The AM Forum

It's not well defined, this vernacular term "Tall Ship".
In some places it means a overly large draft of beverage.
I know what is being talked about, a station that is louder or as loud (in the S-meter) as any other, and heard by all, not only by one or two.. Is that even right?


There is more to it than equipment?

What does the operator have to do with it?

The signal as judged by others?

what is a minimum carrier level if AM?

Are there tall ships of other modes like RTTY and CW?

Height of antenna?

Type of antenna?

Distance heard while the signal is still very good?


What is really meant? Can this term even be defined in a meaningful way, suitable for dictionary use?

that's the most important answer

so be it.

I don't know what makes your station a tall ship, but I do know that if the Timtron has deemed your signal piss weak, then a tall ship you are not. That was even when I was pushing almost 200 watts out of the amp.

More of an euphemism which should not be taken seriously. Probably originally conceived based on power, weight and height of transmitter during the early days of the Heavy Metal rallies. Silliness to the extreme.

It's like being measured with a wobbly stick.

I think in years past a Tall Ship was when all the guys in NE were young, it was running power and having the capability to wipe a piss weaker off the map particularly if they were a slop bucket station. I think it was pretty much the same as the west coast California Kill O Watt stations we heard about here on the east coast. I almost became a Tall Ship when I ran my Westinghouse. I could crank it up to way past 1500 watts but I always ran the transmitter with the antenna one inch off the ground to stay legal.

I think for the most part the Tall Ships around here are solid state types with hollow state operators pretty much put out to pasture nowadays.

Here is a graphic representation of Mike, KO6NM's signal and mine:

It is all in the wearing, as it were.

I've been to the KO6NM QSA many times.

He runs a converted Collins 20V-3 into a simple wire dipole between two palm trees @ about 50'. 

RE-20 into his own DAP-610 for processing.

Simple works OK from Woodland Hills.

73DG

A "Tall Ship" simply has a signal stronger (bigger) than most and the audio to go with it.  Tall Ships are hard if not impossible to strap, they plow away the interference, and can be heard under almost all conditions.

There are Tall Ships in every region of the country.  We have a fair share of them here in New England, but certainly Robert W0VMC qualifies; some of the West Coast stations already mentioned can always be heard out here and with "real" signals, and when W0XV had his pair of 4-1000s on the air, I could hear him from Louisiana up here in Mass into the late mornings (that is amazing for the distance), and with a strong signal.  There are a number of others as well - Bill KD0HG comes to mind, K4HX, etc. etc. 

My memory isn't sufficient to enumerate all of them, but you know a Tall Ship when they're on.  Everyone is 20 over and all of a sudden someone comes on who is 40 over and with big audio from the same area.  The background noise goes quiet and you think your receiver just died.  Suddenly the room is filled with silky smooth sounds that caress your senses and you know at that moment why you're on AM  :D

I'd like to include into the "tall Ship" category systems with clean, equalized, and loud modulation where the positive peaks extend upward to 140%, and have negative peak baseline control to minimize splatter. One example is Timtron's Viking 1.5 that uses 811 modulators instead of 807's along with the QIX three diode circuit. Tim peaks at 150%, and it sounds very good with most receivers, even those that use simple diode detectors. His modulation penetrates above the noise.

Many times I hear "Tall Ships" based upon S-Meter reading, then I find myself twisting all the knobs on my receiver to enhance copy from either a low average modulation, or too much energy wasted below 200 hz resulting in muffled audio when trying to copy at a distance.

I contend that with "enhanced modulation" techniques, that a "Tall Ship" could include a 100 - 150 watt carrier output class transmitter.

Jim
WD5JKO

Is Timtron doing anything to the audio before it goes into the transmitter, or is he just feeding it directly from the mic?

About every qso from him that i hear mentions the merits of a D104 regardless of one actually being in use that day.  Very sensible and decries only those that use insufficient power for the conditions.  Also very tolerant of distance and ionospheric variables when in qso.

Bingo! You nailed it, Steve.

Bill

As far as I know the term was originally coined by K4KYV referenced here:

http://amfone.net/AMPX/102.htm

I personally think upward modulation over 110 or 115% is inadvisable.  Given a choice between high positive peaks and less carrier and lower peaks with more carrier I would recommend the latter for the following reasons:

In ham radio where we don't run 5 KW or more and most communication is via skywave the carrier is important for keeping the frequency quiet.

High average, not high peaks is what really matters.  compression is just as important as a peak limiter, although with some p.l.s you can drive them into gain reduction and achieve compression but it is not quite the same as a multi-band audio compressor.

In big groups where most hams are running average ham audio the guy who is wildly asymmetric can be a nuisance.  The frequency gets passed around everything FB and then Mr. 150 or 200% gets his turn and WOW He's LOUD, and you are knocking stuff out of the way to get to your rx before your speakers blow.

Lots of hams, especially OTs are listening with receivers using envelope detectors that fold at 90%.  Look at Jay W1VDs rx specs--many break into 10% or more distortion at 80% modulation.  Give these guys a break.

Run big carrier, high average, symmetric or slightly asymmetric peaks and to me that is being dialed in.

The ability to pull off a "BANG, lookie here, squashed just like a bug"  ;)  ;D

"No Money Mike" KO6NM does not run artificial asymmetrical modulation.

73DG

A tall ship is whatever you wish it to be.  And it will change as you change.

"Tall ship" is just another of about 100+ words and phrases with special meaning to Amers.  Yallowy, pissweak, microphonium, o'line, 24 pills, etc... it goes on and on.   This is a good thang.

These words and phrases are what makes AM a special nitche from other parts of the hobby. It gives AM character - just like bikers have their own jargon, surfers, skiers, boaters, base jumpers, pilots, drag racers, etc.

And, each hobby has their own "tall ships."    The biggest and baddest race cars are tall ships. The guy who can ride his board thru a 30' wave is a tall ship.  The biker with the long rake and big chrome is a tall ship.

A tall ship is whatever you wish it to be.  When I was a WN1 Johnny novice, a 200 watt General was a tall ship. But that standard has changed, as it always will, as we grow in the hobby.

T

; )

   Rob, all good points!  That said, with headroom well beyond 100% upward, it is possible without many exotic processing boxes to get the average up around 100%. The receiver distortion figures that Jay presents are informative for sure, but they are done with a continuous sine wave, not human speech. Also a good part of the distortion in these receivers is from the audio modulating the AGC bus. A great solution here is at the transmitting end to cut back on the audio power below say 250 hz; don't eliminate it, but maybe make it 6 db less (80 -250 hz) than at 1 Khz. Another-words a D104 into 2-3 meg-ohm often does that. Then non-periodic speech will have much less influence when it comes to AGC bus distortion.  Another issue with diode detectors is that if the load includes some capacitance, then the detector output hangs a bit coming down from a voice peak in a RC decay time constant. When you combine this receiver characteristic with an abrupt transmitter negative peak limiter like the 3 diode circuit, then the diode detector's R-C decay lag actually helps matters since the abrupt limit near the baseline does not come out of the detector making audio with that 'kink' in it. The result is the audio just might sound better!

So last night on 3885, I was listening to Don (KYV) and another station (a 'w1'). The other station was S9+10 into Texas, and I could only copy maybe every third word. He will remain nameless other than he was sitting in his new chair.  ;) His audio was really good at times, but a lot of lows really hampered things since the average level seemed quite low to me. A mere 3 db increase in the average along with a 6 db reduction in the lows would have been huge in terms of readability.

So what is better, transmitting at 3% THD with 30% copy versus transmitting at 10% THD with 90% copy?
 
Jim
WD5JKO

High Jack starts:
Funny, I never heard any of this with my old receivers but I am told it happens with solid state receivers but have not experienced it there either. HIGH JACK ends:

Yea, on 75 meters, running something like 500 watts into a set of phased dipoles at 100 feet would definitely make you a tall ship. On 10 meters, 200 watts (or even less) into a 3 element beam at 50 feet has almost the same potential, depending on conditions.

Hi Jim tnx for the information.  I did not know that about distortion vis a vis sine wave and human speech.

Yes I roll off the low frequencies but my motivation was to conserve power since they don't convey much information and cause the higher mod. levels (and power) to be in the mid-range where the audio is more penetrating. 

73

Rob

Exactly. One man's tag line is another man's punch line. Some see it as a goal to achieve, some see it as a term to elevate some perceived standing, others see it as pointless so long as you can be heard.

Having a big transmitter that is loud but seldom heard doesn't cut it. One only needs to listen to the monthly Collins AM net to understand this. And DX-60s, 32Vs, etc won't cover the distance with the needed strength reliably. A fully-modulated substantial carrier able to be heard with ease over a reasonable or expected distance, that is on the air regularly enough to become 'known' would be something to strive for. Beyond that - ??

W0XV is in Mississippi, although not far from Louisiana. K5IIA is loud here, and he is in Lousiana. I just bought a Globe King 500(drove to North Carolina to get it last Friday). I am trying to do a trade for a 140 foot BC tower to put up here on the ridge.
                                    Joe W4AAB

Apparently, W0XV (I can't remember his name right at the moment!) sold the pair of 4-1000s transmitter to ?? somebody ?? who may even put it on the air sometime!!  But, I can't say that I recall hearing that rig on the air since it's been sold, but maybe it will pop up this fall/winter.  That would be nice to hear...

You just "Touched a Nerve" as we say in the dental profession.  It's been months since my plate modulated 4-1000 rig has had it's filaments lit.  Kinda makes me feel guilty about it.

For me, a Tall Ship is more than a station with an outstanding signal.  It extends into operating his or her station in a manner that projects respectful behavior.   When one builds a station which sounds good and is typically strong but has bullying like tendencies, they get crossed off my list as a "Tall Ship" real fast.   Some examples may include, purposely operating to close to an existing QSO just because one typically gets on a particular frequency nearly every night.  I have heard this done to existing SSB QSO's as well as AM QSO's.  Designed in extreme TX bandwidth to keep other QSO very far from you center frequency.   Coming on the air just looking to pick a fight is another observed characteristic I have seen. Its like if they can't into some ass kicking bitch session they get bored.  

Joe, W3GMS      

Definition of TALL SHIP found online:

  a sailing vessel with at least two masts; especially : square-rigger

No mention of radio.


I'm in the same boat(not ship), Charlie. Though PJP & I made some progress Tuesday night tracking down a couple of stubborn gremlins on one of the big rigs here, it still needs work. Combined with a busy sked, summer band noise, and life changes, it hasn't made for much radio time. I don't feel guilty since I'm not sitting around posting online or simply checking into a net once a month instead of getting on the air. It's more a case of not being part of the solution to so little activity by getting on more.

Fact is, radio is a hobby for most of us. Few of us are or want to be defined by a hobby, and it's not a live-or-die situation. The essential truth is, activity attracts more activity, and cooler temps/lower static levels tend to bring folks back to the airwaves.

On the air or not, you still rate very high in my book for what you pulled off with that dumpster-salvaged/stripped 30K-4 in a matter of days vs months or years. In my opinion, that kind of thing matters much more to the hobby than hooking up any amount of processing gear or running a large signal. Not that this is a bad thing either.

 

name is jeff. w0xv in brookhaven, ms. might have spelled that wrong.

sold the rig to ron n4rt. he had it on a few time and that was about it. he should have retired or maybe very close to. so hopefully the rig will see some air time. i was able to go visit jeff when it was at his hosue and wow what a monster. jeff has a good antenna to. atleast 80 feet or so up in some pine trees fed with open wire line.

Tall ship?

Radio Luxembourg.

1.2 Megawatts into a 3-tower directional array. 234 KC on your radio dial.

I listen to that station a lot on this site: http://websdr.ewi.utwente.nl:8901/
That's a pic of the Junglinster transmitter site, which I understand is a backup. The main transmitter is now at Beidweiler. http://www.drmradio.co.uk/beidweiler.html
And they aren't running just 1.2 MW, the Beidweiler site is capable of 2 megawatts :o, but whether they run it full bore all the time is another story. Evidentally, they are beaming most of their power towards Paris. RTL is now using Junglinster as the transmitter site for their DRM service on 49 meters.

Aye matey, those be no Tall Ships, they be Pie-Rat Ships! Scourge of the Aether Seas!

I'd have to agree that a "Tall Ship" has to come from an overall situation that has earned respect, not emnity.

I wish I could draw a cartoon of it. Pie-eating rats in pirate garb in a shipboard radio room. haha be glad there's no artistic skill here! a little humor makes things better.

(http://rlv.zcache.com/pie_rat_photo_sculpture_photosculpture-p153900488726631974envy7_216.jpg)

Pete,

Cute pix and pumpkin pie just in time for the Harvest Season.

I got 4 pumpkins for $12 at Home Depot of all places yesterday.

I would LOVE to work there! As the static levels drop, I should be able to hear them at night at my place in NJ.. I often hear the European LW stations, although most of them broadcast in French, which is a language that I do not understand. Hmmm...would RL accept a résumé in English or German?

i wonder why QRO longwave broadcasting never happened in this part of the world, only it seems in Europe.

Phil, to work over there, employees are required to provide their own aluminum foil underwear.

Bill

If I remember right, It's because the power companies use the lower part of LF for control signals sent over the lines, and the upper parts are aero beacons. That's also why we don't have an amateur band down around 137 khz like they do over there. There is a part 15 band from 160 to 190 khz, 1 watt into something like a 40 or 50 foot long antenna.

Well!!
 It is about time I got into the discussion here. To me the description of a tall ship is relative to the other typical amateur radio stations that surround it. I look at a tall ship as an outstanding signal that is many DB above the norm . A signal that is strapping far and wide with BIG audio that cuts through the TEE-RASH ( alligator slop bucket term) like few others. A tall ship is a combination of big transmitter and antenna basically . The towers are the masts of the tall ship .  To be a tall ship on 75 meters one must have the capability of generating 1500 watts PEP double sideband power in order to be competitive with the sideband operators. Most people are of the illusion that 375 watts carrier modulated %100 is 1500 watts PEP.  In reality a 375 watt carrier modulated %100 is 187 1/2 watts PEP  DSB. It is from a voltage and phase relationship standpoint that make an AM signal but is not from an actual sideband power standpoint. A full legal limit AM signal is developed when running 3000 watts carrier modulated 100%. My 4-1000 transmitter delivered about 2 Kw carrier modulated %150 at full strap. This would be close to the 1500 watt PEP double sideband limit. The other part of the equation is the antenna. A dipole at 1/2 wave above ground would qualify, as well as directive wire array at a height that out plays a dipole at the same height.A vertical array such as a 4 square with proper ground system would qualify as well. There are many other antenna situations that qualify as well. With being a tall ship comes a greater responsibility in station operation,cleanliness of signal and regard to bandwidth when being nearby another QSO. In many cases it is not necessary to run full strap power for much of the time. Its all about signal to noise ratio in the end. If running 10 watts is putting in a signal that is many DB above the noise floor , then so be it. At that period of time YOU are the tall ship. De Tim WA1HnyLR

Anyone else see this in timmy's post above?

"Most people are of the illusion that 375 watts carrier modulated %100 is 1500 watts PEP.  In reality a 375 watt carrier modulated %100 is 187 1/2 watts PEP  DSB. It is from a voltage and phase relationship standpoint that make an AM signal but is not from an actual sideband power standpoint. A full legal limit AM signal is developed when running 3000 watts carrier modulated 100%."

Anyone else care to reply to the obvious error in this statement or shall I totally debunk it in my next post.  Sheesh!  The above statement is so wrong and will mislead others particulary when coming from an alleged "expert".

Chuck, K1KW

Right.  He should have written 6000 watts carrier.  then each side band would be 1.5KW and there would be equivalence with the slopbucket legal limit p.e.p. bs.

I know what Tim is getting at.  There was a bit of a math error  ;)

I like to look at the signal in two domains: Time and Frequency - then you see a rather different picture of what's happening.  The graphic below is a good illustration.  Both the time domain (what one sees on a standard oscilloscope) and frequency domain (what you see on a spectrum analyzer) are shown.

(http://www.classeradio.com/domains.jpg)

Arguably, it is better to examine signals such as these in the frequency domain because you get a more accurate picture of what's really going on, where the power is, and how much power there really is.  The method works equally well for SSB, AM and a host of other signal types.

This whole concept has been discussed quite a bit elsewhere in this forum so it's probably not worth reiterating  ;D

It's all about understanding average power and the Part 97 definition of PEP. You'll get the same answer in the time or frequency domains, namely that at 100% modulation PEP is 4x the carrier average power.

When I had an inspection (I passed with flying colors), The inspector told me they use HP or Bird meters and the hard and fast rule is 1500 pep no matter the mode. I agree with most that this is wrong for AM mode. 

He told me that if you have an RMS or AVG meter OR a scope,  Take the reading of the carrier and times by 2.828 to arrive at pep.  I knew this before he mentioned it and have used that for years. It works out perfectly every time.

Modulate the rig to 100%. take the carrier and times by 2.828 and get the pep.  Most commercial watt meters use this principal so they also read 2.828 times over.  Take your HP, Bird coax dynamics ect peak reading meter and try it.. When you hitt 100% mod, that meter will read 2.828 times higher period. 

I struggle with the carrier x 4 statement.  If I do that, I am over 100% mod...  Maybe me, the fcc and the inspector are wrong. I really do not know.. However, If my O scope says 100 percent mod, that Bird 43P is reading exactly 2.828 times over the carrier.  The meter I have is the meter they use. so I have to go by that.  I never run over power here and its important that I dont.   So a 500 watt carrier is fine when the pep meter is not reading over 1500.

Oh and I like it when a guy on a ranger or DX60 is the tall ship :)

Maybe for an "AVG" meter.... ( instead of a "peak reading meter")

But I don't think agree with a scope.

Most people seem to say that at 100% modulation, the voltage is double that of the resting carrier.

( "2 divisions at carrier... 4 divisions at 100% modulation")


If the voltage doubles, isn't the power output increased 4X ?

P=(Vrms x Vrms) / R    <  is that not correct?

I believe so..  But if you then compare that transmitter and that o scope to the meter that uncle charlie uses and carried into my home, It does not show 4x.  It shows 2.828.   

If a guy tries to tune his rig for 4 x on a pep meter he will over shoot.  I dont like the 375/1500 suggestion that they give us and people try to use.


C

That makes the limit 530 watts based on what you were told. The best way the FCC could've prevented the confusin would've been to just state a seperate AM limit in terms of carrier power. Isn't that how the Canadians do it?

I agree 100%....  Its confusing...   

C

That argument could date back prior to the 1920s when it was a subject of debate (http://amfone.net/Amforum/index.php?topic=26633.0) amongst engineers whether or not sidebands existed in physical reality, or just in the mathematics that describe the modulation process.  One argument was that an infinitely narrow carrier actually fluctuates in step with the applied modulation waveform, while the opposing argument was that the carrier remains steady and unchanging, and only appears to vary when the measuring instrument (scope, rf voltmeter or the Titanic's crystal set) is not selective enough to distinguish amongst the carrier and the adjacent USB and LSB signals as distinctly separate emissions.  By the late teens or early 1920's, when receivers with adequate selectivity were developed, it was demonstrated once and for all that sidebands in fact do exist in physical reality.  

The fee-cee's definition of p.e.p., the average power of a single rf cycle at the crest of a modulation peak suggests that they are still assuming the now-disproved notion that there is a single carrier wave that actually varies in step with the modulation waveform, as shown in Steve's time-domain diagram.  Physical reality is shown in Steve's frequency domain.  In fact, no component of the sideband products of a full carrier DSB signal ever approaches the amplitude of the steady carrier, even at modulation peaks. The time-domain diagram compared to the frequency domain is like comparing a 2-D photograph with a 3-D one; it shows only a shadow of physical reality.

OTOH, Tim's proposition ignores the carrier altogether, and accounts only for the sideband power.  A 3000 watt carrier does in fact display 1500 watts of additional  peak sideband power at full modulation, since the sideband power of a full carrier AM signal is shown to equal one half the carrier power at 100% modulation.  Let's now take the carrier into account with our power reading; if a 1000 watt carrier is modulated 100%, the p.e.p. of the two sidebands combined is 500 watts.  From the frequency domain point of view, you have a steady 1000 watt carrier and an additional DSB signal (USB + LSB), all of which can be clearly displayed on a spectrum analyser.  Therefore the total power at modulation peaks is 1000 watts of steady carrier plus 500 watts of peak sideband power = 1500 watts total power at modulation peaks.


But how do they connect up that HP or Bird meter if there is no 50-ohm coax link somewhere between the final rf stage and antenna?  In fact, I  recently got rid of my old inefficient coax link to the tower and now run OWL all the way from the PA tank circuit to the base of the tower. And if the OWL runs with a high SWR, according to the ARRL Handbook, the forward power minus  reflected power method of measurement is reasonably accurate only up to about a 5:1 SWR.  Many OWL tuned feeder systems run at 10:1 or higher at some  frequencies.

To digress for a moment since you brought up the subject of specific power meters, one of the reasons the fee cee decided on the p.e.p. standard (aside from John Johnston's longstanding anti-AM bias) for the output power rule instead of a more appropriate average (aka mean) power standard, is that there were no true average-reading wattmeters available on the consumer market.  A so-called average reading wattmeter such as the Bird 43 is in reality an average-reading rf voltmeter, with scale calibrated to indicate watts into a specifically defined resistive load.  The problem is that average power is NOT equal to average voltage X average current, but rms voltage X rms  current.   BTW, there is no such thing as "rms power" or "rms watts". Likewise, average voltage X average current of a complex waveform is a meaningless calculation.  Instruments like the Bird 43 are capable of reading average power only in the case of a steady unmodulated carrier or a non-amplitude modulated carrier such as an FM or FSK signal.  There were no average reading watt meters readily available at the time; the closest we could come at a  reasonable cost was the thermocouple rf ammeter, calculating average power derived from rms current using Ohm's law, just like the Bird 43 calculates power derived from RF voltage via Ohm's law. The main problem with the rf ammeter is that the movement is too sluggish to indicate the average power of a signal with high peak-to-average ratio like slopbucket.  That has changed; Bird now offers the APM-16 (http://www.chuckmartin.com/category/Bird-APM-16-Wattmeters-48), an accurate, true average-reading wattmeter, derived from its active-circuit capability to accurately measure the RMS voltage of a complex waveform.


Yup, simple. As I  recall, they have separate limits for full carrier modes and modes without carriers.  But the fee-cee claimed that would have made the rule overly complicated.  I guess Canadians are just plain smarter than United States-ese.


If it's that confusing for us here in this discussion, imagine how confusing it must be for the Hammy Hambones who occupy frequencies like 3878 and 3892.  ::)

A can of worms. Claiming a certain PEP level by looking at a carrier on the FCC's average reading meter depends on the waveform as well. I trust the scope better.

If they ever do try to measure the power on an open wire line, I'd like to see a video of that.

http://www.youtube.com/watch?v=jocRd-aajW0

You could also place an RF ammeter on each side of the line, then use P=I²R to get the power. Having one on either side would be a good way to tell if there was any imbalance in the feed line. The FCC would accept that for sure, since that's how AM broadcast power is measured at the tower (of course, they're only dealing with a coax line, not open wire).

Watt meters are a major cause of distortion at many stations.

Wow!  When and WHY did you get inspected?  That's really something.   Was there in interference complaint or something?

And I was wondering how they performed the inspection.  Did they just measure the carrier output with the transmitter running, or did they ask you to modulate?  And was that modulation with a tone generator, or just your voice?  Since all voices have different waveforms, an individual's voice test would be questionable. A few months ago someone on this board mentioned that their station had recently been inspected, and the inspector simply placed his Bird wattmeter in the coax line and had him turn on the carrier, and that carrier indicated less than 1500 watts, so the agent said he was OK.

About 20 years ago Roger, N4IBF(SK) was inspected due to the chronic complaints of a nearby nut-case who claimed Roger's signal was preventing him from hearing the baseball game on his portable AM radio.  Roger was running a BC-610 which had been modified with an SO-239 replacing the original output terminals.  The agent did connect his Bird wattmeter to measure his power as part of the inspection, but he kind of laughed about the whole thing,  leaving the impression that the guy was crazy and he was just doing his job, hoping to shut him up.

Both the time domain and the frequency domain show "the physical reality" (whatever that is). They both show the same information. Any claims to the contrary are false. Any claims of anything other and PEP equaling 4x the carrier power at 100% modulation are false. This is getting silly.

So are you saying that the FCC (the ones who made up these rules) are lying? Ok, sure the absolute peak power may be 4x the carrier, but read closely what Don posted:


Or, how the FCC words it under Part 97.3(b)(6):

So here I am modulating my transmitter. Let's make things simple. the final is running 2000 volts at 250ma and is 75% efficient. That gives me 375 watts of carrier at 500 watts input. When my voice causes the transmitter to become 100% modulated, the peak input is will be 2000 watts, which means the peak out is in fact 1500 watts. But, according to their own rules, they are only concerned with the average of the peak. Well, let's jump back to what the inspector told Clark: "2.828x carrier is peak." Where did they get the 2.828? Time for another quote from Don:


That 375 watts of carrier is the RMS value, not the true average. Take 375 times the square root of two, and that gives you the average power, which is about 530 watts. Now take that value times 2.828 and you get about 1500. The FCC got that 2.828 value by dividing 1500, which would be the peak output of the transmitter based on (Ip x2)(Ep x2) / (efficiency), by the average of the carrier, which for a transmitter running at 375 watts RMS volts times RMS amps, would be 530 watts average.

  I found the video to be quite instructive...

All this is moot, just hardware.
People are running 3cx3000's routinely, not to mention .. cx10 k's.
Our real problem is content, "software," being able to even have ham radio stations.
The real fear is that the FCC may kick us off the air entirely.  We'll all be pirates regardless of PEP.  It's apparently easy for the fed to shut down the Internet, ham radio, whatever.
Only the law abiding are affected, of course. Oh, and then we could be shut down by mode, starting with AM.  Easily Monitored digital modes the last to go or to stay very restricted.
We'll be in a real ghetto, that is only allowed to operate from sanctioned hobby clubs.

And speaking of PEP, ave power, etc. it's instructive to look at all the signals on a SDR. Hard to prove who's loud because of power and who's loud from propagation. Over time with signal analysis, location ID, etc., very easily obtained by, say, comparing CW Skimmer calls, a case can be built that John Ham deserves an inspection visit. Most "visits" of course are from complaints, human nature being what it is. 

As to mathematical vs, real waveform constructs, several of us could post or refer to the literature AM analysis. I most usually fall back, from a good mix of practical and math standpoints, on "Electronic Designers Handbook" Landee, Davis, and Albrecht, McGraw Hill.
Modulation is described as a series expansion of the superposition of two signals, and onward to the integration of side ands, etc.  Both time and frequency domain are illustrated as well as a nice vector representation. Suffice to say, "amplitude modulation of a carrier increases the total signal (carrier plus sidebands) power by the amount of power present in the sidebands signals."

Long time ago, I had a chat with one of the people in Johnston's Washington office.

He told me that one of the reasons for the change to the PEP standard (from 1 KW DC input) was that "..We aren't going to put our inspectors in danger by having them measure high voltages inside a transmitter...".

Bill

You will find that labor law, regardless of whether from a zero lift facility including nursing homes all the way to dear FCC techs, is safety biased in favor of the "laborer" not the customer or the proprieter.  There are good reasons but should be clearly thought through.

Safety issues are the most easily leveraged in any negotiations and always have unintended consequences.

Yes, Rick, but I have seen some old buzzard transmitters that I wouldn't ever want to stick my fingers into!

FCC inspectors have never had to go inside of AM broadcast transmitters to measure DC input power, they measure the antenna system impedance with a bridge and then the RF current into the antenna to calculate carrier watts.

They simply instituted a similar system for hams.


Bill

I am speaking of the how the instrument will read steve.

The instruments they use to measure pep power operate on a 2.828 times RMS to arrive at pep.  If you tune your rig for 4 x on such meters, you will be way off carrier to 100% mod period. 

I am not talking about any RF theory of how the carrier and side bands operate. I will leave that to the experts here..  If you own a pep meter and use it to tune your rig and go 4 x like people tell you, You are likely overmoding and splattering all over the band.

Please dont take my word for it I am simply paroting what the inspector told me. Try it yourself.  Simply calibrate your scope on a carrier, Increase modulation until the scope is just touching 100 % mod.   Read carrier and pep on the meter the FCC uses and carried INTO my home.  The reading will be exactly 2.828 times just as the inspector told me it was.

I have tried this on every transmitter I have and every single time. It shows a bit less then 3 times right at 100%. That is unless said transmitter cant reach the 3 times mark :(



C

What waveform is to be used for modulation in this test or does it really matter?

I've never seem any such thing. Why would you use RMS and how would you measure that on a scope (without doing some math)? If the FCC told you this, they are completely wrong.

It's simple. When you measure 100 percent on the scope, you are measuring a 2x voltage level compared to the unmodulated carrier. 2x the voltage is 4x the power. If your meter read differently, it's incorrect. Anything else is pure nonsense.

The issue is not whether or not the power peaks at 4 X the carrier power, but the erroneous definition in Part 97: "The average power supplied to the antenna transmission line by a transmitter during one RF cycle at the crest of the modulation envelope taken under normal operating conditions."

One rf cycle of what?  The carrier? The most prominent audio component of the modulating signal?  As it was demonstrated sometime circa WWI, there is no single frequency in an amplitude modulated signal in which the amplitude of "one rf cycle" can be observed.  It's a conglomeration of numerous rf cycles including the carrier wave and all the resolvable components of the sideband spectrum lying on each side of the carrier.  Try to monitor the envelope pattern of an AM signal with a scope, and then increase the sweep frequency until the rf sine wave of the unmodulated carrier is clearly displayed.  Once the trigger circuit locks the sweep oscillator to the carrier, the screen displays a perfect sine wave, but when modulation is applied, you don't see that sine wave varying up and down in amplitude in step with the modulating frequency; in fact you no longer see a perfect sine wave at all. The entire trace becomes fuzzy and poorly defined. This is observed on a bench scope good up to somewhere beyond 250 mHz even when monitoring the output of a 160m transmitter.

If their intent was the 4X standard, it should read something like "the total mean power delivered to the antenna during the crest of the modulation envelope".


No, they instituted a far different system for hams. The AM broadcast service goes by the real, effective power the transmitter puts out, i.e. the number of calories the rf energy would generate to measurably raise the temperature of a dummy load when the output of the transmitter is delivered to that load.  By "Fee Cee Magic", a 375 watt amplitude modulated carrier in the amateur service is supposed to be equal to approximately 750 real heat-producing watts of slopbucket. (Johnston once said this was "levelling the playing field".)  As noted previously, Canadians are smarter than United States-ese; their regulatory agency found it very simple and no problem at all to word the text of the Canadian power limit without according preferential treatment or discrimination to any mode:

Standards for the Operation of Radio Stations in the Amateur Radio Service                             RIC-2

(a)  where expressed as direct-current input power, 1,000 W to the anode or collector circuit of the
    transmitter stage that supplies radio frequency energy to the antenna; or

(b) where expressed as radio frequency output power measured across an impedance-matched load,

    (i) 2,250 W peak envelope power for transmitters that produce any type of single sideband
        emission, or

    (ii) 750 W carrier power for transmitters that produce any other type of emission.

Completely incorrect. You can easily observe one RF cycle with the proper oscilloscope. Such scopes did not exist in WW1 but they have since at least the 1960's. The variation in the amplitude across the envelope is easily seen using the time base delay. Get a better scope or learn how to use the one you have. Sheesh.

Quite accurate.

There is very little excuse to blame measurement hardships on the scope.

A good scope with a high intensity tube, like a Tek 7904, can allow the viewing of the very few tallest RF cycles by using the trigger level carefully.

A digital scope makes this easier but is not required.

A crappy scope will also do, even if it won't trigger properly by RF. It can be reasonably assumed that the tallest RF cycles occur always during the "crest", so in this case the room can be darkened and the scope free run to see the extent of the vertical deflection. It is enough to say that is a measurement very close to "one RF cycle at the crest of the modulation envelope taken under normal operating conditions." It is true because the only cycles of interest are the tallest ones and this crest is visible because it is not covered up by the lower amplitude ones.

If the scope is really, really crappy, drive the TX with a trapezoid or slightly clipped sine wave to give the RF more time at its crest, and increase the intensity there.

Therefore it is only necessary to calibrate the scope a simple way. most people who have a scope set the TX to 375W with a good meter, observe this on the scope, and then call it 1500W when the trace is grown to twice the height.

Please lets not get into differences between a test using a tone and voice use. I believe "normal operating conditions" refer to the setup and tuning of the transmitter as it is regularly used, more than to whether a sine or voice is applied to the modulator for a test.

What is more important is the accuracy with which the FCC can measure the actual power, aside from reactive loads and impedances not 50 Ohms. Nothing matters except that the FCC inspector is satisfied as to where 1500W is according to his instruments in the context of the amateur's system. How accurate is a Bird 43? Can the scale even be read to that accuracy? Is the FCC going to ding someone for being off by 10% when the very act of field measurement itself is full of compounded errors due to instrument tolerances? Will the discrepancy ever matter at the listener's end?

If the meter is inserted onto the RG-8 line between the TX and the tuner, even though all is perfectly matched, and the true impedance is not really 50 Ohms, the 'bird watts' reading can be off. It won't matter for TX performance with a quite short piece of cable on HF. It's no secret that transmitters with roller inductors as well as variable tuning and loading caps can match all sorts of loads that are not 50 Ohms. Tuners can also accept a rather wide range of input impedance, not just output. It is easy to set the impedance of the coaxial link between the TX and tuner to any Z that works best.

This is mostly nit picking over the last 5% of instrument accuracy. Is the mast of my ship 10% shorter or taller than that of the one across town? I think more matters as to how it's made and how it's sailed, as to whether it is seen as a 'tall ship'.

Yes, I'd focus on the FCC power limit law double talk:

After reading that I'd expect them to therefore show up with all sorts of exotic measuring equipment at a ham's station, but evidently, they show up with a Bird wattmeter, which isn't all that surprising because if you think about the rule and the measurement gear, it seems all rigged for basic continuous wave modes, AM being the only complex emission I can think of off hand (maybe spread spectrum is another one; not sure).

While no one has brought it up, I'd be cautious about challenging FCC on this--their solution to a serious petition might be to not change the rule or the way they measure power for AM on inspections, but to ban AM.    In some cases regulatory bodies see the "solution" as the easiest thing to do--make the problem go away.

 

A better petition might be just to ask them to put a footnote or something in the rules under power limits explaining the carrier to peak ratio for AM. But as to petitioning them to allow something, didn't the ARRL just petition them to allow single-slot TDMA and they allowed it? The whole reason behind that was that these guys were running TDMA repeater systems that they assumed were allowed under the way the rules were written, but the ARRL determined the rules were a little fuzzy, so petitioned the FCC to allow TDMA.  All we have to do is petition to clearly define the way PEP is determined and measured for AM. A less riskier move might be just to contact one of their engineers (if such a thing still exists within the FCC) and ask them personally.

I don't think that anyone here would pass a job interview given by Steve.

Patrick,

I don't agree with your Bird Watts column.  The Bird 43 works by looking at the line current in the center conductor and assumes 50 Ohms load.  The Bird Watts for your 10 Ohms situation would be 7500 Watts and for the 140 Ohms load it would be 536 Watts, and so on through that table column.

Math disCUSSions notwithstanding;

I'd like to know just what circumstances have brought an RI into a shack?

Real visits, not hypothetical if-thens.

In 40+ years of beating on broadcast gear I have been blessed with only two visits, and one was by invitation to resolve an interference complaint against the station.

73DG

Most "wattmeters" look at the RF line voltage and assume 50 ohms load.  I'm almost sure the Bird 43 works the same way, but I could be wrong; I have used them on occasions but don't own one.


What about the other one?


I have noticed in these discussions here and elsewhere it is nearly always assumed that every transmitter has a 50-ohm  coaxial output and that something like RG-8 is used to transfer power from the TX to the tuner, which then couples to the OWL, vertical, longwire or whatever.  But it is not carved in stone that every amateur station has to have a 50-ohm link anywhere between the final amplifying device in the transmitter and the radiating element in the antenna.  Maybe this is true with modern day plastic radios, but a few hams do still roll their own homebrew from scratch,  and may not opt to go the 50-ohm coax route.  Also, many of the popular WWII vintage military surplus rigs were never equipped with 50-ohm outputs.  The command transmitters are a perfect example of this, and so is the ART-13 and unmodified BC-610.  Look through the old 1930s Radio handbooks.  They even show antenna systems fed directly from taps right on the antenna tank coil, with no coupling link at all.  Probably one of the most efficient configurations of all (and less harmonic-prone than tapping onto the tank coil) is to use a push-pull amplifier with a balanced pi-network with a split-stator loading capacitor that works directly into balanced feeders with no link coupling coil or tuner at all (a configuration also described in the pre WWII Radio Handbooks).

The 1983 decision was  not the first time the FCC had proposed replacing input power with output power.  A few years earlier, ARRL had come out flatly against a similar proposal, with words in their formal  comments to the effect that "measuring output power in amateur stations was so unrealistic" that the  League could not support it.  The only change by the 1983 proceeding was the widespread availability of cheap  ready-made Hammy Hambone 50-ohm wattmeters on the commercial market, and the ubiquitous 50-ohm transceiver that had flooded the market in the intervening years. Little or nothing had changed in the actual technology. Even to-day, about the only real advancement in the relevant technology is the advent of the true average-power reading instrument like the Bird APM-16 or its equivalent.

I recall Bill Cross at one of the Dayton FCC forums made a remark about the new power rules.  He said if he had been the one who wrote the rules the way he would have wanted, he would have added the phrase at the end of the text on power standards "...as indicated on a Bird 43 wattmeter".

Interesting on all the SELF qualifications about making "math" work for RF ..

Kind of reminds me of
"she has a great personality"

"50 ohms" is the STANDARD NOW and ubiquitous just like many other U.S. and electronic standards. Electrical codes, 60Hz AC, XLR connectors, 600 ohm telephone standards, etc. Yes, many have changed over the years, trading efficiency for ease of use and manufacture because of standardization.. BUT, the use of the word "hammy hambone" (because of an inherited STANDARD) should then expand to Commercial Broadcasting .. What is their nominal Zo?? 50 OHMS, and has been for a LONG time.. What should we refer to that industry (that I was a part of) as.. " Commy Bonecasting"??

So, in comes the FCC for a spot check on YOUR station (and you all know who you are, (me too!)).. These are the same guys who understand the "hambone" 50 ohm standards..
 If your "PEP" as in "CW" (with no modulation applied)  is greater than 1500 watts......
well, pull out all the non "hammy hambone" old school theories and DANCE, REAL well..

The best thing is to self qualify YOUR math, and "turn up the wick".. (now who said THAT?)

Your saying that a cw carrier of 1500 watts can then be modulated above and beyond the 1500 watts?  I would like to dance to that.  ;D

For years I have been watching just about any ol' scope including a direct to deflection elements of a Navy OS-8C/U and seeing a sine wave modulate a carrier to twice above zero and twice below zero on modulation peaks. How do I know I've reached Peak?  The zero line just shows perfect crossing with just a bead here and there.  The tops are perfectly 'sine' rounded with no flat-topping. 

I've always assumed that that was 100% modulation.  I've noticed with assymetrical modulation, say with my voice, that I can get peaks pretty far above the x2 line but still have very few 'beads' on the zero line.

And for laughs guess what average voltage is for a sine or cos wave?
Zero.  Always crossing the zero line.  I think maybe a lot of us ought to go back a read just a little theory. How do we get from zero to RMS, peak and twice peak voltage and thence to power for starters.

True, for commercially manufactured equipment of all kinds throughout the industry.  But a one-of-a-kind home built amateur rig may be designed for any output impedance and coupling arrangement the builder desires - and in many cases the final outcome is accidental at best, and the output Z may even be unknown to the builder.  But if the rig still gets out, he probably doesn't even care. Now, THAT is real "Hammy Hambone" technology.


I would expect that everyone here understood the meaning of the term "hammy hambone".  I think Derb originated it, when he referred to the clutzy previous owner who had screwed up the Johnson Matchbox that was given to him, and that he was able to rebuild. You know, the same guys who drill a 1/4" hole in the front panel of a 75A-4 to accommodate some trivial modification that ends up not even working.  I wouldn't classify a Bird 43 or APM-16 as "Hammy Hambone" meters, but I would classify a cheap Heathkit, Mirage or MFJ in that category.  I have one of those Mirage meters, and even into a 1% tolerance 50 ohm non-reactive dummy load, on some ranges it indicated more power output than the rig ran DC input, and that's after having been calibrated not too long ago against a Bird 43.  I just ended up using the thing as a reflected power null indicator, since the SWR function seemed to work OK.

I'm not quite sure what Hammy Hambone has to do with commercial broadcast industry standards, commie or otherwise.


To start out, and eliminate a lot of the confusion, I would recommend that one read up on exactly what RMS means, and in exactly what ways it is not the same thing as "average".  And despite a lot of the "expertise" spouted out on various websites by audio buffs, there is NO SUCH THING as "RMS power" or "RMS watts".  The "average power" reading on a Bird 43 will be accurate for CW, FM and RTTY, but for SSB the reading will be substantially low, and for AM the needle indicates carrier power, and does not deflect up or down with modulation (assuming the transmitter has good modulation linearity).  The APM-16 will give an accurate reading of average power for any mode, and with AM, the needle kicks up on modulation.

2.8284271...=2*sqrt(2)

"The only change by the 1983 proceeding was the widespread availability of cheap ready-made Hammy Hambone 50-o :)hm wattmeters"

Yes Don.. I know " like many here" what "Hammy Hambone" SHOULD mean.. (and NOT about commercial wattmeters)...  Ham designed transmitters , coupling schemes, etc. can be designed any way you desire based on ANY design or theory you implement.. That's not the point.. now is it ?

I see, yes I remember now. So, the table is inverted more or less, lower readings occurring as impedance increases.

It was the infamous nazi-guy out of San Diego.  It was 1972, and he hit every station in Yuma.  His line was "I don't go to a station but what I find something wrong".

The station I was CE for was on extension meters without "authorization", so we took a ding and got it "authorized".

73DG

I missed that. But I remember the data in some tube manuals that gives an AM application of the tube running almost full CW rating, with the footnote that modulation must be essentially negative. There's also an article online about running a big carrier and modulating mostly negative. I'm not interesting in doing those things but they are interesting from a technical point of view.


yessir!


I agree with the assumption. I think a test with a symmetrical waveform can be made to prove it.


I recall postulating that before during the past similar power discussion but I was joking. It would rely on subtracting the negative part of the RF cycle from the positive part, leaving zero or very close to it.
http://amfone.net/Amforum/index.php?topic=20087.msg145182;topicseen#msg145182
The catch in the statement, which made it a joke, is that the positive and negative polarities of the cycle don't happen at the same time - one follows the other and so power is moved through the line during both halves. It intentionally confused the four-quadrant with the two-quadrant.

That is, one can not push 100W into the line during the positive half cycle and then withdraw it during the negative half cycle. The aether is heated during both half cycles. Humor's always good.

==
I fixed the chart. One for voltage reading meters and one for current reading meters. Why not?

Hmm, what about short wave broadcasters using balanced feed for curtains and rhombics that is not 50 ohms or unbalanced. 

This is a rather interesting piece of reading that I just found.
http://www.ab4oj.com/test/peptest.html

Based on Clark's experience with having an FCC inspection, I'd say they are using some kind of crest factor to determine PEP. Sounds like they are treating RF AC like a sine wave and using the crest factor for a sine wave, which is the square root of 2, to determine the peak of the carrier. They must be using the peak of the carrier as the average under 100% modulation. Then taking the PEP limit of 1500 and dividing it by 375 times square root of 2, which gives you 2.828. Since the rules state that PEP is the average power delivered to the antenna at the crest of an RF cycle, it sounds like PEP is determined using the crest factor.

The links in his page are worth saving/bookmarking.

The ones on "RMS power" verify what I stated previously: THERE IS NO SUCH THING AS RMS POWER OR RMS WATTS.  I was aware of the FTC proceeding decades ago, which I believe was justifiable action to protect the non-technical consumer (I hate that word) from the widespread deceptive advertising and claims that prevailed at the time, but didn't know the FTC actually promoted the term "RMS watts" in any manner other than exposing it as a fictional term (I suppose the FTC isn't a whole lot different from the FCC). The proper term is "mean power" or "average power", to distinguish between the various legitimate forms of power terminology including peak power. Just plain "watts" fails to make that distinction.

This was precisely how p.e.p. became a familiar amateur radio term.  Back in the 50's and 60's when the conversion from AM to SSB was being aggressively pushed by mainstream ham institutions and equipment manufacturers, linear amplifier vendors began using something like "2 KW (pep)" in their ads. Or "*2000 watts" with a small footnote at the bottom "  *peak envelope power ". This was p.e.p. input, on the assumption that the p.e.p. of a SSB signal would be roughly twice the average power; the real power rating alleged to be 1000 watts input.  The "p.e.p." rating inflated the apparent power capability of the amplifier, even those that used cheap (at the time) TV sweep tubes that would melt down to a puddle with a sustained whistle into the mike.  In the same manner, in the  same era, hi-fi manufacturers used bogus terms like "peak music power", whatever that was supposed to mean, to inflate the power ratings of their amplifiers several fold over their actual power capabilities. The FTC went after the hi-fi manufactures, but didn't bother the amateur radio manufacturers.

Legitimate uses of p.e.p. include describing the undistorted head-room capability of an amplifier or tuning network, before non-linearity, flat-topping or arc-over occurs. It is a useless standard for predicting the interference-producing capability of a radio signal. Signal strength is a function of average power, not the amplitude crest of occasional voice peaks. Limiting signal strength and interference potential is the purported reason for a power limit.


WSM feeds their famous Blaw-Knox tower with a 5-conductor open wire line.  I doubt if it runs anywhere near 50 ohms.  I recall from ads back in the days of tube type transmitters that the advertised output impedance specs of AM broadcast units in the 250-1000 watt range, was typically something like 50 to 300 or maybe 450 ohms; the one exception was the el cheapo Gates BC-1T and its siblings and successors, which were limited to 50-70 ohms. My very first job with a paycheck was CE at a 1000w daytimer that used a BC1-T.  The tower was somewhat less than 90°, and according to the licence that hung on the wall, the antenna base impedance was around 20 ohms. They had a tuning unit mounted on the wall above the transmitter. There was a big wide ground strap to the unit, and the ceramic feed-through terminal at the top of the transmitter (no coax receptacle) fed the tuner via a piece of copper tubing.  From the ATU out to the insulated base about 15' away ran a piece of 3/4" copper pipe, which was brazed to the tower base. There was no coax line anywhere between the transmitter and the tower.

Attached are two crappy scope photos. Both show the familiar AM modulation envelope on the top trace. The bottom trace is the carrier displayed using the time base delay function (B delay). The carrier is 1 MHz and the modulation is 90% with a 100 Hz sinewave. The first photo has a delay near the modulation peak (90% positive). The second is near the trough of the modulation (90% negative). No other controls were changed between the two shots except the delay.

Amazing Steve, who would've guessed?  now show us the "H" plane.  ;D

Might add the unmodulated carrier in next shot, showing your almost 100 percent carrier peak in relation to that.   I like to have three or so complete cycles in my presentations; shows a more sine wave form rather than your gently rounded hills.  urk, don't go there.

My more archaic scope shows the true picture though. Waves are compressed to the right, illustrating the notorious Scotty ring down decay effect of true time warping, heh, heh.

What, not a linear sweep you say?
Zounds!