My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

[carlvenorden]

My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

In the past several years this is the first time I have been able to link any of my sstran products (coil, antenna, ground system) with that of the Rangemaster.

I just heard from a customer who decided to buy a rangemaster after using the sstran. (He is going to use both)

These two installations are different like night and day, but I will describe to you what he told me.

First, he found he needed to install the rangemaster high (unlike the sstran, which needs to be near the coil).
Using the copper antenna I built for him, he installed the rangemaster and CB antenna on top of the antenna (guyed it for stability), and ran his wires down to the "very huge" ground system I had previously built for him, by utilizing the copper. I'm trying to keep the details brief, but he told me that in no uncertain terms that he pulled out his ground rods and kept my ground system intact. The copper antenna provided additional ground (and apparently to keep the wires very short as well, bypassing my insulator)

Great news for me, but better news for Rangemaster users who wish to install an underground ground system (like a standard AM station) to elongate thier signals.
He has a "very clear" daytime signal of over 7 miles in all directions.

The ground system I built for him was 30- 20 foot long radials, attached to an iron mast pipe, and of course that requires 40 square foot of land, not of lot of people have that.
But as I have always said; that AM signal has to hit that ground system thru the air, and if your antenna is elevated as a Rangemaster would be, that ground system would need to be a long one.

If you need to concentrate your radials I can build several rings of smaller radials to fit your yard; even ring each completely on the outside of the radial system if you feel this would help your broadcast.

The ground system is actually very easy to install, and renting a trencher is not necessary.
I send the system with the radials wound into little coils (easier to ship and they are just unrolled and layed out).
To install it:
I personally used an ice chopper (a straight hoe) to push into the soil just an inch (and you really don't want more than that)...moving the chopper forward until I reached the right length. I layed in the radial, and stepped on the sod (soil). That is continued until the entire radial system is buried. Maybe you would have a better/faster way to do it, but for someone with no mechanical yard equipment, that is an easy way to do it.

Just letting you know that it can be done, and it does work!!!!!!!!!!!! and very well for the Rangemaster.
Thanks Bob!!!!!!!!!!!!
Carl @ [email protected]

 

[Neil E.]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Carl,

And it is great news for you also since it illustrates what you have contributed to part15 technology. Thank you for sharing this information.

Neil

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Great news for me, but better news for Rangemaster users who wish to install an underground ground system (like a standard AM station) to elongate thier signals. He has a "very clear" daytime signal of over 7 miles in all directions.

It's great to be enthusiastic about such concepts, but here is what physics and field experience says about this, using the FCC's MW propagation curves.

Freq: 1620 kHz
Tx Power Output: 80 mW (probably optimistic for a Part 15 tx)
Radiator: 1/4-wave vertical monopole (about 150 feet tall for 1620 kHz)
Ground System: 120 buried radials, each at least 1/4-wave long
Path Length: 7 miles
Conductivity of Path: 15 mS/m (better than in most of the US)
Groundwave Field Strength at 7 Miles: 150 µV/m

This system performance is possible when using this "broadcast level" antenna that is 95% efficient, or more, over a clear path (no "urban clutter," overhead wires, etc).

But even a very good Part 15 AM antenna system is only about 1% as efficient as the broadcast radiator described above. So in round numbers for a Part 15 system, that 150 µV/m field at 7 miles would drop to 15 µV/m (other things equal). That is a very weak signal. Broadcast stations don't even claim to offer good coverage to AM listeners beyond their 500 µV/m contour.

So, while that Part 15 signal might be detectable or even listenable to a motivated listener with a very good receiving system, a clear, outdoor path with good conductivity, and lack of interference, it would be "a stretch" to believe that it was very useful there to the general public -- and particularly to indoor receivers. That range would be far shorter.
//

 

[carlvenorden]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Thank you for the kudos, sir! In fact that is exactly what I am trying to do; improve things little by little in a very legal way for part 15 broadcasters.......Now it seems I can branch out to Mr. Hamilton's customers as well....

But for Mr. Fry, who is great at numbers and laws......(most of which we serious posters understood previously),

I understand how you try to shoot down potential part 15 broadcasters by comparing them to standard broadcast stations. This doesn't need to be said, but 95% of people who choose to broadcast part 15 know they won't be owning a blowtorch. And I don't think I've ever posted that they would, nor has anyone else.

However, even the most knowledgable of the 95% of people I mentioned hope for a stellar signal, and ask for just that. Our goals here should be to make people aware of the limitations of part 15, not put down those limitations.
We should be talking about equipment, installation, and ground conductivity, not the fact that no part 15 will be a 500,000 watt WLW.

A rangemaster or sstran will only be as good as it's installation, ground system, and conductivity, installed according to it's instructions. And that is it.
We don't really need numbers and spread sheets showing standard broadcasting stations since it is a known fact that a 108" antenna doesn't compare to a 1/4 wave, or a 5/8 wave.........is that not a given?
And 1/10th of a watt is not even the lowest PSSA power granted a station WITH a 1/4 wave antenna that gets out about 1 mile.

So, we know all of that already, time and again.

Lets discuss how to improve our part 15 systems, not shoot them down.
antenna guy
[email protected]

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Lets discuss how to improve our part 15 systems, not shoot them down.

Technically accurate information about the coverage that can be produced by a Part 15 AM system is important to Part 15 users, is it not? Otherwise they may be mislead into thinking that the inflated claims of coverage often seen on the Internet are real, and be disappointed when they can't be duplicated by their own installations.

Such an approach should even serve the best interests of the manufacturers and suppliers of Part 15 equipment, as it would reduce the number of their customers who are unhappy with their operating results after installing it.
//

 

[Neil E.]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

The copper antenna provided additional ground (and apparently to keep the wires very short as well, bypassing my insulator)

Hi Carl,

I have a bit of a problem understanding what I have quoted above. Can an antenna provide a ground? Maybe you could give a few more details.

Also, we have you relating a report of a range achieved by a customer which according to Mr. Fry is not to be expected with the equipment as described.

It certainly makes sense to use a buried ground radial system as you and Mr. Fry have both stated and I think we can take that for fact.

Do you think, based on what you know regarding part15 AM, that one who uses a transmitter as described in your post can expect a seven mile range?

Thanks,

Neil

 

[carlvenorden]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Hi Neil,
The way the sstran system of grounding works is a way that takes away the wires (thus the idea that the grounding is illegal in any way). Now, what I am understanding from this particular project is from an email from a customer, so I was recanting to readers what he told me: I didn't see this particular installation.
Plus: and a big one: this involves the Rangemaster; a tx I have very little experience with.
I know alot about it, and tested it once many years ago. But the customers point was that he used my ground system (and not the ground rods Rangemaster recommends) to get a 7 mile range.

Things people say can be interpretted different ways. For instance, when I quoted my range of the sstran a couple years ago, I specified a radius.........so when I said I got signal out 3 miles, it was 3 miles in each direction; simple English.
This customer specifically said distance, so I would interpret that to be a 14 mile circumference of signal. True or not, this is about a Rangemaster, which apparently can put out quite a signal (due to it's cost and design).

The point of my post is that a radial system can improve a part 15 signal over rods pounded in the ground, connected by stray wires.....which can be interpreted as being extensions of the transmission wire.
And that has been said before.
Remember, this is all my opinion.

DEFINATE RANGE:
You are right: everyone wants a high powered station out of a 1/10th of a watt tx with a cry of an antenna; I've had 125+ customers, and they all said the same thing. The hardest part, and most time consuming is writing these customers to tell them what to really expect.

You can pinpoint certain things as true with AM broadcasting (like interpreting contours that are published; chances are they are not exactly true)...but you can predict certain things as well.

A customer with any brand of part 15 am tx can expect basic results this way: (again as a general rule)
1. Use the wire antenna on a kit-based tx and you get 50-100 feet daytime and virtually no signal nighttime, no matter where you live.
2. Use a coil based antenna with a properly adjusted tx, in an excellent conductivity scenario, you will get a circular pattern of 1-5 miles total of signal during the day, and 1/4 of that at night, provided you have a clear channel (hehe), and all equipment has been installed correctly (and that is the hard part; people today don't read instructions and wonder why things don't work right).
3. Use a Rangemaster and with it's patented design, and much higher price, you will get more range, but that range is not guarannteed. And I have nothing to do with that organization, I've just read the same reports you have, so that is what I basically know.
4. Rangemaster is installed differently, and is designed totally different; the only thing I really can say is based on a report saying that my radial system works better with the rangemaster than the rods/wire technique of grounding.

I have no real problem with Mr. Fry's reports, except they seem to always be negitive about part 15 radio .......something like this........"do this and you will get in trouble".
My thinking with this board was to make the experience positive; it is not illegal to put up a part 15 radio station, and I feel that most people reading this board are more interested in helpful information than in repetitive posts about rules and regs, and figures most people don't understand,...........or are interested in. The board should be in favor of part 15 broadcasters, not trying to put them down. Do I make myself understood here?

Part 15 radio is not easy. Mostly.
I'll be honest; Rangemaster is a very plug/play system. It works, and it works well, but it is expensive. People like sstran tryed to make it affordable and therefore easier to get started. Some people go up to the Rangemaster after using the sstran, which is fine in my opinion.
Our systems are cheaper but require more work on the part of the consumer; we provide as much advice as possible to make the installation easier, but it is not for everyone; some people just don't understand no matter how easily it is explained. That is ok.

The part 15 rules are available for every one to read especially if they are on the internet.
It is not useful for people to post saying that it doesn't work, or it can't be done, or this is what you will end up with.

Basically, a part 15 broadcaster can count on 50 feet of signal...and maybe that will directional if he puts his wire antenna up against a metal mobile home. But you see, not everyone will tell you that, so you have to go with what they tell you to figure out their problem.

It is absoulutely amazing!!!!!!!!!!!!! the letters I get, (not to mention the letters everyone else gets) about part 15 am.........and I'll give you an example: One man put his tx in his basement, left the wire curled up on the ground (so lets see, this is 9 feet in the ground laying on top of cement, right?).....and wanted to know why he couldn't hear his signal downtown.
What?
Some people in America failed reading, or forgot all about it.......or maybe that is more like paying attention to details.

Setting up a broacasting station is not like spinning a baby toy top. If that is what you want to do, fine.........But pay attention to what we are saying if you ask.....don't just say "well, I layed it on my roof and I got no signal" (another famous quote!)....kind of takes the fun out of trying to teach people how to do this, without getting so technical as to quote the kinds of things Mr. Fry does.....and we don't need to do that at all.
(I'm not poking fun at Mr. Fry; his diatribes are very interesting to read, and I personally find them enjoyable to read and sometimes informative but most part 15'ers don't understand a thing he is saying).

Basically, if a person refuses to understand the information he is asking for, his broadcasting station will not work, and generally, people like me take the blame.
It could happen.
Carl

 

[phatdaddy]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Very well stated Carl! As a long-time licensed ham operator and FCC commercial operator, I understand the technical aspects of Rich's posts. I have also taught ham radio license courses as well as written various technical manuals and it is often quite difficult to present something as abstract as the behavior of RF voltages and currents to those who often do not have a similar technical background. I think that by and large Rich does a good job of doing this even though he is presenting physical realities concerning low power signals to those who do not necessarily like hearing the nitty gritty when it flies in the face of their expectations.

I have designed and built various ham radio antennas over the years with varying success but my experiences with trying to get a successful Part-15 AM running in a condo environment has been one of the most challenging of all. For most of us condo dwellers, outside antennas are verboten therefore we are limited to either inside, attic, or some kind of stealth outside antenna...all of which usually entail various compromises above and beyond those known to exist in a 10 foot antenna running at MW frequencies. After trying a number of different wire antenna configurations with mediocre success it occurred to me that the "ideal" antenna was right in front of me all along. The "lightbulb" came on as I was removing a load of laundry from the dryer last week. I happened to notice that the dryer vent runs vertically through the ceiling, the attic, and through the roof and it's overall length is approximately 10 feet. All that was necessary was to fabricate an insulating sleeve to install in the vent pipe and connect the transmitter to the part of the pipe above the sleeve. I now have my 10 foot vertical antenna (4 inches in diameter!) and a pretty fair signal on the air, given such a stealth antenna. The "car radio range" seems to be about 1 to 1.5 miles, and the "flavoradio" range seems to be most of my condo complex which was my original goal.

The main reason for my posting is that sometimes it is necessary to think "outside the box" when it comes to Part 15 antenna installations, just as the person who emailed you did regarding the Rangmaster radial system. For those Part 15 operators who wish to upgrade their coverage, sit down with a cold drink and take a look at your entire station setup. Perhaps the solution to your antenna problem may be right in front of you like it was in my case.

GEZR Radio
AM-1650
"The Geezer"

 

[Neil E.]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Carl,

Thanks for getting back to me on this. After reading posts for about 1 and a half years now, I conclude that the base loaded vertical antenna working against a buried system of radials such as you have produced is the most effective antenna system considering BOTH the technology and the part 15.219 rules. Though it was designed for the SSTRAN transmitter, there is no reason available to me why this would not be effective with a Rangemaster unit (with appropriate changes to the coil or no coil) and you have presented information which supports this (though it appears that the Rangemaster was not at ground level). Those who choose other configurations such as mast top transmitters are trading what I consider to be compliance for performance.

I didn't read Mr. Fry's posts in this thread as being negative or relating to "getting into trouble". My take is that he has applied many years of professional expertise in the broadcast engineering industry to the subject of part 15 AM and is presenting, factually I believe, data which can guide folks who are interested in part 15 AM in terms of what to expect. You have also done this. His approach is theoretical, yours is based on experience and experiment.

Since AM range depends on so many factors it is hard either by theory or experiment to give a firm number on range, but do you think that your estimates of range are much different from Mr. Fry's? I don't think it is.

Let's play a kids' game for a moment. For a compliant AM transmitter, Range = 10 feet, yes. Range = 100 feet, yes Range = 200 feet, yes if you have a good receiver. Range = 1000 feet, yes with Carl's antenna and ground and a good receiver and minimal electrical noise. Range = 5000 feet, yes under ideal transmitting and receiving conditions. Range = ....... I hope you understand my point. The range is not zero nor is it 10 miles.

I don't think either you nor Mr. Fry are really that far off from each other in stating reality regarding range as long as the conditions of the transmitter installation are equal (meaning ground level with radials). And that is good since we now see it from different perspectives and from what I have read, I would advise someone who asks to expect about a mile car radio range with your antenna and a SSTRAN and less if the listener is using an in home receiver. Is this realistic?

I really enjoyed Phatdaddy's post. Clever lad!

Neil

 

[Black_Shire]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Some Part 15 AM stations help their audience members' radios to "listen better" by offering Select-A-Tenna units or making hombrewed equivalents (20 turns of insulated #20 gauge wire on an oatmeal box, with a 50' wire antenna and a short lead running from the other end of the coil to a ground rod).

Even so, getting 7 miles range from a Part 15 AM installation sounds pretty far-fetched to me, unless perhaps the listeners at that distance are using 1 - 2 wavelength long beverage wire antennas pointed at the station. Also, it is *just* possible that the signal could be being conducted that far by power lines running from the vicinity of the station's antenna to the distant listeners' locations.


-- Black Shire

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

To clarify...

The field strength values I posted are referenced to the FCC's MW propagation charts. These charts are not based on "theory," even though an accurate theoretical analysis will confirm the values in these charts.

The FCC charts were developed from calibrated, real-world field strength measurements performed in the early days of AM broadcasting, and have been confirmed by thousands of real-world field strength measurements ever since.

These are the same charts used by broadcast consulting engineers when designing MW directional antenna systems, which must produce FCC-defined field strength values for that station in various directions from the antenna system, at a standard distance. These field strengths must be measured and shown to comply with the FCC values before the station can begin broadcasting. The FCC charts make that practical, because they are based on accurately-measured values taken in real-world conditions

So my statements about the coverage of a Part 15 AM setup for the conditions shown are not based on theory. They are based on accurately measured data.
//

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

TWIMC:

I know that my posts are technical, and may be hard for some Part 15 hobbyists to follow. But radio transmission systems by their nature are not simple.

The best chance of understanding the true capabilities of Part 15 will be based more on the science of radio, and less on "anecdotal" experiences that have not been documented, and proven accurate.

My goal is to provide accurate technical information, so that Part 15 operators will have it to confirm and compare with other statements and beliefs they read. Whatever course they take after that is up to them.

Rgds,

Rich
//

 

[radiopilot]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

To clarify...

The field strength values I posted are referenced to the FCC's MW propagation charts. These charts are not based on "theory," even though an accurate theoretical analysis will confirm the values in these charts.

The FCC charts were developed from calibrated, real-world field strength measurements performed in the early days of AM broadcasting, and have been confirmed by thousands of real-world field strength measurements ever since.

These are the same charts used by broadcast consulting engineers when designing MW directional antenna systems, which must produce FCC-defined field strength values for that station in various directions from the antenna system, at a standard distance. These field strengths must be measured and shown to comply with the FCC values before the station can begin broadcasting. The FCC charts make that practical, because they are based on accurately-measured values taken in real-world conditions

So my statements about the coverage of a Part 15 AM setup for the conditions shown are not based on theory. They are based on accurately measured data.
//

RFry,

In the past you have posted your results as obtained through your calculations based on the FCC's data which suggests true field measurements over many years or decades so you would assume that the below calculation I did using the FCC program for Predicted Field Strength is correct based on that field research?

The below calculation is of course made with .0001 watts (100 mw
power), I had to use 10 meters for the height (required by program) and 90 radials (required by program) so theorectically not unusual for Part 15 users to do... (my ground system by the way is not much different)...


Using this program from the FCC website:

http://www.fcc.gov/mb/audio/bickel/figure8.html


You have entered a power less than 1 watt = 0.001 kW.
Calculations below are based on the ERP that you entered.

Program FIGURE 8 calculates the Inverse Distance Field for AM broadcast stations with frequencies between 530 and 1700 kHz. The program is a computer version of Figure 8 of Section 73.190 of the FCC Rules.


The Inverse Distance Fields calculated here are in units of mV/m at 1 KILOMETER .

Frequency: 1600.00 kHz
Number of Radials: 90 radials
Correction for number of radials: -6.0000 mV/m @ 1 KILOMETER
Average Length of Ground Radials: 30.000 meters
98.425 feet
0.160 wavelengths
57.640 degrees
Correction factor for length: -16.0000 mV/m @ 1 Kilometer
Wavelength: 187.370 meters
614.732 feet
Tower Height: 10.000 meters
32.808 feet
0.053 wavelengths
19.213 degrees


Predicted Field Strength from Figure 8, Section 73.190:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 220.009 184.603 mV/m @ 1 KILOMETER
At 0.00 kW: 2.200 1.846 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 136.707 114.707 mV/m @ 1 MILE
At 0.00 kW: 1.367 1.147 mV/m @ 1 MILE


So I said: This can't be right so I input 1 watt (.001 KW) for power and got this result:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 220.009 184.603 mV/m @ 1 KILOMETER
At 0.00 kW: 6.957 5.838 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 136.707 114.707 mV/m @ 1 MILE
At 0.00 kW: 4.323 3.627 mV/m @ 1 MILE



And for 10 watts (.01kw) for power, got this result:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 220.009 184.603 mV/m @ 1 KILOMETER
At 0.01 kW: 22.001 18.460 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 136.707 114.707 mV/m @ 1 MILE
At 0.01 kW: 13.671 11.471 mV/m @ 1 MILE




Now you calculate this based on what program and based on years of FCC field results...


http://www.radio-info.com/smf/index.php/topic,43379.0.html



DATA:
Frequency = 1600 kHz
Applied Power = 80 mW
Radiator = 3-meter resonant vertical with base at ground level
Coil Resistance = 2 ohms
R-F Ground Resistance = 10 ohms
Ground Conductivity = 30.0 mS/m
Radiation at 1 mile = 0.2 mV/m

RESULTS:

Contour level > Distance to contour

5.000 mV/m > 0.0340 miles (good signal to cheap, indoor radio)

2.000 mV/m > 0.0850 miles (acceptable, but somewhat noisy signal to cheap indoor radio)

0.100 mV/m > 1.5865 miles (acceptable, but noisy signal to a good car radio in an area with no overhead wires, no local electrical interference, and no co-channel interference)


Now RFry, can you see that based on the FCC's data it shows 1.367 mV/m @ 1 mile Theoretical and 1.147 mV/m @ 1 mile Corrected... now compare that to your 0.2 mV/m @ 1 mile?

If the FCC data is correct and I assume it is.. that is surely a HUGE difference in field strength 1.147 mv/m @ 1 mile compared to 0.2 mv/m @ 1 mile you calculate...

Why is there any discrepency IF the FCC is using their field tested data and made this program available as tools for calculating the field strength?

I believe this data the FCC has provided compared to yours SINCE the FCC has decades of field research built into this program using the curves for field strength, propogation curves, etc.

I'm sure your calculations are correct only perhaps not taking into account the proper FCC field information and curves...

Go to the FCC site above and input any values for any given power, antenna height, and ground radial system... Why would the FCC data be any different?



Radiopilot

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Now RFry, can you see that based on the FCC's data it shows 1.367 mV/m @ 1 mile Theoretical and 1.147 mV/m @ 1 mile Corrected... now compare that to your 0.2 mV/m @ 1 mile? ... Why is there any discrepency IF the FCC is using their field tested data and made this program available as tools for calculating the field strength? Go to the FCC site above and input any values for any given power, antenna height, and ground radial system... Why would the FCC data be any different?

The FCC program at the link you provided does not directly permit a check of the numbers I posted in this thread. It doesn't allow data entries that defined the Part 15 system I was describing. But here is a workaround within the limits of that program, and following the process I used in this thread. The tx power I used was 80 mW, but the FCC program output shows zero.

FROM THE FCC PROGRAM...

The Inverse Distance Fields calculated here are in units of mV/m at 1 MILE .

Frequency: 1620.00 kHz
Number of Radials: 120 radials
Correction for number of radials: 0.0000 mV/m @ 1 MILE
Average Length of Ground Radials: 45.720 meters
150.000 feet
0.247 wavelengths
88.941 degrees
Correction factor for length: 0.0000 mV/m @ 1 Mile
Wavelength: 185.057 meters
607.143 feet
Tower Height: 45.720 meters
150.000 feet
0.247 wavelengths
88.941 degrees


Predicted Field Strength from Figure 8, Section 73.190:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 305.018 305.018 mV/m @ 1 KILOMETER
At 0.00 kW: 2.728 2.728 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 189.529 189.529 mV/m @ 1 MILE
At 0.00 kW: 1.695 1.695 mV/m @ 1 MILE

END FCC PROGRAM

So the FCC program calculated about 1.7 mV/m at 1 mile from this "broadcast quality" antenna system (1/4-wave vertical, 120 radials each 1/4-wave).

A fairly generous efficiency for a Part 15 AM antenna system at 1620 kHz is about 1% of this broadcast system reference, so the field at 1 mile then would change inversely by SQRT(100), or to 1.7/10 = 0.17 mV/m -- which is fairly close to the 0.2 mV/m that you quoted from another post of mine (where I used a slightly different approach).

So the FCC's numbers and the ones I posted agree rather well -- as they should, since they are based on the same measured data.
//

 

[radiopilot]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Now RFry, can you see that based on the FCC's data it shows 1.367 mV/m @ 1 mile Theoretical and 1.147 mV/m @ 1 mile Corrected... now compare that to your 0.2 mV/m @ 1 mile? ... Why is there any discrepency IF the FCC is using their field tested data and made this program available as tools for calculating the field strength? Go to the FCC site above and input any values for any given power, antenna height, and ground radial system... Why would the FCC data be any different?

The FCC program at the link you provided does not directly permit a check of the numbers I posted in this thread. It doesn't allow data entries that defined the Part 15 system I was describing. But here is a workaround within the limits of that program, and following the process I used in this thread. The tx power I used was 80 mW, but the FCC program output shows zero.

FROM THE FCC PROGRAM...

The Inverse Distance Fields calculated here are in units of mV/m at 1 MILE .

Frequency: 1620.00 kHz
Number of Radials: 120 radials
Correction for number of radials: 0.0000 mV/m @ 1 MILE
Average Length of Ground Radials: 45.720 meters
150.000 feet
0.247 wavelengths
88.941 degrees
Correction factor for length: 0.0000 mV/m @ 1 Mile
Wavelength: 185.057 meters
607.143 feet
Tower Height: 45.720 meters
150.000 feet
0.247 wavelengths
88.941 degrees


Predicted Field Strength from Figure 8, Section 73.190:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 305.018 305.018 mV/m @ 1 KILOMETER
At 0.00 kW: 2.728 2.728 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 189.529 189.529 mV/m @ 1 MILE
At 0.00 kW: 1.695 1.695 mV/m @ 1 MILE

END FCC PROGRAM

So the FCC program calculated about 1.7 mV/m at 1 mile from this "broadcast quality" antenna system (1/4-wave vertical, 120 radials each 1/4-wave).

A fairly generous efficiency for a Part 15 AM antenna system at 1620 kHz is about 1% of this broadcast system reference, so the field at 1 mile then would change inversely by SQRT(100), or to 1.7/10 = 0.17 mV/m -- which is fairly close to the 0.2 mV/m that you quoted from another post of mine (where I used a slightly different approach).

So the FCC's numbers and the ones I posted agree rather well -- as they should, since they are based on the same measured data.
//

RFry,

Why are you using a 'Tower Height: 45.720 meters or 150.000 feet' as the height of the radiator? Did I not use 10 meters or 33 feet in my example? Why are you using 150' for the radials instead of the 98 feet?

The power to the transmitter in the program as input .0001 KW or 100 mw is correct as shown using 3 different power levels, and the program actually states you are using less than .001 Kw as shown, there doesn't need to have any corrections to this formula... I believe Sir, that perhaps you're mistaken.

http://www.fcc.gov/mb/audio/bickel/figure8.html

Qutoe:

Figure 8, Section 73.190 Calculations

This program performs calculations of the theoretical inverse distance field strengths in the vicinity of AM broadcast radio stations, using the graphs in Figure 8, Section 73.190 of the FCC's rules. This program will calculate the theoretical field strength generated by the AM station at a distance of 1 kilometer (or one mile if units of feet and miles are selected) at the specified effective radiated power (ERP). It will also find the theoretical field strength using a reference ERP of 1 kW. Calculations may be made in metric or English units, or in electrical degrees (360 electrical degrees = 1 wavelength).

Where the average length of the ground system radials is less than 1/4 wavelength, or if the number of ground radials is more than 90 but less than 120, this program will apply the appropriate correction factors and calculate the corrected theoretical field strengths.

Again I post the data...



You have entered a power less than 1 watt = 0.001 kW. I input: (.0001 kw or 100 mw)

Calculations below are based on the ERP that you entered.

Program FIGURE 8 calculates the Inverse Distance Field for AM broadcast stations with frequencies between 530 and 1700 kHz. The program is a computer version of Figure 8 of Section 73.190 of the FCC Rules.


The Inverse Distance Fields calculated here are in units of mV/m at 1 MILE .

Frequency: 1620.00 kHz
Number of Radials: 90 radials
Correction for number of radials: -6.0000 mV/m @ 1 MILE
Average Length of Ground Radials: 28.042 meters
92.000 feet
0.152 wavelengths
54.551 degrees
Correction factor for length: -18.0000 mV/m @ 1 Mile
Wavelength: 185.057 meters
607.143 feet
Tower Height: 10.058 meters
33.000 feet
0.054 wavelengths
19.567 degrees


Predicted Field Strength from Figure 8, Section 73.190:

(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 221.749 183.124 mV/m @ 1 KILOMETER
At 0.00 kW: 2.217 1.831 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 137.788 113.788 mV/m @ 1 MILE
At 0.00 kW: 1.378 1.138 mV/m @ 1 MILE



The FCC's calculation for the 1/4 wave antenna stands as is calculated above and adding your 1% efficiency for the Part15 antenna is pulling a rabbit out of a hat to be ludicrous at best!

Radiopilot

 

[rfry]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Why are you using a 'Tower Height: 45.720 meters or 150.000 feet' as the height of the radiator? Did I not use 10 meters or 33 feet in my example? Why are you using 150' for the radials instead of the 98 feet?

Because I was emulating the method I used in my earlier post in this thread, which used a 1/-4 wave radiator and 120 radials of 1/4-wave each.

The power to the transmitter in the program as input .0001 KW or 100 mw is correct as shown using 3 different power levels, and the program actually states you are using less than .001 Kw as shown, there doesn't need to have any corrections to this formula... I believe Sir, that perhaps you're mistaken.

Again, I was emulating the input values in my post in thread -- for an apples to apples comparison of the method and results. I used 80 mW as the output power of the Part 15 tx, which is generous, no doubt. I didn't correct any formulas, I just used the right power value for the circumstances.

The FCC's calculation for the 1/4 wave antenna stands as is calculated above...

Your post from which I'm quoting used a 0.054-wave antenna (33 feet tall), not a 0.25-wave antenna (150 feet tall). So if you intended that number to apply to a 1/4-wave system with 120 1/4-wave radials you might want to re-run the program with the correct input values.

...and adding your 1% efficiency for the Part15 antenna is pulling a rabbit out of a hat to be ludicrous at best!

This is calculated by the following equation:

System Efficiency = Radiation Resistance/(Radiation Resistance + Coil Resistance + RF Ground Resistance)

The radiation resistance of an earth-mounted 3-m vertical on 1620 kHz with a very short conductor to r-f ground is about 0.1 ohm. The coil and r-f ground resistance rarely totals less than 15 ohms for most Part 15 AM systems. But plugging those numbers into the equation gives an answer of 0.0066, or 0.7%, approximately (assumes the antenna system is resonant). I used 1% efficiency in my post, to be generous.

Of course, NEC (Numerical Electromagnetics Code) models of a Part 15 AM antenna system also show efficiency values in this range.
//

 

[carlvenorden]

Re: My sstran/ramsey ground systemhat..

I absoulutely LOVED your post.....you hit the nail on the head, spirit and sound all around.

What a killer solution to a problem that seems insolvable.

I designed a sstran antenna, with a top hat, that was shorter, but would fit into an attic, with ground radials, spread across the attic, purchased by three people. I understand it works.
An inside the house antenna could take up your livingroom, but given the buildings's construction, could work. That is one ingenious thought you had.
I had to send kudos.
Carl

 

[carlvenorden]

Re: My sstran/ramsey ground system works "Excellently"Neil..

You too get the point. And I do try to describe my point as directly as possible, as does Mr. Fry. No doubt, he has the knowledge and the numbers, I have nothing at all against him. I would personally enjoy his posts more if they were directed to the numbers of people who read this message board but do not choose to respond or get involved (it's like talk radio; 1 out of 100 call stations, 99 of them just listen).
So, I would like to see information that is understandable to them; informative and factual yes, but understandable more importantly, on this board, and I just think Mr. Fry is altogether too technical for people wanting to put on what amounts to a flea-powered radio station for their community or apartment building.

And your take on range: excellent. There is no certain way to predict range even if the installation of the tx/ant is a perfect match. There are too many variables. So what Mr. Fry is giving you is text book calculations that can be considered average results, there is no certain way to tell someone "this is exactly what you will achieve". And you have nailed that one.

Thanks for the input............You really did hit this one exactly right.
Carl

 

[carlvenorden]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

Mr. Fry, You kind of made my case for me.
Your examples are indeed true FCC field testings.
But we know that field to field those readings can change.
Whats more, and more importantly, you stated that these tests were made many moons ago.
The AM band, as you know is full of interference; both created by radio stations, and .........but mostly, from newly man made noice not "on the air" when these tests were made.

All I am saying is the playing field has changed.

I never really tell my customers to expect more than a miles range, because that is realistic; anything more depending on where they live and interference could make them think they will get miles and miles of range; and WE know that is rediculous.
Personally, yes, I had a 7 mile signal. It happened. Could it happen again?.....Well, if the local AM goes IBOC, and the new house going up next door puts in several computers, Nope, won't happen. These are things I can not control.
So........we can say, as another famous poster already has, that depending on a lot of things we may get some sort of signal. And there really isn't more to say than that.
I think that is a realistic way to look at it in 2007
Carl

 

[carlvenorden]

Re: My sstran/ramsey ground system works "Excellently" with the Rangemaster"!!

This disagreement between Radio Pilot and R.Fry is a rehash from a year or two ago. Gents, look at Radio pilots' FCC results and see the the different imputs result in the same RESULTS. There is something fishy going on here.
In short, these programs do not a lot to develop a plan for a part 15 signal.
They are examples, but nothing but examples.
Good points, but not entirely helpful.

And you don't have to know bupkiss about radio to see that every input of information is either not accurate (lets use 100mw into a 108" antenna:......oh yeah, I forgot we can't use that so we need to go around that).....and the results of the searches are not accurate at all all the way around.

Just for sh's and gigg's, ..lets try putting a couple of these antennas up (put up six like I did and test the real world results) then report your findings.........in todays talk.
It's an investnment, it's a ton of work, but do that, test it, and then tell me what you find out.
A FCC program based on numbers does nothing to prove anything to me in real world enviornmental conditions, and does not take into account today's interference values which vary incredibly from place to place;;;;;;;;;this interference can wipe out entirely even a well tuned antenna.

So, why are we talking about things we should have talked about in the 60's, when that information was more viable?

"MY" job is to help people put on a small part 15 station under the best possible conditions, and to make it possible to overcome the worst conditions. I think that is what it is all about, not FCC measurements taken years ago.
Which have changed.
If we want to help part 15'ers, lets get to the point people, and jump out of the past.
Dig?
Carl