"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 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
_._

"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

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 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

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

"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

"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

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

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