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Author Topic: Define "Tall Ship"  (Read 42951 times)
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W2NBC
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« Reply #75 on: October 27, 2012, 06:24:06 PM »

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?)
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« Reply #76 on: October 27, 2012, 07:21:32 PM »

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.  Grin

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.
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« Reply #77 on: October 27, 2012, 07:46:54 PM »

"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...

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.

Quote
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"??

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.

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.

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.
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« Reply #78 on: October 27, 2012, 07:51:07 PM »

2.8284271...=2*sqrt(2)

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« Reply #79 on: October 27, 2012, 08:04:39 PM »

"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 ?
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« Reply #80 on: October 27, 2012, 09:44:49 PM »

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.

I see, yes I remember now. So, the table is inverted more or less, lower readings occurring as impedance increases.
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« Reply #81 on: October 27, 2012, 10:17:00 PM »

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

What about the other one?

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

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« Reply #82 on: October 27, 2012, 10:38:46 PM »

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.  Grin

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.


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. 


yessir!

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.

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


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.

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?


* z-w-I_meter.png (21.44 KB, 537x601 - viewed 475 times.)

* z-w-V_meter.png (13.69 KB, 475x425 - viewed 494 times.)
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« Reply #83 on: October 27, 2012, 11:20:44 PM »

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"??


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

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« Reply #84 on: October 28, 2012, 09:08:20 AM »

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.
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« Reply #85 on: October 28, 2012, 02:33:15 PM »

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.

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"??

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

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.
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Don, K4KYV                                       AMI#5
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« Reply #86 on: October 28, 2012, 05:13:00 PM »

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.


* delay1.jpg (233.41 KB, 990x768 - viewed 534 times.)

* delay2.jpg (218.96 KB, 980x768 - viewed 543 times.)
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« Reply #87 on: October 29, 2012, 10:18:51 AM »

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

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!
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