Am1000 Rangemaster Test

... I managed to get a solid 1.2 miles clear as crystal sound.  What's so remarkable about this?  No grounding at all. This was on a 6' pole on top of my house (so about 25' up) - zero grounding and a coupler with a 16" extender on my 102" antenna to give me my 3 meters, but totally legally.  ... its doing 1.2 miles in dirty channels.

A 1700 kHz NEC4 model of the configuration you described shows that with radiating conductors having the physical locations/lengths you defined, and using a loading coil with an ESR of 25 ohms with NO other radiating conductors, such system even with 100 mW of r-f power applied to the input of that loading coil would produce a groundwave field of about 106 µV/m at a distance of 1.2 miles, over a perfect ground plane.

Are you stating that the ambient r-f noise level and receive system performance for a ~ 106 µV/m field in the AM broadcast band permits "clear as crystal sound," even for these theoretically perfect conditions (let alone those using dirty channels, and less efficient transmit systems)?

Could the radiating length of your antenna system be longer than assumed?

The Oakland-San Francisco Bay area is especially hilly, as I recall, so perhaps MLR has an advantageous location in terms of height which might explain the good field coverage.

Maybe?

"...perhaps MLR has an advantageous location in terms of height ...

The height of the transmit antenna radiation center above specific terrain profiles along various radial paths is important at VHF frequencies and above, but much less so in the MF (AM Broadcast) band.

The reason for this is related to the difference in their wavelengths.

Perhaps over the centuries the California coast has become salt laden, which I hear is beneficial for improved RF grounding.

Although MLR tells us there was "no grounding" in terms of RF ground, there was probably a ground path through the power connection and there's a type of inductive ground that occurs through natural capacitance.

Must we suspect over-lengthed antenna?

I assume my tape measure works.

I assume that I can read it.

I assume that I know when a ground is connected or not.

Can I also assume the antenna is longer? Sure.. if you like.  It does not change the fact that it is 118" (that american inches.. the kind on the ruler that the nuns used to wack me in the back of the head with in school.)

I have been driving and walking around like a blind bat, not knowing my distances.

Of course the odometer in the auto has a mile-meter, but I can't watch it while I'm driving.

I got one of those foot-measuring tools that rolls on a stick, and I've measured about 400-feet up and down the sidewalks.

But tonight I sat and gawked at Google Map and learned how to use it to plot distances in the area, and can tell you that my AMT5000, using a Wintenna and two-ground radials has a decent coverage on the streets to about 1,000 feet, with more on the south.

A mile is 5,280 feet, and the best I hear at a mile on some days only is a hint of my signal way deep in the noise. Adding more ground radials will push me out farther.

My experience has found that AM radio signals don't like to go uphill, in-as-much as I'm down in a bowel with uphill in all directions, but ground radials help that situation.

I happen to believe that higher is better for AM radio, even if I'm wrong.

Love your sense of humor!

Here are two YouTube range test vidieos (part1 and part2)

His transmitter is about 6 ft high. He has 30 radials each 20 ft long plus 4 ground rods

He is getting a listenable signal to 2 miles and then sporadic to 2.5 miles. His camera is picking up road noise, so its hard to judge how noisy the signal is.

He's using an AMT3000. It would be reasonable to expect a significantly stronger signal and more range with an AMT5000 or a Rangemaster.

We need more of thess drivearound videos to validate range reports.

Perhaps over the centuries the California coast has become salt laden, which I hear is beneficial for improved RF grounding.

True, Carl, the mineral and water content of the soil have an effect on soil conductivity.

But note that I used a perfectly conducting ground plane in my NEC model -- which has even better conductivity than sea water.

The groundwave field at 1.2 miles for 100 mW of r-f output power applied to the loading coil input of a 118" total length of radiating antenna conductor(s) as described by MLR was 106 µV/m.

In localized areas at a range of 1.2 miles that field could be greater than 106 µV/m, depending on re-radiation from conductors near that receiver.  But the opposite also can be true for some receive locations.

It would take some unusual/unknown conditions to produce crystal clear reception from this system at 1.2 miles, over the real conductivity of the earth in that radius from the transmit site.

Drive around tests basically mean nothing.  Every vehicle has varyring ability to receive AM radio. If you want to check the range of my station, for example, my co-worker who lives half a block away from me gets my station for about two blocks in his KIA, I get it for two miles in my Ford, my Wife gets it for about 1.5 miles in her 4 year newer Ford.  Our 1951 Buick with original tube radio gets it for about 3/4 a mile. How about carw tih an antenna that can be raised and lowered?  What is the standard length for testing? Unless someone designs a standard car radio and installation and the ability to control interference generated by the car itself, this really means nothing.  Unless everyone listening has the same year and model of vehicle with the same radio installed.  The variables are impossible to list.

Further, when someone says they're a certain number of miles away, is this off the odometer, or determined off a measured map so you know exactly where a mioe, 1.5 miles, etc is?  I went to the county and got a map of the area that they use for surveying and had .5, 1, 1.5 and 2 mile circles drawn on it.  Then I can go to all the spots with easy access where that circle crosses a road, parking lot, whatever and check my signal.  When I do this is use my car radio, a cheap $5 portable transistor radio, a typical boom box, and the field strength meter that I use for work (certified and calibrated).

A "real world car test" is only valid if everyone is driving the same car.

Tim in Bovey

Drive around tests basically mean nothing.  Every vehicle has varyring ability to receive AM radio.

Ditto. My Pioneer SuperTuner is super on FM but crappy on AM. Honda Pilot is crappy on both because of a wire antenna embedded in the driver rear window.

Ok - simulations are great.  My kid has a goat simulator.  He can sim the perfect goat.  I wouldn't freakin eat it.  The whole purpose I started this place was to get away from armchair experimenters and the people who swore that because of an excel spreadsheet they had, base loaded antennas could not work.. even though we were doing them and seeing real world differences.

I actually got off my lazy butt and physically did this.  Atmospherics and enviromentals change and create variables.  Maybe it was the increased humidity yesterday, maybe it was re-radiating out into the power line that feeds the VTA, I have no clue, and don't really give a rats butt about theory unless its backed by real-worl physical testing and evidence.

You can add my head to the wall of trophies.  I am retiring from here to go to record my findings elsewhere.  

Mister Rich declares: "But note that I used a perfectly conducting ground plane in my NEC model"

The Perfect Fabricator vs. plain experience.

...I have no clue, and don't really give a rats butt about theory unless its backed by real-world physical testing and evidence.

Then the following graphic should help.

It is a comparison of the groundwave fields of a real-world system measured by a broadcast engineering consultant using a calibrated field intensity meter (the plots at the bottom of the page) with those modeled later for that system using NEC (the plots at the top of the page).

The fields calculated by NEC are in very good agreement with those measured earlier for that system, by the consultant.

I am retiring from here...

I certainly hope you will reconsider.