Re: Thunderbolt and lightning, very, very frightening me

M Garza

Here is an interesting video from a UK ham who went through a lightning strike.? Quick summary, Unplugged equipment was damaged also.

Marco - KG5PRT?

Show quoted text

On Tue, May 8, 2018, 3:16 PM Matthew Stevens <matthew@...> wrote:

?> Does any of this stuff protect from a direct hit to the antenna?

Nope.. it's intended to bleed off static charge from nearby strikes and
in the air during storms - just like a lightning rod. There are ways to
handle a direct strike. They aren't within the capabilities (or budget)
of a normal amateur. And they're not even foolproof. I have a friend who
owns a commercial tower company. He has on his desk in his office a set
of spark gap balls from a tower he worked on, hollow galvanized spheres
about 1/2"-3/4" wall thickness and maybe 4" in diameter. Each of them is
blown in half from jumping a direct strike to ground off the tower...

He also has a collection of waveguide in his shop that has holes in it
every 3-4' where lightning hit the tower, and some of the energy was
directed down the waveguide. It burned through the side of the channel
every so often as it traveled down. That was an expensive replacement

So, I have polyphasers clamped to ground rods where the feedlines enter
my shack. They do a great job of bleeding off static, maybe even
employing the antenna as something like a lightning rod and dissipating
the charge from the air before a strike even occurs.

But when I'm done operating, my radio is disconnected from the wall
outlet and the antenna, and the feedline from the antenna is left hooked
to ground. I don't trust myself enough to take chances with lightning,
at least not here in central Florida.

73

- Matt nj4y
On 5/8/2018 3:38 PM, Jerry Gaffke via Groups.Io wrote:
> Ah, good.
> I may have to order some parts.
>
> There's lots of radio towers that somehow take direct hits.
> My best guess is they make sure they have a very attractive lightning
> rod up above any antenna.
> Might work for a VHF antenna, not so much an 80m dipole.
>
> Does any of this stuff protect from a direct hit to the antenna?
>
> Jerry
>
> On Tue, May 8, 2018 at 12:25 pm, Gordon Gibby wrote:
>
>? ? ?Here's a constuction article:
>
>? ? ?
>? ? ??
>
>? ? ?sorry for the misspelling.
>
>? ? ?I would put resistors shunting BOTH sides of the capacitor if you're
>? ? ?going to do the capacitor.
>
>? ? ?You don't want the gas discharge tube popping off all the time ---
>? ? ?it can damage transceivers and also itself with the changes that
>? ? ?occur on its electrodes --- I got that from an engineer with a lot
>? ? ?more experience than me.? ?If you have a choke or something else
>? ? ?that dc shorts your antenna then the resistors will be of less
>? ? ?importance but they are basically non-existent compared to the 50ohm
>? ? ?ac impedances your're working with.
>
>? ? ?Of course, you pick the voltge considering the peak AC voltage for
>? ? ?the peak SWR that you're likely to encounter.
>
>? ? ?For most 50 ohm systems of 100 watts or less and SWRs of 2:1 or less
>? ? ?in general, I tend to go with 230-250 volt GDTs.? ?They are not
>? ? ?perfect, they have tolerances also.
>
>? ? ?If you get hit by a REAL bolt....all of this is going to fry anyway
>? ? ?but your house might not.? ?The real goal is to keep nearby strikes
>? ? ?from taking out your radio gear.? ?I live in Gainesville Florda just
>? ? ?outside the peak in Orlando Florida and knock on wood I have WINLINK
>? ? ?and SHARES gateways going 24/7/365 for 2-3 years now and so far, all
>? ? ?is OK.? The wire antennas are always somewhat lower than the peaks
>? ? ?of their trees.? ?My house DID get hit while being constructed
>? ? ?(before the trees.....) and several feet of home security wiring
>? ? ?ceased to exist.? ?We then spent $3000+ and had enormous wires and
>? ? ?lightning arrestors and ground rods on four sides of the house
>? ? ?creating a virtual low frequency faraday cage with wires that are as
>? ? ?big as my thumb.? ? No problems since.
>
>? ? ?Hope this helps,
>
>? ? ?gordon
>
>

Re: SWR

#48482

Oh, there's no doubt it is a matter of personal preference. Still, SWR
is kind of meaningless when you are trying to check out changes to a
PA. Forward power is the meaningful measurement in that case. 

I use CW, SSB, and JT65. I don't see where the mode has much to do with
whether SWR is a meaningful measure to see or not. What most people see
on an SWR meter is a *reverse* power measurement even if it is
calibrated in "SWR". Even with a dual-movement meter you adjust
your tuner for least reverse power, not for maximum forward power. 

For a rig with no power control, forward power is going to be whatever
you have set RV1 to provide. 

If the nano had unlimited resources to offer, this discussion wouldn't
happen. But it does have limited resources. If having to calculate SWR
and do near-real time measurements to do the calculation is a
requirement then at some point something else is going to wind up
getting cut. 

My preference would be to cut SWR first. 

tim ab0wr

On Mon, 7 May 2018 20:52:41 -0500
"K9HZ" <bill@...> wrote:

"I'm saying swr is a waste of time to try and calculate"

I would say that is a matter of personal taste and preference Tim.
Some people just want reflected power or a blinking led.  Others will
want to see meaningful numbers to compare with others when they make
mods to the PA chain.  There are people that use the uBITx here just
on CW.  Some just on SSB.  Do you have a preference for that as well?


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ 

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email:  bill@...

Re: Thunderbolt and lightning, very, very frightening me

Matthew Stevens

#48481

Does any of this stuff protect from a direct hit to the antenna?Nope.. it's intended to bleed off static charge from nearby strikes and in the air during storms - just like a lightning rod. There are ways to handle a direct strike. They aren't within the capabilities (or budget) of a normal amateur. And they're not even foolproof. I have a friend who owns a commercial tower company. He has on his desk in his office a set of spark gap balls from a tower he worked on, hollow galvanized spheres about 1/2"-3/4" wall thickness and maybe 4" in diameter. Each of them is blown in half from jumping a direct strike to ground off the tower...

He also has a collection of waveguide in his shop that has holes in it every 3-4' where lightning hit the tower, and some of the energy was directed down the waveguide. It burned through the side of the channel every so often as it traveled down. That was an expensive replacement

So, I have polyphasers clamped to ground rods where the feedlines enter my shack. They do a great job of bleeding off static, maybe even employing the antenna as something like a lightning rod and dissipating the charge from the air before a strike even occurs.

But when I'm done operating, my radio is disconnected from the wall outlet and the antenna, and the feedline from the antenna is left hooked to ground. I don't trust myself enough to take chances with lightning, at least not here in central Florida.


73

- Matt nj4y
On 5/8/2018 3:38 PM, Jerry Gaffke via Groups.Io wrote:
Ah, good.
I may have to order some parts.
There's lots of radio towers that somehow take direct hits.
My best guess is they make sure they have a very attractive lightning rod up above any antenna.
Might work for a VHF antenna, not so much an 80m dipole.
Does any of this stuff protect from a direct hit to the antenna?
Jerry
On Tue, May 8, 2018 at 12:25 pm, Gordon Gibby wrote:
Here's a constuction article:

    ?
sorry for the misspelling.
I would put resistors shunting BOTH sides of the capacitor if you're
    going to do the capacitor.
You don't want the gas discharge tube popping off all the time ---
    it can damage transceivers and also itself with the changes that
    occur on its electrodes --- I got that from an engineer with a lot
    more experience than me.? ?If you have a choke or something else
    that dc shorts your antenna then the resistors will be of less
    importance but they are basically non-existent compared to the 50ohm
    ac impedances your're working with.
Of course, you pick the voltge considering the peak AC voltage for
    the peak SWR that you're likely to encounter.
For most 50 ohm systems of 100 watts or less and SWRs of 2:1 or less
    in general, I tend to go with 230-250 volt GDTs.? ?They are not
    perfect, they have tolerances also.
If you get hit by a REAL bolt....all of this is going to fry anyway
    but your house might not.? ?The real goal is to keep nearby strikes
    from taking out your radio gear.? ?I live in Gainesville Florda just
    outside the peak in Orlando Florida and knock on wood I have WINLINK
    and SHARES gateways going 24/7/365 for 2-3 years now and so far, all
    is OK.? The wire antennas are always somewhat lower than the peaks
    of their trees.? ?My house DID get hit while being constructed
    (before the trees.....) and several feet of home security wiring
    ceased to exist.? ?We then spent $3000+ and had enormous wires and
    lightning arrestors and ground rods on four sides of the house
    creating a virtual low frequency faraday cage with wires that are as
    big as my thumb.? ? No problems since.
Hope this helps,
gordon

Re: Low power output on ubitx #ubitx #ubitx-help

richcarter03052

#48480

So I think I'm hearing that the power output I see is normal for this kit.? I'd like to see 5W on all bands for obvious reasons.? I'll be reading the threads to see if I can adapt it.? I'm sure folks will be playing with the thing to achieve this.
Rich - KE1EV

Re: Thunderbolt and lightning, very, very frightening me

#48479

Ah, good.
I may have to order some parts.

There's lots of radio towers that somehow take direct hits.
My best guess is they make sure they have a very attractive lightning rod up above any antenna.
Might work for a VHF antenna, not so much an 80m dipole.

Does any of this stuff protect from a direct hit to the antenna?

Jerry

Show quoted text

On Tue, May 8, 2018 at 12:25 pm, Gordon Gibby wrote:

Here's a constuction article:

?

sorry for the misspelling.

?

I would put resistors shunting BOTH sides of the capacitor if you're going to do the capacitor.? ?

You don't want the gas discharge tube popping off all the time --- it can damage transceivers and also itself with the changes that occur on its electrodes --- I got that from an engineer with a lot more experience than me.? ?If you have a choke or something else that dc shorts your antenna then the resistors will be of less importance but they are basically non-existent compared to the 50ohm ac impedances your're working with.??

?

Of course, you pick the voltge considering the peak AC voltage for the peak SWR that you're likely to encounter.

?

For most 50 ohm systems of 100 watts or less and SWRs of 2:1 or less in general, I tend to go with 230-250 volt GDTs.? ?They are not perfect, they have tolerances also.

?

If you get hit by a REAL bolt....all of this is going to fry anyway but your house might not.? ?The real goal is to keep nearby strikes from taking out your radio gear.? ?I live in Gainesville Florda just outside the peak in Orlando Florida and knock on wood I have WINLINK and SHARES gateways going 24/7/365 for 2-3 years now and so far, all is OK.? The wire antennas are always somewhat lower than the peaks of their trees.? ?My house DID get hit while being constructed (before the trees.....) and several feet of home security wiring ceased to exist.? ?We then spent $3000+ and had enormous wires and lightning arrestors and ground rods on four sides of the house creating a virtual low frequency faraday cage with wires that are as big as my thumb.? ? No problems since.??

?

?

Hope this helps,

gordon

?

Re: Thunderbolt and lightning, very, very frightening me

#48478

Verrrry good information.
Can you point to a recipe with schematic and parts fully specified?

If the antenna does take a direct hit, does it destroy the device?
I find it hard to imagine that a GDT can take everything a lightning bolt has to offer.
Or that the series caps could possibly survive.

Jerry

Show quoted text

On Tue, May 8, 2018 at 12:18 pm, Gordon Gibby wrote:

It is a very simple device.? ?A $3 gas discharge tube.? (I prefer the one with ratings to 20kA)

A series capacitor --- actually two in parallel probably to reduce inductance

A shunt resistor to drain off static so it doesn't build up and then Pop across the gas discharge tube.? ?

I think it might be brighter to put the shunt resistor across the ANTENNA side of the capacitor.? ?And you could even put another one across the Gas Discharge Tube.

Most people seem to think 100K ohm maybe 1 watt or more is reasonable.

?

We buillt these locally.? ?The ground connection (for lightninng) of course is the important part.? Shortest straightest biggest wire to the best ground you have.??

?

Re: Thunderbolt and lightning, very, very frightening me

Gordon Gibby

#48477

开云体育

Here's a constuction article:

?

sorry for the misspelling.

I would put resistors shunting BOTH sides of the capacitor if you're going to do the capacitor.? ?

You don't want the gas discharge tube popping off all the time --- it can damage transceivers and also itself with the changes that occur on its electrodes --- I got that from an engineer with a lot more experience than me.? ?If you have a choke or something else that dc shorts your antenna then the resistors will be of less importance but they are basically non-existent compared to the 50ohm ac impedances your're working with.??

Of course, you pick the voltge considering the peak AC voltage for the peak SWR that you're likely to encounter.

For most 50 ohm systems of 100 watts or less and SWRs of 2:1 or less in general, I tend to go with 230-250 volt GDTs.? ?They are not perfect, they have tolerances also.

If you get hit by a REAL bolt....all of this is going to fry anyway but your house might not.? ?The real goal is to keep nearby strikes from taking out your radio gear.? ?I live in Gainesville Florda just outside the peak in Orlando Florida and knock on wood I have WINLINK and SHARES gateways going 24/7/365 for 2-3 years now and so far, all is OK.? The wire antennas are always somewhat lower than the peaks of their trees.? ?My house DID get hit while being constructed (before the trees.....) and several feet of home security wiring ceased to exist.? ?We then spent $3000+ and had enormous wires and lightning arrestors and ground rods on four sides of the house creating a virtual low frequency faraday cage with wires that are as big as my thumb.? ? No problems since.??

Hope this helps,

gordon

Show quoted text

From: [email protected] <[email protected]> on behalf of Gordon Gibby <ggibby@...>
Sent: Tuesday, May 8, 2018 3:18 PM
To: [email protected]
Subject: Re: [BITX20] Thunderbolt and lightning, very, very frightening me

?

I've disassembled a Polyphaser before to conform what is in it.??

It is a very simple device.? ?A $3 gas discharge tube.? (I prefer the one with ratings to 20kA)

A series capacitor --- actually two in parallel probably to reduce inductance

A shunt resistor to drain off static so it doesn't build up and then Pop across the gas discharge tube.? ?

I think it might be brighter to put the shunt resistor across the ANTENNA side of the capacitor.? ?And you could even put another one across the Gas Discharge Tube.

Most people seem to think 100K ohm maybe 1 watt or more is reasonable.

We buillt these locally.? ?The ground connection (for lightninng) of course is the important part.? Shortest straightest biggest wire to the best ground you have.??

Since your feedline and antenna constitute a low-pass filter....this turns out to have been useful against EMP (regardless of what some say) as proven by articles published by ARRL in the 1980's.???

cheers, gordon

From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Tuesday, May 8, 2018 12:51 PM
To: [email protected]
Subject: Re: [BITX20] Thunderbolt and lightning, very, very frightening me

?

Looks like good advice.
The Polyphaser stuff has been around for awhile, and is designed for this kind of use.
If you are in an area that sees lightning, you want a proven system.
And you want to follow all instructions closely.

Here's a discussion on eham that might put the fear of god in you.
? ??

Unfortunately, those whose budget just barely covers a Bitx40 might decide to go without.
This one is good to a kilowatt, $68.99 plus shipping.? ?
? ??
Plus multiple ground rods, #6 copper wire, ...
Gets worse if you have multiple antennas.

One of these gas discharge tubes might do it for cheap:
? ??
but I'm not about to hazard a guess as to what's appropriate around lightning.
And that eham discussion suggests the Polyphaser thing is more than just a GDT,
has some caps in it too, and I have no idea what else.?

Anybody with a cheaper solution they feel is adequate for QRP levels?

I'm sure lightning could find a way to bite us here.
But being off grid with no landline phone has its advantages.

While in college I spent summers on BLM fire crews, once spent a couple weeks
in a tower spelling the regular lookout.? They take lots of lightning.
Had a special stool you could cower on in the center of the floor during a storm,
big honking glass insulators on the bottom of the legs.
Just sit there and watch the sparks fly about within the cabin a few feet away.
And then when it was over, the VHF radio still worked.

Jerry

On Tue, May 8, 2018 at 08:24 am, ajparent1/KB1GMX wrote:

Doug,? A ground rod outside (preferable a 8ft or longer...) with a Polyphaser arrester at the top of it
and the cable connecting to that first.? Then a COAX coming inside.? That is a generally safer
and brings all static charges to ground first.??

To make it NEC (national Electric code) a wire #6 or heavier from that ground rod to the
house ground usually near the power entrance is required.? (all grounds bonded together.).

I also advise for dipoles and other non DC shorted (and grounded) antennas a resistor at
the feed point of 100K (2W) to bleed static as well.? Static build up from wind can be as
damaging as a bolt from the sky just not as noisy.

Disconnectig is good practice but a grounded and suppred connection outside its advised.

Allison

Re: Thunderbolt and lightning, very, very frightening me

Gordon Gibby

#48476