The AM Forum

Ok, now that I can develop three to four hundred watts of carrier with no issues from my old RCA transmitter the question is what should my carrier power be? People have been telling me something about it having to be no greater than 325 watts of carrier because when you figure in both sidebands the total will be one kW. Sounds fishy to me, I am new to the AM 160 "Ham" world but spent around thirty years working in both radio and TV broadcasting and in the commercial world have seen were the old analog television stuff was rated in peak envelope but every AM and FM radio station I have ever dealt with is rated in carrier power. A 1 kW AM station is 1 kW CW power and I have always assumed 100 percent peak positive to be 2 kW although most broadcasters run above 100 % positive and 100 % negative is 0 kW. Is an armature station responsible for its peak envelope power or its carrier power? And last but not least if I limit my positive peaks to 90% my PEP at 0.5 kW will still be below 1.0 kW so where does 0.325 kW come from?  I have gone thru several field inspections for some of the 5.0 kW AM station I take care of and never have had any issues deterring power with the FCC, Its always plate E and I times efficiency but this whole ham thing is a mystery.
Ray Fantini

On a 100 percent modulated carrier, your PEP value will be 4 times carrier.

IE, you run 350 watts of carrier, you have 1400 watts PEP, modulated 100 percent in the pos and neg directions.

Welcome to the 'armature' world.. :)


--Shane
KD6VXI

1KW carrier with two 375 watt side bands = 100% modulation 1500 watts PEP

It's all there in Part 97, specifically Subpart A, 97.3(b)(6) and Subpart D, 97.313.

For 160M, to figure legal peak power using a shaded dipole, use:


watts= f(x) = f(-x)
f(x) = 2/PI  cos xy dy f(t) cos yt dt
if f(-x) = -f(x) then
f(x) = 2/PI  sin xy dy sin yt dt



If using BIRD watts with a class E rig then:

watts = g(x) = (2/PI)f(t) cos xt dt
xk+1 = (xk + y / (xk)n-1) / 2
g(x) = (2/PI)f(t) sin xt dt




If using CPI watts on 27 mhz then use:
 

Watts = f(-x) = f(x) then
(f(x)) ) = f(x)
If f(-x) = -f(x) then
(f(x)) ) = f



**** (BTW, the above formulas are bogus, just kidding... ;D   - don't ya hate it when someone answers a simple question with complex formulas?)



The real answer:  375 watts of AM carrier will equate to about 1500w pep for 100% modulation. (X4)

Many AMers like to have extra headroom available for asymmetrical audio and use 300 watts of AM carrier and 1500 w pep for ~120%+ modulation. (X5)

T

Peak reading wattmeter makes it easy. Just crank the power till it reads legal limit!

1000 watts carrier power + 500 watts peak sideband power on voice crests @ 100% modulation = 1500 watts.

Huh? Whaz this 1500 watts PEP stuff?

Through the history of ham radio, 1000 watts DC input x 90% class C efficiency = 900 carrier watts out.
4x900 watts = 3600 watts PEP into the antenna load w/ 100% modulation.

That too simple for some people. Eh, Don? Hook up an AC wattmeter and read the load.
1 KW - blowers and filaments.

What about us open-line feed guys?

;-)

Clark Kent = 375w carrier

Superman = 1KW carrier

Batman = 1500w carrier

The Thing = 5KW carrier

Spiderman = 10KW carrier

The Shadow = 50KW carrier


Become a superhero - take your pick.


T

You dont bring a knife to a gunfight so dont expect to bring a peanut whistle to a brawl.

Ive decided to grandfather myself in as Im using the same power I ran in the late 50's which was 1000W input to 250TH's ;D Probably a realistic 700-750W out back then.

Pretty soon I can double that with a single switch and go from DSB to SSB AM 8)....well almost anyway, just need bigger bottles for linear service.

man wa1hlr went into detail on this on 75m the other night. was very entertaining.

i asked a ssb station on 3.882 and he told me a.m. legal limit was 20w carrier with 50 percent modulation.

hihi 73

I'd bet the typical plate modulated amateur transmitter is lucky to get much more than 50% efficiency to the antenna, once you consider  losses in the tank circuit, feedline, antenna tuner, etc.  That 70-75% figure listed in the tube manuals is the ideal plate efficiency of the tube itself, based on the assumption  that the tube is perfectly good and that all the parameters are correct. Pretty much hypothetical in the real world.  90% reportedly is achievable with some of the class D and class E rigs, as well as class C tube rigs with the 3rd harmonic traps installed.  The latter would probably complicate QSYing too much for use in a ham rig, unless you operate like some of those slopbucket groups who never budge a kilocycle off "their" frequency.

My new rig is 72 percent as measured.its all sold state except for output and modulators. Good audio processing is the key to over come the power limitation. More then half the stations out there have low and weak audio. The dap processor really helped my station.

I did the calculation years ago, and came up with the 4X carrier power for PEP on a 100% plate modulated class C carrier.

But, I wonder about AM transmitters that only send out a carrier and one sideband. Doesn't the Collins KWS-1 do that? So what would the PEP vs carrier formula be for that mode?

Jim (Who used to run a pair of link coupled 813's modulated by a pair of 810's, but now only has 375 Watts output available)

A calibrated scope can be used if you know the impedance of the load and it is resistive. It will work for any signal, AM or carrier plus one sideband. The GRC-106 makes carrier + USB and this works fine (but that set is only 400W pep)

Observe peak to peak RF voltage at the crest of the modulation cycle at a convenient point after the transmitter.
1.) p-p volts / 2.828 = RMS volts
2.) RMS volts / load resistance = load current
3.) RMS volts * load current = watts.

If you have an old scope to dedicate to this, you can mark a line on the screen where 1500W is, assuming the load resistance is the same.

or just use this method which is not as accurate but comes close:

1.) peek twice at the bolts, roughly divide by twice the relative SQRT of the sum of the two right sides, then see how many of the bolts are a mess.
2.) divide the messy bolts by the futile resistance to find the borgs' currants.
3.) bolts that are a mess divided by the value of the currants is what.

Some very valuable info here...
The non-calibratede way I do it is:
SCOPE connect to I.F. out on Receiver
Time base set 2ms/div
Adjust for 2 divisions of dead carrier BIG thick GREEN trace

When you modulate you will see the pos and negs. The positves may go two or more divisons UP THats good

FRED

As Steve HUZ mentioned, it's all in the regs, however, it's subject to interesting interpretations. I have several crappy-amateur-consumer-grade "peak power meters" of varying quality and they all seem to agree on my power output within a plus or minus 500 watt range (one says 500, another says 1000, another says 1500 watts PEP). Which one is correct? Well, they all report output that is within the legal limit, so who cares? My observations are that it appears to fall under a "don't ask don't tell" policy. Run what you brung, and if someone asks you over the air how much power you are running, just say, "I'm running a substantial amount of power, enough to maintain contact with you."

Like Patrick, the only measurement I really trust is using my Tektronix scope and dummy load.  The scope calibration is very easy to check/verify (as is the dummy load impedance) and peak output level is clearly visible.  I haven't bothered yet but I really should write a simple program for my Tektronix 7854 scope/waveform analyzer and let it calculate and display power level.

Nothing beats a thermal RF current meter. Here's an easy way to build one:

1. Kill a deer.
2. Gut said deer. Save intestines for sausage casings, other organs for dinner.
3. At one end of deer, attach appropriate RF connector as the input.
4. At other end of deer, attach appropriate RF connector as the output.
5. Attach amplifier to deer input, antenna to deer output.
6. Hang deer.
7. Apply RF. Dependent on frequency, the RF will cause the deer to heat and expand in the RF path only, causing the deer to swing in one direction.

The amount of deer deflection will indicate the amount of heating caused by RF. Once calibrated, this instrument will be very accurate, based on the well-known physical law which states that the Angle of the Dangle is directly proportional to the Heat of the Meat.

I think Bill Orr did a writeup on this, or maybe it was Buddly.

I have a Mirage amateur radio grade wattmeter that was calibrated against a Bird 43.  The SWR function works HI HI FB OM, but the output power indication shows me running more power output than I am running DC input to the final.  I think maybe I have accidentally stumbled upon a solution to the world's energy crisis.  Now, in addition to international fame, I can forget about the money I was about to receive from the former bank CEO turned political refugee who needs my help getting his fortune out of Nigeria... chicken feed.

As for RF power measurement from my ham transmitter, I'll continue to depend on the trusty old thermocouple rf ammeter that has served me well for the past 45-plus years.

Wow, all these formulas make my head hurt! If I get a dead deer from the side of the road will that work just as well as a hunted one? Did read 97.313 and that’s about useless, all it says is thou shall not exceed 1.5 kW peak envelope, so does that mean I can run 1.2 kW of carrier and 10 % modulation? A word about how I am deterring power now. I have the transmitter connected to a Bird 1.5 kW load that has a -40 Db sample port that I use to feed a spectrum analyzer and also have a Bird 43 with a 1 kW slug in front of the load. Have been using the Bird to determine actual power and figuring efficiency backwards by the difference between input power to the PA and power to the load. Can always read the level on the analyzer in Dbm, add 40 to that and convert that back to watts but have not done that yet. Have one of those new fancy HP digital power meters that I can borrow from the TV station but that will only confuse things further. So for now just going to stay at the "Clark Kent" level of 375 watts of carrier but if it warrants it can always stuff the second tube back in and be Superman. How many "Supermen, Batmans and Things" are their out on the bands?
Ray Fantini KA3EKH

Ray,

Yes, on AM you CAN legally set your output carrier to 1KW and then run 1500w pep output - and some guys do. The problem is, yes, it makes a quiet frequency to blot out the static, but the audio is way down. Perhaps the "perceived" s/n ratio is the same as 375w at 1500w pep, I dunno.  

Another advantage of lower audio is that many of the older tube receiver detectors cannot handle high levels of modulation before they distort. So running 700w carrier at 1500 pep for local, quiet contacts works for some guys.

But in general, I would set the ratio to at least X4 most of the time. (and even X5 or X6 for times when cornditions are rough)

Good questions, OM. Keep axing away.


T

A clear demonstration that the FeeCee shot themselves in the food with that p.e.p. bullsh!t.  Even experienced knowledgeable hams either don't agree exactly on what the power limit is, or don't fully comprehend what the regulations say.  That being the case, what could one expect from Joe Bloe Hammy Hambone with the typical level of technical expertise we see from to-day's question-pool licensees?

With 1000 watts DC input, the rule was unambiguous, very simple to understand and simple to measure. Full compliance capability was realistically expected even from brand new holders of the old 5 wpm, 75-watt Novice Class.   How do you attach a Bird 43 to an open wire fed antenna from a parallel or series tuned circuit and no 50 or 75Ω coax link between the transmitter's tank circuit and the ATU?  What about an antenna fed directly off the output tank circuit with no feed line at all?

What is ambiguous about this?

Depends on the definition of "normal".

If the rule is so clear and unambiguous, why do you hear hams on this and other forums, as well as over the air, ask questions because they don't exactly understand it? I never ever heard anyone ask another ham to explain DC plate volts X DC plate current.

I dunno - I think it's pretty straight forward. 1500w pep output for all modes. Since most rigs today (probably 99.99% of them) use 50 ohms as an output, use a standard 50 ohm PEAK reading wattmeter into a 50 ohm dummyload. That should be within 15% accuracy. Plenty close.  Most any ham can do that.


For more accuracy and more sophisticated hams, use a 50 ohm dummyload and measure across it with a scope and use the formula.

As long as the antenna is 2:1 or less swr, the 50 ohm wattmeter will read with "reasonable" ham accuracy. Even if not, the difference between a 1000w pep or 2000w pep signal is negligible.


The argument about using open wire connected to a balanced tank circuit is so rare and out of the mainstream, it akin to keeping rules out there for spark gap or SBE rigs... ;D

That said, the real issue is not how accurately we anally measure 1500 watts pep. It's really about our intentions as shown by the size of the finals and infrastructure we run in reality.  For example for ssb, a pair of 3-500Z's says one thing. A pair of 3CX-3000A7's says another... ;)  
  

T

An honest question, how affordable is test equipment that will measure ONE RF CYCLE for 1500 watts PEP?

Craig,

Craig said:
Now there is an astute question!  :o

A scope across a 50 ohm load will show instantaneous RF voltage peaks. Put in a 100% modulating sine tone. Since the peaks are all the same amplitude, pick one, use the formula and there ya go... ;)

Quite affordable.

T

(6) PEP (peak envelope power). 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.
------------------
OK, I have to get in here and ask.
- First of all, I wonder about capturing one RF cycle at 30,000,000 cps which is exactly at the peak of a complex modulating frequency of 300-3,000 cps.
- Second, the reference says take the average power of that cycle. I thought we were reading PEP, not average.
- Third, if I do have a scope that can capture the (voltage?) event specified, do I measure from top to bottom of the envelope? If so, is the average zero? Or, do I measure from the top to the middle and take the RMS value? Or, is there some other way?
- Fourth, is there really a wattmeter out there that will perform this measurement? What is its accuracy? Can someone give me a model number? Is it FCC certified to make this particular measurement? I have been using a Bird 4314 lately, and if you put it on peak reading, it takes a while for the needle to settle down. Even then, I have to kind of eyeball the average of the needle wiggle. I doubt that it is capturing one cycle in order to make its reading.

Last, at least for this post: Don, I have one of those Mirage meters, but have never tried to read peak power. If I can get my 80m antenna back up this weekend, I will tune to the lowest SWR spot and read average and then peak. I will then report back on my results.

Jim

From the Bird website FAQ section (I don't know who asked  the question):

Question / Issue
 
I recently purchased a Bird 43P I was told I could not use this meter to read AM power...even though I have the peak kit in it. Is this true? Can you please elaborate?

Answer / Solution
 
The 43P was designed to measure Peak Envelope Power (PEP), so yes, it can measure AM power.  However, there a few caveats to this.

First of all, if you are using voice modulation, your reading will jump around a lot based on the variations of PEP seen by the instrument in this case.

Secondly, the 43P is calibrated at Bird using a signal having harmonics of no greater than -50dBc.  If your signal contains harmonics that are higher than -50dBc, the instrument will not read correctly.  The only good way to determine if the signal has some large harmonics would be to use a spectrum analyzer.  The important thing here is that the harmonics represent real power, and this must be accounted for in some way.  Either the harmonics are eliminated through the use of a filter, or the aggregate power including the harmonics should be measured.  While it s possible to measure power using a spectrum analyzer, the accuracy is usually not optimal (+/- 1dB or so), and it is not usually a straightfoward process to measure aggregate power.  If the desire is to make an accurate measurement, a broadband terminating power meter, especially one that measures heating power, is the best choice.  The next best choice would be a terminating square-law diode power meter, as detectors of this type behave much like terminating sensors.  Bird's 5011 sensor would be a good terminating sensor choice once equipped with the proper attenuator on the input.  Following these two types of sensors, next best would be a sqaure-law in-line power meter such as Bird's APM-16.  The main issue with this measurement would be that the directional coupler will not respond the same at the harmonic frequency as it does at the fundamental.

Thirdly, if you are using the 43P in CW mode (carrier wave mode), then the 43P would function just as a 43 and would not be able to read the AM power correctly at all.  The 43 will read quite erratically, based on the modulation depth and scale position.
 


 

What are you wondering about? If you have a scope with a bandwidth greater than 30 MHz, you can observe one cycle on the display.


We are. By definition it is the average power of one cycle at the peak of the modulation envelope, thus peak envelope power.


Remember, we're measuring average power, not voltage. Average power is E²_rms / R. R is 50 Ohms.


Ask yourself this question. If you are using a 4314 and it never reads more than 1500 watts PEP, do you think you are in danger of getting nailed by the FCC?

(6) PEP (peak envelope power). 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.
------------------

Are they talking about one rf cycle of carrier, one rf cycle of one frequency component of one of the sidebands with a complex modulating frequency, or what?  I was always told that an AM signal is NOT a single carrier frequency that varies up and down in amplitude according to the audio waveform of the modulation.  The carrier is a steady, unvarying sine wave of constant amplitude, and the apparent envelope waveform is the result of interactions between the carrier and the sidebands, which are bands of separate, discrete signals, independent from the carrier, that show up on a spectrum analyser as lying symmetrically on both sides of the carrier, each frequency component of which has a far lower amplitude than that of the carrier.

So are we now back to believing that the AM signal is a carrier that varies up and down in amplitude, in sync with the audio that modulates it?

I thought that heated controversy had been resolved long ago, back in the 1920's.

What controversy? Both or true and correct. They are just different ways of displaying the signal.

What you see on a scope is the time display of all the frequency components. You wouldn't see an envelope otherwise.

Another way to look at it is how much variation will there be when the period of the carrier is something like 0.1 uS and the period of the modulation is something like 0.3 mS?

Not picking an argument, are all transmitters operating into a pure 50 ohm load, and I can't remember if I've ever transmitted a 100% modulated sine wave. As a matter of face, I just speak into the mic.

My view point; going to be hard to pick out that one rf cycle with a voice modulating the carrier. Or am I still missing something?

Craig,

I axe myself this question...

I tune up my pair of 3-500Z's linear amp into a 50 ohm dummy load. Using a standard Bird 43 PEAK reading wattmeter I use a dead carrier and adjust the output for 1500 watts. This is about all the amp will put out before saturation.

Now I try my Belcher, a 12% duty cycle pulse on ssb- still 1500 w peak. I try CW - still 1500w peak on the Bird. I try a Yallo on ssb - still 1500 w pep. I then whistle on AM - 1500w pep on the meter.  An atomic Yallo on AM - I still see 1500w peak on the Bird meter.

Bottom line is no matter how the amplifier is driven or modulated, I see 1500w pep (PEAK) on the Bird or using the scope/dummyload method.

Remember that an AVERAGE reading wattmeter will not show all this. It will show 180 watts with the belcher, 375 watts on AM, etc. A FAST integrating PEAK reading wattmeter is what's needed to see 1500w on all the previous examples..

Why make this difficult? One cycle or  1 million RF cycles using any audio waveform will produce about the same peak output as long as the amplifer is loaded up to its max, in this case, about 1500w out.

A class C plate modulated rig should perform similarly with audio if driven to near saturation.  If the peak reading meter says more than 1500 w, then the cookie company will come a-knocking.... ;)  Seriously, 1500w is just a rough guideline.  If invited, I could come to anyone's shack with my peak Bird and 50 ohm dummyload ( must have a 50 ohm rig) and tell you very easily your peak power output with good accuracy. Good enuff to satisfy any regulation. Simple..


T

 ;D

Back up to my post that copied the response from the Bird tech support guy. If I read him right, it is going to be difficult to accurately measure an AM voice modulated signal. He says that the reading with voice modulation jumps around, and harmonics degrade the measurement. He goes on to say that a heating element provides the best measurement, but it probably is not capturing one RF cycle.

In my posts, I am trying to understand how to make the measurement as specified by the FCC regulations. It does not appear to me that the Bird 43 series does that, no matter what the meter reads.

My experience with the 4314 is in measuring a non conventional/conventional two way radio system, and I don't have the instrument available to me to take home and hook up to my AM TX. Wish I did.

Jim

Mr Vu:

Ok,, with the scope/dummy load thing. Have to guess; you are measuring voltage developed across the dummy load? Do you use a probe to keep the voltage developed from zapping the scope? Then its E=IR, or I=E/R, then using I with measured voltage on the scope to get power? Watts=E x I.

If that is the method, not to difficult. But few hams have a scope, let alone a probe. Still the rf pick-up used for my scopes to watch a wave form pattern will not give me that needed info for every day use.

Tnx,
Craig

I've compared my Bird peak readings on AM using speech audio to the readings taken from a scope across a 50 ohm dummy load and find them reasonably close.  

If you suspect the Bird readings, then I would rely on the scope readings across 50 ohms. Not much better than that and no FCC inspector would find fault. AFAIK, don't they themselves use  Bird peak capable reading meters or the equivalent in the field for proof measurments?


T

I liked the old DC/PA figure...it was figgerin' on the best shot up the pipe with all the umph you had. Nobody asked about erp etc....Geeze.....any figure you want to do into a bad feed/antenna might not even light a bulb. ~8^o...

EdZ KG6UTS....who still deals with bad feed and antennas

Hi Craig,

Sorry, I should have posted the power formula... duhh...

Use any standard 500 volt X10 scope probe and measure the peak to peak RF voltage across the 50 ohm dummy load. Say you read 275v p-p. Then square this and divide by the impedance, 50 ohms.  So, 275V (peak to peak) squared = 75,625 /50 = 1512.5 watts peak.


Try it and tell me how close it reads to your wattmeter when into a dummyload - I'd be curious. Use your voice.  You have a peak reading wattmeter to compare to?


T

More on using the scope at these two links.

http://www.ab4oj.com/test/peptest.html

http://www.ab4oj.com/test/pwrmeas.html

The fact that we are still debating and discussing this issue two dozen posts later proves my point.

Steve & Tom,

Good info, I'll have to play with it and see what numbers turn up. Tom, I don't have a peak reading meter. Doubt the Junkston "500" exceeds the limit and if it does, it ain't by much. Now the Desk KW, well I only run it on low power ;D. And that's bout 220 watts of carrier, not even close.

Have to agree with Don, it was so much easier to multiply the voltage times the current. If I remember the regs, those two meters were only required on transmitters which exceeded a certain power level. Was it 750 DC input?

Craig,

I think it was anything over 900 watts.

Yes, E x I is/was simpler. But PEP is the rule of the day. If we AMers want to claim we're technically proficient, we should understand PEP, even if we really never use it.   ;D

Whoops, never mind!

I think the regulation to use in these cases is:
"... enough power to maintain reliable communications!"

I requested the FCC provide a test method and a time constant on PEP when they came up with this crazy method. They never responded. In the Mil world a test method is provided.

And some people want to regulate bandwidth ::)

The guys in my band have been getting wider the last few years!

http://amfone.net/Amforum/index.php?topic=9216.0

BTW, looks like an excellent thread in 2006 here adressed the peak reading issue. Take a look especially at Stu's measurements. He concluded that the scope method is the most accurate and the Bird (using the aftermarket peak reading kit) read ~200 watts low on peaks when using 1400 watts pep. (About -17% low) Interesting.    

However the good news is the unit by N8LP is very accurate for peak power as agreed upon by both Stu and Frank/GFZ.

See:  
http://www.telepostinc.com/  


I use the scope/formula method for accuracy and monitor the peak Bird but may look into this N8LP unit.  


These power discussions may get lively, but in the end we all do more reading and thinking - that's a good thang.... ;)

T

A test method is provided. Measure the average power of one cycle of RF at the peak of the modulation envelope. Pretty simple, most certainly far more simple than the arcance mil-specs.

at what time constant?

That would make sense for measuring average power output, but would be meaningless for PEP. With voice modulation, the average reading meter would be treated much like a VU meter, with a prescribed time constant.  That's the way they prescribed measuring input power for years, by measuring plate current using a DC meter with prescribed time constant. Fluctuations in PEP reading are due to shortcomings in the measuring instruments, and are not inherent to the definition. It is average power (with does fluctuate with voice modulation) that determines how brightly the transmitter lights up a light-bulb dummy load, heats up a resistor, how loud a signal it puts on the air and how much interference it causes, in other words, the purpose of the power limit.  The power at the crest of occasional voice peaks is irrelevant to all the above, except when determining factors like the amount of linear head room available in the amplifier. All told, DC input is a more meaningful measurement of signal loudness than is PEP.  The most relevant method would be to use a true average-reading power meter, like the Bird APM-16 (http://birdtechnologies.thomasnet.com/item/wattmeters-and-line-sections/categories-wattmeters-and-line-sections-wattmeters/apm-16). A thermocouple rf ammeter is also a true rms-reading device and thus may be calibrated to read true average power, but is too sluggish for indicating voice peaks.

The Bird 43 does not indicate true average power except when applied to a steady unmodulated carrier or FM or FSK carrier.  It measures average rf voltage, with the scale calibrated in watts into a 50 (or 75Ω) load. With voice modulation such as SSB, it substantially underestimates average power.  Average power is based on rms voltage and current, not average. A true rms-reading meter is a square-law instrument, requiring active devices and is more complex than a simple diode rectifier feeding a DC movement, which reads average, not rms voltage, and this is the case of the Bird 43 and probably all the hammy hambone wattmeters on the market. This explains the higher cost of the APM-16.

This "average" business can be confusing.  Average power = rms voltage X rms current, not average voltage X average current.

The ITU Radio Regulations define the terms Peak Envelope Power, Mean Power and Carrier Power with regard to a radio transmitter. The terms are defined as:http://www.gira.pt/Docs/RR%20Vol1-e.pdf  (Scroll to page 21, pdf page 33)


Strictly speaking, the PEP bullsh!t hurt the slopbucketeers as much as it did AMers, assuming the leenyar is run cleanly without a lot of processing and not driven to flat-topping.

http://vk1od.net/measurement/SsbTxPower/MeasureSSBTxPower.htm

Any time constant long enough to measure the average power of one RF cycle.  T= 1/f

Measuring AVERAGE power as far as regs are concerned is a dinosaur. A standard Bird average reading meter is worthless here. So is a thermocouple. To play their game, we need to add on the peak reading modification board OR get a better, more accurate peak power meter OR use the scope and formula.  The FCC evidently doesn't give a rat's ass about average power anymore. It's a peak game.

As Huzman suggested, like it or not, peak power is the current rule.  It doesn't matter if it's my 12% duty cycle Belcher putting out 180 watts average (1500w pep) or it's a dead carrier or RTTY or CW at 1500w average. Both are seen as maximum power in the eyes of the regs.

That said, we could choose to be either Clark Kent, Superman, The Thing or Spiderman...  or find a way to change the regs back to the old E X I.


Here's my point... load a linear amplifier up to as high as you can with a dead carrier. Push it to the limit right to the point of saturation. Let's say it's 1500 w output dead carrier. Then put in some ssb or AM voice programming. Assuming the audio is at a certain threshold level, there will be SOME voice peaks that hit 1500 w out at their peaks. Add some audio processing to bring the average up to a higher average  level and the voice peaks are STILL never going to exceed 1500 watts out.  So whats the difference between loading an amp up dead carrier and then choosing what density of audio to run? The highest power peaks are the same in the eyes of the regs.


I realize average power is what lights a bulb and all that, but the regs don't use that guideline anymore. Personally, I'd rather see average power used for everything too - it means more.  But if one wants to monitor their compliance, then a peak reading device is required.  Accuracy in the real whirl will vary as we have already discussed.

T

When they passed the new regs, they deleted the requirement for having instruments capable of accurately measuring transmitter output power, an acknowledgement that the procedure would be too difficult for the expected technical expertise of a typical amateur licensee. In the R&O, they stated that amateurs are able "to use means other than accurate measurement to determine their transmitter power".  Elsewhere in the text they stated something to the effect that amateurs would no longer be required to measure power; they would just be required to comply. Go figure.

Under the old rules, accurate measuring instruments were required for DC inputs exceeding 900 watts.  That had little more meaning than the above, since one could always claim to have been running 899 watts, while their "inaccurate" measuring instruments failed to indicate that they were really running 3 kw.

As for time constant for measurements of average voice signal levels, by definition a VU meter is supposed to take "300ms to stabilise, and should show only minor overshoot". IIRC, the FCC prescribed a 250ms time constant for the plate current meter in a slopbucket linear. There is no such thing as mechanical meter movement with a time constant short enough to measure the average power of one RF cycle,  T= 1/f. By the nature of the laws of physics, it necessarily integrates average power taken over the time required for several audio cycles of modulation.

Sure, if you use the meter to directly make the measurement. Remember, a meter is just an indicating device, not a measuring device. A powered, peak reading circuit can make the measurement and drive the meter. It's been done for decades.

My point exactly Don. Even 1/F is too fast as Mr. Nyquil would tell you

I really can't agree with that statement, even with the sly smilie.

The person that previously owned JAWS II the 3CX3000A7 amp was using SSB and the story is that it was built and then used to "prove a point". I have no more info on what point. The only point really available for examination was that someone did excellent work.

How many SSB 3CX3000's does it take to equal an AM BC rig? It appears the question of tybe types is a sacred cow that is best left undefiled. Otherwise before we know it, people will be arrested for felony posession of shoestrings.

Nixon's the one.



klc

"I really can't agree with that statement, even with the sly smilie. "


If you knew me better you'd find you're preaching to the choir... ;D


T

I think the FCC gave up trying to measure PEP. There is nothing out there that is affordable for a Ham to own that meaures PEP. That's the kicker for this PEP mess. Adjust your TX for whatever power makes you smile and schwang the monkey. Remember that higher power will start stresing antenna parts and tuners and PL259's,,,,,,,,this is getting closer to 2.5kw outpoot. heeee heeee Has anyone read any FCC arrests for excessive PEP?,,,,,,,,,
FRED

Nope! I haven't seen one for the amateur service in recent years. Most enforcement actions regarding power levels in the last year seem to be for 11 meter infractions, and run something like this:

  "It has come to the attention of the Federal Communications Commission that
   at various times in the last several months you have operated overpowered
   transmitting equipment on 11 meters that has interfered with communications in
   the 10 meter band, for which a license is required."

or...

  "The general rule is that consumer electronics are protected only by
   manufacturer design from receiving any unwanted radio signals
   and home electronics have no priority over any radio or broadcast
   service. Nevertheless, if a CB operator is operating at excessive power
   levels, it is the responsibility of the CB operator to correct the
   problem."

It's always interesting to browse the "Warning Letters" section.

http://www.fcc.gov/eb/AmateurActions/Welcome.html (http://www.fcc.gov/eb/AmateurActions/Welcome.html)

Incidentally, I do love the wording used by the FCC when they respond to consumer complaints about interference to their toasters and other such important appliances:

  "...consumer electronics are protected only by manufacturer
   design from receiving any unwanted radio signals and home
   electronics have no priority over any radio or broadcast
   service."

I sure wish that kind of language was thrown around 30 years ago when I had a nasty complaint about TVI (neighbor 500 feet away with a Radio Shack mast mount preamp) and one for telephone RFI (neighbor 1000 feet away with a horrific self-installed phone-intercom system). It seems like we were pretty much on our own back then to sort that crap out.

Funny thing ... the CB regs talk about AM carrier output at 4W.

And besides, isn't there something about meter inaccuracies from where the meter is located on a length of coax? IMHO Feces is just giving us a guideline and really do not intend the compliance be one of accurate measurement. They are implying just don't run 5kW when 1.5kW will do. The FCC just doesn't care until they get complaints, and even then it's only complaints from other services that are important to them at a given moment in time.

325W carrier 100% mod is fine for most. Is it 1500W PEP ... yup. But who cares. Apparently nobody. Take it from me. Worry about your antenna and radiated power. I've run 450W carrier 100% mod and I haven't strapped anybody.  "50W Fred" straps me! ;D

John, W2WDX

I recall at a hamfest FCC forum shortly after the power output rule went into effect, someone asked that very same question. The moderator  responded something to the effect that for the purposes of power output measurement,  the FeeCee inspector would place the meter at the "output terminals" of the transmitter.

Now, that might be clearly defined and unambiguous for the typical appliance operator working his ricebox or leenyar directly into the coax feedline of his G5RV.  But what if he is using a tuner; is the "output terminal" defined as the SO-239 on the transmitter or amplifier, the output terminals of a transmatch, or if he is using open wire feeders, the ceramic terminals on the tuner where the "ladder line" is attached?

In the case of homebrew transmitters, it could be a whole different story. It is the operator who designed and built the transmitter who defines exactly what constitutes the "output terminals".  If one decides to construct a rig so that part of the output tank circuitry is located remotely from the rest of the transmitter and coupled via a link of coax, twisted pair or parallel-wire transmission line, then the "output terminals" could be the ones located on the wall of the "dawg house", feeding the transmission line that leads directly to the antenna.

This is particularly true with solid state rigs that have untuned outputs. With hollow-state transmitters, the tank circuit is an impedance matching network, usually a link-coupled, PI or PI-L network, contained in the cabinet as an integral part of the transmitter. With to-day's solid state designs, the tank circuit is no longer included in the transmitter cabinet but is sold as a separate unit and called a "transmatch", which the owner must pay extra bux for. The rig will work without the transmatch if and only if the load is close to purely resistive 50 ohms.  As soon as anything more than a slight mismatch occurs as indicated by a SWR that is a little higher than 1:1, the transmatch is needed to allow the rig to deliver full power into the load.  In other words, a tank circuit is still required after all, but it is now sold as an "extra" or "accessory".

That brings up a good point. The transmitter ends at the point where the antenna is connected. It is reasonable to push 1800W peaks into a tuner when the match is so difficult that only 1500 comes out. There are reasons why antenna tuners are large enough to dissipate heat. Consider those 'wideband' folded dipoles with the 600 Ohms termination in the center. The power converted to heat in the termination should be subtracted from the TX output because it is not being radiated. Nonetheless Uncle Charlie is going spot the largest cabinet in the room and ask where the coax connector is. That is just how things are. Those running QRO could make use of a T pad before the PA for special occasions.

From what I understand, a high profile generated, sneak QRO visit from Charlie might work something like this...

They park down the street and take a field strength measurement while you're on the air. They stop by (with another car) and axe you to load up the rig. It doesn't matter what power you load up as long as they can measure it with their wattmeter and take an identical field strength reading down the street.

Let's say you load up to a measured 1500w out for them. If the previous field strength reading was 3db louder, you're busted... ;D


Assuming you were previously using a horizontal antenna, the way around this would be to switch on a vertical antenna the second time, giving a stronger local groundwave signal - providing a much stronger field strength reading. This would make your 2nd test pass easily. Something akin to faking a urine drug test, I suppose.

I've never heard of this type of visit actually being done in practice, but seems like a viable method if their motivation was high due to high profile jamming complaints, etc..

T

Then you show him there is no coax connector.  Just a ceramic feed-through with a bare wire attached.  ;D

Roger, N4IBF (SK) was paid a visit after a guy down the road had persistently complained about RFI to his AM broadcast radio, keeping him from listening to the baseball game. The inspector measured the power output from Roger's BC-610.  The only measuring instrument he had with him was a Bird 43.

Don said:

See, all they care about is 'dem Bird Watts'.  ;)

 "  See, all they care about is 'dem Bird Watts'.  ;)  "


Thats cause the Bird watts are the best watts there is...  havent you heard that the Bird is the word?



klc


.--. .- .--. .-   --- --- --  .-  -- --- .--   -- --- .--

BAH-BAH-BAH-BAH-BAH-BAH-BAH-
BAH-BAH Omma Maw Maw Bah Bah Omma Maw Maw


http://www.youtube.com/watch?v=9QypTBjlFCM

Poppa eeew maux maux

hey man, don't be tryin to mau mau me wid dat jive..

Good ol' Uncle Charlie! I hope to be half as crabby some day. He was a man to be admired for his principles!

LOL!!!  ;D

Old age does that Buddly

FRED

seems to be a lot of that going around!!  ;D  ;D  ;D