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Re: SWR

 

While I agree with most of your post, measuring PEP power from a
modulating audio signal is not quite as simple as it looks. The terms
"peak" and "average" power typically are associated with a CW signal.

If you are using the nano as a DC voltmeter then you are probably
measuring a CW signal, not modulated SSB signal.

Measuring a CW signal doesn't help much in setting mic gain to prevent
IMD distortion in a SSB signal.

While all kinds of stuff can be calculated from forward and reverse
power, much of it doesn't help much with someone trying to make a
contact on 7277khz. What you *really* need to know at that specific
point in time is if your tuner is providing a proper match between the
antenna and the transmitter. And it is reverse power that is the best
measure of that.

tim ab0wr

On Tue, 8 May 2018 18:26:01 -0600
"Arv Evans" <arvid.evans@...> wrote:

Tim AB0WR, and others...

Peak power is based on a calculation from average power, or from a
peak power
(doubler) type detector. The Arduino provides capability to do that
calculation,
either from peak to average or from average to peak. By using a
calibrated detector
to measure RF voltage and a current transformer to measure RF current
it is possible
to use software to calculate feed-point impedance at the measurement
location.

Dr. Bill will probably be quick to point out that this does not take
into account any phase
relationships, but neither do traditional forward and reverse power
meters. If your
forward power peak and reverse power dip do not coincide then there
may be a
problem with impedance match involving phase angle errors in the
measurements.

An SWR bridge can be designed to subtract reflected power from forward
power, or
to provide separate readouts for each of them. If using a NANO as
the DC voltmeter
it becomes possible to use forward and reflected power to provide many
different
displays (DB, FWD, REF, SWR, RF Volts, RF Amperes, Watts, Efficiency,
Impedance,
etc.).

It is also possible to install a 1 meter long pickup antenna a few
yards from the
antenna to monitor near-field signal strength and display it on the
NANO DC meter
reading, in DB, Volts, or some other relative field intensity
measurement. Using such
a pickup will tell you whether the FWD peak or REF dip represents
maximum power
into the aether.

Antennas, feed-lines, output filters, and final amplifiers are complex
interrelated
subjects that usually require complex analysis of each component to
arrive at an
accurate statement of fact.

Arv K7HKL
_._


On Tue, May 8, 2018 at 4:47 PM, Tim Gorman <tgorman2@...> wrote:

How are you going to get pep power on voice using the nano in order
to set your mic level? How many ubitx users have even implemented a
mic gain control?

Not everyone uses an antenna that is perfectly resonant on all
frequencies. If you never see any reverse power then your antenna
setup is probably unique.

I'll repeat, probably 99% of people that think they are seeing SWR
on their consumer swr meters are actually seeing nothing but a
reverse power reading. You are saying that most amateurs are not
getting sufficient information from their swr meters.

I disagree. They are getting exactly what they need.

tim ab0wr

On Tue, 08 May 2018 15:08:42 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Yes, you want peak power to minimize distortion.
But peak or average, some indication of forward power is better
than none for this.

If I have blown a PA fuse, I'd expect to see zero reverse power.
And if that is all I could see, I'd think all was well.

Once you have the two ADC voltage readings from a Tandem match,
the resources required for computing forward and reverse power
and SWR are given in post 48223. Quite insignificant. And I
have the Nano pins.

SWR is an easy and customary way of showing at least some aspects
of how the antenna system is doing. Most hams are comfortable
with it. For me, showing forward and reverse power would be
sufficient. Also showing SWR seems a reasonable thing to do, and
trivial. Just reverse power, not enough information
Re: SWR

 

Some one has already done some nice SWR work with the Arduino. I am implementing this in my uBITX



73. Nick VK4PLN
Re: SWR

 

On Tue, 08 May 2018 16:24:59 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

If they have no mike gain control, they might well be twiddling RV1
instead to get somewhat more uniform power output across the bands.
Any forward power indication be it peak or average or somewhere
inbetween would help here.? Perhaps set it while in CW mode.
How do you set mic gain in CW mode in order to minimize distortion?
What does RV1 have to do with mic gain and distortion?



I never suggested that I have a perfectly resonant antenna.
An SWR indication is a clue about how far off resonance an antenna is
that most hams are familiar with.? Just seeing reverse power?
would be rather confusing, as an acceptable number there would
vary from rig to rig depending on whether it is putting out 1W or
100W.?
No, reverse power is the indication of how far off resonance an antenna
is that most hams are familiar with. They just don't know it.

I use the 10watt reverse power setting on my MicroMatch with both my
ubitx and my AL811H. I use the tuner to minimize reverse power in both
cases. When the tuner has matched the antenna system, reverse power
should be zero whether you are running 1W or 1000W.


I haven't bought a lot of consumer SWR meters, but I'm pretty sure
they all make an attempt to show SWR.? ?Not just reflected power.
What the meter label shows has nothing to do with what they are
measuring. Again, you get 1:1 SWR when reflected power is zero
regardless of what the forward power is. You don't adjust your tuner
for maximum power out, you adjust it for minimum reflected power.



At any rate, build what you wish.
I have no problem with that.
And the rest of us will do the same.

I'm done here.

Jerry
Calculating SWR when it is not needed could prevent implementation of a
feature I would rather see. I will continue to advocate for what I see
as the most efficient feature design.

You may advocate for what you to see as the most efficient feature
design as well.

That's how the free market works!

tim ab0wr
Re: ND6T AGC implementation for uBIT-X

 

Have you figured out what the price will be?

I assume you'll take paypal?

tim ab0wr

On Tue, 08 May 2018 17:33:28 -0700
"Kees T" <windy10605@...> wrote:

DHL tracking says the AGC and Click boards will be here by the end of
the day Wed May 9th, 2018.

73 Kees K5BCQ
Re: ND6T AGC implementation for uBIT-X

 

DHL tracking says the AGC and Click boards will be here by the end of the day Wed May 9th, 2018.

73 Kees K5BCQ
Re: boosting the power on 28 MHz #ubitx

[email protected]
 

Just out of curiosity, what sort of power levels can be had with the finals wide open without doing the rest of the mod? Not that I am planning on doing that. Just wondering.

Dave, WS1ETI
Re: ubitx audio #ubitx

 

Great looking case.

I would suggest you calibrate the bfo first to see if that improves the audio. My ubitx bfo was substantially off from the factory. I used a pc and the spectrogram software to center the receive audio. That worked great, even with stock firmware.
Mike Ku4qo?

On Tue, May 8, 2018, 2:54 PM pat griffin <patgriffin@...> wrote:
I finally got the ubitx finished.? It is mounted in a Ten-Tec clamshell box such that it can be opened for service.? Other than a 4-line display and rf gain control (not connected) for future work, it is stock.? First contact from Birmingam AL to east Texas last night.? So far, no problems have surfaced with the Cat5 cable connecting the display and board.
For my bit40, I used the VK3YE mod () in which the local oscillator frequency is shifted slightly to enhance the 2K audio region.? I claim this made a difference in my transmit audio based on anecdotal reports.? I assume to make a similar mod to the ubitx would involve modifying the software to change CLK#0.? I haven't looked at the software yet.? Any opinions (are you kidding!!??) about whether this audio mod is necessary on the ubitx and if so is moding the software the way to go?
Thanks es 73,
Pat AA4PG

Re: SWR

 

Tim AB0WR, and others...

Peak power is based on a calculation from average power, or from a peak power
(doubler) type detector.? The Arduino provides capability to do that calculation,
either from peak to average or from average to peak.? By using a calibrated detector
to measure RF voltage and a current transformer to measure RF current it is possible
to use software to calculate feed-point impedance at the measurement location.?

Dr. Bill will probably be quick to point out that this does not take into account any phase
relationships, but neither do traditional forward and reverse power meters.? If your
forward power peak and reverse power dip do not coincide then there may be a
problem with impedance match involving phase angle errors in the measurements.

An SWR bridge can be designed to subtract reflected power from forward power, or
to provide separate readouts for each of them.? If using a NANO as the DC voltmeter
it becomes possible to use forward and reflected power to provide many different
displays (DB, FWD, REF, SWR, RF Volts, RF Amperes, Watts, Efficiency, Impedance,
etc.).?

It is also possible to install a 1 meter long pickup antenna a few yards from the
antenna to monitor near-field signal strength and display it on the NANO DC meter
reading, in DB, Volts, or some other relative field intensity measurement.? Using such
a pickup will tell you whether the FWD peak or REF dip represents maximum power
into the aether.

Antennas, feed-lines, output filters, and final amplifiers are complex interrelated
subjects that usually require complex analysis of each component to arrive at an
accurate statement of fact.

Arv? K7HKL
_._


On Tue, May 8, 2018 at 4:47 PM, Tim Gorman <tgorman2@...> wrote:
How are you going to get pep power on voice using the nano in order to
set your mic level? How many ubitx users have even implemented a mic
gain control?

Not everyone uses an antenna that is perfectly resonant on all
frequencies. If you never see any reverse power then your antenna setup
is probably unique.

I'll repeat, probably 99% of people that think they are seeing SWR on
their consumer swr meters are actually seeing nothing but a reverse
power reading. You are saying that most amateurs are not getting
sufficient information from their swr meters.

I disagree. They are getting exactly what they need.

tim ab0wr

On Tue, 08 May 2018 15:08:42 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=[email protected]> wrote:

> Yes, you want peak power to minimize distortion.
> But peak or average, some indication of forward power is better than
> none for this.
>
> If I have blown a PA fuse, I'd expect to see zero reverse power.
> And if that is all I could see, I'd think all was well.
>
> Once you have the two ADC voltage readings from a Tandem match,
> the resources required for computing forward and reverse power and SWR
> are given in post 48223.? Quite insignificant.? And I have the Nano
> pins.
>
> SWR is an easy and customary way of showing at least some aspects of
> how the antenna system is doing.? Most hams are comfortable with it.
> For me, showing forward and reverse power would be sufficient.
> Also showing SWR seems a reasonable thing to do, and trivial.
> Just reverse power, not enough information
>





Re: ubitx audio #ubitx

Daniel Conklin
 

That should be 45MHZ IF filter...
Re: ubitx audio #ubitx

Daniel Conklin
 

Nice looking rig!? The KD8CEC software has a feature called ATT (45KHZ filter IF shift) that will do that, and it has a lot of other great features too.? Here's the link:??? You should also check out ubitx.net for a nicely organized journal of everything uBiTX.
73, Dan? W2DLC
Re: SWR

 

If they have no mike gain control, they might well be twiddling RV1 instead
to get somewhat more uniform power output across the bands.
Any forward power indication be it peak or average or somewhere inbetween
would help here.? Perhaps set it while in CW mode.

I never suggested that I have a perfectly resonant antenna.
An SWR indication is a clue about how far off resonance an antenna is
that most hams are familiar with.? Just seeing reverse power?
would be rather confusing, as an acceptable number there would
vary from rig to rig depending on whether it is putting out 1W or 100W.?

I haven't bought a lot of consumer SWR meters, but I'm pretty sure
they all make an attempt to show SWR.? ?Not just reflected power.

At any rate, build what you wish.
I have no problem with that.
And the rest of us will do the same.

I'm done here.

Jerry



On Tue, May 8, 2018 at 03:47 pm, Tim Gorman wrote:
How are you going to get pep power on voice using the nano in order to
set your mic level? How many ubitx users have even implemented a mic
gain control?

Not everyone uses an antenna that is perfectly resonant on all
frequencies. If you never see any reverse power then your antenna setup
is probably unique.

I'll repeat, probably 99% of people that think they are seeing SWR on
their consumer swr meters are actually seeing nothing but a reverse
power reading. You are saying that most amateurs are not getting
sufficient information from their swr meters.

I disagree. They are getting exactly what they need.

Re: FT8 on uBITX experiences

 

Since we're on the topic of FT8 and other digital modes, is it common practice to use an online log?? I've been logging my voice QSO's in a notebook and just counting on the log file for WSJT-X for FT8.? I really only use FT8 to test propagation and don't consider myself a heavy user.? Of course there is no requirement to log online but is it expected with digital modes?? I would just assume stick to best/common practices if there is such a thing.
--

Re: SWR

 

How are you going to get pep power on voice using the nano in order to
set your mic level? How many ubitx users have even implemented a mic
gain control?

Not everyone uses an antenna that is perfectly resonant on all
frequencies. If you never see any reverse power then your antenna setup
is probably unique.

I'll repeat, probably 99% of people that think they are seeing SWR on
their consumer swr meters are actually seeing nothing but a reverse
power reading. You are saying that most amateurs are not getting
sufficient information from their swr meters.

I disagree. They are getting exactly what they need.

tim ab0wr

On Tue, 08 May 2018 15:08:42 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Yes, you want peak power to minimize distortion.
But peak or average, some indication of forward power is better than
none for this.

If I have blown a PA fuse, I'd expect to see zero reverse power.
And if that is all I could see, I'd think all was well.

Once you have the two ADC voltage readings from a Tandem match,
the resources required for computing forward and reverse power and SWR
are given in post 48223.? Quite insignificant.? And I have the Nano
pins.

SWR is an easy and customary way of showing at least some aspects of
how the antenna system is doing.? Most hams are comfortable with it.
For me, showing forward and reverse power would be sufficient.
Also showing SWR seems a reasonable thing to do, and trivial.
Just reverse power, not enough information
Re: SWR

 

Yes, you want peak power to minimize distortion.
But peak or average, some indication of forward power is better than none for this.

If I have blown a PA fuse, I'd expect to see zero reverse power.
And if that is all I could see, I'd think all was well.

Once you have the two ADC voltage readings from a Tandem match,
the resources required for computing forward and reverse power and SWR
are given in post 48223.? Quite insignificant.? And I have the Nano pins.

SWR is an easy and customary way of showing at least some aspects of how?
the antenna system is doing.? Most hams are comfortable with it.
For me, showing forward and reverse power would be sufficient.
Also showing SWR seems a reasonable thing to do, and trivial.
Just reverse power, not enough information

Speaking of post 48223
For all the carping about how my programming style,
nobody actually found a bug.? Here's one.
<? lcd.print((val/div) + 0x30);
>? lcd.print(val/div);

They both compile.
The original worked fine in my C program testbed on a linux box.
But in ArduinoLand, lcd.print() is an overloaded function, does different stuff
when fed an ascii character than it does if fed an integer.
For an old school C programmer, ascii characters are integers.

Jerry, KE7ER


On Tue, May 8, 2018 at 01:50 pm, Tim Gorman wrote:
Everything you mention has to do with forward power, not with SWR. And
unless you can get the nano to read peak envelope forward power
it isn't going to help much in setting the mic level to minimize
distortion.

If your reflected power is high then exactly what does knowing forward
power tell you? It's the high reverse power that is going to lead you
to look to your connectors and antenna, not the forward power. And if
you have a blown PA fuse, exactly how much reverse power do you expect
to see?

When we used to chase echo problems in the telephone network we never
worried about forward power, only about reverse power. We looked for
things like a bad hybrid in a trunk circuit that was causing reflected
power to generate echo.

And none of this has anything to do with the resources required to
calculate SWR! As I've said before, what most people think of as SWR is
really nothing more than a measure of reverse power. I don't have a
single general-consumer SWR meter in my shack, and I have a lot of them,
that actually calculates SWR. In SWR position they all just measure
reverse power. And you adjust your tuner for minimum reverse power.

Using finite nano resources to calculate SWR just appears to me to be
waste of resources. Measure reverse power and label it "SWR". How many
people will ever notice?
Re: Thunderbolt and lightning, very, very frightening me

R. E. Klaus
 

Great post. For anyone that would like to know how the pros do it, look up the Motorola rc56 manual.
73 K1AUS
Re: Thunderbolt and lightning, very, very frightening me

Gordon Gibby
 

¿ªÔÆÌåÓý

?Allison --- thanks, that is GREAT information.....

From: [email protected] <[email protected]> on behalf of ajparent1/KB1GMX <kb1gmx@...>
Sent: Tuesday, May 8, 2018 4:53 PM
To: [email protected]
Subject: Re: [BITX20] Thunderbolt and lightning, very, very frightening me
?
I've worked with shelters and all for land mobile.? They are ringed underground with rods and wires,
same with surfaces and corners and then everything that goes into teh building is though a copper
plate with with polyphasor or similar before it geto to anything inside. IT's bonded to the tower with
copper straps usually wide like 4 to 6 inches and more than one.? They can take a direct hit.

Many years before a AM BC station.? You have the filed with the 120 wire ground plane,
ground rods most 12ft abound.? Tower is up on insulators for base feed but thereis an
arc gap from each leg spaced maybe 3 inches? the feed sire goes to the load coil in the
doghouse next to the base and that has straps to ground for RF and sparks.? ?The feed lines
are arranged to arc ro ground before the TX shed.? Been there during a storm, the
sparks are impressive and frightening.? About 1 in 10 caused the big 5kw RCA to shut down
usually a reset of breakers was all it took to start running the heaters(tubes) then B+ and
the modulator.? About twice a year the power company feed was a problem so we were
1KW off genset backup.

Me I've gotten hit twice one direct to the house antenna, fried the #6 wire to BBs and
much of the electronics in the house.? Second time it hit a pole down the hill before
it went underground about a mile away the surge got me, mostly minor.

The big thing is to protect so two things happen.? You do not burn the house down.
Your insurance then will cover any damage (or they do their best to weasel out).
Complying with NEC code is more for the prevention of insurance issues.

Call me pragmatic.? Prepare for the worst be, happy if it doesn't happen.

Allison

Re: Thunderbolt and lightning, very, very frightening me

 

I've worked with shelters and all for land mobile.? They are ringed underground with rods and wires,
same with surfaces and corners and then everything that goes into teh building is though a copper
plate with with polyphasor or similar before it geto to anything inside. IT's bonded to the tower with
copper straps usually wide like 4 to 6 inches and more than one.? They can take a direct hit.

Many years before a AM BC station.? You have the filed with the 120 wire ground plane,
ground rods most 12ft abound.? Tower is up on insulators for base feed but thereis an
arc gap from each leg spaced maybe 3 inches? the feed sire goes to the load coil in the
doghouse next to the base and that has straps to ground for RF and sparks.? ?The feed lines
are arranged to arc ro ground before the TX shed.? Been there during a storm, the
sparks are impressive and frightening.? About 1 in 10 caused the big 5kw RCA to shut down
usually a reset of breakers was all it took to start running the heaters(tubes) then B+ and
the modulator.? About twice a year the power company feed was a problem so we were
1KW off genset backup.

Me I've gotten hit twice one direct to the house antenna, fried the #6 wire to BBs and
much of the electronics in the house.? Second time it hit a pole down the hill before
it went underground about a mile away the surge got me, mostly minor.

The big thing is to protect so two things happen.? You do not burn the house down.
Your insurance then will cover any damage (or they do their best to weasel out).
Complying with NEC code is more for the prevention of insurance issues.

Call me pragmatic.? Prepare for the worst be, happy if it doesn't happen.

Allison
Re: SWR

 

Jerry,

Everything you mention has to do with forward power, not with SWR. And
unless you can get the nano to read peak envelope forward power
it isn't going to help much in setting the mic level to minimize
distortion.

If your reflected power is high then exactly what does knowing forward
power tell you? It's the high reverse power that is going to lead you
to look to your connectors and antenna, not the forward power. And if
you have a blown PA fuse, exactly how much reverse power do you expect
to see?

When we used to chase echo problems in the telephone network we never
worried about forward power, only about reverse power. We looked for
things like a bad hybrid in a trunk circuit that was causing reflected
power to generate echo.

And none of this has anything to do with the resources required to
calculate SWR! As I've said before, what most people think of as SWR is
really nothing more than a measure of reverse power. I don't have a
single general-consumer SWR meter in my shack, and I have a lot of them,
that actually calculates SWR. In SWR position they all just measure
reverse power. And you adjust your tuner for minimum reverse power.

Using finite nano resources to calculate SWR just appears to me to be
waste of resources. Measure reverse power and label it "SWR". How many
people will ever notice?

tim ab0wr

On Mon, 07 May 2018 18:04:05 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Tim,

It's useful to see forward power when setting mike gain to avoid
distortion. Especially on a rig where transmit power levels vary
significantly by band.

And it can be useful to get most any information on how the rig is
performing. If reflected power looks a little odd, the first thing I
would want to know is forward power. Could be trouble with the BNC
connector, or with that 24 gauge magnet wire dipole, or a blown
PA-PWR fuse.?

No, you don't need a forward power indication if you know everything
is working. What's more, if you know everything is working, you don't
need to know reverse power. Many rigs that are used with resonant
antennas don't have either. And if your cell phone works, you don't
need a ham rig at all. Heck, you don't need a cell phone, you're
better off reading a book.

Bottom line:
We're having fun.
It's useless to argue.
?
Regarding your i2c ADC, I'm not 100% sure how much i2c traffic
it takes to switch between reading samples from two input pins.
You could be right, it might be done in less than my estimated 10
bytes. If all you want to do is read reflected power, yes that will
be considerably less. But not faster than an analogRead() of a Nano
pin. And I'm not inclined to add electronics if the Nano is
sufficient.
Jerry, KE7ER

On Mon, May 7, 2018 at 05:22 pm, Tim Gorman wrote:


No twist. We are saying the same thing. Just different ways.

The only difference is that I'm saying swr is a waste of time to try
and calculate. Even in a dual-pointer swr meter you are really
looking to minimize the reverse power indicator with a tuner, not
maximize forward power.

In fact, in some cases maximum forward power and minimum reverse
power don't occur at the same matching point. So what do you do?
You minimize reverse power. So what does forward power and swr buy
you?

tim ab0wr
Re: Thunderbolt and lightning, very, very frightening me

Gordon Gibby
 

¿ªÔÆÌåÓý

"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."



The schematic & some of the parts information is in this article:

?

See page 3 for suggestions for the Gas Discharge Tube.


Use .01 uf ceramic capacitors.? 1 Kv types and two of them in parallel.? ?Were cheap on Digikey.

I would recommend 100K 1 or 2 watt composition or thin/thick film resistors in parallel with both the antenna and the gas discharge tube.


Or just forget the series capacitor and just put one 100K across the Gas Discharge tube.



If there is a direct hit all of this is likely to be vaporized or toast.

I would suggest that you replace the gas discharge tube every few years depending on how active your area is.? ?an expert to whom I spoke indicated that repeated small discharges slowly raise the break-over voltage of the device.? ??


i'm in a very high activity area so maybe I should do it every 2 or 3? years.? ?You might be in a very minimum area and only every decade or so???


Who knows.


Anyway, while I have had friends have radios destroyed,? I have never ever had one destroyed.? ?


Hope this helps.? ?The important thing is NOT the metal construction, instead the important thing is the SIZE OF THE GRouND WIRE and how good your ground is, and a pretty good ground wire between the two SO-239's also!!!!!!? ? ?ideally these things should be placed on the OUTSIDE of your house.? ?What I have tended to do since my radios are on the second floor, is to position a ground wire right near the coax (you can wrap that or even connect it to the shield) or "near" the balanced line......? ?to create a spark gap that the lightning will jump THERE.


Coax jumps around 5 kV.??


Hope all of this is helpful!!

Gordon kx4z




From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Tuesday, May 8, 2018 3:30 PM
To: [email protected]
Subject: Re: [BITX20] Thunderbolt and lightning, very, very frightening me
?
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



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

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?

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
>
>



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