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Using commercially-available equipment is cheating anyway. What does it take to modify PCS cellular phone firmware for digital communication on 902? Is it just a matter of firmware or isn't the RF section able to tune that far out of band? At the time, cell phone equipment was not readily available. |
To oversimplify a bit: Low frequencies (like AM broadcast) pass through
the body without being absorbed. Microwave frequencies bounce off the body without being absorbed. ROTFFL!!! Why not PROVE your ridiculous theory by putting your head into a microwave oven! ........yeah. I didn't think so. |
"Bob Haberkost" wrote in message ... "David Eduardo" wrote in message ... Huh? AM stations essentially always have vertical radiators, especially in Europe where there are so many high powered stations. In general, AMs don't work very well otherwise. This concludes your antenna theory class for the day. ;-) Very interesting discussion. Thanks. How about introducing the masses to franklin antennas, such as the system still in use at KFBK in Sacramento. I believe KDKA once had one, too. I saw one in South America that had no real ground system, just the two elements of the Frnklin and a ground mat at the base. |
"Richard Fry" wrote in message ... "Bob Haberkost" wrote Huh? AM stations essentially always have vertical radiators, especially in Europe where there are so many high powered stations. In general, AMs don't work very well otherwise. H-Pol radiators have little to no ground wave. H-pol would not be used on VHF and above (FM/TV broadcast etc) if that was true. A linear, horizontal dipole antenna at MW or any other band generates its maximum field strength at all angles perpendicular to its longitudinal centerline -- which includes all angles from below the antenna out to the radio horizon; i.e., a "ground" wave. [Free-space radiation with respect to the dipole itself is the same whether its axis is horizontal or vertical.] H-Pol is used on VHF, such as TV and FM, not because there's no ground wave (which there still isn't) but because, in historical times, the antennas used to receive TV and FM were H-Pol (most still are, if you look around). However, vhf broadcasters (you know?) have been allowed to used V-Pol (to the limits of the H-Pol authorisation) or elliptical or C-Pol as well since the early 70s, due to the number of portable receivers coming into use at the time whose antennas are, frequently, vertically-oriented. And while all dipole radiators have the characteristic radiation pattern you describe, this isn't a "ground" wave since there's no bias for radiation along the horizontal plane when the radiator is oriented horizontally - it's only when this radiator is vertical that the omnidirectional radiation perpendicular to the centreline is a "ground" wave, as significantly less power goes skyward, in conformance with your description. Further, since medium wave radiation has a significantly larger wavelength when compared to the size of the earth, the diffractive effects make for over-the-horizon transmission, further enhancing the phenomena called "ground wave propagation". The reason h-pol is not used for MW is because path losses are much higher for h-pol than v-pol in that part of the radio spectrum. And, as noted above, because for the same amount of coverage, more power would be necessary, since well over half of the radiated power goes uselessly skyward. This is why a vertical radiator is sometimes called a "ground plane" antenna, snip for those installations on the ground, this counterpoise is usually buried. The radial ground system used with MW broadcast antennas reduces antenna system losses (I^2R), and keeps maximum radiation directed more toward the the horizontal plane, rather than at some elevation angle above the horizontal. The FCC defines the minimum efficiency of radiators licensed for MW broadcast in terms of producing a field strength of so many mV/m at 1 km from the antenna, per kW of antenna input power. These efficiencies cannot be met without using a good ground system. Right....but how is this information inconsistent with my description, which is to say that a vertical radiator needs a ground plane? You also fail to note that the rules specify different minimum efficiencies for differring antenna lengths. Those familiar with 11-meter Citizens Band know this antenna in its 27MHz form, snip the reason why this particular configuration has these radials at a 45-degree angle from the horizontal is because a ground plane antenna has an intrinsic impedance of about 30 ohms....the farther towards being vertical, the more it's like a dipole, with a dipole's characteristic 72 ohm impedance. Thus, at 45 degrees or so, the ground planes typically used for C-Band are about 50 ohms without the need for a matching network.) Possibly more important is the point that drooping the radials also tends to lower the angle of maximum radiation, which can improve field strength for receiving antenna sites at/near ground level. Perhaps. But isn't it interesting that the angle selected is the same angle as what produces a 50-ohm impedance? If the effect were more pronounced at a different angle, one would think that that angle would be preferred, and then using a matching network, bring it back to 50 ohms. Of course, there would be some loss in that network, which might overwhelm the additional advantage gained by dragging down the lobe. The nice thing about the low radiating impedance of a vertical radiator is that the high base current necessary for a given power means that the magnetic vector is bigger than the electrostatic vector, and since ferrite loops used in most AM radios respond to the magnetic vector, the "connection" is more intimate. ?? The table below shows the efficiencies for MW vertical radiators with a good ground system. The self-impedance of a 90 degree vertical is about 50 ohms, and for a 180 degree vertical it is over 100 ohms. So for the same input power, base current is lower in a 180 degree radiator than in a 90 degree radiator. Yet the efficiency of the 180 degree radiator is higher -- the opposite of the above quote statement. The ground wave field strength of a MW vertical radiator per kilowatt of input power is related only to the current distribution in the radiator, not its base impedance. Whatever the base impedance is, it can be matched to 50 ohm line at the tower base, using the right network. But the network doesn't affect the relative field radiation pattern of that radiator. But....I've seen (and fortunately NOT had to deal with) antenna systems with very high base impedances (one, if my memory serves me correctly, was 800 ohms! Not much current, but do the math...any appreciable power, like 3 or 4 kW, and there's a real danger of getting tangled in with some pretty high voltages). While it's not a scientific survey, I can tell you that those systems, watt-for-watt, perform worse than lower impedance systems, and that's not even counting the difficulties in having 1kV base voltages! And it's more than just current distribution that affects efficiencies. It's the integral of the loop currents, which is why your chart shows better efficiencies for those taller radiators. The larger fields generated by the longer radiators makes for more power transferred (which also explains why a taller radiator has a higher intrinsic impedance, as you have above, so 1kW into a 90 degree stick will be about half as effective as a 180 degree stick (actually, shy of twice, due to the I-squared-R losses you mention.. AM Radiator Efficiencies, 1kW input Twr Hgt, Deg Effic 70 182mV/m 90 190 100 195 180 237 190 246 225 274 Note here that "efficiency" is the FCC definition for MW broadcast. Efficiency falls for short radiators because the ohmic loss even in the best ground system becomes a bigger percentage of the resistive term of the radiators base impedance. I appreciate the effort and time you've made trying to teach me something about antenna theory, but be assured that there's not much more that need to know, and I sincerely doubt that going into much more detail than this is warranted for this particular thread. -- ----------------------------------------------------------------------------- If there's nothing that offends you in your community, then you know you're not living in a free society. Kim Campbell - ex-Prime Minister of Canada - 2004 ----------------------------------------------------------------------------- For direct replies, take out the contents between the hyphens. -Really!- |
Mister Fact wrote:
Certainly my reply was not related to any physical harm which might result from radio waves themselves- but since the message board has to do with radio broadcasting in general- I thought it would be a good opportunity to inject ANOTHER TYPE OF MEDICAL HARM which I see inherent in AM broadcasting today. Isn't that what Rush Limbaugh was doing? Injecting another type of harmful medicine? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
Within these hallowed halls, Truth of added the
following to the collective conscience: To oversimplify a bit: Low frequencies (like AM broadcast) pass through the body without being absorbed. Microwave frequencies bounce off the body without being absorbed. ROTFFL!!! Why not PROVE your ridiculous theory by putting your head into a microwave oven! .......yeah. I didn't think so. I was actually wondering what this post of yours had to do with broadcasting. Even if it was off topic but informative or entertaining, it would have been better than just being a post about being rude to someone. |
"Bob Haberkost" wrote in message ... But....I've seen (and fortunately NOT had to deal with) antenna systems with very high base impedances (one, if my memory serves me correctly, was 800 ohms! Not much current, but do the math...any appreciable power, like 3 or 4 kW, and there's a real danger of getting tangled in with some pretty high voltages). While it's not a scientific survey, I can tell you that those systems, watt-for-watt, perform worse than lower impedance systems, and that's not even counting the difficulties in having 1kV base voltages! At medium wave (AM Broadcast) many Class A stations (formerly "clear channel") use antennas of about 190 or 200 degrees tall. The FCC requires a minimum antenna effectiveness for that class which is higher than for the other classes of stations. The base impedance of these sticks near a half-wave tall is going to be pretty high - and all but one US Class A station run 50 kW. One of the factors in deciding AM tower height is to place the first null in the vertical pattern such that the nighttime skywave interferes as little as possible with the ground wave toward the edges of the groundwave coverage. Of course Class A AM stations are a Big Deal and generally have very good ground systems. |
"Bob Haberkost" wrote these clips:
The larger fields generated by the longer radiators makes for more power transferred (which also explains why a taller radiator has a higher intrinsic impedance, Have to disagree with that. The reason that a 180 degree MW vertical generates a stronger ground wave than a 90 degree vertical (other conditions equal) is due SOLELY to the shape of their respective elevation patterns. Their radiation efficiency or "power transferred" has nothing to do with their base impedances. If properly matched to their transmission lines, both of them radiate the same total power. But the elevation pattern of the 180 degree radiator has more intrinsic gain in the horizontal plane -- which produces the stronger ground wave of the two. so 1kW into a 90 degree stick will be about half as effective as a 180 degree stick.) Not following that conclusion. Using the FCC's numbers, a 180 degree MW radiator with 1 kW input produces a groundwave field of 237 mV/m at one mile, while a 90 degree radiator produces 190 mV/m. So for same input power and other conditions, the 90 degree radiator produces 80% of the field strength of the 180 degree radiator. Put another way, the input power to the 90 degree radiator would have to be increased about 1.56X in order to produce the same ground wave field at one mile as the 180 degree radiator. RF |
Truth wrote:
Harris wrote: To oversimplify a bit: Low frequencies (like AM broadcast) pass through the body without being absorbed. Microwave frequencies bounce off the body without being absorbed. ROTFFL!!! Why not PROVE your ridiculous theory by putting your head into a microwave oven! I said this was a simplification. The point is that maximum absorption occurs in the 30 to 300 MHz range. Microwave frequencies are used for cooking because they are more practical to produce, not because they are more effective at heating. See the ANSI (American National Standards Institute) exposure limits curve below: http://www-training.llnl.gov/wbt/hc/.../slide34lg.gif Greatest rf absorption (minimum allowable exposure) is in the 30 to 300 MHz range. Art H. |
At medium wave (AM Broadcast) many Class A stations (formerly "clear channel") use antennas of about 190 or 200 degrees tall. A Clear Channel is a Clear Channel is a Clear Channel. Any of 540, 640, 650, 660, etcetera. The average height over all ND-U Class As is 195 degrees. The real goal here is to get 400 mVm/kW at 1 km, or better, without also having high-angle radiation which could cancel the groundwave in the fringe area ... that area where the primary service area ends and the secondary service area begins. Taller than about 200 degrees requires sectionalization to do this. 225 degrees is a real killer for a Class A, but is perfectly fine for a Class B or C, which doesn't have a large primary service area, anyway. The best performing Standard Broadcast radiator is 360 degrees tall, and consists of a 180 degree bottom section, and a 180 degree top section. The FCC requires a minimum antenna effectiveness for that class which is higher than for the other classes of stations. 362.10 mV/m/kW at 1 km for Class A. 281.63 mV/m/kW at 1 km for Class B and D. 241.40 mV/m/kW at 1 km for Class C. Of all lower 48 Class As, two don't have conforming radiators, and both of these are in San Francisco. Of all Alaska Class As, only one has a conforming radiator. The base impedance of these sticks near a half-wave tall is going to be pretty high - and all but one US Class A station run 50 kW. The only such Class A in the lower 48 is 1560 in Bakersfield, CA. There are numerous such Class As in Alaska. |
"Richard Fry" wrote in message ... "Bob Haberkost" wrote these clips: The larger fields generated by the longer radiators makes for more power transferred (which also explains why a taller radiator has a higher intrinsic impedance, Have to disagree with that. The reason that a 180 degree MW vertical generates a stronger ground wave than a 90 degree vertical (other conditions equal) is due SOLELY to the shape of their respective elevation patterns. Their radiation efficiency or "power transferred" has nothing to do with their base impedances. And yet it does. How, if I may ask, do you think that the radiation pattern of a 180 degree vertical element is lower than a 90 degree radiator? As you mention, it's current distribution, but it's not as simple as you've characterised. The field is generated by the summation of the currents over the length of that antenna that combine to provide the "pull-down" effect you mention, and in the process, since the infinitesimal slices of the radiator, each contributing its own part to the overall field, also interact with each other in much the same way as separate elements in a directional array interact, the phasing and amplitude over the length of the radiator serve to enhance the direction towards the horizon and reduce radiation towards the sky. Now, the reason why the base impedances are different for these two examples is the same as why the effective impedance for one element in a directional array changes when a second element is introduced into the nearspace around that first element, because the interactions between the infinitesimal slices serve to increase the "coupling" of the radiator to space. It's all calculus, with a heaping serving of trigonometry thrown in for good measure. If properly matched to their transmission lines, both of them radiate the same total power. But the elevation pattern of the 180 degree radiator has more intrinsic gain in the horizontal plane -- which produces the stronger ground wave of the two. I long ago recognised that, in the physical world, you don't get something for nothing (a concept which, it's pretty clear, the current administration in Washington doesn't get...or maybe they do?). Nothing in what I've discussed is ignorant of this, although admittedly it's not explicitly stated. We broadcast engineers tend to look at radiation patterns as they relate to the potential audience, knowing that the areas we've pulled power from won't miss it, and then pat ourselves on the backs for having designed an antenna system with "gain." so 1kW into a 90 degree stick will be about half as effective as a 180 degree stick.) Not following that conclusion. Using the FCC's numbers, a 180 degree MW radiator with 1 kW input produces a groundwave field of 237 mV/m at one mile, while a 90 degree radiator produces 190 mV/m. So for same input power and other conditions, the 90 degree radiator produces 80% of the field strength of the 180 degree radiator. Put another way, the input power to the 90 degree radiator would have to be increased about 1.56X in order to produce the same ground wave field at one mile as the 180 degree radiator. Well, there you have it. 1.56 times, while not exactly 2, is closer to 2 than it is to one. Consider that, since radiated field is over an area for our purposes, a radiator half as effective as the reference would have 70.7% as much field, or the reciprocal of the square root of two. It was a gross approximation, Richard. From what I've seen of broadcast engineers, many have only a practical knowledge of the underlying theoretical concepts...whether it's the understanding of modulation theory (how many people do you know who think that amplitude modulation actually manipulates the amplitude of the carrier? Or that FM actually changes the centre frequency?) or antenna design, or solid state theory...never mind quantum theory. I don't believe that getting down to this level would serve any practical purpose in this newsgroup, however, especially since I'm not prepared to start introducing mathematical equations into a text-based format. -- ----------------------------------------------------------------------------- If there's nothing that offends you in your community, then you know you're not living in a free society. Kim Campbell - ex-Prime Minister of Canada - 2004 ----------------------------------------------------------------------------- For direct replies, take out the contents between the hyphens. -Really!- |
Sequence #1...
B. Haberkost: The larger fields generated by the longer radiators makes for more power transferred (which also explains why a taller radiator has a higher intrinsic impedance, R. Fry: Have to disagree with that. The reason that a 180 degree MW vertical generates a stronger ground wave than a 90 degree vertical (other conditions equal) is due SOLELY to the shape of their respective elevation patterns. Their radiation efficiency or "power transferred" has nothing to do with their base impedances. B. Haberkost: And yet it does. How, if I may ask, do you think that the radiation pattern of a 180 degree vertical element is lower than a 90 degree radiator? etc Not because of any change in base impedance. The electrical height of the tower determines BOTH the elevation pattern it produces, AND the base impedance of that tower. Base impedance is an effect, not a cause. If base impedance determined efficiency and "power transferred," then a 90 degree tower should have very nearly the same elevation pattern as a 245 degree tower, because the base impedance for those two heights are very similar (90 degree is about 63+j105 ohms; 245 degree is about 64 +j50 ohms). Yet the elevation patterns for these two verticals are greatly different. The elevation pattern of a 245 degree vertical has two distinct major lobes; one centered on the horizontal plane, and one at about 45 degrees. The 90 degree tower produces an elevation pattern with a single lobe centered on the horizontal plane. These verticals can be computer-modeled to show their shapes and intrinisic gains in dBi. I'll e-mail you a graphic I generated in NEC to compare them for you. Sequence #2... R. Fry: Put another way, the input power to the 90 degree radiator would have to be increased about 1.56X in order to produce the same ground wave field at one mile as the 180 degree radiator. B. Haberkost: Well, there you have it. 1.56 times, while not exactly 2, is closer to 2 than it is to one. Consider that, since radiated field is over an area for our purposes, a radiator half as effective as the reference would have 70.7% as much field, or the reciprocal of the square root of two. It was a gross approximation, Richard. To help you compare geographic areas covered by a 90 degree vs a 180 degree radiator, here are the numbers using the FCC's MW coverage program. For 1kW input power to the tower base, a 1,000 kHz carrier, and conductivity of 8mS/m, the radial distance to the 2mV/m contour is 25.6 miles from 90 degree tower, and 28.5 miles from the 180 degree tower. The areas covered are 2,058 miČ and 2,550 miČ respectively. So the 90 degree vertical covers about 80% of the area served by the 180 degree vertical. Not very close to a 2:1 difference at all. Sequence #3: From what I've seen of broadcast engineers, many have only a practical knowledge of the underlying theoretical concepts...whether it's the understanding of modulation theory (how many people do you know who think that amplitude modulation actually manipulates the amplitude of the carrier? Or that FM actually changes the centre frequency?) The instantaneous frequency DOES change with frequency modulation, although the average center frequency stays close to the unmodulated value. In fact, a very common FM exciter design uses the incoming program audio to change the resonant frequency of the frequency-determining components of an RF oscillator, whose resting frequency is the stations licensed carrier frequency. RF Visit http://rfry.org for FM broadcast RF system papers. |
"Bob Haberkost" wrote (clip):
The nice thing about the low radiating impedance of a vertical radiator is that the high base current necessary for a given power means that the magnetic vector is bigger than the electrostatic vector, and since ferrite loops used in most AM radios respond to the magnetic vector, the "connection" is more intimate. This concludes your antenna theory class for the day. ;-) ____________________ The above calls for a bit of discussion, IMO The base current of a MW vertical radiator depends on the resistive term of the base impedance of that radiator, according to the equation I = sqrt(P/R), where P is the applied power and R is the base resistance. However current is not uniform over the height of the radiator. It must satisfy the physical reality that a current node (minimum) always must exist at the top of the tower. Other current nodes occur at 1/2 -wave intervals below the top, if the tower is tall enough. Between the nodes, current rises to a loop, or maximum, at intervals of 1/4 wave. The maximum current present at the loop(s) is a function of the amount of power applied to the base of the radiator -- not to the base impedance of the radiator. So for a given input power, the same absolute value of current will be present starting 1/4 wave below the tower top, and repeating every 1/2 wave below that -- regardless of the base impedance of the radiator. Far-field radiated EM waves from MW vertical radiators of any height are identical in that they all have equal electric and magnetic vectors at right angles to each other. A ferrite receiving antenna performs well on MW frequencies for reasons unrelated to the ratio of the E & H fields in which it is immersed. RF Visit http://rfry.org for FM broadcast RF system papers. |
900 MHz are NOT microwaves
Interesting. Especially since the older microwave ovens operated on 800 and 900 Mhz. Why are people who are uneducated in certain subjects always the first to jump in on a conversation and tell everyone else how they think things really are? |
To oversimplify a bit: Low frequencies (like AM broadcast) pass through
the body without being absorbed. Microwave frequencies bounce off the body without being absorbed. ROTFFL!!! Why not PROVE your ridiculous theory by putting your head into a microwave oven! I once worked with a guy who claimed he could hear microwaves. He said that he could tell when the radar system was in operation and when it wasn't by the sound. We did a simple blind test up on the roof, and it became pretty clear that he could tell. Turns out that what he was hearing was conducted noise from his skull expanding due to heating effects. Admittedly this was with well over a megawatt ERP. But it was definitely being absorbed. What a very bright individual. It frightens me that someone like that was allowed to get close to that equipment in the first place. They put all the rest of us at risk. SOME microwave frequencies get absorbed very well by water, some do not. The body being mostly water, Especially the EYES in our heads, so close to the cell phone antennas. |
Truth wrote:
900 MHz are NOT microwaves Interesting. Especially since the older microwave ovens operated on 800 and 900 Mhz. Why are people who are uneducated in certain subjects always the first to jump in on a conversation and tell everyone else how they think things really are? Because they want to appear educated. |
"Truth" wrote in message ... 900 MHz are NOT microwaves Interesting. Especially since the older microwave ovens operated on 800 and 900 Mhz. Why are people who are uneducated in certain subjects always the first to jump in on a conversation and tell everyone else how they think things really are? ref http://www.naval.com/radio-bands.htm ref http://chemindustry.intota.com/multi...ve%20frequency ref http://www.k5rmg.org/A-soup.html in most definitions microwaves start at 1GHz or 30CM what frequencies "microwave ovens" use is irrelevant as marketers can pretty much name anything what they want. |
"Truth" wrote in message ... 900 MHz are NOT microwaves Interesting. Especially since the older microwave ovens operated on 800 and 900 Mhz. Why are people who are uneducated in certain subjects always the first to jump in on a conversation and tell everyone else how they think things really are? Yeah, why is that? http://en.wikipedia.org/wiki/Microwave (For the non-curious, the paragraph of interest says: Microwaves, also known as Super High Frequency (SHF) signals, have wavelengths approximately in the range of 30 cm (1 GHz) to 1 mm (300 GHz). ) -- ----------------------------------------------------------------------------- If there's nothing that offends you in your community, then you know you're not living in a free society. Kim Campbell - ex-Prime Minister of Canada - 2004 ----------------------------------------------------------------------------- For direct replies, take out the contents between the hyphens. -Really!- |
Is AM Radio Harmful? Only if you listen to it.
|
Microwaves, also known as Super High Frequency (SHF) signals, have wavelengths
approximately in the range of 30 cm (1 GHz) to 1 mm (300 GHz). This is a pathetic attempt to avoid the real issue and turn the argument another way to avoid the statement they were unable to dispute. Saying microwaves magically start at 1000 Mhz, and saying 999 Mhz is not, and 800 Mhz is not, is bull**** talk. Regardless of where you want to call it, the FACT remains that Microwave Ovens were manufactured that cooked your food with frequencies in the 800 Mhz region. So, since we can cook food and heat at 800 Mhz, and since cell phones are using the same frequency range, we can make a definite connection here. Any attempt to shift the discussion to one about where we now want to classify the word "microwaves" to be appropriate is just childish and ignorant, and nothing more than diversion from the point about cell phones being dangerous. LEGAL exposure to certain RF in Russia can be different than the LEGAL limits in the US. As if RF follows any of these laws, or as if a cell phone is not going to harm you just because you change the definition of what can be legally called microwaves. What was considered low blood pressure a decade ago, is now being called high blood pressure in an attempt to sell more medication and make more money. Just the AMA changing the imaginary boundary line did not make us all suddenly have high blood pressure, just as your changing what is now considered microwaves has no effect on this issue either. ----------------------------------------------------------------------------- If there's nothing that offends you in your community, then you know you're not living in a free society. If there is nothing that offends you in your community, then you ALSO know you're not living in a dictatorship either. This is a stupid play on words that is meaningless! You can NEVER have any society in which nothing offends anyone! Not under ANY government. Idiots. |
Truth wrote:
Regardless of where you want to call it, the FACT remains that Microwave Ovens were manufactured that cooked your food with frequencies in the 800 Mhz region. So, since we can cook food and heat at 800 Mhz, and since cell phones are using the same frequency range, we can make a definite connection here. Three things: 1) You need to recheck the frequency of the magnetrons in microwave ovens. 2) You need to recompare the power levels between microwave ovens and cell phones (*cough* 0.3 W v. 1500 W, a factor of 5000 difference *cough*) 3) *Plonk* |
So, since we can cook food and heat at 800 Mhz, and since cell phones are using the same frequency range, we can make a definite connection here. since we will die if we walk into a blast furnace we has best not even light a candle. great logic Any attempt to shift the discussion to one about where we now want to classify the word "microwaves" to be appropriate is just childish and ignorant, and nothing more than diversion from the point about cell phones being dangerous. cell phones don't even make good blunt instrument any more, just too light. LEGAL exposure to certain RF in Russia can be different than the LEGAL limits in the US. As if RF follows any of these laws, or as if a cell phone is not going to harm you just because you change the definition of what can be legally called microwaves. your wild allegations are unsupported by any credible sources. What was considered low blood pressure a decade ago, is now being called high blood pressure in an attempt to sell more medication and make more money. an unwarranted assumption Just the AMA changing the imaginary boundary line did not make us all suddenly have high blood pressure, just as your changing what is now considered microwaves has no effect on this issue either. since the dawn if time he earth has been drenched in radio waves and radiation. since the advent of electromagnetic telecommunications and power grid distribution mans lifespan has dramatically increased. therefore radio waves are good for you. |
"Truth" wrote in message ...
So, since we can cook food and heat at 800 Mhz, and since cell phones are using the same frequency range, we can make a definite connection here. Where is the scientific data on this? Cite? Link? -- McWebber No email replies read If someone tells you to forward an email to all your friends please forget that I'm your friend. |
"Truth" wrote in message ...
What if the government issues a statement that smoking cigarettes is good for you and gets rid of cholesterol? Would you start smoking? Uhhhhhh.... yes? How sad for you. Go have another Diet Coke with Aspartame. What's wrong with aspartame? Just wait until all the kids using cell phones today don't live to even get to retirement age. There are people using cell phones now that have been using them for more than 20 years in Japan. How long do you think it will take for the epidemic to show up? -- McWebber No email replies read If someone tells you to forward an email to all your friends please forget that I'm your friend. |
Tim Perry wrote:
since the dawn if time he earth has been drenched in radio waves and radiation. since the advent of electromagnetic telecommunications and power grid distribution mans lifespan has dramatically increased. therefore radio waves are good for you. By that reasoning, so are carbon dioxide and feces. -- "The Democrats are all over this. Democratic strategists feel John Kerry's war record means he can beat Bush. They say when it comes down to it, voters will always vote for a war hero over someone who tried to get out of the war. I'll be sure to mention that to Bob Dole when I see him." -- Jay Leno |
Truth wrote:
To oversimplify a bit: Low frequencies (like AM broadcast) pass through the body without being absorbed. Microwave frequencies bounce off the body without being absorbed. ROTFFL!!! Why not PROVE your ridiculous theory by putting your head into a microwave oven! .......yeah. I didn't think so. .....or by leaning against a 50,000 watt AM antenna while standing on the ground. |
McWebber wrote:
"Truth" wrote in message ... What if the government issues a statement that smoking cigarettes is good for you and gets rid of cholesterol? Would you start smoking? Uhhhhhh.... yes? How sad for you. Go have another Diet Coke with Aspartame. What's wrong with aspartame? Just wait until all the kids using cell phones today don't live to even get to retirement age. There are people using cell phones now that have been using them for more than 20 years in Japan. How long do you think it will take for the epidemic to show up? No one knows. |
Scott Dorsey wrote:
Mister Fact wrote: Certainly my reply was not related to any physical harm which might result from radio waves themselves- but since the message board has to do with radio broadcasting in general- I thought it would be a good opportunity to inject ANOTHER TYPE OF MEDICAL HARM which I see inherent in AM broadcasting today. Isn't that what Rush Limbaugh was doing? Injecting another type of harmful medicine? --scott The thread is a bit ambiguous. I think AM radio can be harmful if talk show hosts thereon are dividing peoples. |
Tim Perry wrote:
"Truth" wrote in message ... There is still no commercially-available equipment for the 902 MHz amateur band that I am aware of. Using commercially-available equipment is cheating anyway. What does it take to modify PCS cellular phone firmware for digital communication on 902? Is it just a matter of firmware or isn't the RF section able to tune that far out of band? Think of it this way. When you have an FM broadcast antenna and transmitter, it makes quite a difference when switching within the same band from 88 Mhz to 100 Mhz. (only 12 Mhz) Now you want to take something from around 850 Mhz to 902 Mhz (52 Mhz difference) Plus the higher up you go, the more critical the circuitry. Even in the 440 band you are already dealing with microsurgery when using the miniature surface mount components. pretty might the same for all hand held electronics these days Besides, working with microwaves is never a good idea. everyone has to have a hobby... 900 MHz are NOT microwaves (we call it microwave in brroadcast, but it is a slang term for high UHF) Might as well just take up smoking cigarettes instead. I would play with mercury and use lead paint in my home no problem, but I would not ever build a transmitter and use microwave frequencies. gunplexers are friendly... bi-directional line-of-sight audio How did a disussion about AM radio (later microwave RF) change to audio? |
David Eduardo wrote:
"Bob Haberkost" wrote in message ... "David Eduardo" wrote in message ... Huh? AM stations essentially always have vertical radiators, especially in Europe where there are so many high powered stations. In general, AMs don't work very well otherwise. This concludes your antenna theory class for the day. ;-) Very interesting discussion. Thanks. How about introducing the masses to franklin antennas, such as the system still in use at KFBK in Sacramento. I believe KDKA once had one, too. I saw one in South America that had no real ground system, just the two elements of the Frnklin and a ground mat at the base. There's a Franklin at N 41.6 and w 93.3: http://www.desmoinesbroadcasting.com...use _9867.jpg |
Sir Circumference wrote:
Is AM Radio Harmful? Only if you listen to it. Oh, yeah? Try dropping a Satellite 800 on your foot. -- "The Democrats are all over this. Democratic strategists feel John Kerry's war record means he can beat Bush. They say when it comes down to it, voters will always vote for a war hero over someone who tried to get out of the war. I'll be sure to mention that to Bob Dole when I see him." -- Jay Leno |
"Dan Robbins" wrote in message ... There's a Franklin at N 41.6 and w 93.3: http://www.desmoinesbroadcasting.com...use _9867.jpg I don't know if it still exists, but KELO 1320 used to even advertise it had a Franklin. |
On 8 Sep 2004 19:00:59 GMT, clifto wrote:
Tim Perry wrote: since the dawn if time he earth has been drenched in radio waves and radiation. since the advent of electromagnetic telecommunications and power grid distribution mans lifespan has dramatically increased. therefore radio waves are good for you. By that reasoning, so are carbon dioxide and feces. No carbon dioxide, no plants, little oxygen. No feces, little agriculture. Well, some places anyway. :-) OTOH, no feces, very few politicians. |
"clifto" wrote in message ... Tim Perry wrote: since the dawn if time he earth has been drenched in radio waves and radiation. since the advent of electromagnetic telecommunications and power grid distribution mans lifespan has dramatically increased. therefore radio waves are good for you. By that reasoning, so are carbon dioxide and feces. by George i think hes got it! consider: CO2 is necessary for tree/plant life. human/animal waste products enrich the soil, which aids plant growth. which provides healthy food, which gives us humans more time to build and operate radio stations for the enjoyment of the multitudes. the more people the more the cume and TSL therefore the more cash flow and life is wonderful. searching back trying to find who added all these freaking cross posts... this thread just started out in alt.radio,alt.radio.broadcasting |
"clifto" wrote in message
... Tim Perry wrote: since the dawn if time he earth has been drenched in radio waves and radiation. since the advent of electromagnetic telecommunications and power grid distribution mans lifespan has dramatically increased. therefore radio waves are good for you. By that reasoning, so are carbon dioxide and feces. Read what he was replying to. That's his point. The reasoning doesn't hold water. -- McWebber "Richter points to the lack of legal action against his company as proof that he's operating appropriately." Information Week, November 10, 2003 |
"David Eduardo" wrote in message ... "Dan Robbins" wrote in message ... There's a Franklin at N 41.6 and w 93.3: http://www.desmoinesbroadcasting.com...use _9867.jpg I don't know if it still exists, but KELO 1320 used to even advertise it had a Franklin. In deference to Steve who says the previous thread is dead, let me answer David's question about KDKA's "Franklin"....but only to say that KDKA's Franklin wasn't truly that. A Franklin radiator looks like two self-supporting towers, one inverted on top the other, fat ends touching. The one such that I remember (and I'd have to think that most of us have seen the picture) is WLW's tower that participated in the superpower experiments in the 30s. KDKA's radiator was simply described in the license as a center-fed vertical radiator, where the base impedance and input power was determined through quasi-indirect means at the input to the balun necessary to match the balanced feed point with the unbalanced transmission line (in years past, this stick was fed with balanced feed line, not unlike VHF twin lead on acid...hams know this feed line as "ladder" feedline, because of the characteristic cylindrical insulators placed at regular lengths along the conductors to maintain the correct separation between those conductors). KDKA's antenna was fairly broadbanded, which if I remember correctly is a feature of center-fed radiators. But WLW's Franklin, because of the larger cross-section where current was higher, had a very nice, minimally-sloped reactance curve, and thus a very consistent, symmetrical impedance...if you ever heard WLW when they played music in the 70s, it really sounded great. KDKA's system had, of course, a ground system, to help pull down the skywave, but due to the fact that my manager (who shall go nameless to protect the embarassed) let the neighborhood kids ride their BMX motorcycles on the property (she thought that the presence of life on the transmitter grounds would deter vandalism), breaking a significant number of radials that were exposed by rutting after heavy rains dredged out the BMX paths, it didn't work all that well...on solar max periods, we'd often get fading well within our local metro coverage area because so much power went skyward and came back down, just slightly out-of-phase with the ground wave. The antenna I had direct experience with was replaced in the mid 90s, but from what I've heard the only thing that was changed was the steel....the basic design was retained, and the counterpoise was repaired. -- ----------------------------------------------------------------------------- If there's nothing that offends you in your community, then you know you're not living in a free society. Kim Campbell - ex-Prime Minister of Canada - 2004 ----------------------------------------------------------------------------- For direct replies, take out the contents between the hyphens. -Really!- |
A Franklin radiator looks like two self-supporting towers, one inverted on top the other, fat ends touching. Nope. A Franklin is defined as a center-fed sectional, which is 180 degrees over 180 degrees. The base of the bottom section is connected to the ground system by an impedance, usually a capacitor. KSTP's Franklin is not a Frankin on account it is 179 degrees over 179 degrees. A true Franklin has an efficiency of 510 mV/m/kW at 1 km. KSTP's certainly equals that, although it is classified by the FCC as a conventional sectional. KDKA's sectional is just that. As was WOAI's. 120 degrees over 120 degrees. WHO's radiator isn't a Franklin, either, it is a "WHO Type", and is so classified by the FCC. It is 300 degrees tall. A true Franklin has the best horizontal field of any radiator. A WHO-type radiator probably has the best anti-fading performance of any radiator. |
A Franklin radiator looks like two self-supporting towers, one inverted on top the other, fat ends touching. Naw ... that's a Blaw-Knox, named for the company which manufactured them. Not many still standing today. |
Peter H. wrote:
A Franklin radiator looks like two self-supporting towers, one inverted on top the other, fat ends touching. Nope. A Franklin is defined as a center-fed sectional, which is 180 degrees over 180 degrees. The base of the bottom section is connected to the ground system by an impedance, usually a capacitor. So it is asymmetric, with the two sections slightly different lengths, or the base capacitor is used to compensate for that? If it were in free air, it would simply be a vertical dipole, but since the ground is below it, the electrical lengths of the bottom leg is changed, right? KSTP's Franklin is not a Frankin on account it is 179 degrees over 179 degrees. What does this do to the pattern in real terms? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
"Peter H." wrote in message ... A Franklin radiator looks like two self-supporting towers, one inverted on top the other, fat ends touching. Naw ... that's a Blaw-Knox, named for the company which manufactured them. Not many still standing today. I think there are a couple. New Hampshire (WFEA?), WSM, WLW, and the WBT installation. WADO took theirs down when the new 50 kw DA was built 3-4 years ago. |
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