"There are 4 "spokes" that go from each tower to the radiating element located in the center."
Those four towers are support towers only. There is no electrical connection between the support towers and the capacitative hat. Read in my the link:
" This top hat is electrically isolated from the towers, and is electrically connected to a downlead suspended from the center of the top hat. The downlead serves as the radiating element."
"There are two of these antenna's, aligned north and south and spaced about 3/4 mile apart forming a phased array. The phased array gives the signal a little more strength in the east/west direction, less north and south."
In your dreams. Look at the radiation pattern. Pretty much omnidirectional, as far as I can make out.
Mathematically, it does not appear that a potato will work. The antenna-to-ground plane capacitance of a 30-inch monopole antenna at 1 MHz is only about 10 pF. calculatoredge.com/electronics/whip%20antenna.htm If the antenna is broken off at the stem, that is roughly the amount of capacitance that must be replaced to keep the antenna tuned. Just from the size of a potato one would guess the potato’s capacitance is in the µF range.
There are instruments in the biological and medical fields that measure the electrical reactance and resistance of organic tissue. For whatever reason, an instrument manufacturer (RJL Systems) measured the reactance of a fresh potato between two probes at 50 kHz. They found the reactance to be 176.1 Ω (First graph of rjlsystems.com/experiment04.shtml). This reactance corresponds to approximately 18 nF or 18,000 pF. electronics2000.co.uk/calc/reactance-calculator.php That is, the capacity of a potato is roughly (very roughly) 2000 times too large to keep the antenna tuned to 1 MHz.
Note: The 50 kHz test probe frequency is not reported in the above article. It is the standard frequency used in such measurements and is not settable. A user’s manual for the specific instrument used in the experiment points this out. The manual can be found on the internet.
Thank heaven’s for engineers that understand this stuff, but who has a metal antenna anymore anyway? Mine are in the windshield or someplace. Would you have to mash the potato first and spread it on the windshield?
Mechaniker, you first asked “Where are the “spokes” radiating outward from the top?” I answered your question. The spokes are supported by the towers and yes they are electrically isolated. In most hat antennas, the spokes are much shorter so they don’t need additional support. The spokes are electrically connected to the radiating element. The term “downlead” used in your reference is misleading, it is the antenna, not a “downlead”.
If you know anything about phased array antenna’s you would know that this antenna is slightly bi directional. In this case, by slightly, I mean a little more east west than north south. This signal is meant to cover the whole United states, which is oriented slightly more east west than north south, not counting Alaska and Hawaii. If the radiating elements were exactly a half wavelength apart (8200’) and fed in phase, then it would be bidirectional east west.
Mechaniker, if you are really interested in antenna theory, I suggest that you get a copy of the ARRL Antenna Handbook. It is the best reference that I have found anywhere on this subject, and I have read a lot of references on this. BTW, the Navy still uses the lesson guides I wrote for them on antenna theory in their advance electronics courses.
Hey Bing, if you want a good signal from a distant station while in your shop you might connect a cheap after market AM-FM unit to a 12v source and run coax to an automotive antenna mounted at the roof.
keith —
If you know anything about phased array antenna's you would know that this antenna is slightly bi directional. In this case, by slightly, I mean a little more east west than north south. This signal is meant to cover the whole United states, which is oriented slightly more east west than north south, not counting Alaska and Hawaii. If the radiating elements were exactly a half wavelength apart (8200') and fed in phase, then it would be bidirectional east west.
" Operation of the two WWVB antennas as a two-element array was briefly investigated. One concern was that due to the separation of the antennas, the antenna pattern variation would be fairly large, making this mode of operation impractical. For the antenna spacing and frequency, it was found that the pattern variation, for equal in-phase currents, was less than 1 dB."
A map of the WWVB antenna gain pattern is on page 16 of the report.
Operation of WWVB as a phased array was NOT recommended in the report.
But let’s carry this a little bit further:
keith —
... this antenna is slightly bi directional. In this case, by slightly, I mean a little more east west than north south. This signal is meant to cover the whole United states, which is oriented slightly more east west than north south ...
In the discussion of operating WWVB in phased array mode (which was NOT recommended), the report had this to say (page 19):
" The array pattern can be adjusted by changing the phase difference between the two elements. Adjusting the antenna current phase to provide an end-fire pattern toward the south end of the array would provide better overall coverage since more power would be directed south where the noise is greater and correspondingly less power directed north where noise is lower."
No mention is made in the report of your bi-directional east-west theory.
Do you just make these things up?
Finally,
keith —" If you know anything about phased array antenna's ...
" Mechaniker, if you are really interested in antenna theory, I suggest …
" BTW, the Navy still uses the lesson guides I wrote for them on antenna theory in their advance electronics courses."
I do have B.E.S. and M.S. degrees in Electrical Engineering (I won’t say from which university for fear of laying it on too thick), and I also worked on the design of the AWACS radar system from 1966 to 1970. However, I never wrote any lesson guides for the Navy on advanced antenna theory like you did. You have me there.
The map of the gain pattern on page 16 is affected by geography. Since you have so many degrees, you should know that a vertically polarized, grounded LF wave front will follow the terrain of the earth. In following the terrain of the earth, the signal is more attenuated going over mountains than following them. And you know that the Rocky Mountains, along with other mountain ranges in the Americas run North and South, so that attenuation of the signal is greater in the east west direction.
Now you should also know that a phased array that is fed in phase will concentrate its power perpendicular to the plane of the array. When fed out of phase, the power will concentrate parallel to the plane of the array, AKA an end fire array.
Adjusting the phase relationship of the feeds anywhere between 0° and 180° will adjust the angle the antenna concentrates its power in. This technique is used in the large arrays of the radars on ships and at some airports.
So did I make up this east west gain, no. I know that two vertically polarized antenna’s fed in phase will have more gain perpendicular to the plane of the array. The plane of the array in this case is North South, so the higher gain will be in the East West direction. It happens that there is more attenuation in the East West direction so when you look at the signal strength at 1000 miles or more away, the beam pattern won’t be the same as it would be at ten wavelengths (about 8 miles).
I read through this report that your are referencing and I have a few comments about it. First, I have served in a staff command and I have a very jaded view on these. I see you have a little experience with the government too. The government wastes a lot of money every year on useless reports like this one. Somebody gets an inside edge, usually via some politician, and gets a contract to make a report for an agency who likely doesn’t even want the report int he first place. We used to call these guys “beltway bandets”.
Their recommendation to change the array to an end fire was totally stupid, they clearly did not understand the purpose and intent of this signal, which is to serve the needs of United States citizens, not Mexico. An end fire would cover more total area, but not more of the US. A lot of the report was about the deteriorating condition of the antennas, which I’m sure that the people of NIST were already painfully aware.
Much of those sections were probably authored in various memos by the NIST people and plagiarized for this report. That is another common practice in the government. Another saying we had was that “in government, plagiarizing is not a crime, its an art form”. I admit to using it myself a time or two and I have plagiarized as well.
Many times these reports are only used to justify funding for projects. Congress doesn’t seem to take any agencies word for needed projects or improvements, an outside report is needed. I can cite an example here, I put in a recommendation for the combining the fire control rate with the avionics rate. This was not really a new idea, I had heard it from the time I joined the Navy and became a fire control technician, but when I wrote a point paper about it while in a staff command, it got the attention of the Chief Of Navel Operations. It was the first time they had heard the idea.
BTW, I did let them know that the idea was not mine but that just about everyone in the fleet had heard it and thought it was a good idea as well. The Navy commissioned a study by a beltway bandit at a cost of $300k to review my idea. The first recommendation by the beltway bandit was to split the rates even further. It was sent back with a Note to “get it right this time”. They basically resubmitted my point paper and Congress approved the change. The rate of Aviation Fire control Technician disappeared the day after I retired.
Just for your information, I live in the mountains very near Puebla, Mexico. I have an atomic clock, and have brought several of them for a doctor friend who was totally enchanted by the clock.
The signal here is very erratic. Right now, 2:19 pm I have a good signal, but at times, hours pass with no signal at all. I think I am around the same distance from Boulder as Bangor, Maine, but am too lazy to find GPS coordinates and calculate it correctly. I do wonder if Bangor has a better signal or if it is also erratic.
I studied some antenna theory when I learned electronics. But, in most cases, the experts said to know what the actual pattern of any antenna is, one must wander around and record the signal strengths and plot them on a map. The surrounding terrain modifies the theoretical pattern of a given antenna.
It would make sense to change the pattern to cover the entire US and not worry about other locations.