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Author Topic: High Power, High Splatter  (Read 1563 times)
SCUBA
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Posts: 74




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« on: October 30, 2008, 04:02:47 AM »

This posting assumes the possibility of disregard for the 1.5kw legal limit.

Last weekend I would have liked to have checked into one of the 14.300 nets*, but, as I soon discovered, those nets were overwhelmed or otherwise shut down by adjacent splatter from contest operators. So, I put on my shortwave listener hat and discovered that the most powerful splatter affecting 14.300 was coming from a contest operator on 14.314, who was dominating about 1/4 of the 20M band.  Very careful tuning of the FT-897D left no doubt that the offending station was most intelligible at 14.314, and that his sidebands stretched down below 14.300 and way above 14.314.  Two extra class local hams told me that I did the right thing by refraining from contacting the offending station.

Local hams enlightened me about typical causes of splatter.

For a station to be “jamming” such a wide chunk of spectrum, is it likely he was using a broadcast power amplifier (far in excess of legal limit)?  Or, is it likely he was using one of the CB Radio “competition-class” amps (ie. Fat Boy, Texas Star, etc.)?  Are there hams out there that use extreme power (above 5kw). in defiance of the legal limit?

One more question, if I may.  Would it offend a ham if I politely informed him of the amount of spectrum he was transmitting on, eg, "Sir your signal is S-9 from 14.301 thru 14.320."

If I ever engage in splattering, I would hope that someone tells me early on; I'll back off and fix the problem.

73,
Jack

*Not a big deal for me, since I didn't have emergency traffic.
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KB9CRY
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« Reply #1 on: October 30, 2008, 05:32:37 AM »

is it likely he was using a broadcast power amplifier (far in excess of legal limit)?

Maybe so and maybe no.  

Damn contesters!
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K0BG
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Posts: 9860


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« Reply #2 on: October 30, 2008, 05:40:00 AM »

You did do the right thing, but this sort of thing can happen with just 100 watts PEP out!

Band conditions can be very poor, or very good between two given points. Just this past week, while operating mobile, a station broke in to tell me I was 60 over 9 in Florida. At the time, I didn't have the amp on, so the PEP was about 70 watts.

While I don't doubt the offending station was running power, and perhaps even 3 or 4 thousand watts PEP, the biggest offender typically is an over-zealous operator who believes that all knobs should be to the right. You get that, by the way, all the time, not just during contests.

Lastly, while it seems like contest weekends are worse, just remember; a lot more people operate on a contest weekend, so comparisons are hard to make.

By the way, I don't do contests.

Alan, KØBG
www.k0bg.com
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AD4U
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Posts: 2164




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« Reply #3 on: October 30, 2008, 05:58:53 AM »

Some dedicated contest and Top Gun DX stations run many times the 1500 watt legal limit.  That is just a fact of life.  But when properly adjusted, even a station running 25KW will not splatter all over the band.

Assuming your receiver was not being overloaded by the strong signal, my bet is this operator was grossly over driving his amp, legal limit or not.

Dick  AD4U
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W3LK
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Posts: 5639




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« Reply #4 on: October 30, 2008, 07:04:53 AM »

<< Some dedicated contest and Top Gun DX stations run many times the 1500 watt legal limit >>

And you can prove this statement?

73,

Lon - W3LK
Naugatuck, Connecticut
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AD4U
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Posts: 2164




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« Reply #5 on: October 30, 2008, 08:12:01 AM »

"Can I prove that some contest and / or Top Gun DX stations run many times the legal limit?"

Yes I can, but the HAM I know of running the 3CX15000A7 amp is wary of "unknown" visitors for obvious reasons.

I have an Alpha 77SX if that counts, and I welcome all visitors.  Next time you are near my QTH give me a call and stop by.  I will show you 5KWDC into a dummy load.

73 Dick  AD4U
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W5RKL
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Posts: 891




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« Reply #6 on: October 30, 2008, 08:35:52 AM »

In most, not all, cases of splatter the transmitter's speech amplifier is being over driven by one or more of the following occurrences:

1. Microphone gain is turned up too high

2. Use of an amplified microphone that is not properly adjusted

3. Improperly adjusted speech processing

4. All of the above.

In many cases of splatter, simply reducing the Microphone gain to achieve a mid scale or less ALC meter reading will greatly reduce if not eliminate most splatter issues.

No, it is not true that a sideband transmitter is not operating properly unless the ALC meter reading is at maximum. The higher the ALC reading the higher the distortion in your output signal.

No, it is not true that a sideband transmitter is not operating properly unless full output is read on an average watt meter by increasing the MIC gain. A quick look at the ALC meter will clearly indicate a splattering signal.

No, it is not true that over driven speech amplifier's can be fixed by the transmitter's ALC. Transmitter ALC is not designed to nor will it reduce speech amplifier distortion. The only way to reduce and/or eliminate speech amplifier distortion is to lower the transceiver's MIC gain and/or the audio signal applied to the microphone socket.

An amplifier that is over driven causes that amplifier to no longer operate in a linear state which causes distortion in the amplifier's output which then leads to adjacent frequency interference.



73
Mike
W5RKL
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WB2WIK
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Posts: 20595




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« Reply #7 on: October 30, 2008, 10:09:44 AM »

>RE: High Power, High Splatter       Reply
by AD4U on October 30, 2008    Mail this to a friend!
 Next time you are near my QTH give me a call and stop by. I will show you 5KWDC into a dummy load.<

::Holy cow!  Your amplifier puts out DC?

;-)

WB2WIK/6
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WB2WIK
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Posts: 20595




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« Reply #8 on: October 30, 2008, 10:13:12 AM »

I'd want to know:

-Who is SCUBA?  (Callsign?)  Without this, I can't take the post seriously.

But also:

-The majority of cases I've personally seen where a signal appears to occupy such a wide spectrum are caused by receivers being overloaded or operated with a noise blanker turned on, when it should be turned OFF to provide best immunity.

Even some old and very experienced hams make this mistake.

I was called for "splattering up and down the 20 meter band" by a guy about 4 miles from me.  I said, "I really doubt that," and asked several other hams to see if they could detect anything like that: They could not.

So, I visited that ham the following day.  He had is NB turned on and several very strong signals on the band occupied a lot of apparent bandwidth.  I turned it off, and all that went away.

He was embarrassed.

Normally, I wouldn't even guess at anybody's occupied bandwidth unless he seemed wide when his signal was *weak.*

WB2WIK/6
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W3LK
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Posts: 5639




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« Reply #9 on: October 30, 2008, 10:40:06 AM »

<< -Who is SCUBA? (Callsign?) Without this, I can't take the post seriously. >>

SCUBA is a character that starts unsubstantiated threads like this but never stays around to answer questions. Another such thread is ...

http://www.eham.net/forums/Licensing/4128

73,

Lon - W3LK
Naugatuck, Connecticut
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AD4U
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Posts: 2164




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« Reply #10 on: October 30, 2008, 11:10:47 AM »

"Holy cow, your amplifier puts out DC"??

When I first got licensed in the 1960's, even the experts at the FCC told me I could only run a 1000 watts DC (input).  I resist change so guess I have been running DC for the past 40+++ years.  No wonder I can't get anybody to answer my CQ.

I will change my amp over to RF tonight and let you know how it works.

HI  Dick  AD4U
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K6AER
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Posts: 3514




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« Reply #11 on: October 30, 2008, 12:41:19 PM »

Just to add to what Steve said, last weekend was the CQ World Wide contest. I can guarantee just about everyone on twenty meters was running 1500 watts into a 4 or 5 element mono bander at 100 feet or more. The signal norm was 20-30 dB over S9. Plus the band condition were good.

These signal levels are brutal for hams who have high end equipment and a directional antenna that can reject signals from the back and side of the antenna. Even then your receiver will get overloaded.

If you have a dipole or a vertical and a receiver whose selectivity is under 90 dB at 5 KHz, you will get hammered. The average contest spacing of signals was under 2 KHz and three deep.

Contrary to popular belief most contesters do not want to splatter their signal. The increase bandwidth does nothing to add to the reliability of your signal. There is enough QRM on the band without generating your own background noise.

One of the greatest devices on receiver is the RF control. I bet 80% of the hams on HF have never used it and leave the receiver AGC to suffer through the RF overload problem
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W7ETA
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Posts: 2527




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« Reply #12 on: October 30, 2008, 01:41:10 PM »

"For a station to be “jamming” such a wide chunk of spectrum, is it likely he was using a broadcast power amplifier (far in excess of legal limit)? Or, is it likely he was using one of the CB Radio “competition-class” amps (ie. Fat Boy, Texas Star, etc.)? Are there hams out there that use extreme power (above 5kw). in defiance of the legal limit?"

Splatter does not equal Jamming.

Broadcast amplifiers are not designed to splatter.  

A few ham amps exceed legal limit out.

Amps like the Henry 8K a local Tucson ham runs, when loaded correctly, don't splatter.  He sure does over load my receiver tho when we compete in a DX pile up.

I heard a rumor, that some hams like to cheat in contests, run amps past legal limits, and load them to splatter so that other people in the contest are forced to be farther away from the transmit.

As others have said, simply because a sig is strong and wide in your receiver isn't proof they are splattering or running excess power.

Never seen or heard of a contest station using 11 meter amplifiers.  The few I've known either build their own for each band or tend to use amps that can be run at legal limit for 48 hours at a shot.

Bob

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N3OX
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« Reply #13 on: October 30, 2008, 07:52:15 PM »

"I resist change so guess I have been running DC for the past 40+++ years"  

Well, you'd have to.  If you changed the level now it would just be very, very low frequency AC.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N3OX
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Posts: 8847


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« Reply #14 on: October 30, 2008, 08:02:58 PM »

"
For a station to be “jamming” such a wide chunk of spectrum, is it likely he was using a broadcast power amplifier (far in excess of legal limit)?"

Ha!

See, here's the thing about amplifiers.  Seems a lot of hams think that a loud signal means a big amplifier.

But let's say ye olde splatterer was running 25,000W, certainly "far in excess of the legal limit"

Well that's just a hair over measly 12db over 1500W.  Awfully close to the difference between 1500W and 100W.

But when I tune across 20m, the Texans with awesome propagation and decent stations are 30dB over S9.  (as are, for that matter, WB2WIK and K6AER) Some other parts of the country are S2 or S3.  On my rig, that's around 60dB difference.

So I guess I should conclude the following:

The S2 or S3 stations are 5W QRPers.  

All the S9+30dB stations are running ... lessee here... what's 60dB over 5W?

Oh yeah,

Five MEGAWATTS.

People with bad splattery signals have badly adjusted setups, not necessarily excessive power.  And you know when I have a really big problem with all those awful, splattery contesters when I tune across the band with my FT-857D, cousin to your rig?  You know when they're just tearing me up?

When I forget to shut the noise blanker off.

I'm sure you had yours off in your careful tuning exercise, not trying to disparage your measurement technique, just sayin'.

73
Dan

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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