In article ,
wrote:

I have never heard an American use the word "aerial" in reference to
an antenna.


I have. About the time of the end of World War II I was given a
home-made crystal set by my great-aunt, which she had used back in the
early days of AM broadcast radio in Cincinnati but which she hadn't used
for quite a few years. She referred to the wire thrown down on the floor
as an aerial. She lived about 2 miles from WKRC, 550 kHz and 5 kW, and
maybe 20 miles from super-high-power WLW, 700 kHz which came in even
stronger than WKRC. So a short wire thrown down on the rug was good
enough.

About four or five years later when I got my first ham license my
grandmother also referred to the wire connected to my ARC-5 transmitter
as an aerial. But her daughter, my aunt, called it an antenna. Everyone
else, especially the other radio amateurs I met around Cincinnati,
called the things antennas.

So yes, maybe "aerial" was used by some Americans, several generations
ago.

My great-aunt's Crosley table model radio had a short wave band on it,
and my aunt's large RCA console radio had two short wave bands. The
Crosley had a short piece of wire connected to a terminal on its back,
and the RCA had a length of wire thrown on the floor underneath it.
That's how I first bumped into amateur radio, 75 m and 20 m AM phone
operators. Our grade school library had a book about radio, and I
learned enough by reading it to know that if I wanted to be able to hear
more than clicks and buzzes near the lower ends of those two bands I had
to supply another signal for the CW signals to beat against. So I used
another table model radio placed on top of the RCA, tuned so a harmonic
of its local oscillator would beat against the incoming signal. That's
the only way I was able to listen to code transmissions for a year or
two until I had saved up enough money to get a used Hallicrafters S20R
receiver. That one got an antenna wire running out my bedroom window to
a nearby tree. Six months later my code speed was good enough to get my
first license.

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

David, VE7EZM and AF7BZ

--
David Ryeburn

To send e-mail, change "netz" to "net"

On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

--

Rick C

rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp



--
Jim Pennino

On 5/23/2016 6:52 PM, wrote:
rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp

Lol! Devices that have to work should be designed to work properly in
the very low level fields that occur in every day life. It's not really
hard. There are any number of engineers who can do that.

Here's the list from your reference. Notice that even MP3 players with
earbuds are a risk!



Devices with risk

Anti-theft systems (also called electronic article surveillance or EAS):
Interactions with EAS systems are unlikely to cause clinically
significant symptoms in most patients. However, the American Heart
Association recommends that you:

Be aware that EAS systems may be hidden or camouflaged in entrances
and exits in many businesses.
Don't stay near the EAS system longer than is necessary.
Don't lean against the system.

Metal detectors for security: Interactions with metal detectors are
unlikely to cause clinically significant symptoms in most patients.
However, the American Heart Association recommends that you:

Don't stay near the metal detector longer than is necessary.
Don't lean against the system.
If scanning with a hand-held metal detector is necessary, tell the
security personnel that you have a pacemaker. Ask them not to hold the
metal detector near the device any longer than is absolutely necessary.
Or ask for an alternative form of personal search.

Cell phones: Currently, phones available in the United States (less than
3 watts) don't appear to damage pulse generators or affect how the
pacemaker works.

Technology is rapidly changing as the Federal Communications
Commission (FCC) makes new frequencies available.
Newer cellphones using these new frequencies might make pacemakers
less reliable.
A group of cellphone companies is studying that possibility.
Bluetooth® headsets do not appear to interfere with pacemakers.

MP3 player headphones: Most contain a magnetic substance and research
has documented that placing the headphones too close to the pacemaker
caused interference.

Keep your headphones at least 1.2 inches (3 cm) away from your
pacemaker.
Never rest your head on the chest of a person with pacemaker while
you're wearing headphones.
Both the earbud and clip-on types of headphones can cause interference.
Do not place headphones in a breast pocket or drape them over your
chest.

Extracorporeal shock-wave lithotripsy (ESWL): a noninvasive treatment
that uses hydraulic shocks to dissolve kidney stones.

This procedure may be done safely in most pacemaker patients, with
some reprogramming of the pacing.
You'll need careful follow-up after the procedure and for several
months to be sure your pacemaker is working properly.
ESWL should be avoided in patients with certain kinds of pacemakers
implanted in the abdomen.
Discuss your specific case with your doctor before and after the
treatment.

Magnetic resonance imaging (MRI): a noninvasive diagnostic tool that
uses a powerful magnet to produce images of internal organs and functions.

Metal objects are attracted to the magnet and are normally not
allowed near MRI machines.
The magnet can interrupt the pacing and inhibit the output of
pacemakers.
If MRI must be done, the pacemaker output in some models can be
reprogrammed.
Discuss with your doctor the possible risks and benefits before you
undergo MRI scanning.

Power-generating equipment, arc welding equipment and powerful magnets:
Such as found in some medical devices, heavy equipment or motors can
inhibit pulse generators.

If you work closely with or near such equipment, be aware of the
risk that your pacemakers may not work properly in those conditions.
Follow your healthcare provider's instructions about being around
such equipment.

Radiofrequency ablation (RFA): A medical procedure that uses radio waves
to manage a wide variety of arrhythmias.

RFA is usually performed before the pacemaker is implanted.
Studies have shown that most permanent pacemakers aren't adversely
affected by radio frequencies during catheter ablation.
However, if RFA is performed with a pacemaker, a variety of changes
in your pacemaker are possible during and after the treatment.
Your doctor should carefully evaluate your pacing system after the
procedure.

Short-wave or microwave diathermy: A medical procedure that uses
high-frequency, high-intensity signals for physical therapy. These may
bypass your pacemaker's noise protection and interfere with or
permanently damage the pulse generator.

Therapeutic radiation (such as for cancer treatment): May damage the
pacemaker's circuits.

The degree of damage is unpredictable and may vary with different
systems.
The risk is significant and builds up as the radiation dose increases.
The American Heart Association recommends that the pacemaker be
shielded as much as possible and moved if it lies directly in the
radiation field.
If you depend on your pacemaker for normal heart pacing, your
electrocardiogram (ECG) should be monitored during the treatment, and
your pulse generator should be tested often after and between radiation
sessions.

Transcutaneous electrical nerve stimulation (TENS): A medical device
used to relieve acute or chronic pain with electrodes placed on the skin
and connected to a pulse generator.

Most studies have shown that TENS rarely inhibits bipolar pacing.
It may sometimes briefly inhibit unipolar pacing. This can be
treated by reprogramming the pulse generator

--

Rick C

rickman wrote:
On 5/23/2016 6:52 PM, wrote:
rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp

Lol! Devices that have to work should be designed to work properly in
the very low level fields that occur in every day life. It's not really
hard. There are any number of engineers who can do that.

According to the article, they ARE designed to work properly in the
very low level fields that occur in everyday life and the biggest risks
are from medical equipment.

Here's the list from your reference. Notice that even MP3 players with
earbuds are a risk!

I read the article; there was no reason for you to copy it.

Here's another article with numbers in it:

http://europace.oxfordjournals.org/content/15/3/388



--
Jim Pennino

On 5/23/2016 9:08 PM, wrote:
rickman wrote:
On 5/23/2016 6:52 PM, wrote:
rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp

Lol! Devices that have to work should be designed to work properly in
the very low level fields that occur in every day life. It's not really
hard. There are any number of engineers who can do that.

According to the article, they ARE designed to work properly in the
very low level fields that occur in everyday life and the biggest risks
are from medical equipment.

Your reference contradicts what you say. Are MP3 players "medical"
equipment? I think they are every day devices. If I read the reasoning
correctly, I'd bet holding an old style telephone receiver to your chest
(commonly done to mute it when you are calling for someone to get the
phone) puts a pacemaker patient at risk too. That's the sort of thing
that happens automatically without thinking.


Here's the list from your reference. Notice that even MP3 players with
earbuds are a risk!

I read the article; there was no reason for you to copy it.

Then why do you continue to contradict it?


Here's another article with numbers in it:

http://europace.oxfordjournals.org/content/15/3/388





--

Rick C

rickman wrote:
On 5/23/2016 9:08 PM, wrote:
rickman wrote:
On 5/23/2016 6:52 PM, wrote:
rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp

Lol! Devices that have to work should be designed to work properly in
the very low level fields that occur in every day life. It's not really
hard. There are any number of engineers who can do that.

According to the article, they ARE designed to work properly in the
very low level fields that occur in everyday life and the biggest risks
are from medical equipment.

Your reference contradicts what you say. Are MP3 players "medical"
equipment?

What part of the word 'biggest' did you fail to understand?


--
Jim Pennino

"rickman" wrote in message ...

On 5/23/2016 6:52 PM, wrote:
rickman wrote:
On 5/23/2016 6:05 PM, David Ryeburn wrote:

I've kind of liked end-fed wires as antennas ever since, though now I'm
well aware of their limitations, and, with a pacemaker inside me, I no
longer dare use one. Balanced lines and center-fed doublets are a
nuisance when you go backpacking, but I do want to be able to hike back
out to the car afterwards.

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?

Lack of space for installing the faraday cage.

Pacemakers DO function around radios and microwaves.

http://www.heart.org/HEARTORG/Condit...13_Article.jsp

# Lol! Devices that have to work should be designed to work properly in
# the very low level fields that occur in every day life. It's not really
# hard. There are any number of engineers who can do that.

# Here's the list from your reference. Notice that even MP3 players with
# earbuds are a risk!

After getting a pacemaker, I chatted with the manufacturer about RF
interference, etc.
The only concern shown was for magnetic fields, and no problems were
expected if the field was removed. I was encouraged to avoid airport metal
detectors mainly because the manufacturer couldn't be sure what kind of
contraption TSA would come up with.

RF ablation didn't affect it. The circuitry seems to be solidly designed.

On Mon, 23 May 2016 20:20:29 -0400, rickman wrote:

Here's the list from your reference. Notice that even MP3 players with
earbuds are a risk!

The risk is not so much any RF but rather from magnetic fields. All
the items on your list have magnets somewhere. MP3 player ear bugs
are a good start. Magnets are used to program and control a
pacemaker. A friend managed to make a mess of his pacemaker
programming with an electric drill motor.
https://www.google.com/#q=pacemaker+magnets

As for RF shielding:
"Shielded pacemaker enclosure"
http://www.google.com/patents/US5895980
See citations for more.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article , rickman
wrote:

What is wrong with pacemakers that they can't make one that functions
around radios and microwaves?


They can and do, for most situations. But an end-fed antenna will have
common mode currents and I'd just as soon not have such flowing in my
pacemaker wiring.

My pacemaker is located just to the right of, and below, my left
shoulder. There are two wires leading out of it which go to my right
atrium and right ventricle. These wires bring signals up from the heart
to the pacemaker telling the pacemaker when the heart is beating, and,
when necessary, take much stronger signals down from the pacemaker to
the heart to get it to behave correctly if it is not doing so. There
must in effect also be a "ground" connection with the metallic pacemaker
case embedded in tissue in front of my ribs. Common mode current from an
unbalanced antenna sysem flowing in my body might do the pacemaker no
good. I'd just as soon not find that out 10 miles from a trailhead. So I
use balanced antennas, balanced feedline, and a good 1:1 current balun
at the bottom of the feedline. The tuner inside my KX3 then makes the
KX3 final amplifier happy.

I have also used a coax-fed balanced antenna with balun at the antenna
feedpoint, but a doublet with open-wire feedline and balun at the bottom
is a better multi-band solution.

Magnetic fields are also bad for pacemakers. When my cardiologist tests
things he brings a magnet close to my chest while monitoring the
pacemaker performance. This is done in a controlled way with observation
of the effect. I have been warned that high intensity magnetic fields
are very dangerous. At airports I present a card indicating I have a
pacemaker, and I get gone over by hand instead of magnetically. I
definiely don't put my iPod earbuds in my shirt pocket! The iPod itself
is often placed there when I use it while walking or hiking. I have been
warned that I must never have an MRI done on me.

There is no reason to believe that the very low power cordless phones
used with our landline telephone, or cell phones, pose a problem. The
magents in them are up by my ear, not near the pacemaker, and aren't all
that strong. The electromagnetic fields aren't all that strong either.
But consider how much RF current flows, especially in a low-resistance
high-reactance short unbalanced antenna, even at QRP levels. That's why
I want what comes out of my KX3 to be radiated and do some good, not
generate common mode current that may make my pacemaker, and then me,
unhappy.

Maybe I'm being too cautious. But better safe than sorry. And anyway, I
suspect my balanced doublet fed with open wire is a lot more efficient
than the typical random length end-fed wire connected to a transmitter
through a possibly very lossy Unun. It does require two trees, unless
erected as an inverted V, whereas an end-fed wire gets by with one.
Doing it the safer way is correct from an engineering standpoint too. It
would be a shame if one had to choose between efficiency and safety.

David, VE7EZM and AF7BZ

--
David Ryeburn

To send e-mail, change "netz" to "net"