? on neon light as static discharge device
Dave
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
ji...@specsol.spam.sux.com
> 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.
Highland Ham
> 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
> 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
ji...@specsol.spam.sux.com
> > Thanks,
> > Dave
I should have added that you can't use the neon if there is a transmitter
attached to the same line.
Dave
<ji...@specsol.spam.sux.com> wrote in message
news:aeqqc4-...@mail.specsol.com...
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
Dave
"Highland Ham" <abcgm0csz...@dsl.pipex.com> wrote in message
news:XPGdna0PRImVI2fY...@pipex.net...
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
Dave
<ji...@specsol.spam.sux.com> wrote in message
news:8duqc4-...@mail.specsol.com...
No problem, no transmitter here. Receiver only.
Thanks.
Dave
Highland Ham
> that be inductive and mess with my incoming signal?
Dave , My apology , I meant indeed metal 'film' resistor.
Frank GM0CSZ / KN6WH
Dave
Aah. Gotcha. Thanks for the ideas and the info.
73
Dave
Dave
"Dave" <db5...@hotmail.com> wrote in message
news:12vlmot...@corp.supernews.com...
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
Yukio YANO
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
Dave
"Yukio YANO" <ya...@shaw.ca> wrote in message
news:j3BKh.25152$DN.7632@pd7urf2no...
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
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
Uncle Peter
> >> 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
>
Chris Jones
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
Dave
"Chris Jones" <lugn...@nospam.yahoo.com> wrote in message
news:12vmhne...@corp.supernews.com...
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
Uncle Peter
"Dave" <db5...@hotmail.com> 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.
.
>
> 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
>
Dave
"Uncle Peter" <radioco...@cox.net> wrote in message
news:F%DKh.14670$mJ1....@newsfe22.lga...
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
Chris Jones
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 _
.
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.
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.
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.
Chris
Dave
Gotcha. Thanks.
Dave
Dave
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
Arv
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
_._
Dave
"Arv" <arvid...@gmail.com> wrote in message
news:1174103602.5...@o5g2000hsb.googlegroups.com...
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
Chris Jones
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.
| / / |
*--|>|-------|<|---* Two Zeners, in series, opposite directions
| / / |
| |
'--||--To Rx ___ Earth
Cap _
.
> My only hesitation there is the power dissipation capabilities
> of Zeners, compared to standard diodes.
You can get very high pulse power rated Zeners, designed for clamping
pulses. They do not call them Zeners though, they call them something
different (TVS? Transzorb?) I think these may have too much capacitance
for 30MHz work.
http://www.vishay.com/diodes/protection-tvs-esd/trans-zorb/
Chris
LenAn...@ieee.org
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
Uncle Peter
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
Dave
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
Jimmie D
>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...
>
>
> 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
Roy Lewallen
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
**THE-RFI-EMI-GUY**
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:
--
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
mcal...@ksu.edu
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 <w7...@eznec.com> 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