Quarter wavelength question

If, in a few years, Industry Canada would allow operate an AM transmitter more than 3 meters (let's say a quarter of wavelength). In this case, with the same power (100 mW), how range will be with a quarter wavelength vertical antenna *WITH* 12 radials of 10 foot copper wire? And *WITH* 120 radials of a quarter wavelength?

As always, MW "range" will depend on ground conductivity and path obstructions, quality of the receiving equipment, and interference levels at the receive site. But here are some general numbers based on the FCC's propagation curves, and estimating that the system with 12 radials each 10 feet long will be about 10% as efficient as with 120 radials each 1/4-wave long...

Freq = 1,600 kHz
Ground conductivity = 8 mS/m
Radiator = 1/4-wave vertical monopole
Distance to 250 uV/m contour:
- using 120 buried radials each 1/4-wave long = 7.7 miles
- using 12 buried radials each 10 feet long = 3.8 miles

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Thanks Rich!

Yves

Hello Rich,

I know that a 3-meter base loaded vertical antenna with some 10 or 12 buried radials is 250 uV/m at 30 meters. My question is how range will be if the ground system would be 120 radials of quarter wavelength with 3-meter base loaded vertical antenna?

I know that is a very expensive task for installing 120 buried radials but i am just curious to see how far does go with this configuration?

Yves

I'm curious how a hamilton rangemaster would behave when placed at the top of a 1/4 wave monopole. Frequency would be 1700khz, NW NJ Ground Conductivity, hamilton grounded to 1/4 wave monopole and attached to the top of monopole which is attached to a 120 1/4 wave radials. of course it would have the 3m whip on the RF output.

Thank You,

Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.org

Moderator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree

I know that a 3-meter base loaded vertical antenna with some 10 or 12 buried radials is 250 uV/m at 30 meters.

I believe that is too low, but I didn't bother to calculate the value.

My question is how range will be if the ground system would be 120 radials of quarter wavelength with 3-meter base loaded vertical antenna?

Using NEC and the FCC propagation curves for 1,600 kHz and 8 mS/m conductivity, the 250 µV/m contour from the system you describe would occur about 3 miles away.
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Hello Rich,

I know that a 3-meter base loaded vertical antenna with some 10 or 12 buried radials is 250 uV/m at 30 meters.

I believe that is too low, but I didn't bother to calculate the value

So, at the frequency of 1600 kHz, can you give me how range is for a 10 foot base loaded vertical antenna with some 10 or 12 buried radials for 250 uV/m ? And with some 64 buried radials? My buried radials is 10 foot long of 20 GA copper wire.

Thanks in advance

So, at the frequency of 1600 kHz, can you give me how range is for a 10 foot base loaded vertical antenna with some 10 or 12 buried radials for 250 uV/m ? And with some 64 buried radials? My buried radials is 10 foot long of 20 GA copper wire.

There are too many unknowns here even to make a decent guess. It mostly depends on the r-f resistance in the ground system, and I have seen no published data relating this to your question.

The PDF paper in the link below shows an estimated field strength for what probably is a best case for a base-loaded Part 15 antenna system. But more likely than not, the r-f resistances in the two radial systems you ask about will be higher than the 10 ohms shown in this paper -- perhaps ~ 4X, or more.

http://filebay1.home.comcast.net/Elevated_Part_15_AM_Antennas.pdf

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