? on neon light as static discharge device
I saw somewhere that you could use an NE-2 bulb between the antenna "hot"
lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a ..22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave |
? on neon light as static discharge device
Dave wrote:
I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave This was fairly common in WWII era radios. A NE-2 fires at around 90-110V, which is more than a lot of solid state equipment can handle, so the protection offered is dubious with modern radios. That said, it certainly can't hurt anything to try it if you have some weird problem with static. You can still get them, but probably not locally. Jameco (http://www.jameco.com/) still carried them last I looked. To see where a particular bulb actually fires, put the bulb in parallel with a capacitor and feed it with around a 100V or so DC though a resistor of a few K. You will have built a relaxation oscillator. The larger the cap and/or resistor, the lower the flash rate. If you don't have a 'scope to measure the voltage, increase the resistor size until the flash rate is slow enough to watch the cap charge with a voltmeter. -- Jim Pennino Remove .spam.sux to reply. |
? on neon light as static discharge device
Dave wrote:
I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a ..22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... ============================================ To avoid building-up of static you can fit a say 47 Kilo Ohms non-inductive resistor between what you call the 'hot' lead and earth. This would not affect the received or transmitted signal. I have fitted 2 non-inductive (carbon) 1 Watt resistors (47 KOhms) from the incoming balanced feeder to earth at the Antenna Matching Unit. This approach is obviously also OK with an incoming coax feeder. At 100 W RF output the voltage would be 71 V at the transceiver. This would dissipate a little over 0.1 Watt in the 47K resistor fitted at the transceiver. Metal-oxyde resistors can for this purpose also be considered as non-inductive. Frank GM0CSZ / KN6WH |
? on neon light as static discharge device
wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave This was fairly common in WWII era radios. A NE-2 fires at around 90-110V, which is more than a lot of solid state equipment can handle, so the protection offered is dubious with modern radios. That said, it certainly can't hurt anything to try it if you have some weird problem with static. You can still get them, but probably not locally. Jameco (http://www.jameco.com/) still carried them last I looked. To see where a particular bulb actually fires, put the bulb in parallel with a capacitor and feed it with around a 100V or so DC though a resistor of a few K. You will have built a relaxation oscillator. The larger the cap and/or resistor, the lower the flash rate. If you don't have a 'scope to measure the voltage, increase the resistor size until the flash rate is slow enough to watch the cap charge with a voltmeter. -- Jim Pennino Thanks for the reply, Jim. While waiting I set up a charging system for a cap and then tested to see whether the bulb would discharge the cap. No go. I am sure that at a high enough voltage the bulb might help, but I am going to have to use a resistor in parrallel with the bulb, or some other setup, to guard against relatively low voltage static buildup. Thanks for the relaxation osc. idea. I might actually use that in m search. Never would have thought of it. Much appreciated... Dave |
? on neon light as static discharge device
"Highland Ham" wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a ..22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... ============================================ To avoid building-up of static you can fit a say 47 Kilo Ohms non-inductive resistor between what you call the 'hot' lead and earth. This would not affect the received or transmitted signal. I have fitted 2 non-inductive (carbon) 1 Watt resistors (47 KOhms) from the incoming balanced feeder to earth at the Antenna Matching Unit. This approach is obviously also OK with an incoming coax feeder. At 100 W RF output the voltage would be 71 V at the transceiver. This would dissipate a little over 0.1 Watt in the 47K resistor fitted at the transceiver. Metal-oxyde resistors can for this purpose also be considered as non-inductive. Frank GM0CSZ / KN6WH Thanks for the input, Frank. I believe this, or something like it, is what I am going to have to do. I've already got the bulb installed in the receiver case, and I guess I'll leave it there to warn me of impending doom, but the resistor idea is what will probably save my bacon. Is a metal-oxide resistor the same thing as a metal-film resistor? Or would that be inductive and mess with my incoming signal? Thanks much, Dave |
? on neon light as static discharge device
wrote in message ... wrote: Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave This was fairly common in WWII era radios. A NE-2 fires at around 90-110V, which is more than a lot of solid state equipment can handle, so the protection offered is dubious with modern radios. That said, it certainly can't hurt anything to try it if you have some weird problem with static. You can still get them, but probably not locally. Jameco (http://www.jameco.com/) still carried them last I looked. To see where a particular bulb actually fires, put the bulb in parallel with a capacitor and feed it with around a 100V or so DC though a resistor of a few K. You will have built a relaxation oscillator. The larger the cap and/or resistor, the lower the flash rate. If you don't have a 'scope to measure the voltage, increase the resistor size until the flash rate is slow enough to watch the cap charge with a voltmeter. I should have added that you can't use the neon if there is a transmitter attached to the same line. -- Jim Pennino No problem, no transmitter here. Receiver only. Thanks. Dave |
? on neon light as static discharge device
Is a metal-oxide resistor the same thing as a metal-film resistor? Or would
that be inductive and mess with my incoming signal? ========================= Dave , My apology , I meant indeed metal 'film' resistor. Frank GM0CSZ / KN6WH |
? on neon light as static discharge device
"Highland Ham" wrote in message ... Is a metal-oxide resistor the same thing as a metal-film resistor? Or would that be inductive and mess with my incoming signal? ========================= Dave , My apology , I meant indeed metal 'film' resistor. Frank GM0CSZ / KN6WH Aah. Gotcha. Thanks for the ideas and the info. 73 Dave |
? on neon light as static discharge device
"Dave" wrote in message ... "Highland Ham" wrote in message ... Is a metal-oxide resistor the same thing as a metal-film resistor? Or would that be inductive and mess with my incoming signal? ========================= Dave , My apology , I meant indeed metal 'film' resistor. Frank GM0CSZ / KN6WH Aah. Gotcha. Thanks for the ideas and the info. 73 Dave BTW, this brings up another question: I have read that carbon composition resistors have a small amount of capacitive reactance due to the tiny particles that make up their mass, and should not be used for RF projects. But metal film resistors are inductive. So what kind of resistors should I be using in my RF projects? Is there a third type? Thanks, Dave |
? on neon light as static discharge device
Dave wrote:
I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Most CB radios use a pair of back to back diodes across the receiver input. I also recall the input of the ECG amplifiers also have the same network to protect the Input circuitry from being blasted by the Pulse from Defibrillator Paddles (1~5 KV.). These Back to back Diodes Clamp the Voltage to the Forward Voltage Drop of the Diodes in question at around 0.6 Volts. This circuit works much better and for cheaper than the NE2 at ~60 Volts. If Static Electricity (lightning) is a problem at a specific Frequency, a Grounded 1/4 wavelength shorted Stub could be wired into the Feedline to present a DC ground to the entire antenna system. Yukio YANO VE5YS |
? on neon light as static discharge device
"Yukio YANO" wrote in message news:j3BKh.25152$DN.7632@pd7urf2no... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Most CB radios use a pair of back to back diodes across the receiver input. I also recall the input of the ECG amplifiers also have the same network to protect the Input circuitry from being blasted by the Pulse from Defibrillator Paddles (1~5 KV.). These Back to back Diodes Clamp the Voltage to the Forward Voltage Drop of the Diodes in question at around 0.6 Volts. This circuit works much better and for cheaper than the NE2 at ~60 Volts. If Static Electricity (lightning) is a problem at a specific Frequency, a Grounded 1/4 wavelength shorted Stub could be wired into the Feedline to present a DC ground to the entire antenna system. Yukio YANO VE5YS Of course! Back to back diodes! Why didn't I think of that? Thank you, thank you, thank you. How obvious! :) But is there any way that I could still use my neon bulb to let me know if a pulse of high-voltage static hits the input to the receiver? I would love it if there were some way to make that still work... 73's Dave |
? on neon light as static discharge device
"Dave" wrote in message ... "Yukio YANO" wrote in message news:j3BKh.25152$DN.7632@pd7urf2no... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Most CB radios use a pair of back to back diodes across the receiver input. I also recall the input of the ECG amplifiers also have the same network to protect the Input circuitry from being blasted by the Pulse from Defibrillator Paddles (1~5 KV.). These Back to back Diodes Clamp the Voltage to the Forward Voltage Drop of the Diodes in question at around 0.6 Volts. This circuit works much better and for cheaper than the NE2 at ~60 Volts. If Static Electricity (lightning) is a problem at a specific Frequency, a Grounded 1/4 wavelength shorted Stub could be wired into the Feedline to present a DC ground to the entire antenna system. Yukio YANO VE5YS Of course! Back to back diodes! Why didn't I think of that? Thank you, thank you, thank you. How obvious! :) But is there any way that I could still use my neon bulb to let me know if a pulse of high-voltage static hits the input to the receiver? I would love it if there were some way to make that still work... 73's Dave Question on this last note: What if I put the back to back diodes in series with a 100K resistor, and they together in parrallel with the neon bulb. Would that slow the discharge of a fairly large static pulse enough to light the neon bulb, even briefly? I have the input to the receiver protected by a fairly high-voltage (non-electrolytic) capacitor, so I'm not too worried about the slowed-down pulse getting through to the rest of the circuit. And if it did get through it would find an air-gap transmitting variable capacitor next in line as the tuning cap. Is this a dumb idea, or might it behave as I desire? Any ideas? Thanks, Dave |
? on neon light as static discharge device
"Dave" wrote in message ... Frank GM0CSZ / KN6WH Thanks for the input, Frank. I believe this, or something like it, is what I am going to have to do. I've already got the bulb installed in the receiver case, and I guess I'll leave it there to warn me of impending doom, but the resistor idea is what will probably save my bacon. Is a metal-oxide resistor the same thing as a metal-film resistor? Or would that be inductive and mess with my incoming signal? Thanks much, Dave Why would the inductance be of any concern? It would be effectively in series with the resistance, thus raising the device's impedance... I'd think that would lessen the loading on receive or transmit signals. Pete |
? on neon light as static discharge device
Dave wrote:
I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.: http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris |
? on neon light as static discharge device
"Chris Jones" wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.: http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. Still, I am thinking that a couple of back-to-back diodes each with a 100K resistor in series would probably do what I want. Going to try my hand at building a test-bed and give it a shot. Will check out the gas discdharge surge arrestor though. Sounds much simpler, and likely more reliable. Appreciate your feeback. Dave |
? on neon light as static discharge device
"Dave" wrote in message even in very strong Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. snip .. Appreciate your feeback. Dave The neon lamp works the same as a gas voltage regulator--about 80 volts or so IIRC... The resistor serves to limit the current. Pete |
? on neon light as static discharge device
"Uncle Peter" wrote in message ... "Dave" wrote in message ... Frank GM0CSZ / KN6WH Thanks for the input, Frank. I believe this, or something like it, is what I am going to have to do. I've already got the bulb installed in the receiver case, and I guess I'll leave it there to warn me of impending doom, but the resistor idea is what will probably save my bacon. Is a metal-oxide resistor the same thing as a metal-film resistor? Or would that be inductive and mess with my incoming signal? Thanks much, Dave Why would the inductance be of any concern? It would be effectively in series with the resistance, thus raising the device's impedance... I'd think that would lessen the loading on receive or transmit signals. Pete Hello Pete, I was actually thinking something similar, that the diodes would prevent any current from flowing through the circuit so long as the voltage remained on the small-signal level. And if a large pulse did come through, the inductance of the resistors would be the least of my worries. Any interferrance it caused in my receiver would be brief and likely go unnoticed. Does this sound plausible, or at least somewhat predictive of likely real-life events in the case of a static charge coming down the line? Dave |
? on neon light as static discharge device
Dave wrote:
"Chris Jones" wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.: http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. Still, I am thinking that a couple of back-to-back diodes each with a 100K resistor in series would probably do what I want. Going to try my hand at building a test-bed and give it a shot. Will check out the gas discdharge surge arrestor though. Sounds much simpler, and likely more reliable. Appreciate your feeback. Dave I think that the diodes with resistors in series will probably not be ideal. If you want to just discharge small steady currents of static electricity being picked up by your antenna then all you need is a 100k (or 10k) resistor from the antenna to ground. If you want to protect against voltage spikes (e.g. caused by distant lightning), (practically nothing will stop direct lightning) then your diodes, connected in parallel, and one pointing in each direction, will offer some protection, but in that case you must leave out the series resistors because the series resistors will stop the diodes from performing any useful function. If you are likely to experience strong radio signals that could produce more than 0.2V on your antenna (and I would guess that the answer is likely to be yes), then maybe the diodes will introduce intermodulation (a form of interference) into your signal. In this case, a number of diodes in series, in each direction, will allow larger RF signals to pass without excessive distortion. \|/ | Antenna | *-----\/\/\/\------. 100k resistor | | *--||--||--||---* 3x diodes, one direction | | *---||--||--||--* 3x diodes, other direction | | '--||--To Rx ___ Earth Cap _ |
? on neon light as static discharge device
"Uncle Peter" wrote in message ... "Dave" wrote in message even in very strong Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. snip . Appreciate your feeback. Dave The neon lamp works the same as a gas voltage regulator--about 80 volts or so IIRC... The resistor serves to limit the current. Pete Gotcha. Thanks. Dave |
? on neon light as static discharge device
"Chris Jones" wrote in message ... Dave wrote: "Chris Jones" wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.: http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. Still, I am thinking that a couple of back-to-back diodes each with a 100K resistor in series would probably do what I want. Going to try my hand at building a test-bed and give it a shot. Will check out the gas discdharge surge arrestor though. Sounds much simpler, and likely more reliable. Appreciate your feeback. Dave I think that the diodes with resistors in series will probably not be ideal. I was intendending to connect the diodes in parallel, such as you describe below. Sorry for the lack of clarity... If you want to just discharge small steady currents of static electricity being picked up by your antenna then all you need is a 100k (or 10k) resistor from the antenna to ground. If you want to protect against voltage spikes (e.g. caused by distant lightning), (practically nothing will stop direct lightning) then your diodes, connected in parallel, and one pointing in each direction, will offer some protection, but in that case you must leave out the series resistors because the series resistors will stop the diodes from performing any useful function. Why would the resistors disable the diodes? I expected they would merely limit the current through the diodes... If you are likely to experience strong radio signals that could produce more than 0.2V on your antenna (and I would guess that the answer is likely to be yes), then maybe the diodes will introduce intermodulation (a form of interference) into your signal. In this case, a number of diodes in series, in each direction, will allow larger RF signals to pass without excessive distortion. \|/ | Antenna | *-----\/\/\/\------. 100k resistor | | *--||--||--||---* 3x diodes, one direction | | *---||--||--||--* 3x diodes, other direction | | '--||--To Rx ___ Earth Cap _ . For very high frequencies, small diodes such as 1N4148 may be needed, though for lower frequencies you may be able to get away with using larger, more robust diodes. At higher frequencies, big diodes may have too much capacitance. I am working in the HF region, 2-30 MHz. This won't give all that much protection against powerful surges, so if your radio is especially valuable then a commercial protection device might be a good idea, and in any case unplugging the antenna when not in use would be sensible. Oh yes, I do unplug it when not in use. Definetly. Instead of the above circuit using the diodes in parallel, you could also try using a pair of zener diodes in series, one pointing in each direction. I was thinking about Zener diodes, and trying to figure how they might be applied. My only hesitation there is the power dissipation capabilities of Zeners, compared to standard diodes. Chris Thank you very much for the input. I appreciate the chance to bounce ideas off of other people and hear their responses. Dave |
? on neon light as static discharge device
On 16 Mar, 19:40, Chris Jones wrote:
Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.:http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris The so-called 125 volt neon bulb is probably a 50 volt neon bulb with a 47K to 150K resistor in series. Without the resistor it would draw too much current from the 125 volt mains and either trip a circuit breaker or destroy the NE-2 bulb, probably both. An NE-2 bulb has a breakdown potential of approximately 50 volts (slightly more or less depending on external light conditions). If your transmitter never puts more than 50 volts on the feed line you could conceivably use this for a impulse suppression device, but bear in mind that it will not protect your receiver from voltages of less than 50 volts. Once the gas in a neon bulb reaches the breakdown point (50 volts in an NE-2) it becomes a short circuit until the voltage drops below the breakdown point. If you are plagued by static build up on your antenna, and if your feed line normally operates at a low impedance (i.e. 50 ohms) you can use a 10K ohm 2-watt non-inductive resistor to bleed off the static build up. Do not use a wire wound resistor because it's inductance may have a negative impact on feed line SWR. If you want to prevent close-in lightning strikes from causing impulse voltage of over 50 volts you can use that NE-2, but there are better devices like the telephone protector that a previous post recommended. Many persons use a simple impulse protector that is homemade from two pointed sections of metal with one tied to your feed line and the other connected to a good earth ground. This method is documented in most ham radio antenna handbooks. Arv _._ |
? on neon light as static discharge device
"Arv" wrote in message ups.com... On 16 Mar, 19:40, Chris Jones wrote: Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.:http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris The so-called 125 volt neon bulb is probably a 50 volt neon bulb with a 47K to 150K resistor in series. Without the resistor it would draw too much current from the 125 volt mains and either trip a circuit breaker or destroy the NE-2 bulb, probably both. An NE-2 bulb has a breakdown potential of approximately 50 volts (slightly more or less depending on external light conditions). If your transmitter never puts more than 50 volts on the feed line you could conceivably use this for a impulse suppression device, but bear in mind that it will not protect your receiver from voltages of less than 50 volts. Once the gas in a neon bulb reaches the breakdown point (50 volts in an NE-2) it becomes a short circuit until the voltage drops below the breakdown point. If you are plagued by static build up on your antenna, and if your feed line normally operates at a low impedance (i.e. 50 ohms) you can use a 10K ohm 2-watt non-inductive resistor to bleed off the static build up. Do not use a wire wound resistor because it's inductance may have a negative impact on feed line SWR. If you want to prevent close-in lightning strikes from causing impulse voltage of over 50 volts you can use that NE-2, but there are better devices like the telephone protector that a previous post recommended. Many persons use a simple impulse protector that is homemade from two pointed sections of metal with one tied to your feed line and the other connected to a good earth ground. This method is documented in most ham radio antenna handbooks. Arv _._ Wow. Thanks for the info on how the neon bulb works. I had no idea it became a short once the gas was ionized, but now that makes sense. I need to check out the pointed-metal device you describe. Sounds good, but I am really trying to build the static protection into my RF amplifier so that it goes wherever the amplifer goes. Afraid of someone scruffing their feet on the carpet and touching the built-in extendable antenna. Thanks, Arv, for the informative post. Much food for thought... Dave |
? on neon light as static discharge device
Dave wrote:
"Chris Jones" wrote in message ... Dave wrote: "Chris Jones" wrote in message ... Dave wrote: I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave Your "standard neon bulb rated at 125 VAC" probably contains a series resistor of maybe 100kOhms, and so will be not much use for protecting anything, because any current would develop too much voltage across the series resistor. If you open it up and remove the resistor then it will be able to shunt larger currents, though it still may not be ideal for protecting receivers. (The main advantage of the neon as a protection device is very low capacitance which could be important on the higher frequency bands, but another advantage would be that it would introduce practically no intermodulation even in very strong signal conditions, but the breakdown voltage is probably so high that it may not protect solid - state receivers very well, as someone else already mentioned. You can buy a ceramic cased gas discharge surge arrestor, they are popular for telephone circuits. e.g.: http://www.epcos.com/inf/100/ds/ec350xx0810.pdf ) You can probably make the bare neon bulb flicker by charging up something with static electricity (e.g. rub a balloon on your head or on a jumper) and then hold this near the bulb so you can hear crackling. Chris Hey Chris, Thanks for the input. I am wondering why a neon bulb would include a 100K resistor... To maybe lessen the current being driven through the bulb? I'm going to have to check that out. Still, I am thinking that a couple of back-to-back diodes each with a 100K resistor in series would probably do what I want. Going to try my hand at building a test-bed and give it a shot. Will check out the gas discdharge surge arrestor though. Sounds much simpler, and likely more reliable. Appreciate your feeback. Dave I think that the diodes with resistors in series will probably not be ideal. I was intendending to connect the diodes in parallel, such as you describe below. Sorry for the lack of clarity... If you want to just discharge small steady currents of static electricity being picked up by your antenna then all you need is a 100k (or 10k) resistor from the antenna to ground. If you want to protect against voltage spikes (e.g. caused by distant lightning), (practically nothing will stop direct lightning) then your diodes, connected in parallel, and one pointing in each direction, will offer some protection, but in that case you must leave out the series resistors because the series resistors will stop the diodes from performing any useful function. Why would the resistors disable the diodes? I expected they would merely limit the current through the diodes... Yes it will limit the current through the diodes. That is the problem: the current that is not able to flow through the diodes will flow through your RX instead. It is better to remove the resistors in series with the diodes, since the current will do less harm (or less expensive harm) if it flows in the diodes instead of your RX. If you are likely to experience strong radio signals that could produce more than 0.2V on your antenna (and I would guess that the answer is likely to be yes), then maybe the diodes will introduce intermodulation (a form of interference) into your signal. In this case, a number of diodes in series, in each direction, will allow larger RF signals to pass without excessive distortion. \|/ | Antenna | *-----\/\/\/\------. 100k resistor | | *--||--||--||---* 3x diodes, one direction | | *---||--||--||--* 3x diodes, other direction | | '--||--To Rx ___ Earth Cap _ . For very high frequencies, small diodes such as 1N4148 may be needed, though for lower frequencies you may be able to get away with using larger, more robust diodes. At higher frequencies, big diodes may have too much capacitance. I am working in the HF region, 2-30 MHz. This won't give all that much protection against powerful surges, so if your radio is especially valuable then a commercial protection device might be a good idea, and in any case unplugging the antenna when not in use would be sensible. Oh yes, I do unplug it when not in use. Definetly. Instead of the above circuit using the diodes in parallel, you could also try using a pair of zener diodes in series, one pointing in each direction. I was thinking about Zener diodes, and trying to figure how they might be applied. \|/ | Antenna | *-----\/\/\/\------. 100k resistor | | | / / | *--||-------||---* Two Zeners, in series, opposite directions | / / | | | '--||--To Rx ___ Earth Cap _ |
? on neon light as static discharge device
On Mar 16, 5:37�am, "Dave" wrote:
I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. *Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? *Or how I could test it? *I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. *I have *a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Back in the pre-history of most folks here (like 1940), the old ARC-5 Command Set Receivers for HF had little neon bulbs connected in parallel to the high-impedance antenna input. Being IN aircraft that naturally developed some static electricity charges on their wire antennas, the bulbs' kept the static charges from accumulating beyond the (approx) 70 volt bulb breakdown. It was a rudimentary noise reduction scheme back then. For receiving or transmitting, a simple 1:1 (or any other ratio) balun will both DC-ground the antenna and offer DC isolation between antenna and feedline. Any static that tries to accumulate on the antenna is quickly drained away by the DC path to ground. A 1K to 10K half- to 2-watt resistor at a receiver antenna input shunted across it will serve to drain away static electricity charges without seriously changing the antenna impedance. For a balanced antenna input (like 300 Ohm line common with TV and FM BC receivers), just use two of them with the common point to ground. Static electricity build-up is common on insulated long- wire antennas in locations with lots of thunderstorm activity (where I grew up in Illinois, for example). By itself it could, possibly, pose a danger (certainly a very rude shock). A continuous drain-away device such as a balun (preferred) or a resistor will lessen that. Above all - especially in thunderstorm locations - USE A LIGHTNING ARRESTER ON ANTENNAS! 73, Len AF6AY |
? on neon light as static discharge device
Dave
A Zener acts like a regular diode in one direction, the Zener is actually a back biased diode that is run into it's reverse breakdown point (over simplification). You could use two Zeners in SERIES to clamp an AC voltage. I think you should start by giving us some parameters. 1. What kind of receiver are you trying to protect; tube or solid state? 2. Are there any transmitters nearby (ham or CB)? 3. What kind of antenna (long wire, dipole, etc.) 4. Urban or rural environment, nearby AM broadcast facilities? Some other things that you might consider would be adding a sacrificial fuse in line with the protection, say when the diodes or gas arrestor clamp you could have a 47 pilot lamp wired in series with the antenna to limit the current to diodes. Pete |
? on neon light as static discharge device
"Uncle Peter" wrote in message ... Dave A Zener acts like a regular diode in one direction, the Zener is actually a back biased diode that is run into it's reverse breakdown point (over simplification). You could use two Zeners in SERIES to clamp an AC voltage. I think you should start by giving us some parameters. 1. What kind of receiver are you trying to protect; tube or solid state? 2. Are there any transmitters nearby (ham or CB)? 3. What kind of antenna (long wire, dipole, etc.) 4. Urban or rural environment, nearby AM broadcast facilities? Some other things that you might consider would be adding a sacrificial fuse in line with the protection, say when the diodes or gas arrestor clamp you could have a 47 pilot lamp wired in series with the antenna to limit the current to diodes. Pete Hello Pete, Thank you for your reply, and for the questions. My RF amplifier (HF) is solid state, and there is a Ham transmitter two doors down on the same side or the street I live on (urban environment) but no other AM transmitters *that I know of* in the vicinity. I live on the industrial side of town however, and imagine that there probably are some for the various trucking companies etc. which operate within five or ten miles of my home. The antenna is a longwire, consisting of approximately 100' of four (insulated) parallel strands of #24 AWG copper wire running along the ridge-vent of my house. This feeds into another 60' or so of RG-59 coax to shield against noise from the A/C compressor on that side of the house. It is grounded both where it comes off the roof and again where it comes in my window with 10' copper-clad steel grounding rods driven into the moist earth. The RF amplifier is a home-brew version of the MFJ 1020-A, using an air-gap (I hope I have this right) transmitter style variable capacitor for tuning, and has a 630V .1uF capacitor salvaged from the guts of an old TV connecting the center conductor of the coax to this tuning capacitor. I do not know the internal composition of this .1uF capacitor, but assume (hate that word) it is compatible with RF applications since it came out of the RF circuitry of a TV. I used to have a .22uF 50V polyethylene capacitor in its place, but that got blown, alerting me to the possibility of static charges coming down the feedline. Since my antenna is a longwire on the roof of my house, and it does routinely get windy, I imagine static will be an ongoing threat. You mention that two Zener diodes in series could be used to clamp an AC voltage. Could they be used to defend against static? I have two 5.6V Zeners rated at 5W, and would love to employ them in this endeavor. I also have a couple of standard diodes rated at 600 volts PIV and 1 amp. I was thinking of using these, reversed and in parallel with the neon bulb, to take any voltage over the .6 volt threshold of silicon PN devices to ground. Do you think they would do this if I put them between the center conductor of the coax and ground? I am thinking that the "normal" signal level coming from the antenna would probably be something on the order of a couple hundred microvolts, and would therefore not be enough to drive the diodes into conduction. Does this sound reasonable, or am I way off base here? Thank you for your time and interest. I really have no idea what I am doing here, but I am trying to figure it out and plan as best I can. Best regards, Dave |
? on neon light as static discharge device
"Dave" wrote in message ... I saw somewhere that you could use an NE-2 bulb between the antenna "hot" lead and ground as a static discharge device for a receiver, but can't find an NE-2 and don't know anything about neon bulbs. Anybody know if a standard neon bulb rated at 125 VAC could be used in this manner? Or how I could test it? I'm thinking about charging up a 50V electrolytic capacitor and hitting the bulb with that, to see if it discharges the cap. I have a .22uF 630V mylar cap between the antenna and the input to the tuner because the 35V disc I had there got blown, so I know that static can be a problem with my setup even though it is grounded at two points. Would welcome any ideas anyone has on how to make this work... Thanks, Dave A resistor will do as good, a high value of resistance relative to he impedance of the receiver. I use 100K. The neon bulb can be fun though. I used to have one attached to a long wire(200 Ft) or so and it was fun watching it flash during storms. Jimmie |
? on neon light as static discharge device
Sorry, I disagree with many of the suggestions being made. Putting a
nonlinear device or devices like a zener or a series of diodes across your antenna terminals can produce intermodulation among incoming signals. These will appear at your receiver as hash and spurious signals at various frequencies. When transmitting, they can create harmonics. The advice I do go along with is to put a resistor or RF choke across the terminals if static is a problem. Either will prevent it. You won't be able to tell any difference between carbon, carbon film, and metal film in just about any RF application -- any are just fine. Don't use a wire wound resistor, however. I don't see much sense in letting static build up to several tens of volts, then have a neon bulb ignite to discharge it -- with a loud pop you'll hear in your receiver -- down to a slightly lower level. A resistor or RF choke will keep it at near zero. By all means, have fun impressing your friends with blinking NE-2s, but use something else to drain off the static. Roy Lewallen, W7EL |
? on neon light as static discharge device
Back in the good old days of CB, in Chicago, I had a ground plane
antenna which had no DC return path. My Lafayette CB radio started making some very strange noises so I disconnected the PL259 and was surprised to see a spark jumping across the connecter. This continued for hours as the voltage built up and discharged. Pretty impressive display of precipitation static. Roy Lewallen wrote: Sorry, I disagree with many of the suggestions being made. Putting a nonlinear device or devices like a zener or a series of diodes across your antenna terminals can produce intermodulation among incoming signals. These will appear at your receiver as hash and spurious signals at various frequencies. When transmitting, they can create harmonics. The advice I do go along with is to put a resistor or RF choke across the terminals if static is a problem. Either will prevent it. You won't be able to tell any difference between carbon, carbon film, and metal film in just about any RF application -- any are just fine. Don't use a wire wound resistor, however. I don't see much sense in letting static build up to several tens of volts, then have a neon bulb ignite to discharge it -- with a loud pop you'll hear in your receiver -- down to a slightly lower level. A resistor or RF choke will keep it at near zero. By all means, have fun impressing your friends with blinking NE-2s, but use something else to drain off the static. Roy Lewallen, W7EL -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P |
? on neon light as static discharge device
I've never written a follow-up to a Lewallen post, but here is
another advantage to using resistors that Roy didn't mention: If you put your resistor(s) at an OUTside grounding point and if you can remember their value(s), you may be able to make a quick test of the integrity of your feedline from INside the shack with an ohm-meter! (But NOT during a storm, of course!-) Roy Lewallen writes: Sorry, I disagree with many of the suggestions being made. Putting a nonlinear device or devices like a zener or a series of diodes across ....[snip].... The advice I do go along with is to put a resistor or RF choke across the terminals if static is a problem. Either will prevent it. You won't ....[snip].... -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge NRA Life Member & Certified Instructor for Rifle, Pistol, & Home Firearm Safety Also Certified Instructor for the Kansas Concealed-Carry Handgun (CCH) license |
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