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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
>
>



Re: SWR

 

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 ¨C K9ZC
Staunton, Illinois

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

Moderator ¨C North American QRO Group at Groups.IO.

email: bill@...
Re: Thunderbolt and lightning, very, very frightening me

Matthew Stevens
 

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
 

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

 

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: 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

Gordon Gibby
 

¿ªÔÆÌåÓý

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



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
 

¿ªÔÆÌåÓý

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
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