OK, let's discuss dipoles vs length
 

On 10/13/2014 2:23 PM, Ian Jackson wrote:
In message ,
Lostgallifreyan writes
Jerry Stuckle wrote in news:m1gvg0$9v8$1@dont-
email.me:

One side note. Copper clad anything is not certified for any ethernet
cables. Even though ethernet runs at very high frequencies, only solid
or stranded copper is acceptable.


Telewest, who became Blueyonder, then after merging with ATL got
bought by
Vitgin Media here in Britain, used copper clad steel cores. I don't know
enough to comment on their reasons, but it's definitely true, I just
waved a
magnet at a few cables of theirs to prove it. My guess is that because
the
lines were ostensibly for cable TV, they just coerced them into internet
wiring later. ADSL on the phone lines later beat them for speed,
presumably
because the phones were using solid copper, but I'm not sure they used
in the
external cables because I can't reach one right now.

Are you confusing the internet being carried (like cable TV) over coax
at RF, and via ADSL on twisted-pair phone lines? The coax drop cables
are usually RG6, which has a copper-plated steel inner.


The cheaper RG6 has copper clad steel. The stuff we use is
quad-shielded with a solid copper core.

If it's anything like some coax I worked with in the 60s, there might be
a small 'kink' in the frequency response* at around 40MHz, which is
probably the frequency at which all the RF has moved out of the steel
core, and into the copper plating.
*Above 40MHz, the attenuation might become somewhat lower than you would
expect from extrapolating loss figures obtained below 40MHz. While I
have to say that I've never noticed this with RG6, this may be because
I've never looked for it. In any case, it often has been in the
guardband where the crossover between the cable TV forward and reverse
RF paths occur.

I never tested it, but I think the skin effect would move the rf out of
the core at a lower frequency. Perhaps some ferromagnetic effect with
the steel?

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

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

OK, let's discuss dipoles vs length
 

On 10/13/2014 1:05 PM, wrote:
Jerry Stuckle wrote:
On 10/12/2014 4:29 PM, wrote:
Ralph Mowery wrote:

"Ian Jackson" wrote in message
...
In message ,
writes
Like I said, there is no difference in free space between a V and an
inverted V.

There are slight differences when close to ground.

Assuming it's a halfwave dipole, I would have thought it was better to
concentrate on getting the centre (where the current is) as high as
possible, rather than the ends. [Obviously this depends on whether you
have a suitable sky-hook available for and at the centre.] However, I
believe that there is at least one commercial loaded dipole (essentially
for portable use, I think) that has a short mast, and the ends of the V
are up in the air.



In free space I would not think there would be much of any differance.

Near the ground where most of us are is what we have to live with. In my
back yard I have enough room to string wire dipoles for 80 meters and
shorter. I don't have a way to support the antennas in the middle. I can
go up about 60 feet or so at the ends.

60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole.


I'll argue with that. I got WAS on 75 meters with an inverted vee with
an apex of 50'. I was in Iowa at the time - but had a pretty good
signal across the continental U.S. late at night.

There are many things to consider, and blanket statements like yours are
pretty much worth what people pay for them.

The only "blanket statements" in there is that 1/2 lambda is the OPTIMUM
height for an antenna. Above and below that height a good deal of the
patten goes to warming clouds.

Note the word "optimum"; that means that antennas at other heights do work,
just not as well as they could.


"60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole."

I have proof that is not the case. If the antenna were not crap, how
could I work both Alaska and Hawaii on 75 meters with an inverted V
having an apex at only 50'?

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

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

OK, let's discuss dipoles vs length
 

Jerry Stuckle wrote:
On 10/13/2014 1:05 PM, wrote:
Jerry Stuckle wrote:
On 10/12/2014 4:29 PM, wrote:
Ralph Mowery wrote:

"Ian Jackson" wrote in message
...
In message ,
writes
Like I said, there is no difference in free space between a V and an
inverted V.

There are slight differences when close to ground.

Assuming it's a halfwave dipole, I would have thought it was better to
concentrate on getting the centre (where the current is) as high as
possible, rather than the ends. [Obviously this depends on whether you
have a suitable sky-hook available for and at the centre.] However, I
believe that there is at least one commercial loaded dipole (essentially
for portable use, I think) that has a short mast, and the ends of the V
are up in the air.



In free space I would not think there would be much of any differance.

Near the ground where most of us are is what we have to live with. In my
back yard I have enough room to string wire dipoles for 80 meters and
shorter. I don't have a way to support the antennas in the middle. I can
go up about 60 feet or so at the ends.

60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole.


I'll argue with that. I got WAS on 75 meters with an inverted vee with
an apex of 50'. I was in Iowa at the time - but had a pretty good
signal across the continental U.S. late at night.

There are many things to consider, and blanket statements like yours are
pretty much worth what people pay for them.

The only "blanket statements" in there is that 1/2 lambda is the OPTIMUM
height for an antenna. Above and below that height a good deal of the
patten goes to warming clouds.

Note the word "optimum"; that means that antennas at other heights do work,
just not as well as they could.


"60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole."

I have proof that is not the case. If the antenna were not crap, how
could I work both Alaska and Hawaii on 75 meters with an inverted V
having an apex at only 50'?

What part of "optimum" is it that you did not understand?

If your point is that you disagree with what I said about 60 feet,
run a NEC analysis for 60 feet versus 1/2 lambda for the bands mentioned
and show me the error of my ways.



--
Jim Pennino

OK, let's discuss dipoles vs length
 

On 10/13/2014 3:21 PM, wrote:
Jerry Stuckle wrote:
On 10/13/2014 1:05 PM, wrote:
Jerry Stuckle wrote:
On 10/12/2014 4:29 PM, wrote:
Ralph Mowery wrote:

"Ian Jackson" wrote in message
...
In message ,
writes
Like I said, there is no difference in free space between a V and an
inverted V.

There are slight differences when close to ground.

Assuming it's a halfwave dipole, I would have thought it was better to
concentrate on getting the centre (where the current is) as high as
possible, rather than the ends. [Obviously this depends on whether you
have a suitable sky-hook available for and at the centre.] However, I
believe that there is at least one commercial loaded dipole (essentially
for portable use, I think) that has a short mast, and the ends of the V
are up in the air.



In free space I would not think there would be much of any differance.

Near the ground where most of us are is what we have to live with. In my
back yard I have enough room to string wire dipoles for 80 meters and
shorter. I don't have a way to support the antennas in the middle. I can
go up about 60 feet or so at the ends.

60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole.


I'll argue with that. I got WAS on 75 meters with an inverted vee with
an apex of 50'. I was in Iowa at the time - but had a pretty good
signal across the continental U.S. late at night.

There are many things to consider, and blanket statements like yours are
pretty much worth what people pay for them.

The only "blanket statements" in there is that 1/2 lambda is the OPTIMUM
height for an antenna. Above and below that height a good deal of the
patten goes to warming clouds.

Note the word "optimum"; that means that antennas at other heights do work,
just not as well as they could.


"60 feet is good for 30M, marginal for 40M, and crap for 80M and below
for a dipole."

I have proof that is not the case. If the antenna were not crap, how
could I work both Alaska and Hawaii on 75 meters with an inverted V
having an apex at only 50'?

What part of "optimum" is it that you did not understand?

If your point is that you disagree with what I said about 60 feet,
run a NEC analysis for 60 feet versus 1/2 lambda for the bands mentioned
and show me the error of my ways.




You didn't say "optimum". You said it was "crap". What part of "crap"
don't you understand?

You think an NEC analysis is the slickest thing since snot on a
doorknob. But what about HAAT or ground conductivity, for instance?
You have considered neither when telling me my antenna was "crap" -
which it provably was not.

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

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

OK, let's discuss dipoles vs length
 

In message , Jerry Stuckle
writes
On 10/13/2014 2:23 PM, Ian Jackson wrote:
In message ,
Lostgallifreyan writes
Jerry Stuckle wrote in news:m1gvg0$9v8$1@dont-
email.me:

One side note. Copper clad anything is not certified for any ethernet
cables. Even though ethernet runs at very high frequencies, only solid
or stranded copper is acceptable.


Telewest, who became Blueyonder, then after merging with ATL got
bought by
Vitgin Media here in Britain, used copper clad steel cores. I don't know
enough to comment on their reasons, but it's definitely true, I just
waved a
magnet at a few cables of theirs to prove it. My guess is that because
the
lines were ostensibly for cable TV, they just coerced them into internet
wiring later. ADSL on the phone lines later beat them for speed,
presumably
because the phones were using solid copper, but I'm not sure they used
in the
external cables because I can't reach one right now.

Are you confusing the internet being carried (like cable TV) over coax
at RF, and via ADSL on twisted-pair phone lines? The coax drop cables
are usually RG6, which has a copper-plated steel inner.


The cheaper RG6 has copper clad steel. The stuff we use is
quad-shielded with a solid copper core.

As a copper-plated steel core has relatively high DC and low-frequency
resistance, solid copper core is usual anything carrying power (eg the
LNBs of satellite dishes). Tap-to-subscriber drop cable doesn't carry
power, and the cheaper steel/copper works just as well.

http://tinyurl.com/o89gfa8

If it's anything like some coax I worked with in the 60s, there might be
a small 'kink' in the frequency response* at around 40MHz, which is
probably the frequency at which all the RF has moved out of the steel
core, and into the copper plating.
*Above 40MHz, the attenuation might become somewhat lower than you would
expect from extrapolating loss figures obtained below 40MHz. While I
have to say that I've never noticed this with RG6, this may be because
I've never looked for it. In any case, it often has been in the
guardband where the crossover between the cable TV forward and reverse
RF paths occur.

I never tested it, but I think the skin effect would move the rf out of
the core at a lower frequency. Perhaps some ferromagnetic effect with
the steel?

I'm trying to remember what my kinky cable was. It might have been RG59.
I also think that the skin effect can produce some slightly odd effects
with stranded copper inner. However, it's got to be fairly long for you
to notice.


--
Ian

OK, let's discuss dipoles vs length
 

Jerry Stuckle wrote:

snip

You didn't say "optimum". You said it was "crap". What part of "crap"
don't you understand?

I will not engage in a ****ing contest with you.

You think an NEC analysis is the slickest thing since snot on a
doorknob. But what about HAAT or ground conductivity, for instance?

What about it?

Feel free to include all the above in your analysis.

You have considered neither when telling me my antenna was "crap" -
which it provably was not.

Where is the data that proves that?


--
Jim Pennino

OK, let's discuss dipoles vs length
 

On Mon, 13 Oct 2014 12:26:23 -0500, Lostgallifreyan
wrote:

If any given directional antenna can radiate at its best to one particular
direction, is it safe to assume that it will be at its best similarly aimed
when receiving?

Yes. For purposes of calculations and under most conditions, the
pattern is the same for transmit and receive for most antennas.

However, there are plenty of confusing exceptions. A common exception
is putting a 2.4GHz USB Wi-Fi dongle at the focus of a dish or corner
reflector. The USB dongle is almost an isotropic radiator, which
spews RF in all directions. If you transmit from the USB dongle, most
of the RF will never hit the dish antenna and wander off to parts
unknown. Only the part that hits the dish eventually ends up going
towards the other end of the wireless link. However, in receive,
almost all of the signal that hits the dish, gets reflected to the USB
dongle. Therefore the gain is higher in receive, than in transmit.

If the USB dongle were replaced with a proper dish feed, where the
bulk of the transmit RF hits the dish, the dish becomes more
"efficient". About 50% to 70% efficiencies are typical. However, it
is also possible to mess that up in the opposite direction. Instead
of a very non-directional feed, suppose I use as a feed, a high gain
directional antenna with a very narrow beamwidth. Instead of spraying
RF outside of the dish edge (over-spray), It puts all of it into a
narrow diameter spot somewhere on the dish surface. This time, the
symmetry is in the opposite direction. Transmit is fine, because all
of the power produced by the feed hits the spot and is radiated in the
direction of the other end of the link. However, receive is now a
problem because none of the RF seen by the dish OUTSIDE the area of
the spot is "seen" by the spot. Therefore, the gain is higher in
transmit, than in receive.

Gone to move some firewood...

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

OK, let's discuss dipoles vs length
 

"Jerry Stuckle" wrote in message
...
On 10/13/2014 1:06 PM, Lostgallifreyan wrote:
I did see a video about a couple of guys free climbing an television
antenna about 2K feet in the air. I lost count how many safety
practices they violated. If OSHA had seen them doing that, they would
have been grounded big time. The fines would have probably put the
company out of business.


I saw that video also. Don't think I would have been up there like that.

Saw another with a man and woman on the tower all dressed up for a formal
diner and singing a song.

Most I have climbed was 100 ft of Rohn 25. I did climb some silos at work
that were about 130 feet up. Just a ladder up the side, but they did have a
stepoff offset platform about every 30 feet.



---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

OK, let's discuss dipoles vs length
 

Jerry Stuckle wrote in news:m1h7sm$9bc$1@dont-
email.me:

I did see a video about a couple of guys free climbing an television
antenna about 2K feet in the air. I lost count how many safety
practices they violated. If OSHA had seen them doing that, they would
have been grounded big time. The fines would have probably put the
company out of business.


I can't find it to check, but I do remember it being very up-front about who
and where they were, and it was connected to soem company. The one I had was
probably kosher enough, if was effectively a promotional video, because
other, as you say, the effect would have been dramatically unwanted for them.
I could be wrong, but I won't know till I find it, and I have no idea where I
stowed it yet..

OK, let's discuss dipoles vs length
 

"Ralph Mowery" wrote in
:

Saw another with a man and woman on the tower all dressed up for a formal
diner and singing a song.


Whatever I saw, it wasn't that. Ò^O :)