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eHam Forums => Amplifiers => Topic started by: SCUBA on October 30, 2008, 04:02:47 AM



Title: High Power, High Splatter
Post by: SCUBA 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.


Title: High Power, High Splatter
Post by: KB9CRY 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!


Title: High Power, High Splatter
Post by: K0BG 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


Title: High Power, High Splatter
Post by: AD4U 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


Title: High Power, High Splatter
Post by: W3LK 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


Title: High Power, High Splatter
Post by: AD4U 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


Title: High Power, High Splatter
Post by: W5RKL 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


Title: High Power, High Splatter
Post by: WB2WIK 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


Title: High Power, High Splatter
Post by: WB2WIK 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


Title: High Power, High Splatter
Post by: W3LK 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


Title: High Power, High Splatter
Post by: AD4U 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


Title: High Power, High Splatter
Post by: K6AER 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


Title: High Power, High Splatter
Post by: W7ETA 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



Title: High Power, High Splatter
Post by: N3OX 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.


Title: High Power, High Splatter
Post by: N3OX 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



Title: High Power, High Splatter
Post by: W8ZNX on October 31, 2008, 01:53:16 AM
ad4u
you did say 5 kw dc into a dummy load

not 5 kw dc input to the final stage

high power has nothing to do with it

running 1 kw, 10 kw or 50 kw makes no matter

a 75 watt signal can be wide dirty
50 kw signal can be tight and clean

it all has to do with how it is run

along with
how well the receiver can handle strong signals
and does the op know how to use the receiver
lots of things can make a strong signal
seem to be wide when its not

was your noise blanker turned on
did you try turning back rf gain

oh by the way
the FT-897 does not have much of a receiver

and
yes SCUBA
do you have a call
all real ops
use their call letters

dit dit
mac


Title: High Power, High Splatter
Post by: K0WA on October 31, 2008, 07:02:30 AM
KB9CRY - Damn Contesters....

Before you go damning people...maybe you should think a little.  Today's HF rigs and the technology they are using has been driven by contesters demanding performance.

Contesting has kept Ham Radio alive over the past several decades. - IMHO

Contesters are good ops...and most of them are great guys and gals.  They are very good ops.  I am sure there some bad apples, but I have found very few in the 40 years I've been contesting.

So, don't damn the people who operate the contests.

Lee - K0WA


Title: High Power, High Splatter
Post by: KB9CRY on October 31, 2008, 07:47:59 AM
I haven't seen your call much on eHam Lee.  I know others know that I'm a contester also and love it.


Title: High Power, High Splatter
Post by: VR2AX on November 01, 2008, 08:40:06 AM
Assumptions are generally dangerous. And more often incorrect than correct

Illegality can take many forms. Some examples might be closer to the observer than the object of observation.  

So by whose standard is 1.5kw necessarily 'legal'? Some licences worldwide still limit power to 10 watts  or so, depending on class.

10 watts can splatter too.


Title: High Power, High Splatter
Post by: AA4PB on November 01, 2008, 11:50:13 AM
Any contester who is really splattering all over the band obviously doesn't know what he is doing. Splattering just wastes power. He'd make a lot more contacts with a clean signal.

On the other hand, it is quite possible that with a band full of strong signals the receiver just can't handle it and the stronger signals "appear" to be splattering. That's what they make RF gain controls and attenuators for (as well as the preamp OFF switch).


Title: High Power, High Splatter
Post by: SCUBA on November 08, 2008, 11:58:43 AM
Hi K0BG, thanks for replying and thanks for other replies as well.  The extent of my involvement was amazement in the amount of spectrum the offending station was encumbering.

For readers who noted that I use a login in lieu of a callsign, I attempted to explain in this message thread:
http://www.eham.net/forums/SiteTalk/1415?page=2

Thanks again, and 73,
Jack


Title: High Power, High Splatter
Post by: K1DA on November 12, 2008, 02:20:19 PM
   And it's always a "BROADCAST" transmitter that is the villain.  Darn few "Broadcast" transmitters have a bandswitch on the front which lets them go from 160 -10.  Most HF broadcast transmitters are single frequency devices.  I can think of a number of sources of "non-broadcast" high power shortwave transmitters
very few of which would occur to the new generation of crackerbox license holders, such as  ex-military, civilian point to point, airline (yes, the airlines once used hf ssb for many purposes) and maritime.  What I have  noticed is there is an inverse relationship between receiver quality and number of "splatter incidents" observed, not that a mal- adjusted transmitter system won't splatter.  SSB operators used to speak with some understanding of things like exciter output, power supply headroom, tube performance curves and such.  Now it's "I can get 1500 somethings out into a dummy load", so yes, there is some splatter on the bands.  
Just check your noise blanker before you jump on a guy.  


Title: High Power, High Splatter
Post by: W8JI on November 13, 2008, 02:06:42 AM
What a bunch of misinformation!!!!!

First, limiter and processors often REDUCE bandwidth by holding levels constant. They certainly do not have to increase bandwidth!!

You can have all the distortion you want in the speech amplfiers and microphones and it will not make the signal wide. The distortion has to be BEYOND the filter in the transmitter to create excessive bandwidth.

The filter is normally in the transmitter IF section, unless it is a DSP rig. In a DSP rig the only way to get distortion is AFTER or in the DSP system (it contains the "filter"), not from from the audio amps.

The reason 99% of stations have excessive bandwidth is they either don't know how to tune the amplifier, they use tetrode amps or cheap solid state 12 volt amps, or they have dicked up their radios.

For example, a well-known contester in this area was bringing me his FT1000MP's for service. EVERY radio he brought had the internal power limiting pot set to allow the radio to run 130 watts PEP or more. With a zero distortion audio chain, that radio would still have terrible IMD and splatter because the POWER level was set too high. I would turn the pots back to 100 watts and the next time I would see the radio it would be right back up to 130 watts or more.

I also would not go around handing out certificate of splatter with a radio noted for having a pretty poor receiver, and I would make sure my receiver noise blanker was OFF before giving any reports!!!

I agree there are a lot of trashy signals on 20 meters. I count about one out of four with grossly excessive bandwidth. But it is usually not anything but how they tune the amps or the type of amps they have. They can run any amount of processing they like BEFORE the filtering in the transmitter or power, and it will not cause bandwidth problems. The problem is caused by flat topping stages AFTER the filtering that sets the bandwidth.

If we can't get this right and understand what really causes the problems we will never solve the problem.

73 Tom


Title: High Power, High Splatter
Post by: N6AJR on November 17, 2008, 06:15:52 PM
I am also a causal contester, and armchair dxer.  I am a memeber of the northern california contest club.  it is a super bunch of some of the most  honorable folks I have met.  We like to contest. I find the thought of running an outlandish amount of power is silly.

In this weekends SweepStakes phone contest, I actuall turned my output down to less than 800 watts, why you ask??  

I am running a Alpha 87 a on the main rig, the orion, and  my friend was using about 800 watts on the FT 990 and al 1200 amp.   we could operate fine  with each other on different bands with full power but  then we kept getting those darn ESP calls returning all the time.

At limit with my 3 ele steppir, I put out a fair signal to the east coast, . Folks on a 100 watt radio and a dipole can hear me fine. but when they come back they can barely be heard out here.  

so if you cut the powe down by half,  a lot less ESP calls come in and I can run a little faster.  I may use 1500 watts on shooting DX, but in day to day and in a contest, I will usually run a lot less power than I could.  I don't know if this makes sense to you but it works for me.    all the knobs all the way to the right is not they way to keep you equipment from breaking or you fellow hams