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Bird Brained Question
Woudn't the bird consitute but a tiny capacitance to ground and thus not
experience an RF burn of consequence? "Cecil Moore" wrote in message ... AA5QT wrote: For the first time in many years, I'm about to put up a 20 meter monobander on a tower. The XYL is asking questions I cannot answer, specifically relating to RF and birds. I wouldn't want to be a bird sitting on an element when a KW is supplied to it? Are my concerns valid? I've tried to chase Starlings away by applying 100W to my 20m rotatable dipole. Some fly away. Some just sit there and tingle, jumping around and ruffling their feathers. On my antenna, the only place guaranteed to chase away a bird is the feedpoint with one foot on each side. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Chuck wrote in message ... Woudn't the bird consitute but a tiny capacitance to ground and thus not experience an RF burn of consequence? After all, birds sit on high voltage distribution lines with no ill effects. At some point, I guess, corona leakage becomes a factor. You don't see them sitting on the 100kv+ stuff. |
"WB2JKX" wrote in message ... Chuck wrote in message ... Woudn't the bird consitute but a tiny capacitance to ground and thus not experience an RF burn of consequence? Let's see here... First, The bird must have some fundamental capacitance to the rest of the known universe. lets take a stab and say it is 10pf since he is pretty far away from almost everything. I'm sure there is a formula for the capacitance of a 4 inch diameter sphere somewhere... Second, Lets model this as 10pf to ground. Now, what's the current through this 10pf at the tip of the antenna (assuming his foot-element contact resistance is well below the Xc)...We're at 20M, 15M or 10M, so, without resorting to math, Xc is pretty low, in general terms. Hmmm could be substantial even at 100W, no? Sounds like his poor feet could indeed get enough to make life difficult. After all, birds sit on high voltage distribution lines with no ill effects. At some point, I guess, corona leakage becomes a factor. You don't see them sitting on the 100kv+ stuff. Completely different situation due to the 60 HZ. The 10pf would lead to negligible current... "Just don't get one foot on each wire, Son. Your Unkle Tweety did that and there was a loud pop and he was gone in a bright flash. Some feathers and a bad smell was all that remained." "On the other hand, son, getting to the top of one of those really high man made trees with wires and your feathers'll all stand on end! Its really cool! Just don't let your mother catch you doing that." -- Steve N, K,9;d, c. i My email has no u's. |
Birds also sit on high-tension lines carrying many amps at thousands of
volts. Makes you wonder if it interferes with their built-in compass. "AA5QT" wrote in message ... For the first time in many years, I'm about to put up a 20 meter monobander on a tower. The XYL is asking questions I cannot answer, specifically relating to RF and birds. I wouldn't want to be a bird sitting on an element when a KW is supplied to it? Are my concerns valid? Gary K5QT --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.708 / Virus Database: 464 - Release Date: 6/18/2004 |
"WB2JKX" wrote in message ... Chuck wrote in message ... Woudn't the bird consitute but a tiny capacitance to ground and thus not experience an RF burn of consequence? After all, birds sit on high voltage distribution lines with no ill effects. At some point, I guess, corona leakage becomes a factor. You don't see them sitting on the 100kv+ stuff. A more valid comparision is how much of a wavelength does the bird's two feet shunt on the antenna wire? I'd suspect the problem would increase with frequency; becoming very painful in the VHF regions. Peter |
Hal wrote,
Birds also sit on high-tension lines carrying many amps at thousands of volts. Makes you wonder if it interferes with their built-in compass. There seems to be a general belief, around here (Belmont CA), that the changing magnetic fields from power lines retards children's development and lowers their collective IQ. Has anyone noticed whether or not birds are acting any more retarded than usual? 73, Tom Donaly, KA6RUH |
Hal wrote,
Birds also sit on high-tension lines carrying many amps at thousands of volts. Makes you wonder if it interferes with their built-in compass. There seems to be a general belief, around here (Belmont CA), that the changing magnetic fields from power lines retards children's development and lowers their collective IQ. Has anyone noticed whether or not birds are acting any more retarded than usual? 73, Tom Donaly, KA6RUH |
"Steve Nosko" wrote in message ... "WB2JKX" wrote in message ... Chuck wrote in message ... Woudn't the bird consitute but a tiny capacitance to ground and thus not experience an RF burn of consequence? Let's see here... First, The bird must have some fundamental capacitance to the rest of the known universe. lets take a stab and say it is 10pf since he is pretty far away from almost everything. I'm sure there is a formula for the capacitance of a 4 inch diameter sphere somewhere... Second, Lets model this as 10pf to ground. Now, what's the current through this 10pf at the tip of the antenna (assuming his foot-element contact resistance is well below the Xc)...We're at 20M, 15M or 10M, so, without resorting to math, Xc is pretty low, in general terms. Hmmm could be substantial even at 100W, no? Sounds like his poor feet could indeed get enough to make life difficult. After all, birds sit on high voltage distribution lines with no ill effects. At some point, I guess, corona leakage becomes a factor. You don't see them sitting on the 100kv+ stuff. Completely different situation due to the 60 HZ. The 10pf would lead to negligible current... "Just don't get one foot on each wire, Son. Your Unkle Tweety did that and there was a loud pop and he was gone in a bright flash. Some feathers and a bad smell was all that remained." "On the other hand, son, getting to the top of one of those really high man made trees with wires and your feathers'll all stand on end! Its really cool! Just don't let your mother catch you doing that." i havent noticed a problem with injured birds on the broadcast towers. FMs up to 100,000 W ERP. (about 14,000 W per bay in my case). 5,000 W AM towers both non and directional including top loaded arrays. not a problem either (in fact i have had birds nest in them) I have one site that uses open wire transmission lines to feed a 5 tower array... 10.4 amps of RF at the common point. up to 10 amps of base current. located in a wildlife refuge. still no birds frying themselves. now i have been burnt a few times working on this thing... maybe it goes to show that birds ARE smarter then radio engineers. |
Tdonaly wrote:
Has anyone noticed whether or not birds are acting any more retarded than usual? I trap Starlings and House Sparrows, enemies of my Purple Martins. I caught two Cardinals in my ***unbaited*** bird trap. I moved the trap to my enclosed front porch where the lattice work has one inch square openings. I caught two House Wrens in my unbaited trap sitting on my front porch inside the lattice work. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Tdonaly wrote:
Has anyone noticed whether or not birds are acting any more retarded than usual? I trap Starlings and House Sparrows, enemies of my Purple Martins. I caught two Cardinals in my ***unbaited*** bird trap. I moved the trap to my enclosed front porch where the lattice work has one inch square openings. I caught two House Wrens in my unbaited trap sitting on my front porch inside the lattice work. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Tim Perry wrote:
now i have been burnt a few times working on this thing... maybe it goes to show that birds ARE smarter then radio engineers. Birds are smart enough not to stand on the ground and put their wings on the hot wires. :-) -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
-- Lamont Cranston The Shadow Knows "Cecil Moore" wrote in message ... Tim Perry wrote: now i have been burnt a few times working on this thing... maybe it goes to show that birds ARE smarter then radio engineers. Birds are smart enough not to stand on the ground and put their wings on the hot wires. :-) And the ones that don't go into the Field Day Bird Stew pot. Field day -- participate -- you may need the experience when the BIG one hits. Grumppp no power, no phones, no cell phones, no internet |
"Da Shadow" wrote in message news:T6BCc.7593$rn1.2467@okepread07... -- Lamont Cranston The Shadow Knows "Cecil Moore" wrote in message ... Tim Perry wrote: now i have been burnt a few times working on this thing... maybe it goes to show that birds ARE smarter then radio engineers. Birds are smart enough not to stand on the ground and put their wings on the hot wires. :-) actually in this case grounded or ungrounded makes no difference. the RF just burns a very painful hole in what ever part of your skin you carelessly brush against the hot wires. some of the vacuum variable caps have adjustment knobs with metal set screws... ouch try to remember to only adjust with your fingertips touching the bakelite. this is a very old array built in 1949. And the ones that don't go into the Field Day Bird Stew pot. Field day -- participate -- you may need the experience when the BIG one hits. Grumppp no power, no phones, no cell phones, no internet |
Tim Perry wrote:
"---this is a very old array built in 1949." In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI |
Tim Perry wrote:
"---this is a very old array built in 1949." In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI |
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Richard Harrison wrote:
In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI Thanks to all; these are nice stories when they show up. Almost a thread of it's own, hint hint. Too bad a lot of the current generation just coming online to do rf systems engineering won't have such good ones to pass on - "Well we fired up the 1W 5600Mhz biaamp and the female inverse TNC connector on the antenna side was shorted! The amp got warm to the touch after 15 minutes! It was a close thing. Funny though, the users within 300m could still get decent throughput." tom K0TAR |
Richard Harrison wrote:
In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI Thanks to all; these are nice stories when they show up. Almost a thread of it's own, hint hint. Too bad a lot of the current generation just coming online to do rf systems engineering won't have such good ones to pass on - "Well we fired up the 1W 5600Mhz biaamp and the female inverse TNC connector on the antenna side was shorted! The amp got warm to the touch after 15 minutes! It was a close thing. Funny though, the users within 300m could still get decent throughput." tom K0TAR |
Richard Harrison wrote:
Tim Perry wrote: "---this is a very old array built in 1949." In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI I worked at KWLO in Waterloo, IA back in the late 70's. It was only a 5Kw station with a five element directional array. During the day only two of the towers were fed and the night time pattern used all five. During my initial instruction on how to read the current meters at the tower bases, the chief engineer was showing me how to put the meter in the clips and then rock the shorting bar out of the parallel clips that were in the circuit. One side of the shorting bar was always in a clip. then you would read the meter and put the shorting bar back into the clips. After that you could remove the meter. Well, he was behind the transmitters and the phasing cabinet in a fairly confined space showing me how to do the task. Set the meter in place, rock the shunt out of one clip, take the measurement, rock the meter out of the clips. How many of you caught the problem in that sequence? Yup, that is the way he did it. The arc from the clip to the current meter made the prettiest ohm sign I have ever seen. I saw the engineer starting to rock the meter and was already moving away when he broke the connection. The relexes of youth are a wonderful thing. The only thing that happened to him was that he banged the back of his hand on the inside of the cabinet as he got it out of the way of the arc. The transmitter didn't even miss a beat on that little shenannigan. It may have shown an overload on some of the warning lights but I can't recall right now. |
Richard Harrison wrote:
Tim Perry wrote: "---this is a very old array built in 1949." In 1949 I worked at the KPRC (950 KHz) / KXYZ (1320 KHz) plant at Deep Water, TX. They shared a main tower which was built for KTRH (740 KHz), which had moved to Cedar Bayou. The tower was near 1/2-wavelength at 1320 KHz and a high impedance for both stations. One operator responsibility was periodic logging of tower currents. For lightning protection, the RF ammeters were shunted with knife switches which must be open during reading. Since the main tower was so hot at its feedpoint, we had a wooden stick with a bent nail in one end to operate the knife switches. RF burns are unpleasant. This stick would burn a carbon trail to your hand in a couple of weeks and be replaced. The sparks along the carbon trail were spectacular but benign if the stick was replaced soon enough. Best regards, Richard Harrison, KB5WZI I worked at KWLO in Waterloo, IA back in the late 70's. It was only a 5Kw station with a five element directional array. During the day only two of the towers were fed and the night time pattern used all five. During my initial instruction on how to read the current meters at the tower bases, the chief engineer was showing me how to put the meter in the clips and then rock the shorting bar out of the parallel clips that were in the circuit. One side of the shorting bar was always in a clip. then you would read the meter and put the shorting bar back into the clips. After that you could remove the meter. Well, he was behind the transmitters and the phasing cabinet in a fairly confined space showing me how to do the task. Set the meter in place, rock the shunt out of one clip, take the measurement, rock the meter out of the clips. How many of you caught the problem in that sequence? Yup, that is the way he did it. The arc from the clip to the current meter made the prettiest ohm sign I have ever seen. I saw the engineer starting to rock the meter and was already moving away when he broke the connection. The relexes of youth are a wonderful thing. The only thing that happened to him was that he banged the back of his hand on the inside of the cabinet as he got it out of the way of the arc. The transmitter didn't even miss a beat on that little shenannigan. It may have shown an overload on some of the warning lights but I can't recall right now. |
So, that's their excuse.
"Tdonaly" wrote in message news:20040623235522.19052.00000561@mb- There seems to be a general belief, around here (Belmont CA), that the changing magnetic fields from power lines retards children's development and lowers their collective IQ. |
So, that's their excuse.
"Tdonaly" wrote in message news:20040623235522.19052.00000561@mb- There seems to be a general belief, around here (Belmont CA), that the changing magnetic fields from power lines retards children's development and lowers their collective IQ. |
On 23 Jun 2004 12:17:49 GMT, in rec.radio.amateur.antenna you wrote: For the first time in many years, I'm about to put up a 20 meter monobander on a tower. The XYL is asking questions I cannot answer, specifically relating to RF and birds. I wouldn't want to be a bird sitting on an element when a KW is supplied to it? Are my concerns valid? Some where around here I have several photos of Cormorants (I think that's how it's spelled) sitting on the beams. Those are *big* birds and it shows in the droop of the booms and elements. They didn't seem to be concerned about 1500 watts. I couldn't get rid of the darn things. They had decided that was where they were staying for the night. When I'd chase them off they'd just come back. Worse than a load of ice. They are bigger than ducks and there were 8 or 10 of them up there. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Gary K5QT Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
On 23 Jun 2004 12:17:49 GMT, in rec.radio.amateur.antenna you wrote: For the first time in many years, I'm about to put up a 20 meter monobander on a tower. The XYL is asking questions I cannot answer, specifically relating to RF and birds. I wouldn't want to be a bird sitting on an element when a KW is supplied to it? Are my concerns valid? Some where around here I have several photos of Cormorants (I think that's how it's spelled) sitting on the beams. Those are *big* birds and it shows in the droop of the booms and elements. They didn't seem to be concerned about 1500 watts. I couldn't get rid of the darn things. They had decided that was where they were staying for the night. When I'd chase them off they'd just come back. Worse than a load of ice. They are bigger than ducks and there were 8 or 10 of them up there. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Gary K5QT Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
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