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Where Did All The AM Transmitters Go?

Rob Martin's sugestion to write a book might not be a bad idea. It is obviously very important to Mr. Fry to be regarded as a technical expert, and he wants to be the final authority on Part 15. A book will enhance his status much more than just some posts on a radio forum. In researching his book, he might learn some new things about his subject he doesn't know already, making him a better-qualified teacher.
 
Ermi Roos said:
Rob Martin's sugestion to write a book might not be a bad idea. It is obviously very important to Mr. Fry to be regarded as a technical expert, and he wants to be the final authority on Part 15. A book will enhance his status much more than just some posts on a radio forum. In researching his book, he might learn some new things about his subject he doesn't know already, making him a better-qualified teacher.

He's a legend in his own mind. An egomaniac if you will. It would be the blind leading the blind. How can Rich Fry, by his own admission, having NO PRACTICAL hands on experience with a Part 15 AM transmitter claim to be an expert on the subject?
 
William C. Walker said:
How can Rich Fry, by his own admission, having NO PRACTICAL hands on experience with a Part 15 AM transmitter claim to be an expert on the subject?

Just to note that my hands-on experience includes the installation, repair and maintenance of AM and FM transmitters, antennas and r-f systems over a professional career of 45+ years in the electronics industry, and that I am the co-author of the FM Transmitters section of the NAB Engineering Handbook, 8th edition, and that by written examination I was granted an FCC First Class Radiotelephone Operator License (1957), and that I am a lifetime holder of a Certified Professional Broadcast Engineer's certificate from the Society of Broadcast Engineers.

Most reasonable people would conclude that such a background would enable a very good understanding of a 100 milliwatt Part 15 AM installation.
 
OK, William, Bill if I may be famialiar. Here's how.

Mr Fry has transmitters right there "in print" in his brain, and knows scale matters not, but is mesaurable and predictable.

Once again I'm going to intercede nicely to describe where we ALL stand, and what "we're" looking at in a part 15 AM MW
animal. Note that I've been whapped by the FCC in 1991 for an N.A.L. at 100 watts at 7.415 +/- the calculated FM component.
I'm trying to be REAL sure here that my MW AM pt 15 is compliant. I have been making RF of devices my own design for
almost thirty years now, and had the same sort of formal RF training I'm sure Rich had.
The 100w was designed to be exactly that, my current part 15 AM rig was built to make no actual power at all;
it was designed to "drive" 4 push-pull parallel 807s with 27 volts cathode bias for class AB sub 1 ( no grid current) for about
140 watts. That last stage never got built, but the modulator can be coupled...
That modulator is my part 15. It calculated out to about .085 watts (that's 85 mw), and it runs 150% modulation with
no distortion. It sounds insanely huge within the two-three blocks, because of the processing.
Nothing I have been able to do, even with years of experimenting, has been able to appeciibly extend the range I can
achieve "here"...and I could resonate a chain link fence if I felt like it...

Results: in dense urban housing/apartments: 3-4 good blocks coverage.



There is nothing magical about part 15 AM.
It is simply a power level "as defined" into a radiating element "as defined".

As an engineer, and fellow part 15 operator, let me assure you there is no real argument to find here.

Results vary. Mine are poor because of dense urban signal absorbtion/reradiation/noise but helped by fine local
conductvity in general and the very nearby river.....

There is no part of analog radio behavior that is not completely scale-able and that does not work exactly the same
regardless of scale.

I will restate that tourtous statement with too many negators.

All MW AM analog behavior is the same regardless of scale.

Power is power. Loss is loss. Ground IS zero volts. ( Impedances and efficiency notwithstanding) ...
Etc Etc. Your milage may vary.


I am sure Mr Fry's presented information is authoriatative and worthy reference.

So many things influence exactly how well a signal gets out, that why it's worth working to
eliminate losses and optimize modulation to 150%.


In the real world, what this means for my station is that I'm all gone at a mile.
At that point depending on which way you're traveling, you'll hear one of four signals.
I think this is in keeping of the spirit of of pt 15 "for MY area", and its character, density etc.
A permitted signal, intentional ( part 15 AM ) or or even an unintentional ( lamp dimmer, bad xfrmer),
should die off within a pretty well defined distance or it is a VERY big problem.

There is a lot of information available. All of it should be considered and incorporated as useful.
A really careful read of pt 15 regulations would reveal a loophole or two....

Of course there's nothing stopping anyone from increasing the efficiency of their ground common point,
throwing dozens of long radials out haphazardy on the ground, bonding to water, electrical, and sinking a few ground
rods about the property.

I honestly think what is needed is maybe a type acceptance on twisted-pair feedline
for AM mw part 15. It theoretically does not radiate, I think it's 300 ohm impedance and would balun just fine,
and could eliminate the "plus feedline" spec.


But jeez, Bill, you seem to be getting mad about numbers and taking it out on the messenger.
 
Tom. Many of us including some broadcast engineers that post on this forum and others take issue with someone that claims to be an expert in this area of broadcasting when he has no experience in it whatsoever. This is not unlike many of the politicians we now have in DC. No hands on experience in public service at the local level but they claim to be well qualified at running the country.

I have personal friends that are broadcast engineers and others with a engineering background in other areas of communication. When I need and expert opinion or explanation about something I don't understand I go to them. If Mr. Fry ever decides to start up a Part 15 AM and uses a Type Certified transmitter like a Talking House, Rangemaster or ISS Infomax etc. then I will have more respect for his theories and opinions.

I do not believe any one man, no matter how educated he may be, has all the answers when it comes to technical matters concerning radio or TV. Too many variables have to be taken into account as to why or why not a signal can or cannot propagate a certain distance or act a certain way. And there is always the case to be made that any one man has not uncovered every secret that exists in the area of signal propagation.

Time and time again, I see people on a TV forum exclaim how they cannot believe why they are getting a perfect signal around the clock of a TV channel or several that according to the laws of physics they should not be able to watch except when skip is present. I have a friend that has nearly as much broadcast engineering experience as Mr. Fry that has experienced this first hand at his home. He gets two TV stations perfectly all the time OTA in HDTV that presumably are so weak with a negative NM and 2 edge path that under normal circumstances one would believe they should not be viewable. That being the case it is evident that man still has a long way to go at fully understanding the finer technical points of broadcasting.

Please excuse me for not jumping on the bandwagon and worshipping someone that claims to be the first and foremost expert in the field of Part 15 AM broadcasting.
 
Respect is not the same as worship.

I believe there is only agreement, our measures and experiences differ. That is proper.
It is well known that micro signals can really get out when given a chance.

I don't think Rich ever suggested he had all the answers.

He is plotting data on graphs for anyone to relate to their own situation understanding that each has untold variables.
Don't get agitated but try to incorporate the useful info.
 
William C. Walker said:
If Mr. Fry ever decides to start up a Part 15 AM and uses a Type Certified transmitter like a Talking House, Rangemaster or ISS Infomax etc. then I will have more respect for his theories and opinions.

Note that the same, proven physical laws (which are neither theories nor opinions) apply to the installations of all r-f transmission systems regardless of their radiated power, their legal status with the FCC, and/or the understandings and expectations of their operators and promoters.

Whether or not Mr Walker, I, or anyone else ever buys or sells, installs or promotes, or operates an unlicensed transmitter that is FCC-certified under Part 15 is meaningless if the final installation of such is functionally non-compliant with Part 15 as shown by physical law.

Recently the FCC has issued citations to some users of AM transmitters expected to be Part 15 compliant due to their FCC certification, when due to their installation conditions that wasn't the case.

Just a reality check...
 
^^^Yeah. And another reality check. Just because someone is well versed in the mechanics of a Cadillac does not mean he knows how to work on a Subaru.

And the "proven" laws of physics are subject to the misinterpretation of man. Man has not unlocked all of the secrets of the laws of physics as they apply to signal propagation. My post about my engineering friend that is able to pick up perfect signals on his HDTV OTA that by all accounts SHOULD NOT be receivable according to the laws of physics is proof of that. And a decade ago WVRM AM 1620 in Montclair, NJ somehow skipped at night and was heard by at least one DXer several hundred miles distant. WVRM AM 1620 aka Village Radio was a Part 15 compliant AM station that passed FCC inspection. Explain that... So, as far as I am concerned, yes these "laws of physics" are largely theories because there are obviously exceptions to the laws of physics that arise and cannot be explained by the self appointed experts like yourself. Or perhaps the person or persons that wrote the rules of the laws of physics made a few mistakes? 2 plus 2 is always 4,am I correct? Well, that is not the case with signal propagation.

I said it before and I will say it again. A much greater percentage of licensed broadcasters and users of other communications devices are being written up by the FCC than Part 15 AM broadcasters. A recent look at the FCC Enforcement database bears this out.
 
I don't doubt that Mr. Fry is authoritative and expert, but he is not omniscient. Sometimes he is just wrong (which sometimes happens to experts) and this is something he is not capable of accepting. Some topics on this and other Part 15 forums drag on forever, debating some point where he is mistaken, but he won't give in. My opinion is that he is counting on there not being enough expertise among the general readers of a Part 15 forum to judge the outcome of a debate he is engaged in.

His debating tactics include creating a "paper blizzard" of NEC simulations, citing textbooks without context, and just blustering by referring to his own experience and expertise.
 
Mr Roos writes that I "won't give in" when I am wrong. But that is disproven by our exchange on a board in another forum several years ago. I posted a link showing the SWR bandwidth of a Part 15 AM antenna system, and he pointed out that it was incorrect. After investigation I found the reason for the error, corrected it, and posted so in that thread -- stating that he was correct.

In a more recent exchange we had, Mr Roos wrote, "To find the ground loss with distance requires solving the Sommerfeld equation. The solution is difficult, and NEC can't do it, but wipl-d can."

This position puzzled me, as NEC does have that capability. So I e-mailed the developers of WIPL-D, who answered,

QUOTE WIPL-D can account reflection coefficients from infinite real ground, but the ground is considered as flat.

This is a very difficult simulation for an exact 3DEM simulation. At this moment, in order to get accurate result, we need to model piece of the ground (clump) of the size where you want to calculate near field. Even for the largest field (10 mV/m), we need piece of the ground of size 75 km or 150 lambda. Such simulation would require enormous number of unknowns and huge simulation time, if it would be possible at all.

We plan to introduce so called Sommerfeld integral simulation for real and infinite ground in one of our next releases.

At this moment, we are unable to simulate this scenario." /QUOTE

I posted their response in that thread, but to date Mr Roos has not retracted his statement about WIPL-D vs NEC. Instead he posted this: "Yes, wipl-d has limitations, due to computing complexity, in dealing with finite ground conductivity, but it is not practically useless for that purpose, like NEC is."

If Mr Roos cared to, he could use even the demo (free) version of EZNEC to calculate the effect of finite ground conductivity on surface wave radiation from a monopole. When correctly modeled, the field calculated by NEC agrees closely with the field measured by a calibrated field intensity meter.
 
Reciprocity failure is a very long discussion Mr. Fry and I had on another web site some years ago, where I maintained that a short monopole over ground has 6dB more gain transmitting than receiving. The notion is not mine, and I thought that it was very well known. Fry cited numerous textbooks showing I was wrong. I suggested an NEC simulation which Fry claimed that he was not able to duplicate. As he has demonstrated frequently, Fry knows NEC very well, and I doubt that he was not able to duplicate my rather simple results. I also offered to mail him the papers I had on the subject of reciprocity failure, because the file was too long to send by e-mail, but he refused to e-mail me his mailing address.

I notified Prof. Valentin Trainotti, the world's leading authority on short MW antennas, about this discussion with Fry, and he found the subject interesting enough to write a lengthy paper about it for the IEEE Transactions on Broadcasting. I had previously linked the paper on this and another forum. Trainotti additionally discovered that the presence of any antenna of any polarity over a ground plane results in different gains transmitting and receiving. He and his graduate students are working on yet another paper for publication about this general principle.

Because of Mr. Fry's extreme stubborness about admitting he is wrong, I got my name in print because Prof. Trainotti gave me credit for bringing this subject to his attention.

Yes, about five years ago Fry publicly admitted he was wrong. This must have really stung, because he wouldn't let that happen again.
 
Oh, there are issues, but they are all imagined and internally amplified.

I'd love to give everyone a hug, and a double portion of understanding.

As many have pointed out, there is no end to list of variables that can and do affect how well a MW
antenna system works. From corn to mountains to rich soil to sand to rock and salt water, these matters are
not much anyone can completely overcome. There are many gains to be made in efficiency, and these alone
can account for any discrepancies which can lead to contention in this matter.

There is the pudding, and then there is a recipe for pudding.


Let's not argue that there is pudding.

Now, how anyone gets there is the million variables.

In sailboat racing, you can be disqualified for "pumping" the sail. Look it up.
I wish this were applicable to financial markets, because lots of money makes more money in our system based on pure speculation as wealth permits. It is permitted for Wall St to pump the sail, they make money both ways, up and down,
and it has been decided that this benefits the greater good.

In Part 15 AM, you can get as much as the best possible situation imaginable can achieve, then maybe a little bit more
for the sake of pure rf magic, but then at some point, it is non-compliant.

It is far better to share and discuss everything imaginable and learned about effiency gains than waste
a minute arguing over data and perceptions.

Beyond that is a huge variation in receivers and conditons to also skew perceived signal levels.


Returning to the actual topic, about two-three years ago there was a website, I'll try to find it again, that listed a
cathode modulated tube AM xmtter (used an xtal) and it seems the last time I looked there weren't any available.
There were other types available, just not the tube based one.
They stated that it was based on a Stromberg-Carlson oscillator or something.
Google has been unable lead me to such a schematic. Anyone have a lead on this schematic?
Anyone used such a beast? They claiimed wonderful sounding modulation, and 100 mw.

I either need to buy or build a backup. My main is almost 20 years in service and needs some "looking at".
I've never bought one before, but time is scarce right now.

Is it possible they stopped selling this model because of "problems" others have had in selling
low-production AM xmttrs?
 
N/A
 
Veering the discussion back to the main topic rather than the public urination contest:

I have a couple of Talking House transmitters sent to me by a realtor friend getting out of the business. I was going to use them in the High School Gym to do basketball until I left the local radio station. I'll take $50 each plus shipping...
 
Wyatt Cox said:
Veering the discussion back to the main topic rather than the public urination contest:

I have a couple of Talking House transmitters sent to me by a realtor friend getting out of the business. I was going to use them in the High School Gym to do basketball until I left the local radio station. I'll take $50 each plus shipping...
What Model are they?
 
Back in May, 2011, I posted the following in this thread -

"... In a more recent exchange we had, Mr Roos wrote, "To find the ground loss with distance requires solving the Sommerfeld equation. The solution is difficult, and NEC can't do it, but wipl-d can."

This position puzzled me, as NEC does have that capability. So I e-mailed the developers of WIPL-D, who answered,

QUOTE WIPL-D can account reflection coefficients from infinite real ground, but the ground is considered as flat. ... This is a very difficult simulation for an exact 3DEM simulation. ... At this moment, we are unable to simulate this scenario. /QUOTE"

If Mr Roos cared to, he could use even the demo (free) version of EZNEC to calculate the effect of finite ground conductivity on surface wave radiation from a monopole. When correctly modeled, the field calculated by NEC agrees closely with the field measured by a calibrated field intensity meter.


Normally I use NEC releases other than EZNEC to calculate the surface wave (groundwave) field of an antenna system. But a week or so ago I did use EZNEC, and compared its calculated results to those of the FCC groundwave propagation charts, and the inverse distance field produced by a zero-loss, 1/4-wave monopole driven against a zero loss ground plane (link below).

It would be interesting to learn Mr Roos' response to the comparison in this link. Does he agree with it, or does he maintain that "NEC can't do it?"

http://i62.photobucket.com/albums/h85/rfry-100/PropChart1700kHz.gif

RF
 
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