Long Wire Antenna Story

[dbdigital]

There's an interesting article on the LA Radio.Com site ( http://www.laradio.com/kppchistory.htm ) about Pasadena, CA station KPPC-AM 1210 which began broadcasting in 1924 with 100 watts of power. Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. The ground system was installed under the tarpaper of the roof, with a fan of copper wire running into a series of grounds on a lot next door. They kept this antenna (and licensed power of 100 watts) until the late 60's.

Here is how one of their engineers described it: "Murley referred to KPPC-AM’s engineering in 1968 as “atrocious.”...While the antenna design looked good, Murley described it this way: “It’s roughly parallel with all the leaky auto ignitions of Colorado Boulevard. It’s anchored to a structure that anchors the printing press of the daily paper published next door. KPPC has a static machine for an AM long-wire (antenna), the sort of static machine that does a job on 1240 and local adjacent channel operations, such as the black-programmed KGFJ on 1230.”

Even though at night KPPC could be heard as far east as Philadelphia and as far north as British Columbia it's local coverage was not too good (although it did cover its city of license). The article described the stations coverage as, "barely reaching West Hollywood’s Sunset Strip, never reaching the Pacific and covering less than a third of the Los Angeles market within the half-millivolt contour."

While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

db

 

[rfry]

Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. ...
While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

To pick a nit, a long-wire antenna is different than a Tee antenna, though. A long-wire antenna usually is ~ horizontally polarized and directional in the horizontal plane (pattern depending on the number of wavelengths and the wire geometry), while a Tee antenna is vertically polarized and ~omnidirectional in the horizontal plane.

Horizontal polarization in the medium wave band has very high propagation loss for the ground wave, so if that's what they really used, it could explain why their local coverage was so poor, yet they got DX reports from distant listeners in some compass directions.
//

 

[dbdigital]

Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. ...
While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

To pick a nit, a long-wire antenna is different than a Tee antenna, though. A long-wire antenna usually is ~ horizontally polarized and directional in the horizontal plane (pattern depending on the number of wavelengths and the wire geometry), while a Tee antenna is vertically polarized and ~omnidirectional in the horizontal plane.

Horizontal polarization in the medium wave band has very high propagation loss for the ground wave, so if that's what they really used, it could explain why their local coverage was so poor, yet they got DX reports from distant listeners in some compass directions.
//

I'm simply going by their description of the antenna in this story.

To add a little more to it, here's another quote: "The actual radiating element of the antenna was the 121-foot vertical lead, with the horizontal wire element acting as a capacitive load...Many of those grounds were silver-soldered to buried, large copper stills, reportedly used by bootleggers during Prohibition."

db

 

[Black_Shire]

Here is one of the remaining (as of late 2004) AM wire antennas: www.earthsignals.com/Collins/KGFJ/index.htm . This one is (was?) an end-fed "clothesline" flat-top antenna, and is (was?) somewhat directional off the far end.

KIAL 1450 AM in Unalaska, Alaska (in the Aleutian Islands) uses a multi-wire "clothesline" flat-top with a vertical downlead wire in the middle and is a Marconi "Tee" antenna. It looks just like a Non-Directional Beacon (NDB) antenna, and may in fact be a "surplus" one.


-- Black Shire

Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. ...
While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

To pick a nit, a long-wire antenna is different than a Tee antenna, though. A long-wire antenna usually is ~ horizontally polarized and directional in the horizontal plane (pattern depending on the number of wavelengths and the wire geometry), while a Tee antenna is vertically polarized and ~omnidirectional in the horizontal plane.

Horizontal polarization in the medium wave band has very high propagation loss for the ground wave, so if that's what they really used, it could explain why their local coverage was so poor, yet they got DX reports from distant listeners in some compass directions.
//

I'm simply going by their description of the antenna in this story.

To add a little more to it, here's another quote: "The actual radiating element of the antenna was the 121-foot vertical lead, with the horizontal wire element acting as a capacitive load...Many of those grounds were silver-soldered to buried, large copper stills, reportedly used by bootleggers during Prohibition."

db

 

[Black_Shire]

Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. ...
While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

To pick a nit, a long-wire antenna is different than a Tee antenna, though. A long-wire antenna usually is ~ horizontally polarized and directional in the horizontal plane (pattern depending on the number of wavelengths and the wire geometry), while a Tee antenna is vertically polarized and ~omnidirectional in the horizontal plane.

Horizontal polarization in the medium wave band has very high propagation loss for the ground wave, so if that's what they really used, it could explain why their local coverage was so poor, yet they got DX reports from distant listeners in some compass directions.
//

Also, isn't a true Long Wire antenna at least 1 wavelength long at its operating frequency? If I recall correctly, they are used as simple directional antennas because the strongest signal comes off the far end. (They'll work at higher frequencies as well, but the patterns can become quite complex with plenty of lobes and nulls.)


-- Black Shire

 

[dbdigital]

Here is one of the remaining (as of late 2004) AM wire antennas: www.earthsignals.com/Collins/KGFJ/index.htm . This one is (was?) an end-fed "clothesline" flat-top antenna, and is (was?) somewhat directional off the far end.

KIAL 1450 AM in Unalaska, Alaska (in the Aleutian Islands) uses a multi-wire "clothesline" flat-top with a vertical downlead wire in the middle and is a Marconi "Tee" antenna. It looks just like a Non-Directional Beacon (NDB) antenna, and may in fact be a "surplus" one.


-- Black Shire

Typical of that time was the long wire, top-loaded "T" antenna and KPPC had theirs attached between two wooden masts on top of their building. ...
While long wire antennas are successfully used for receiving AM, the article makes plain to me why the design was abandoned for transmitting it.

To pick a nit, a long-wire antenna is different than a Tee antenna, though. A long-wire antenna usually is ~ horizontally polarized and directional in the horizontal plane (pattern depending on the number of wavelengths and the wire geometry), while a Tee antenna is vertically polarized and ~omnidirectional in the horizontal plane.

Horizontal polarization in the medium wave band has very high propagation loss for the ground wave, so if that's what they really used, it could explain why their local coverage was so poor, yet they got DX reports from distant listeners in some compass directions.
//

I'm simply going by their description of the antenna in this story.

To add a little more to it, here's another quote: "The actual radiating element of the antenna was the 121-foot vertical lead, with the horizontal wire element acting as a capacitive load...Many of those grounds were silver-soldered to buried, large copper stills, reportedly used by bootleggers during Prohibition."

db

Those are great photos. I've seen this antenna in downtown L.A. many times. I believe KYPA still keeps it as a back up. I notice their new TX is a BE AM 1A with built-in C-Quam. Maybe they'll go AMS.

I suspect that with KPPC they began with a true long wire antenna in the 1920's and when their antenna was rebuilt in 1936 went to a "T" design. Their former engineer still refers to it as a long wire.

Anyway, the reason I mention this story at all is that when it describes the KPPC antenna as being susceptible to environmental noise, is it because of the antenna design, the fact it's in the city or that it's radials are on a roof as opposed to buried in earth, or all of the above?

Would a folded unipole provide better spurrious r-f rejection over a "T" or long wire design regardless of where it is located?

db

 

[PaulBWalkerJr]

Reading KIAL's website, I can't tell if they are still using the Wire Antenna but asusmably since they are only operating at 50 Watts.. they probably are.

 

[Flying-Dutchman]

More than 30 years ago, we converted a Heathkit ham transmitter to the AM broadcast band.
We connected a 200 foot long wire antenna.

That signal went 10 miles strong, and could be heard 50 miles on a car radio.

The FCC was quite impressed too. That transmitter cost us a $250 fine each.

 

[Black_Shire]

dbdigital wrote:

<Those are great photos. I've seen this antenna in downtown L.A. many times. I believe KYPA still keeps it as a back up. I notice their new TX is a BE AM 1A with built-in C-Quam. Maybe they'll go AMS.>

A crazy thought: Why not approach them about demonstrating AM Stereo to them using your "Alfredo Lite" transmitter and their wire antenna? You could even get an FCC Part 5 Experimental License to do this.

<I suspect that with KPPC they began with a true long wire antenna in the 1920's and when their antenna was rebuilt in 1936 went to a "T" design. Their former engineer still refers to it as a long wire.>

Inverted L (end-fed as opposed to center-fed flat-top) antennas were common back then.

<Anyway, the reason I mention this story at all is that when it describes the KPPC antenna as being susceptible to environmental noise, is it because of the antenna design, the fact it's in the city or that it's radials are on a roof as opposed to buried in earth, or all of the above?>

If an RF noise source near an antenna is radiating at the antenna's resonant frequency, it will excite the antenna (like a tuning fork) and the antenna will re-radiate the noise. The noise can also find its way back into the transmitter and wreak havoc with the signal.

<Would a folded unipole provide better spurrious r-f rejection over a "T" or long wire design regardless of where it is located?>

Perhaps not, as a folded unipole is still an electric field antenna (as opposed to a magnetic field antenna such as a loop). I don't have much experience with loops, but the literature says that they are quieter with respect to noise (although at least some of that is due to them being closed DC circuits that keep static charges from accumulating on the loop).

I've never heard of loops being used for AM broadcasting (full-wavelength loops are pretty big at Medium Wave frequencies), but it might have been done back then, as some early AM stations also used horizontal dipoles.

Being that low to the ground in terms of wavelength, an AM band horizontal dipole has a pretty much omni-directional pattern, with Near-Vertical Incidence Skywave (NVIS) propagation as well. An AM band transmitting loop antenna at normal heights (lower than a skyscraper!) above the ground would have similar characteristics. Low-mounted loops are sometimes used in Pacific Island nations for NVIS Short Wave broadcasting on the ~4500 kHz - ~5000 kHz tropical bands.

I have a Radio Systems 20 watt AM transmitter "crystalled" for 850 kHz, and a friend of mine has a horse pasture large enough to accomodate a full-wavelength 850 kHz NVIS loop antenna. I've sometimes thought to myself, "hmmm..." while driving past the pasture. Naw, I could never afford to pay the NAL.


-- Black Shire

 

[Black_Shire]

Reading KIAL's website, I can't tell if they are still using the Wire Antenna but asusmably since they are only operating at 50 Watts.. they probably are.

I think so too, since they have yet to find the real estate to put up a tower. I tried to find an online picture of their wire "Tee" antenna (I saw one once), but it must have been on another web site. Where the "Tee" is located is a pretty desolate-looking place.


-- Black Shire

 

[PaulBWalkerJr]

I just sent them a nice email and will let y'all know what I hear back from them.

 

[Black_Shire]

More than 30 years ago, we converted a Heathkit ham transmitter to the AM broadcast band.
We connected a 200 foot long wire antenna.

That signal went 10 miles strong, and could be heard 50 miles on a car radio.

The FCC was quite impressed too. That transmitter cost us a $250 fine each.

Congratulations! (sort of) How much power were you all running, and on what frequency? Also, what kind of ground system did you all use and how was the antenna strung up and how high (Inverted L, or sloped up to a pole from the feed point, etc.)?


-- Black Shire

 

[Black_Shire]

I just sent them a nice email and will let y'all know what I hear back from them.

Thank you! Given their 50 watt power, I'd guess that their transmitter is an LPB unit. Their wire "Tee" antenna looks just like NDB antennas you'll see all over the US, especially in the West (a 3 wire flat-top with a single vertical downlead wire [the actual radiating element] in the middle).


-- Black Shire

 

[dbdigital]

dbdigital wrote:

<Those are great photos. I've seen this antenna in downtown L.A. many times. I believe KYPA still keeps it as a back up. I notice their new TX is a BE AM 1A with built-in C-Quam. Maybe they'll go AMS.>

A crazy thought: Why not approach them about demonstrating AM Stereo to them using your "Alfredo Lite" transmitter and their wire antenna? You could even get an FCC Part 5 Experimental License to do this.

<I suspect that with KPPC they began with a true long wire antenna in the 1920's and when their antenna was rebuilt in 1936 went to a "T" design. Their former engineer still refers to it as a long wire.>

Inverted L (end-fed as opposed to center-fed flat-top) antennas were common back then.

<Anyway, the reason I mention this story at all is that when it describes the KPPC antenna as being susceptible to environmental noise, is it because of the antenna design, the fact it's in the city or that it's radials are on a roof as opposed to buried in earth, or all of the above?>

If an RF noise source near an antenna is radiating at the antenna's resonant frequency, it will excite the antenna (like a tuning fork) and the antenna will re-radiate the noise. The noise can also find its way back into the transmitter and wreak havoc with the signal.

<Would a folded unipole provide better spurrious r-f rejection over a "T" or long wire design regardless of where it is located?>

Perhaps not, as a folded unipole is still an electric field antenna (as opposed to a magnetic field antenna such as a loop). I don't have much experience with loops, but the literature says that they are quieter with respect to noise (although at least some of that is due to them being closed DC circuits that keep static charges from accumulating on the loop).

I've never heard of loops being used for AM broadcasting (full-wavelength loops are pretty big at Medium Wave frequencies), but it might have been done back then, as some early AM stations also used horizontal dipoles.

Being that low to the ground in terms of wavelength, an AM band horizontal dipole has a pretty much omni-directional pattern, with Near-Vertical Incidence Skywave (NVIS) propagation as well. An AM band transmitting loop antenna at normal heights (lower than a skyscraper!) above the ground would have similar characteristics. Low-mounted loops are sometimes used in Pacific Island nations for NVIS Short Wave broadcasting on the ~4500 kHz - ~5000 kHz tropical bands.

I have a Radio Systems 20 watt AM transmitter "crystalled" for 850 kHz, and a friend of mine has a horse pasture large enough to accomodate a full-wavelength 850 kHz NVIS loop antenna. I've sometimes thought to myself, "hmmm..." while driving past the pasture. Naw, I could never afford to pay the NAL.


-- Black Shire

Thanks for the great info, Black Shire. As for your 20 watt TX/loop antenna idea, do you think the FCC would even notice up in Alaska? It would be fun to try it.

db

 

[Black_Shire]

<Thanks for the great info, Black Shire. As for your 20 watt TX/loop antenna idea, do you think the FCC would even notice up in Alaska? It would be fun to try it. >

You're most welcome. I was mistaken about one thing--a folded unipole (also called a folded Marconi antenna) is electrically a closed DC circuit like a loop antenna and also bleeds off static charges.

The folded unipole also has a "smaller cousin" called the hairpin monopole antenna (see: www.antennex.com/preview/monopole.htm ). The hairpin monopole is a capacitively-loaded version of the folded unipole that can be made physically very small--using the design formulas in the article, a hairpin monopole antenna for 1610 kHz would be only about 17 feet tall!

Regarding my "dream" 20 watt TX/NVIS loop, my 850 kHz AM transmitter is within 30 kHz of KCBF 820 here in town, which would undoubtedly soon earn me a dreaded "visit" if I lit it up and fed it into a full-size loop.


-- Black Shire

 

[Tom Wells]

Those old long-wires changed tuning every time a streetcar passed.
That they did not behave well is an understatement.
They put a lot of energy into nearby steel building structure, wasting power.


I know it's not long -wire related, but as a standard CB 1/8 wave antenna with ground plane is about 8' 6", coudn't
one build an appropriate tuning unit for AM MW just as a car radio whip input was once reasonated?
I mean a meaty, high q coil from copper refrigeration tubing.

Assuming you perfectly match the feedline, there is no radiation, so isn't the antenna/ground plane the only
meaningful radiator?

Coax or ladder should not radiate if the SWR is low, and if coax is grounded, it still shouldn't radiate much.

Feedline isn't mentioned in pt 15, I don't think....

Opinion?

 

[Black_Shire]

Those old long-wires changed tuning every time a streetcar passed.
That they did not behave well is an understatement.
They put a lot of energy into nearby steel building structure, wasting power.


I know it's not long -wire related, but as a standard CB 1/8 wave antenna with ground plane is about 8' 6", coudn't
one build an appropriate tuning unit for AM MW just as a car radio whip input was once reasonated?
I mean a meaty, high q coil from copper refrigeration tubing.

Assuming you perfectly match the feedline, there is no radiation, so isn't the antenna/ground plane the only
meaningful radiator?

Coax or ladder should not radiate if the SWR is low, and if coax is grounded, it still shouldn't radiate much.

Feedline isn't mentioned in pt 15, I don't think....

Opinion?

Actually, it is. In Part 15.219 (under which the commercially-available Part 15 AM transmitters are certified), the 3 meter length limit applies to the combined total length of the antenna + feed line (if any) + ground lead.


-- Black Shire

 

[PaulBWalkerJr]

I sent an email to two people at KIAL 1450 in Unalaska and never heard back from them. Oh well.... I tired.

 

[Black_Shire]

I sent an email to two people at KIAL 1450 in Unalaska and never heard back from them. Oh well.... I tired.

I wouldn't give up just yet. I'm part native myself, and many of the native folks here (especially in the small communities) operate on "village time," which is like "island time."


-- Black Shire

 

[PaulBWalkerJr]

I sent them one more email, lets see if this one makes it thru to them.......