not even 3 khz so we have to adapt. Mature analog IF rigs with good xtal filters do not have this problem and will out preform entry level IF DSP rigs easily here. I have been using a modern analog IF TS-480 for 3 years now with a optional 1.8 khz SSB filter and when it gets busy and 3 khz is a breeze and it can handle 2 khz in a pinch with some tweaking and rejects strong signals well.  Again I will never knowingly start a QSO closer than 3 khz from someone else but there are those that do not follow this rule and will sometime try to wedge you out and you need a tight front end and a strong signal of your own to deal with this.
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W0BTU
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« Reply #8 on: March 22, 2012, 12:58:54 AM »

I use at least 3 khz. Unless you have a rig with a loose/wide front end this is usually enough. If you use a much wider spread you will have trouble finding a hole. At 3 khz I can tune them out completely unless they have a broad signal or splatter. 

This is a truism. Bookmark this post!

3 KHz spacing on SSB is plenty. If it's not, either the TX station has a wide signal, or he's overloading your receiver.
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VE7REN
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« Reply #9 on: March 22, 2012, 05:54:34 AM »

i to use the 3 khz rule. i tighten my tx and keep my power down.. i hear some guys so wide they splatter 15 khz.............
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KATEKEBO
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« Reply #10 on: March 22, 2012, 06:08:02 AM »

If the band is not too crowded, 5 kHz is a very comfortable spacing.  This is what commercial SW station use, and if somebody tells you that your SSB signal 5 kHz apart is causing QRM, he needs a better radio.   Any radio, even the cheapest one, should be able to properly filter out station 5 kHz away from the desired station.

When the bands are crowded, 3 kHz is perfectly acceptable, and most radios will cope with it.

That said, one problem is that many operators use way too much power than needed.  FCC rules clearly state that one should use the minimum power necessary.  Unfortunately, all the time you will hear hams engaged in ragchews running 1 kW or more, when 100 W or less would be perfectly sufficient.  This "mine's bigger than yours" mentality is just plain stupid.  There are occasions where running full legal power is perfectly justified.  But this does not mean that you should use it all the time.  Just because it's legal, it doesn't mean that it is a good operating practice.



« Last Edit: March 22, 2012, 06:09:39 AM by KATEKEBO » Logged
KJ6TJX
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« Reply #11 on: March 22, 2012, 08:15:02 AM »

Thanks for all the input!
Jon - KJ6TJX
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W4VR
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« Reply #12 on: March 22, 2012, 08:55:40 AM »

It really depends on what the guy you're trying to avoid is using for a transmitter and amplifier, and how strong he is.  I hear lots of radios, Japanese and American SDR, that run pretty wide.  Sometimes you have to move as much as 10 kHz away to avoid hearing the interference.  But, being under 3 kHz away is a no-no in all cases.  Under normal circumstances I try staying 4 kHz away to protect the other guy and to protect me as well.
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W0BTU
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« Reply #13 on: March 22, 2012, 01:18:14 PM »

...  I hear lots of radios, Japanese and American SDR, that run pretty wide. 

Yes, and by design. But I don't hear most SSB signals if I'm 3 KHz away from them. And I've run enough tests over the years to know that they don't hear me, either.
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W8JX
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« Reply #14 on: March 22, 2012, 02:20:42 PM »

...  I hear lots of radios, Japanese and American SDR, that run pretty wide. 

Yes, and by design. But I don't hear most SSB signals if I'm 3 KHz away from them. And I've run enough tests over the years to know that they don't hear me, either.

I think the problem is more with poor receiver selectivity than broad signal most of the times. Basically if you can cannot tun out a signal 3khz away is because one's receiver is lacking not because transmitter is broad. Many modern low end IF DSP rigs have poor skirt selectivity and near by strong signal rejection and their owners tend to blame someones transmitter more than their own receiver.  This is not 1970 or even 1980 when HF bands were not as crowded as they are today. Lot of times your luck to even get 3 khz.
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