Military HF communications under attack

Dave Holford wrote:



Gene Storey wrote:

"John Keeney" wrote

Don't they tend to be directional off the pointy end?

No. Electrical waves are right angles to the conductor, often shaped
like a doughnut. But it doesn't matter in the near-field, as the signal will be
everywhere.


"LONG" wires, multiple wavelength antennas, exhibit gain in the
direction of the wire - bidirectional if not terminated, unidirectional
if terminated at the non-fed end.

You are thinking of the classic basic dipole.

Dave

That's exactly correct...I was going to reply to that but thought
someone could likely describe it better...you just did Dave.
--

-Gord.

"Dave Holford" wrote in message
...


Tarver Engineering wrote:


BTW John - Long (very long) wires make excellent antennas provided
that
they are at least several wavelenghts long.

Self cancelling at a short distance, do the math.


Nonsense, their main use is as directional gain antennas.

My goodness Holford.

Stick to sniffing Stickney's ass.

"Gord Beaman" ) writes:


Isn't ADSL really about the same?...(perhaps lower power
though)...they broadcast a ~one megaHertz RF carrier on
unshielded telephone cables...what's the difference really?...I
have this coming right into my 'radio room' where my (ham) HF
radio is located, I don't see any problem at all.

Telco cable is twisted pair; that's the difference....

[Twisted pair is in effect shielded cable, through the miracles
of 3-D integral calculus....]

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Let's not fly totally off the handle here folks!

I'd like to have a clean radio environment too, but this power-line Rf stuff
may not fly, or may not be a problem, for any one of many reasons:

#1: It's cheap, if you ignore the cost of fitting RF pasthru's to every
pole transformer.

#2: Will people stick with a service that could very likely be slowed down
or shut down by any noisy vacuum-cleaner motor in the neighborhood?

#3: Exactly how noisy is it, and is this added noise any worse than your
typical urban background hash from HV corona, salty insulators, Harley's,
corona-globes, shavers, light-duimmers, touch-lamps, flourescent tubs,
computer monitors, computer keyboards, christmas lights with flashers and
dimmers, and whatnot?

Let's get the facts before we go toss mudballs at the FCC building.

"George R. Gonzalez" wrote in
message news:8XAeb.653512$uu5.106982@sccrnsc04...

Let's not fly totally off the handle here folks!

I'd like to have a clean radio environment too, but this power-line Rf
stuff
may not fly, or may not be a problem, for any one of many reasons:

#1: It's cheap, if you ignore the cost of fitting RF pasthru's to
every
pole transformer.

#2: Will people stick with a service that could very likely be slowed
down
or shut down by any noisy vacuum-cleaner motor in the neighborhood?

#3: Exactly how noisy is it, and is this added noise any worse than
your
typical urban background hash from HV corona, salty insulators,
Harley's,
corona-globes, shavers, light-duimmers, touch-lamps, flourescent tubs,
computer monitors, computer keyboards, christmas lights with flashers
and
dimmers, and whatnot?

Let's get the facts before we go toss mudballs at the FCC building.

Isn't this how some broadband services are distributed in the British
Isles, Finalnd and the Netherlands? How has it worked there? Keith
Willshaw reported that ham ops do not seem to have been adversely
affected. Are they using the same frequency régime?
--
Andrew Chaplin
SIT MIHI GLADIUS SICUT SANCTO MARTINO
(If you're going to e-mail me, you'll have to get "yourfinger." out.)

"Andrew Chaplin" wrote:



Isn't this how some broadband services are distributed in the British
Isles, Finalnd and the Netherlands? How has it worked there? Keith
Willshaw reported that ham ops do not seem to have been adversely
affected. Are they using the same frequency régime?

Sure...ham radio has bands of frequencies all through the radio
spectrum starting at just above the AM broadcast band at 1.8 to
2.0 mHz, then (~) each multiple of that to way up in the gHz
area. Something like 3,000 MEGAHERTZ of bandwidth all told.
That's a BUNCH of bandwidth indeed. Especially if one remembers
that the whole regular 'AM broadcast band' is one megaHertz wide.
--

-Gord.

In message , Tarver Engineering
writes

"Dave Holford" wrote in message
.. .


Tarver Engineering wrote:


BTW John - Long (very long) wires make excellent antennas provided
that
they are at least several wavelenghts long.

Self cancelling at a short distance, do the math.


Nonsense, their main use is as directional gain antennas.

My goodness Holford.

Stick to sniffing Stickney's ass.

Look up Beveridge aerial.

Mike
--
M.J.Powell

"Andrew Chaplin" wrote in message
...



Isn't this how some broadband services are distributed in the British
Isles, Finalnd and the Netherlands? How has it worked there? Keith
Willshaw reported that ham ops do not seem to have been adversely
affected. Are they using the same frequency régime?

There was an article in IT Week back in August about the UK
trials. They are being carried out in a number of locations including
Crieff and Campbeltown in the north of Scotland and Winchester
in Southern England. A spokesman was quoted as saying

"We have worked with the Radiocommunications Agency and have had
no reports of interference during the trials in Scotland, as we comply with
all current interference legislation."

They report that while there were some early problems with
radiated RF these have been overcome. They are offering a 1 mb service
for £30 per month which is quite competitve with ADSL.

Keith

"M. J. Powell" wrote:


Look up Beveridge aerial.

Mike

It's 'Beverage antenna' Mike...here's a URL

www.geocities.com/kb1gw/bev-page.html
--

-Gord.