It's so nice that they allow pacemakers all the time! I'd hate to think
people would have to turn them off for flights...
Why the ban on AM/FM receivers?
-Dave
- Original Message -
From: Thomas A. Frank ka2...@cox.net
To: Discussion of precise time and frequency measurement
Why the ban on AM/FM receivers?
I assume it's EMI from the local oscillator.
Is anybody shipping an AM/FM radio that isn't superhet?
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On Sun, Oct 04, 2009 at 12:20:26AM -0700, Hal Murray wrote:
Why the ban on AM/FM receivers?
I assume it's EMI from the local oscillator.
Is anybody shipping an AM/FM radio that isn't superhet?
FWIW, I have read and been told that there was an era when some
cheap AM/FM radios put
Although not exactly trivial, it is actually not only possible but
surprisingly easy to design a setup that can indeed withstand repeated
direct lightning strikes without damage.
Large AM transmitters deal with this all the time. Polyphaser
sells a lightning strike *counter* so you can schedule
Hi,
This is correct. There was also an issue with harmonics from the local
oscillator in the aircraft's own VHF nav/comm receivers blocking the GPS. The
answer is a 1575MHz notch filter, e.g.
http://www.edmo.com/index.php?module=productsfunc=displayprod_id=18006
Another problem was bias
Kevin,
That is a very informative description.
I've not lived in a lightning-probable area with antennas. Here
lightining is a remote possibility, but I'm trying to digest what you
have told us.
You said, For example, if you have equipment plugged into two different
surge suppressors, you
Am Sunday 04 October 2009 10:57:22 schrieb kevin-use...@horizon.com:
Consider a lightning strike to be the closest thing to an ideal current
source you are going to encounter. You *cannot* stop it with series
impedance alone, no matter how high; you have to provide it with a very low
shunt
Am Sunday 04 October 2009 12:43:16 schrieb Rex:
Kevin,
That is a very informative description.
I've not lived in a lightning-probable area with antennas. Here
lightining is a remote possibility, but I'm trying to digest what you
have told us.
You said, For example, if you have equipment
Just one little wire that's not tied into the system provides a path
that will let damaging currents come in through any other wire, no matter
how well protected they are.
I had one strike here that came *up* out of our 300 foot deep water well,
when a tree several hundred yards away took a
i have an sr620 and i tried to measure 10 MHz frequency of Z3805
the clock is extarnal lpro101 , gate 1 sec , sample size 10 sec .
with sample size lower then 10 sec there are to much jitter on lower
digit , is this correct ?
there are a better configuration to measure 10 MHz faster with more
Hi Alfredo:
See:
Fast High Precision Set-up of SR 620 Counter
http://www.prc68.com/I/FTS4060.shtml#SR620Fast
Have Fun,
Brooke Clarke
http://www.prc68.com
Dott. Alfredo Rosati wrote:
i have an sr620 and i tried to measure 10 MHz frequency of Z3805
the clock is extarnal lpro101 , gate 1 sec
I dis-agree - call me an old fart or whatever. Your points are valid
and proper logic, but every situation is just not the same.
Bonding everything is proper, but without an effective ground, lightning
will still seek a path to dissipate itself. We are taught if the ground
is not good to
Brooke:
NO NO NO. these devices are hokum. It's true that sharp points will
release shielding charge under a strong electric field such as under or
near a thunderstorm. But think what happens to that charge under any kind
of wind-it goes away. Also, the shielding effect of the charge under
no-wind
On 10/4/09 6:00 AM, Brooke Clarke bro...@pacific.net wrote:
Hi Kevin:
I agree with all you have said regarding how the wiring should be to minimize
currents in equipment, but . . .
It is possible to greatly lower the possibility of lightening striking some
location. It's done by
On Sun, Oct 04, 2009 at 09:14:29AM +, Robert Atkinson wrote:
Hi,
This is correct. There was also an issue with harmonics from the local
oscillator in the aircraft's own VHF nav/comm receivers blocking the
GPS. The answer is a 1575MHz notch filter, e.g.
After doing some online research myself into this topic recently, I am
in the process of providing some protection for my Amateur Radio
station. I don't have the proper tools at home, so I am having a
stainless steel panel made that will attach to a steel window frame,
replacing the bottom glass
On 10/4/09 11:08 AM, David I. Emery d...@dieconsulting.com wrote:
On Sun, Oct 04, 2009 at 09:14:29AM +, Robert Atkinson wrote:
Hi,
This is correct. There was also an issue with harmonics from the local
oscillator in the aircraft's own VHF nav/comm receivers blocking the
GPS. The
Another non scientific observation for the lead lighting where you want it
camp. A fellow ham who lives in a valley and wanted better reception. The
location was selected for economic reasons but he was free of lighting for ten
or more years. To improve his reception he persuaded the power
As I understand it, the Z-Sensor is basically a Z-12 without the front panel.
The design uses more modern ICs, etc.
Most of the Z-12s have sold from $1000-$1400. Best to get one with a good
L1/L2 antenna... those will set you back several hundred doallars. I have
seen Z-sensors offered
I found the spec on the Z-12 1PPS output... it is within 1 microsecond of GPS
time. You can offset it up to 999. milliseconds. I suspect that your
standard Z-12 and cousins are not the best timing receiver around. It is hard
to beat a Thunderbolt in terms of bang for the bucks...
I have read that there have been studies with a spectrum
analyzer system on planes that have shown that compliance with the no
radiating device rules and electronics off during takeoff and
landing is
far less than 100% though I certainly would not personally
deliberately
violate the
On 10/4/09 1:06 PM, Bill Hawkins b...@iaxs.net wrote:
Group,
As to interference with other GPS receivers, my son runs a deep-sea fishing
party
boat out of Ocean City, MD. He is famous for knowing where the fish will be.
There
may be 5 to 20 people on a 50' fiberglass boat using GPS
But that doesn't change the fact that if a drunk businessman or a
bored 6 year old with a new toy can stealthily endanger all the
passengers on a plane, the responsibility - and liability - should be
with the aircraft designer.
Bringing it back to the normal topic at hand, I wonder - if
Something I should've mentioned is that the connections are all
essentially in series. For example. If you have a wire going to a
ground rod and you connect several devices to it, they are all
meeting at the top of a resistor. If a device attaches part way
down a wire or you have a wire
Hi Burt and all:
Only a reminder: lightning is a pulse, and especially at the ground
terminus can have frequency components in excess of tens of MHz. Think in
terms of impedance rather than resistance. Many of the freaky things
lightning pulses do are more clearly seen this way. A sharp bend in a
Mark Sims wrote:
As I understand it, the Z-Sensor is basically a Z-12 without the front panel.
The design uses more modern ICs, etc.
By the looks of things, I agree.
Most of the Z-12s have sold from $1000-$1400. Best to get one with a good
L1/L2 antenna... those will set you back
On Sun, Oct 04, 2009 at 03:06:12PM -0500, Bill Hawkins wrote:
See Joe Mehaffey's list of airlines at
http://gpsinformation.net/airgps/airgps.htm
The list of airlines that allow GPS have the caveat that the Captain has the
final decision.
It is interesting that American is listed as
Mark Sims wrote:
I found the spec on the Z-12 1PPS output... it is within 1 microsecond of GPS
time. You can offset it up to 999. milliseconds. I suspect that your
standard Z-12 and cousins are not the best timing receiver around. It is hard
to beat a Thunderbolt in terms of bang for
Don Latham wrote:
Use of brush or radioactive lightning rods, as has been pointed out, is
pointless and even dangerous. If you feel you have to experiment with
such, at least just use a sort of ball of barbed wire rather than paying
someone a small fortune for junk. Any brush discharge
See Joe Mehaffey's list of airlines at
[1]http://gpsinformation.net/airgps/airgps.htm
The list of airlines that allow GPS have the caveat that the Captain has the
final decision.
It is interesting that American is listed as banning them as of
October 2009 (apparently they have switched
- Original Message -
From: Chuck Harris cfhar...@erols.com
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Sunday, October 04, 2009 7:24 PM
Subject: Re: [time-nuts] Lightning and grounds...
Don Latham wrote:
Use of brush or radioactive lightning
Don Latham wrote:
Hi Burt and all:
Only a reminder: lightning is a pulse, and especially at the ground
terminus can have frequency components in excess of tens of MHz. Think in
terms of impedance rather than resistance.
I think the use of frequency components is a bit of missguiding when
On 10/4/09 4:24 PM, Chuck Harris cfhar...@erols.com wrote:
Don Latham wrote:
Use of brush or radioactive lightning rods, as has been pointed out, is
pointless and even dangerous. If you feel you have to experiment with
such, at least just use a sort of ball of barbed wire rather than
Perhaps they are to dissipate local static charges, like the tinsel on the
wing tips of airplanes, rather than protect from strilkes per se. They
might prefer a slight, steady state, rise in system noise temperature,
over something wildly varying.
-John
=
Don Latham wrote:
Right, Magnus.
Right, Phil. The first leader from a common strike starts in the cloud and
steps downward. The result resembles a charged piece of coax. As it nears
the earth, an actual breakdown occurs, shorting the coax (sort of). It's
this short (on the order of 10 m) breakdown that's really got
Thanks to everyone for the very useful information about the Ashtech
devices.
I now realize that there's probably no need for me to spend the money for
either a Z-12 or Z-Sensor, since after reading the great reviews that the
Trimble Thunderbolts have been getting, I've decided that it will be
One last follow-on to this thread: In order to speed up the calibration
process by being able to see the measurement results in real time while
adjusting the two CalByte values, I connected the SR620 scope outputs and
monitored the graphical output on my oscilloscope. It turns out that the
Hello, sorry for a slightly off topic post. I recently acquired an old BK
1820 6 digit counter. My google skills don't seem to be up to finding any
info re this device and I'm not inclined to purchase a reproduction manual for
this device (the cost for the manual is several times more than
Brooke wrote:
Note old fashioned Lightening Rods do not work as well as the brushes.
Sorry to say, but they're heavily marketed hokum. Nobody who's not selling
something has *ever* been able to measure the slightest difference from
such Early Streamer Emission devices.
A variety of designs
I'd also think twice before using a shortwave receiver on a comercial air craft
(: I'd be worried about the emissions from the various local oscilators
interferring with the HF and VHF radios on board the air craft.
Many years ago I used to use a portable sony shortwave receiver as a simple
I disagree - call me an old fart or whatever. Your points are valid
and proper logic, but every situation is just not the same.
Bonding everything is proper, but without an effective ground, lightning
will still seek a path to dissipate itself. We are taught if the ground
is not good
I have a Thunderbolt (that I am using to teach Heather some nifty new tricks)
sitting on the floor in the room adjacent to the kitchen. The temperature has
been quite stable here lately and the graph was cruising along at 2
millidegrees per division.
I went to the 'fridge to get a beer.
Does anyone know anything about these? The USB units look interesting.
I'm almost afraid to find out what one costs, though.
http://vigo.com.pl/index.php/en/english_menu/products/measurement_instruments/time_frequency_counters
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