antenna theory made easy
 

On Fri, 24 Jan 2014 20:35:38 -0500, Jerry Stuckle
wrote:

On 1/24/2014 6:16 PM, Jeff Liebermann wrote:
On Fri, 24 Jan 2014 15:06:27 -0500, Jerry Stuckle
wrote:

Reminds me of a friend who put up a ground mounted HF vertical in his
back yard (back in the 60's). He was sitting in the shack checking it
out when his wife let the dog out. The dog saw the new fire hydrant in
the back yard, but my friend was ready. Just as the dog lifted his leg,
my friend hit the key - with a full KW going to the antenna.

From then on, the dog gave the antenna a wide berth, always watching it
suspiciously.

Mythbusters did a test of urinating on an electrified 3rd rail.
http://www.youtube.com/watch?v=pDY-0ijiOEQ
It didn't work. Surface tension causes the urine stream to break up
into non-connected globules, which will not conduct electricity.
Later, they managed to get it to work with a 3 inch stream.

Who cares about the 3rd rail? That's 60hz, not RF. A HUGE difference.
And they probably weren't 3-4" from the third rail like the dog was.

The 3rd rail is usually about 1500 VAC. Last time I checked, there
has to be current flowing though the conduction path. The losses
involved in jumping the air gap are just too high to electrocute the
dog. The RF field from the antenna might cook the dog, but not
electrocute. If you hadn't witten "Just as the dog lifted his leg" I
wouldn't have said anything.

Incidentally, I've gotten some rather nasty RF burns in the past. In
all cases, I was in physical contact with the antenna. Unless the
transmitter can produce an arc or possibly a corona discharge, there's
not going to be much in the way of RF current or electrocution.

Do you understand ANYTHING?

Are you able to discuss anything technical without resorting to
insults?

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

antenna theory made easy
 

On Fri, 24 Jan 2014 19:44:38 -0800 (PST), W5DXP
wrote:

On Friday, January 24, 2014 5:16:15 PM UTC-6, Jeff Liebermann wrote:
Mythbusters did a test of urinating on an electrified 3rd rail.
It didn't work.

I got a severe static electricity shock in Odessa, TX one time
while urinating into a hotel john. I saw the arc between my stream
and the water in the john. The hotel had wool carpets and the
humidity was very low.

Ouch. I feel your pain. Wikipedia claims 3 million volts/meter (or
about 75,000 volts/inch) which seems a bit high:
http://en.wikipedia.org/wiki/Dielectric_strength#Breakdown_field_strength
I've always used 10,000 volts/inch but I don't recall the conditions
for which that's accurate. In any case, you had quite a (static) high
voltage buildup, which could jump the broken parts of the urine flow.

1000 watts into a ground mounted HF vertical? Is that a good idea? It
might be too close to the operator to be within accepted RF exposure
(MPE) limits. Checking:
http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65b.pdf
See table 4a on Pg 23. For 1000 watts the minimum distances for a
typical 0dBi gain antenna is:
Band Controlled Uncontrolled (meters)
160m 0.5 0.7
80m 0.6 1.3
40m 1.1 2.5
20m 2.2 4.8
15m 3.2 7.2
10m 4.5 10.
So, if he's operating on 20 meters, a ground mounted antenna with no
gain and 1000 watts can't be any closer than about 14 ft from the
operator. Maybe with a big yard and if you don't care about cooking
the dog or the neighbors.

In order to put the voltage node of the vertical near where the dogs
urine stream can reach, it would need to be fairly close to the
ground. That leaves very little room for the ground radials, any
possible control box, or a balun. Seem an odd vertical antenna with
the loading coil at ground level. Maybe for 160 meters or a mono band
antenna.

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

antenna theory made easy
 

On Fri, 24 Jan 2014 13:38:08 -0700, "Irv Finkleman"
wrote:

I don't want to get any more complex or expensive than is absolutely
required.

Have you ever seen a project that gets simpler and less expensive as
it progresses? I haven't. I suggest you resign yourself to the
inevitable. It will become more complicated and more expensive.

I have an old plastic ball point pen cut to match the motor to the cap
which should suffice -- if not, I'll find a better pen! :-)

Maybe something slightly flexible might be better. I suggest a length
of Sharkbite 1/4" or 3/8" PEX tubing. Home Depot sells it in various
lengths and diameters. I've been using it for coil forms at HF
frequencies with acceptable results. However, I haven't tested the
high voltage characteristics yet. Give me a few days.

The chair is plastic. Hmmmm, wonder if my ex-mother-in-law
would like to sit in the sun!

Please resist the temptation to convert your antenna into a weapon.

Let me know when you're ready to build my inflatable antenna tower.

Now that sounds interesting. Is it anything like my inflatable dart board?

No. I'm serious. I've been playing with the inflatable concept for
several years. I have the material to build a small prototype. The
plan was to have an all inflatable Field Day. However, every year, I
either lack the time, have a crisis pending, have a paying project in
progress, or am so fed up with ham radio, that I stall until it's too
late to do anything. Maybe next year.

And don't forget that antenna
they used to advertise in QST et al which was no more than a dummy
load with some wire attached. At least you could get a great match!

That's what I like about antennas. You can't see the RF, it's
difficult to measure antenna characteristics, and the difference
between quality and junk is difficult to distinguish. If I were a
crook, I would definitely be in the antenna business.

I remember the antenna but can't recall or find the name. I do recall
that the ARRL got suspicious during a product review and ran an xray
on the matching box. Inside was just a resistor.

My favorite is the 1950's "Turn your house wiring into a giant 500 ft
TV antenna". Inside the box was a "capacitator". That was my
introduction to antenna design.

I rely on the MFJ Analyzer for a lot of things and don't know how
I got along without it.

I do. I loaned mine to a friend and he refused to give it back. At
least he paid me for it twice. Once to buy it and once to fix it
after he blew it up. I still don't have one. What I use is a return
loss bridge, sweep generator, detector, and scope. Not exactly
portable like the MFJ, but good enough.

And other than a cheap $20 Canadian
Tire Digital Multimeter that is about as far as my test equipment
goes. When I sold my house I gave all my 50 years accumulation
of test equipment, rigs, and such to the local ham club. Most of
all miss my Fluke Multimeter (Model 75 or 77 -- I forget now)
which Sony allowed me to keep when I retired. I keep watching
for one on E-bay although some of the newer multimeters are
reasonably economical and have lots of nice features.

I have several Fluke meters including a Model 75. I stole my Model
12(?) from a previous employer. If you're shopping for a new meter, I
think you'll do better with a cheaper brand. I have a bunch of Extec
meters. Something like this model (but older):
http://www.extech.com/instruments/product.asp?catid=48&prodid=644
I really like the large LCD display. No failures or surprises in
about 8 years.

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

antenna theory made easy
 

On 1/25/2014 2:11 AM, Jeff Liebermann wrote:
On Fri, 24 Jan 2014 20:35:38 -0500, Jerry Stuckle
wrote:

On 1/24/2014 6:16 PM, Jeff Liebermann wrote:
On Fri, 24 Jan 2014 15:06:27 -0500, Jerry Stuckle
wrote:

Reminds me of a friend who put up a ground mounted HF vertical in his
back yard (back in the 60's). He was sitting in the shack checking it
out when his wife let the dog out. The dog saw the new fire hydrant in
the back yard, but my friend was ready. Just as the dog lifted his leg,
my friend hit the key - with a full KW going to the antenna.

From then on, the dog gave the antenna a wide berth, always watching it
suspiciously.

Mythbusters did a test of urinating on an electrified 3rd rail.
http://www.youtube.com/watch?v=pDY-0ijiOEQ
It didn't work. Surface tension causes the urine stream to break up
into non-connected globules, which will not conduct electricity.
Later, they managed to get it to work with a 3 inch stream.

Who cares about the 3rd rail? That's 60hz, not RF. A HUGE difference.
And they probably weren't 3-4" from the third rail like the dog was.

The 3rd rail is usually about 1500 VAC. Last time I checked, there
has to be current flowing though the conduction path. The losses
involved in jumping the air gap are just too high to electrocute the
dog. The RF field from the antenna might cook the dog, but not
electrocute. If you hadn't witten "Just as the dog lifted his leg" I
wouldn't have said anything.


Try again, troll. Here in Washington, DC, it's 750V.

And the rest of your comment is pure BS, also.

Incidentally, I've gotten some rather nasty RF burns in the past. In
all cases, I was in physical contact with the antenna. Unless the
transmitter can produce an arc or possibly a corona discharge, there's
not going to be much in the way of RF current or electrocution.


So what?

Do you understand ANYTHING?

Are you able to discuss anything technical without resorting to
insults?


I get real tired of trolls who continue to show their ignorance while
trying to contradict science.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

antenna theory made easy
 

On 1/25/2014 2:42 AM, Jeff Liebermann wrote:
On Fri, 24 Jan 2014 19:44:38 -0800 (PST), W5DXP
wrote:

On Friday, January 24, 2014 5:16:15 PM UTC-6, Jeff Liebermann wrote:
Mythbusters did a test of urinating on an electrified 3rd rail.
It didn't work.

I got a severe static electricity shock in Odessa, TX one time
while urinating into a hotel john. I saw the arc between my stream
and the water in the john. The hotel had wool carpets and the
humidity was very low.

Ouch. I feel your pain. Wikipedia claims 3 million volts/meter (or
about 75,000 volts/inch) which seems a bit high:
http://en.wikipedia.org/wiki/Dielectric_strength#Breakdown_field_strength
I've always used 10,000 volts/inch but I don't recall the conditions
for which that's accurate. In any case, you had quite a (static) high
voltage buildup, which could jump the broken parts of the urine flow.

1000 watts into a ground mounted HF vertical? Is that a good idea? It
might be too close to the operator to be within accepted RF exposure
(MPE) limits. Checking:
http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65b.pdf
See table 4a on Pg 23. For 1000 watts the minimum distances for a
typical 0dBi gain antenna is:
Band Controlled Uncontrolled (meters)
160m 0.5 0.7
80m 0.6 1.3
40m 1.1 2.5
20m 2.2 4.8
15m 3.2 7.2
10m 4.5 10.
So, if he's operating on 20 meters, a ground mounted antenna with no
gain and 1000 watts can't be any closer than about 14 ft from the
operator. Maybe with a big yard and if you don't care about cooking
the dog or the neighbors.

In order to put the voltage node of the vertical near where the dogs
urine stream can reach, it would need to be fairly close to the
ground. That leaves very little room for the ground radials, any
possible control box, or a balun. Seem an odd vertical antenna with
the loading coil at ground level. Maybe for 160 meters or a mono band
antenna.


Who said how close it was to the operator? And who said there was a
control box or balun involved? Neither are required for a properly
tuned vertical.

And radials on a ground mounted vertical go (preferably) UNDER the ground.

When I first started out in ham radio, I used a Hy-Gain 18AVQ vertical -
80-10, with the instructions saying to mount one foot (that's twelve
inches for the trolls) above ground with an SO-239 to connect to the
coax. Quite within range of a large dog.

But once again you show your ignorance of facts. OTOH, your lack of
knowledge really is entertaining. More so than most trolls, anyway.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

I would laugh if any of these CB'rs ever had the FCC knock at their door and do a station inspection. Without doing a field survey, their butt would be fried, especially if on the right frequency such as 60 meters....
All it would take is for one neighbor to complain and that would be it!

This kind of stuff gives all amateurs a black eye when it comes to proper operating procedures.
There is a lot of idiots out there that thinks that if they HAVE a 1000 watt amplifier that they automatically HAVE to turn it on in order for everyone to hear them!

Too bad there isn't more O&O's out there that would be willing to get involved. I would like to see a lot of these big time operators cited for their actions.. S T U P I D!

antenna theory made easy
 

On Saturday, January 25, 2014 5:08:43 PM UTC-6, Channel Jumper wrote:


This kind of stuff gives all amateurs a black eye when it comes to

proper operating procedures.

There is a lot of idiots out there that thinks that if they HAVE a 1000

watt amplifier that they automatically HAVE to turn it on in order for

everyone to hear them!

A KW is chump power in the overall scheme of things.
I knew a guy who ran 21.5 KW on 75m several years ago.
And the FCC finally got after him. What did they do?
Not much. They made him dismantle the amp, and restricted
him to a small section of 75m for a while. No real biggie.
They were actually kind of impressed with his station.
His signal was always very clean.
I knew another guy in New Orleans that got caught running
about 8 KW. Again, they didn't do too much about it.
Both are silent keys now..

antenna theory made easy
 

On Saturday, January 25, 2014 9:43:57 AM UTC-6, Jerry Stuckle wrote:

And radials on a ground mounted vertical go (preferably) UNDER the ground.

Actually, for a given number of radials, slightly above ground is
better than under ground. But not by too much.
Most would probably not notice the difference, but there is a bit..
Elevated radials really need to be a good ways up in wavelength
to really live up to their potential.
Four radials at 1/4 wave up is equal to about 50-60 in the ground.
At 1/8 wave up, you need at least 20 or so to equal 50-60 on the ground.
At one foot up, you probably need 50-55 to equal 60 in the ground.
So really, the real advantage to burying them in such a case is less to
trip over when walking across the yard. :|

antenna theory made easy
 

On 1/25/2014 6:34 PM, wrote:
On Saturday, January 25, 2014 9:43:57 AM UTC-6, Jerry Stuckle wrote:

And radials on a ground mounted vertical go (preferably) UNDER the ground.

Actually, for a given number of radials, slightly above ground is
better than under ground. But not by too much.
Most would probably not notice the difference, but there is a bit..
Elevated radials really need to be a good ways up in wavelength
to really live up to their potential.
Four radials at 1/4 wave up is equal to about 50-60 in the ground.
At 1/8 wave up, you need at least 20 or so to equal 50-60 on the ground.
At one foot up, you probably need 50-55 to equal 60 in the ground.
So really, the real advantage to burying them in such a case is less to
trip over when walking across the yard. :|


Not necessarily. Above ground, the radials provide only a (very low)
capacitive link to the ground. Below ground, they provide a direct link
to the soil. The effect creates a better ground plane for the antenna(s).

But an even more important point here is maintenance. It's very hard to
cut the grass when radials are above ground. Also, the exposure to the
elements will change the characteristics of the radials.

These are the main reasons why AM radio stations bury their radials.
It's not unusual for a station to have 360 radials per tower, at one
degree intervals. Then there are rings spaced every one to three feed
apart, around the tower. These rings are then soldered (often silver
soldered) to the radials at the points they cross. The result is a very
effective ground system for the antennas. But can you imaging trying to
mow if these were above ground?

A station I worked part time for in Iowa had such a system; so does the
one in my back yard.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

antenna theory made easy
 

wrote in message
...

On Saturday, January 25, 2014 5:08:43 PM UTC-6, Channel Jumper wrote:


This kind of stuff gives all amateurs a black eye when it comes to

proper operating procedures.

There is a lot of idiots out there that thinks that if they HAVE a 1000

watt amplifier that they automatically HAVE to turn it on in order for

everyone to hear them!

# A KW is chump power in the overall scheme of things.
# I knew a guy who ran 21.5 KW on 75m several years ago.
# And the FCC finally got after him. What did they do?
# Not much. They made him dismantle the amp, and restricted
# him to a small section of 75m for a while. No real biggie.
# They were actually kind of impressed with his station.
# His signal was always very clean.
# I knew another guy in New Orleans that got caught running
# about 8 KW. Again, they didn't do too much about it.
# Both are silent keys now..

Many years ago, I did a few shifts handling emergency traffic from
Richardson, TX to Wichita Falls after a tornado.
We used the Collins radio station at their facility, and had the blessing of
the FCC to go up to 10 KW if needed.

We had to do that once or twice on 40 meters. Amazing how well 10 KW and a
log periodic antenna at 100 feet can clear out a "hole".