"N2EY" wrote in message
om...
| "Phil Kane" wrote in message
t.net...
| On Wed, 09 Jul 2003 03:02:43 GMT, Jim Hampton wrote:
|
| Phil, I doubt you're kidding, but a single wire with a ground
return? That
| is going to have a ton of problems even *without* putting
broadband on it.
|
| That amazed me too - but there's only one insulator on the pole
pig
| and one wire crossing the street to same. Three phase primary
is
| three wire, so there isn't even a Wye Neutral for return.
|
| I first saw this system along the Trans-Canada highway in
Alberta in
| 1970 and I put it down to the rural-ness of the area. But
suburban
| Portland in the 21st Century?
|
| Are there NO other wires on the pole?
|
| Here in EPA, most residential areas have three-phase going down the
| larger streets (like South Devon Ave. here in Wayne), with
| single-phase feeders going to the side streets. The return is partly
| through the dirt but mostly through the main messenger that carries
| the 120/240 twisted wires.
|
| Earth return will work fine, if the ground is good enough. The few
| HVDC lines that have been installed can be operated that way if one
| conductor fails.
|
73 de Jim, N2EY
The problem is, in most parts of the country the ground conductivity
is VERY poor. Just ask anyone who is familiar with commercial AM
broadcast station operation. They all wouldn't bury literally MILES
of copper wire around their towers in order to get somewhat of a
ground if they didn't have to. Besides our local electric utility
had nothing but big problems with 3-phase feeder lines without a
neutral along with the hot lines. They lose transformers whenever we
have a dandy lightning storm.

As far as BPL is concerned, BIG PROBLEMS LOOM for almost all licensed
services, including amateur radio if this is allowed.

73, Sam

\"Sparky\" wrote:

"N2EY" wrote in message
om...
| "Phil Kane" wrote in message
t.net...
| On Wed, 09 Jul 2003 03:02:43 GMT, Jim Hampton wrote:
|
| Phil, I doubt you're kidding, but a single wire with a ground
return? That
| is going to have a ton of problems even *without* putting
broadband on it.
|
| That amazed me too - but there's only one insulator on the pole
pig
| and one wire crossing the street to same. Three phase primary
is
| three wire, so there isn't even a Wye Neutral for return.
|
| I first saw this system along the Trans-Canada highway in
Alberta in
| 1970 and I put it down to the rural-ness of the area. But
suburban
| Portland in the 21st Century?
|
| Are there NO other wires on the pole?
|
| Here in EPA, most residential areas have three-phase going down the
| larger streets (like South Devon Ave. here in Wayne), with
| single-phase feeders going to the side streets. The return is partly
| through the dirt but mostly through the main messenger that carries
| the 120/240 twisted wires.
|
| Earth return will work fine, if the ground is good enough. The few
| HVDC lines that have been installed can be operated that way if one
| conductor fails.
|
73 de Jim, N2EY
The problem is, in most parts of the country the ground conductivity
is VERY poor. Just ask anyone who is familiar with commercial AM
broadcast station operation. They all wouldn't bury literally MILES
of copper wire around their towers in order to get somewhat of a
ground if they didn't have to.

I still wonder about that AM tower I once passed in Santa Clara,CA that was
sitting on a salt marsh right at sea level....do they have all that wire in the
ground, er, water, too?



As far as BPL is concerned, BIG PROBLEMS LOOM for almost all licensed
services, including amateur radio if this is allowed.

That was exactly what I said in my comments to FCC on the docket:

"The use of the HF part of the spectrum as we have always known it
will be ended".

Dick

(snip)

|
| I still wonder about that AM tower I once passed in Santa Clara,CA
that was
| sitting on a salt marsh right at sea level....do they have all that
wire in the
| ground, er, water, too?


Not sure on that one. I haven't ever seen AM towers with salt marsh
surrounding it, but in that case they sure would put out a much better
signal than a tower located away on dry rocky ground with all the
buried radials.
|
| As far as BPL is concerned, BIG PROBLEMS LOOM for almost all
licensed
| services, including amateur radio if this is allowed.
|
| That was exactly what I said in my comments to FCC on the docket:
|
| "The use of the HF part of the spectrum as we have always known it
| will be ended".
|
| Dick

Well stated, Dick. I totally agree.

73, Sam

On Thu, 10 Jul 2003 19:04:29 -0600, \"Sparky\" wrote:

| I still wonder about that AM tower I once passed in Santa Clara,CA
that was sitting on a salt marsh right at sea level....do they have all
that wire in the ground, er, water, too? Not sure on that one.

There's no AM tower in Santa Clara (or at least none in the last 40
years that I know of), let alone one that meets that description.
There's one in Palo Alto (1220 kHz) and yes, it has the standard
120-radial ground system. The ground there isn't all -that- wet.

In "the good old days" the radials were 8 AWG copper, but after
several stations got their ground systems torn out by thieves who
sold the copper on the scrap metal market, almost everybody replaced
them with 8 AWG Copperweld, which has the same rf electrical
properties but has no value on the scrap metal market.

I haven't ever seen AM towers with salt marsh surrounding it,

There are several other AM stations in the Bay Area whose antenna
arrays are located right at the water line. In those cases, the
radials go out from the base and into the Bay, which is tidal.

but in that case they sure would put out a much better signal than a
tower located away on dry rocky ground with all the buried radials.

The ground system and conductivity are but two elements in the
antenna efficiency. Other factors are the electrical height and the
spacing and phasing of elements in a directive array.

AM antenna design is more of an art than a science.

--
73 de K2ASP - Phil Kane

Phil Kane wrote:

On Thu, 10 Jul 2003 19:04:29 -0600, \"Sparky\" wrote:

| I still wonder about that AM tower I once passed in Santa Clara,CA
that was sitting on a salt marsh right at sea level....do they have all
that wire in the ground, er, water, too? Not sure on that one.

There's no AM tower in Santa Clara (or at least none in the last 40
years that I know of), let alone one that meets that description.

OOP! that Should have been Santa Cruz. Ya know, the place with the big boardwalk
and all the thong bikinis.......



There's one in Palo Alto (1220 kHz) and yes, it has the standard
120-radial ground system. The ground there isn't all -that- wet.


This one is right above the water level on a slough of some sort, I didn't get
that good a look but observed it as we drove past. Sure looked like an local AM
tower
of the sort I've worked around.




In "the good old days" the radials were 8 AWG copper, but after
several stations got their ground systems torn out by thieves who
sold the copper on the scrap metal market, almost everybody replaced
them with 8 AWG Copperweld, which has the same rf electrical
properties but has no value on the scrap metal market.

We still had all the copper radials at the (smaller) stations I worked for.
Evidently the locals were adverse to working for it.