On 12/26/2011 2:57 PM, DEFCON 88 wrote:
On Dec 26, 5:52 pm, DEFCON wrote:
I've seen pictures (which I can't seem to find on the internet) of old
AM
broadcast antennas consisting of multiple parallel wires strung
between
two towers on the rooftop of a building. These were typically located
on
top of a hotel, with the broadcast studio in the hotel.

Were these wires truly parallel, or were they strung in a zig-zag
pattern
(which I'll try to illustrate below)? If parallel, what's the theory
and
advantage of having them parallel?

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Dammit, I figured my illustration wouldn't display correctly. Does
anyone know why the text in my posts become fragmented? Is it
Google or Windows (or both) that can't even process simple text
correctly?

It is your choice of font ... try an non-variable width font with equal
spacing of all characters ...

What you want is a fixed-width font, as opposed to a non-proportional
font ...

THIS:
"Most examples of ASCII art require a fixed-width font (non-proportional
fonts, as on a traditional typewriter) such as Courier for presentation."

FROM HE
http://en.wikipedia.org/wiki/ASCII_art

Regards,
JS

On 12/26/2011 5:52 PM, DEFCON 88 wrote:
I've seen pictures (which I can't seem to find on the internet) of old
AM
broadcast antennas consisting of multiple parallel wires strung
between
two towers on the rooftop of a building. These were typically located
on
top of a hotel, with the broadcast studio in the hotel.

Were these wires truly parallel, or were they strung in a zig-zag
pattern
(which I'll try to illustrate below)? If parallel, what's the theory
and
advantage of having them parallel?
[...]


Another poster referred to cage dipoles, and it is possible that a
few early broadcast arrays were cage dipoles, just as some were
inverted Ls, but the vast majority of these early parallel wire
antennas were "T" antennas. What looks like the feeder in these
antennas is actually the vertical radiating element, and the
symmetrical horizontal wires (yes, typically all in parallel) are a
non-radiating capacity hat to lower the system's resonant frequency.
Multiple wires have somewhat more capacity than single wires, and
also make the antenna more broadbanded and thus easier to tune, but
I think their use had more to do with early semi-mythical antenna
lore than it did with real-world benefits.

These antennas weren't understood too well at the time they were
first developed, but early spark transmitter and LF alternator
operators knew that they could tune an antenna system's reactance
out and make it "take power" on the desired frequency by varying the
width and length of the capacity hat.

When mathematical models began to be used to design antennas, in the
late 20s / early 30s I think, it was found that the same or better
performance could be had with simpler designs that survived the
weather better.

T antennas are seldom used on the Standard Broadcast Band today, but
amateurs still use them fairly often on 160 meters, where the
requisite height for a quarter wave vertical is hard to achieve.


With all good wishes,


Kevin, WB4AIO.
--
http://nationalvanguard.org/
http://kevinalfredstrom.com/

In article ,
Kevin Alfred Strom wrote:
On 12/24/2011 12:14 PM, Mark Zenier wrote:
[...]
Funny that they picked the second harmonic of the old KXA. To properly
resurrect the old KXA, they would be running dreary classical music.
And running a dipole on the roof of a local department store. (The
last medium wave wire antenna in the country, I think.)
[...]


Interesting on the 'last wire antenna' -- anywhere I get more info
on that, or pictures?

That may have been hearsay from one of the former staffers, (probably
in a Seattle Times article).

After a half an hour of searching, I still haven't found a good picture,
just a lot of local radio people discussing it on various fora. Perhaps
some combination of the search terms "KXA", "Rhodes Department Store",
"Roof", "Seattle", etc. might find something.

It was a folded dipole, running East/West about 30-50 feet above the
roof with self supporting truss towers supporting each end. It was
a short block in length. (I think that's still less than a half wave).
As I remember, the feed was balanced open wire. Most of the surrounding
buildings were shorter, but you could clearly see it from the taller ones
further up the hill.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

On Dec 26, 6:51*pm, "Brenda Ann"
wrote:
"DEFCON 88" *wrote in message

...

Dammit, I figured my illustration wouldn't display correctly. Does
anyone know why the text in my posts become fragmented? Is it
Google or Windows (or both) that can't even process simple text
correctly?

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Your illustration appears to have come out fine here, showing a series of
parallel lines with "pipes" between each on the left hand side.

The "pipes" are actually at alternate ends, but for some reason
Windows deletes the spaces that precede the right-hand side pipes.

On Dec 26, 7:11*pm, Zaphod Beeblebrox wrote:
On Mon, 26 Dec 2011 14:52:22 -0800, DEFCON 88 wrote:
I've seen pictures (which I can't seem to find on the internet) of old
AM
broadcast antennas consisting of multiple parallel wires strung between
two towers on the rooftop of a building. These were typically located on
top of a hotel, with the broadcast studio in the hotel.

I've seen pictures of antennas like that strung between the masts of
old steamships. Folded dipoles. The high-impedance feedline (ladder
line) fed the center of the center wire. Instead of a single additional
wire connecting the ends of the center wire, a bunch of parallel wires
were used, separated by several circular spreaders.

When you make an antenna with a large-diameter radiator, it is inherently
more broad-band than just a wire. The multiple parallel wires created the
equivalent of a radiator with the diameter of the circular spreaders.
In those days, antenna tuners were standard equipment anyway.

Thanks for the info. And don't forget your towel.

On Dec 26, 7:53*pm, John Smith wrote:
On 12/26/2011 2:57 PM, DEFCON 88 wrote:





On Dec 26, 5:52 pm, DEFCON *wrote:
I've seen pictures (which I can't seem to find on the internet) of old
AM
broadcast antennas consisting of multiple parallel wires strung
between
two towers on the rooftop of a building. These were typically located
on
top of a hotel, with the broadcast studio in the hotel.

Were these wires truly parallel, or were they strung in a zig-zag
pattern
(which I'll try to illustrate below)? If parallel, what's the theory
and
advantage of having them parallel?

----------------------------------------------------------------
|
----------------------------------------------------------------

|
----------------------------------------------------------------
|
----------------------------------------------------------------

|
----------------------------------------------------------------

Dammit, I figured my illustration wouldn't display correctly. Does
anyone know why the text in my posts become fragmented? Is it
Google or Windows (or both) that can't even process simple text
correctly?

It is your choice of font ... try an non-variable width font with equal
spacing of all characters ...

What you want is a fixed-width font, as opposed to a non-proportional
font ...

THIS:
"Most examples of ASCII art require a fixed-width font (non-proportional
fonts, as on a traditional typewriter) such as Courier for presentation."

FROM HEhttp://en.wikipedia.org/wiki/ASCII_art

Regards,
JS- Hide quoted text -

- Show quoted text -

Thanks, I will try that.

On Dec 26, 8:52*pm, Kevin Alfred Strom
wrote:
On 12/26/2011 5:52 PM, DEFCON 88 wrote: I've seen pictures (which I can't seem to find on the internet) of old
AM
broadcast antennas consisting of multiple parallel wires strung
between
two towers on the rooftop of a building. These were typically located
on
top of a hotel, with the broadcast studio in the hotel.

Were these wires truly parallel, or were they strung in a zig-zag
pattern
(which I'll try to illustrate below)? If parallel, what's the theory
and
advantage of having them parallel?

[...]

Another poster referred to cage dipoles, and it is possible that a
few early broadcast arrays were cage dipoles, just as some were
inverted Ls, but the vast majority of these early parallel wire
antennas were "T" antennas. What looks like the feeder in these
antennas is actually the vertical radiating element, and the
symmetrical horizontal wires (yes, typically all in parallel) are a
non-radiating capacity hat to lower the system's resonant frequency.
Multiple wires have somewhat more capacity than single wires, and
also make the antenna more broadbanded and thus easier to tune, but
I think their use had more to do with early semi-mythical antenna
lore than it did with real-world benefits.

These antennas weren't understood too well at the time they were
first developed, but early spark transmitter and LF alternator
operators knew that they could tune an antenna system's reactance
out and make it "take power" on the desired frequency by varying the
width and length of the capacity hat.

When mathematical models began to be used to design antennas, in the
late 20s / early 30s I think, it was found that the same or better
performance could be had with simpler designs that survived the
weather better.

T antennas are seldom used on the Standard Broadcast Band today, but
amateurs still use them fairly often on 160 meters, where the
requisite height for a quarter wave vertical is hard to achieve.

With all good wishes,

Kevin, WB4AIO.
--http://nationalvanguard.org/http://kevinalfredstrom.com/

Very interesting. Thanks!

On Dec 26, 5:53*am, dave wrote:
On Sat, 24 Dec 2011 17:14:05 +0000, Mark Zenier wrote:
Isn't the mega-talker in Sacramento that runs/(used to run?) HD-Radio on
1530 or 1540? *Having 50kw in their digital sideband would sure screw
that up.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

- KFBK has a 2 tower Franklin antenna, 50KW on 1530
http://www.oldradio.com/archives/stations/ccs/kfbk.htm

On Dec 26, 4:01*pm, (Mark Zenier) wrote:
In article ,

dave wrote:
On Sat, 24 Dec 2011 17:14:05 +0000, Mark Zenier wrote:

Isn't the mega-talker in Sacramento that runs/(used to run?) HD-Radio on
1530 or 1540? *Having 50kw in their digital sideband would sure screw
that up.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

KFBK has a 2 tower Franklin antenna, 50KW on 1530

That's the one. *They seem to have quit running HD at night.
Back when all that mess was starting, they were one of the only
two or three HD signals I could hear, here in Seattle.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

KFBK on 1530 kHz was running HD Buzz at
least until 2 AM last night; and KFI on
640 kHz seems to be running the HD Buzz
all night long : As heard here in Twain
Harte, CA ~ RHF

'Tradio' on KDUN-AM 1030 kHz @ 8:30 AM PST
on 28 DEC 2011

'Tradio' with Blair and Kent
http://www.kdune.com/tradio.html
Just two old guys a talking and
having fun on-the-radio )

KDUNe from Oregon 'Dune' Country
http://www.kdune.com/
http://en.wikipedia.org/wiki/KDUN
http://www.radio-locator.com/info/KDUN-AM