Do you have a picture of the balcony?

----- Original Message -----
From: "Herbert Poetzl" herbert@13thfloor.at
To: time-nuts@febo.com
Sent: Thursday, August 04, 2016 5:29 PM
Subject: [time-nuts] GPS antenna selection

Hi

That’s the spec on the interference  rejection filter. Tighter is better
as long as it still passes the desired signal(s).

The better ones will have a TNC connector on them

You want one that is designed for permanent outdoor use. That eliminates the $10
car mounts. These days, I’d get one that does both GPS and GLONASS

They can’t. It’s just luck. The ones you see for about $40 and up that are designed
for mast mounting are usually pretty good.

The real question is how much of a sky view you get. Ideally you would like a clear view
of the sky from about NE clear around to NW (270 degrees). You also would like to be
able to “see” down to within 10 degrees of the horizon over that range. The segment from
E to W (180 degrees) is pretty important. Being able to see to within 30 degrees of the
horizon is also pretty important.

Some receivers put out +12V, most antennas don’t like +12 and want +5. Some modern
antennas will only handle +3.3V.

If you have a long run to the antenna, feed line loss is what matters. To some degree
you can cope with this by buying an antenna that has a higher gain amp in it. They
range from about 21 db to about 50 db. You also don’t want to over drive your receiver
so just getting the 50 db version is not a perfect solution.

Grounding the antenna is always a good idea. A surge suppressor  in the line could save
you some real cost if there is a lightning strike. I don’t know about Austria, but here in
the US, both are required.

Bob

Hi Herbert,

just look the loss of the cable at 1500 MHz, and you will start to cry
at 1500MHz tha cable will have cca 30dB for a 30meter long
piece....basically that RG174 looks very nice with that small antenna
but that is the only positive aspect. Meinberg in Germany has one
up/down converting system, which makes it possible to go more than 50 meter.
On the other hand if you could stay on the balcony and use the cable
which came with the antenna, 2m  to 3 meter,  you could have a good
working system, but with 15m RG174  is asking to much. For 1500 MHz BNC
is not the best solution,
73
KJ6UHN
Alex
P.S.: wo ist diese "Austrian countryside"

On 8/4/2016 2:29 PM, Herbert Poetzl wrote:

On Thu, Aug 04, 2016 at 06:26:28PM -0400, Bob Camp wrote:

Hey Bob!

Understood!

Hmm, I had to google TNC (Threaded Neill-Concelman).
Is it worth the trouble in the < 2GHz range?

Even under somewhat protected conditions like on the
covered balcony?

Makes sense.

Okay, thanks!

That would opt for the balcony, as it faces north
and extends the slanted roof, so basically clear
view from NE to NW down to the horizon.

Understood! Is there some rule of thumb at what
cable lengths which amplifier gain is best suited?

I did a quick search for SMA/BNC/TNC based surge
protectors and not much did come up, any suggestions
what to use there?

Outside definitely, "inside" I'm not sure, but it
won't hurt to have additional protection for the
receiver(s).

Thanks a bunch,
Herbert

Hi

It threads on rather than latches on like a BNC. That makes it
more water tight in the outdoor environment.

You still have fog / condensation / humidity and the other sources
of moisture. So not quite so important, but we rule out the balcony below.

It needs to face south and have a clear view over a 270 degree arc.
If it faces north …. not going to work very well at all.

The more money you pay for the cable the lower it’s loss. For $10 a meter you
get a lower loss cable than $1 a meter or $0.10 a meter. Figure that anything over
about a 30 meter run will require either a high gain antenna or some money invested
in LMR-400 cable.

There are a lot of them on eBay. Many of them have N connectors on them.

It is a good bet that the antenna will be outside. I’d plan it that way.

Bob

What matters more than anything else is how good is the view of the sky.

Next You want one that will last basically "forever" outdoors.  The
best kind have a plastic radome over a metal base.  The base has pipe
threads for mounting on a standard 3/4" galvanized plumbing pipe.  The
coax wires goes down this pie and never sees the light of day or rain
water either

The shape of the dome does matter, you want the pointed kind that
birds can not perch on.  If the top is flat od even hemispherical it
will get covered with bird poop.

When I put mine up on the roof most of the work was done in the attic.
I drilled a 1 inch hole and pushed the mast (1" pipe" up through the
hole then secured it with U-straps to a rafter and joist and tugged on
it hard from all directions to make sure it would not move.  Put a
level on it first and check for vertical.  It is no more work to use
a longer pipe than a short one so go up 3 feet above the roof line.

Then while ion top of the roof just flash the hole to prevent a leak
and drop the coax cable down the pip and screw on the antenna to the
mast.

You local building code likely wants you to ground the antenna mast
lust like you would with an old TV antenna.  It is a good idea to
prevent lightening damage to the house.

With the radome typically sealed by o-ring to the base plate and the
lead wire hidden inside a galvanized pipe there is nothing to degrade
over time.  It should be maintenance free for decades or until hit by
lightening

Al the other stuff about what kind of coax to buy and what connectors
are best and so on are "in the noise" the important stuff is (1) view
of the sky and (2) build so you will never in your lifetime have to
fix it

If you must place it near a balcony or window make sure it faces south
as that is where the satellites are, they don't orbit over the poles.

I just wrote that the type of cable hardly matters.  I did not think anyone
would try to use RG174.  That is for 1 foot long jumper cables and
oscilloscope probes at most.  If cost is an issue the 75ohm cable TV wire
is cheap and works better then that tiny sized rg175.

There is no need to buy the high priced stuff as you can buy an antenna
with 30db gain and that makes up for the loss in any reasonable cable.

On Thu, Aug 4, 2016 at 3:32 PM, Alex Pummer alex@pcscons.com wrote:

--

Chris Albertson
Redondo Beach, California

On Thu, 04 Aug 2016 23:29:06 +0200, Herbert Poetzl wrote:

I'm using this type (26dB, N Connector) on my balcony (South).
It's mounted on a 1m waterpipe, that is "stripped" to the balcony fence.

I initially bought a 40dB , but had to change to 26dB , due to too much
gain.

www.ebay.com/itm/PCTEL-GPS-TMG-26N-26-dB-Internal-Amplifier-Timing-
Reference-Antenna-/232037804675

www.ebay.com/itm/Lucent-Datum-KS24019L112C-GPS-26dB-5V-Antenna-Telecom-
Timing-N-Conn-Andrews-NEW-/361510967153

I use a Tbolt, that have 75ohm impedance , and am using about 25m quad
shielded 75 ohm , quality sattelite cable from the balcony to the Tbolt.

I'm using a N-->F adapter at the antenna end, that makes it super easy to
make a diy F-->F connector cable.

I now have installed a quad active antenna splitter (50ohm) , using the
same 75ohm cable , and a F-->N adapter at the splitter end. And see no
noticable problems using 75ohm cable there.

CFO
Denmark

Take a look at (yes M$ Silverlight is needed...:( )

 http://www.gnssplanningonline.com/

On "Settings" enter
1) your position (lat, lon, h) - or chose approx position from map.
2) change "cutoff" to 0 deg
3) change "Time span" to max (24h).

On "Satellite library"
1) Disable Glonass, Galileo, BeiDou and QZSS (only GPS remain selected)

Then view "Sky Plot". This is an illustration where the satellites can be
seen by your antenna, with no blocking from house, trees, mountains etc.
The blue outer circle represents the horizon, north up, etc. Circle center
is straigt up into the sky. The fainter grey circles shows 30 and 60 deg
elevation from the horizon.

- Moving the time-ruler (lower-right corner) will show the satellites

move over the selected position.
- While moving the time-ruler around, notice that there is a circle
from north horizon:ish and down (with a latitude of ca N45deg, where
there are never any satellites.
- Where this circle is depends on your latitude.  (check N90deg -north
pole and N0deg (equator) to get a feel of how the priority
directions(azimuth)/elevations are.

You can model your specific obstruction environment at different possible
antenna sites with "Settings" -> "Obstructions".

What is an obstruction? it depends, but first order approx is that
anything that blocks your view will count.

What kind of GPS-receivers will you use? Old receivers (10+years) will
need better installations/locations. Modern high sensitivity receivers
will work decently within many houses. For long cable runs, older receiver
will be more picky, etc.

Good luck!

--

Björn

Unfortunately, an antenna, cable, or piece of electronics located indoors is just as susceptible to lightning surges as one that is outdoors.

Lightning-induced surges couple into these systems electromagnetically across a wide range (VLF to SHF) of frequencies. When you think about your home from an electromagnetic viewpoint, just imagine your structure with all non-conductive materials absent. For a typical wood or brick/stone house in North America, what you are left with is:
metal plumbing pipes and fixtures, with their geometry suspended in space
house wiring, CATV, Ethernet, and telephone cabling, and their service drops, all suspended in space
electrical & electronic circuits of every kind (WiFi note, computer, appliances), their power supplies and AC power cords, also suspended in space
metal furniture? That’s hanging out there, suspended in space, too.
any I-beam or other steel structural elements, some random aluminum flashing, door knobs, and other similar metal construction materials used in the home.
That is what an electromagnetic pulse sees as it approaches and sweeps over your home… all hovering over a lossy ground plane (earth) its varying dielectric constant.. Each one of those pieces of metal, hanging in space, is an unintentional antenna that experiences voltage differentials and current flows.

A GPS antenna and its coax line that is installed next to a window is no different from the same antenna/coax installed one meter outside the window… or 10 meters away outside the window. All three installations are effectively “outdoors” from an electromagnetic viewpoint, and all three need effective surge protection from lightning-, cloud-, and precipitation-induced voltage surges.

(N.B.: Snow can be particularly bad for voltage surges. I’ve seen thousands of volts per meter potential differences in moderate-to-heavy snowfall that produced very significant current flows on cables.)

Surge protection for your antenna, its attachment to your receiver(s), AC/DC power supply lines, and any other signal lines of significant length is cheap insurance.

My continuously-operating electronics lives in an enclosed rack cabinet — not too much worse than a proper Faraday cage. Every cable entering the cabinet has surge protection at the point of entry. The cabinet is bonded to earth ground by 2” copper flashing. In the past this system lived 22 years on a mountaintop home, 1200 ft above surrounding terrain. Lots of thunderstorms — zero damage/disruptions during that time… a sample size of one, admittedly, but during the first 18 months at that site I had two lightning-surge damaging events before I got serious about protection.

I have equipment at a coastal site with multiple 130-ft towers. That site had damage events every 2 years or so — even when cables to the “outside” were disconnected, and AC mains power was shut off at the main circuit breaker box. After implementing comprehensive surge protection, we have had zero damage over the last 12 years.

— Eric

Hi

A ten foot long antenna cable is no more or less an issue indoors than a ten foot serial cable
to a laptop or a ten foot test lead running off of a DVM. They all will pick up a spike if the field
is strong enough. If you are in a high risk location, then yes you will need to go to extremes
for all of those cables. In some cases the only real answer is an external faraday cage around
the entire structure (plus a lot of other stuff).

Bob

Herbert Poetzl wrote:

Yes, lots of variety! See: http://leapsecond.com/museum/gps-ant/

/tvb

Flying a plane with a plexiglas windshield through a snowstorm will give
you a lightning show on your windshield.

Willy

On 8/5/2016 10:37 AM, Eric Scace wrote:

On 08/05/2016 01:45 PM, Bob Camp wrote:

My outside GPS aerial came with the NTBW50AA that's still available
from RDR Electronics. It is on a plastic pole tied to the corner of my
deck and is about 12 feet above the ground. It works with the Lucent
RFTG-u pair as well. The 70 ohm cable is about 40 feet long and both
GPSDOs lock quickly from cold in my cellar lab/shack.

My first venture with GPS was with my Trimble Flightmate Pro that
I bought in October 1993. I knew GPS was supposed to be a precise time
signal. I had built and programmed a Science of Cambridge SC/MP
(INS8060) based computer that decoded the MSF Rugby (no longer there)
60 kHz signal in 1979, still using it in 1994. Comparing it to the
received GPS time on the Trimble, I was dismayed. My records show
that on 1994 June 23 1700 UTC, GPS, or the Trimble, was a whopping
3 seconds slow,vbehind. 1994 July 03 1538 UTC, zero, seemed to be
synchronous. Same day, 1545, 1/2 a second slow. 1552, 2 seconds slow.
1556 1/2 a second slow. I suspect this was due to Selective Availability
that was not turned off until President Clinton ordered it off
in May 2000.

I have a Navsync CW12-TIM that I bought in 2009. Its diminutive
antenna sticks magnetically to a steel filing cabinet in my office.
I get a good signal and lock there.

 In August 2003, I put my hand out of the back door to test the rain.

A lightning bolt split a tree 60 feet away - my wife called me Thor
for many years. The doorbell rang, the garage door control board was
fried and needed replacing, a router in my upstairs office was
blackened, and in 2003, every television and computer monitor in the
house was a CRT - every one of them had to go through several degaussing
sessions.

Best wishes,
Ian, G4ICV, AB2GR

Hi Eric,

On Fri, 5 Aug 2016 10:37:28 -0400
Eric Scace eric@scace.org wrote:

Please please please do NOT spread dangerous information like this!

While it is true, that an indoor antenna is suceptible to surges like
an outdoor antenna, it is not true that an outdoor antenna is equivalent
to an indoor antenna when it comes to lightning protection.

Because an outdoor antenna can be directly hit by a lightning.

To protect the house and its inhabitants from the lightning strike,
an external antenna needs to be either lower than any lightning rod
and within its 45m ball or needs its own conductor and grounding
to discharge any lightning energy and thus preventing it from following
the antenna cable into the house.

Please be aware that the grounding of the antenna is not to protect
the equipment from surges, but to prevent conduction of the lightning
into the house that could cause electrocution and fires.

		Attila Kinali

--
Malek's Law:
Any simple idea will be worded in the most complicated way.

Yo Attila!

On Fri, 5 Aug 2016 22:51:06 +0200
Attila Kinali attila@kinali.ch wrote:

I agree there are differences.  But not as mmuch as you think.

And so can an indoor antetnna.  I live it lightning country, and it is
common for a lightning bolt to travel right through an asphalt roof to
hit metal pipes and/or wire inside a house.

I have seen this many times, it has happened to my next door neighbor and
to my son.  If you are lucky your homeowners insurance will cover a lot of
the damage.

A direct hit on an antenna will laugh at your surge protector.  Nothing
at all can protect your electrical system from a direct hit.

I have seen 440V main switchboards exploded from lightning hits.  The
mess is incredible.  The switchboard case looks like a large bomb went off
inside and the cover leaves a dent on the far wall.

The surge protector on your antenna coax will try to limit the static
voltage on the center conductor to about 1,500V.  Now you have turned
your antenna into a passable lightning rod.

If you have any doubt about lightning you need to get some lightning rods
on your roof.  A usually passable solution is to run #8 wire from your
offical building ground directly up to an antenna mast or two on your
roof.  Best if it can be done with zero splices.

The point of the lightning rod is not to dissipate a lightning strike,
nothing can do that.  Instead it bleeds away static before it becomes
a lightning strike.

In the midwest in the winter the humidity in a house can get well below
5% and 1,500V of statis is quite common.  So indoor surge protectors
can also be useful.

RGDS
GARY

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com  Tel:+1 541 382 8588

lightening protection:

http://www.ul.com/wp-content/uploads/2014/04/LightningProtectionAG.pdf

73
KJ6UHN
Alex

On 8/5/2016 1:51 PM, Attila Kinali wrote:

Hi

Ummm ….. It’s a lot more fun to focus on the 0.001% case :)

Bob

A very good reference for EMP protection is MIL-HDBK-419.
This is downloadable for a number of web sources.
It is about 600 pages and is in two volumes.
This discusses a number of different sources of EMP such as nuclear and
lightning.
A lot is for protection of military industrial complexes, but, there is
a lot that pertains to us.

I worked for a military complex that assembled nuclear missiles.
The site was built to this handbook specs.
We had no EMP related damage at the site.

Number one rule, bond all grounds together. If something on your
property takes a hit, you want everything on your property to elevate to
the same level and the same rate.
If you have multiple, non bonded grounds, there is a different reference
for each ground. This is a major source for disaster.

I spent seven years in lightning mitigation. I was told by professionals
that I was wrong. The third time that their tower was struck, destroying
all of the lights and attached equipment, they followed my
recommendations. That was ten years ago. The three hits were within four
months of each other. The site has been free of destructive hits since then.

73
Glenn
WB4UIV

On 8/5/2016 10:37 AM, Eric Scace wrote:

--

Glenn Little                ARRL Technical Specialist  QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv@arrl.net    AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM  NRA LM  SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

Glenn wrote:

Tisha Hayes has a big fat folder full of good stuff relating to
"Grounding Surge and Filtering" at her dropbox site, and another one
full of "Transient Protection Documents."  See:

https://www.dropbox.com/sh/qjnu6cp03ahajpc/AAABcWVmOZdyPWquiz3az58Ha?dl=0

Best regards,

Charles

On 8/7/16 8:06 PM, Bill Hawkins wrote:

No - strap is about the same inductance as a wire of the same length.
The advantage of strap is a lower RF resistance, which is important if
the strap is part of your antenna system, because it's less resistive
loss than a wire.

For lightning impulses, either conducted or radiated, the inductance
dominates the voltage rise (e.g. Xl is much larger than Rac).

Strap or bar may be easier to make connections to (drill a hole in some
1/8x1" bar, tap it, and hook your lug up)

Hi

We tend to look at all this lighting / EMP stuff very much as a “get to the ground”
sort of thing. For whatever reason the whole thought process stops once we get
to a coper weld rod driven however far into the dirt.

If you try to operate a vertical antenna against that same rod in the middle of a nice dry
summer.  You will quickly find out that dirt != ground. The same fun and games
that get you a low impedance ground for your antenna also apply to a low impedance
ground for your protection system. Its not an identical process, but it’s the same idea.

You can argue that a good bond of everything to a single point is sufficient. Looking around
my house, there is most certainly not a single point of entry for everything. Various
utilities and other wires / chunks of conductive stuff go off in a variety of directions. Like
most homes in the US, it’s a wood frame structure. There is no nice steel frame to
tie everything to. I suppose the first step would be to tear the house down and re-build
it from scratch …..

Bob