US Domestic Shortwave

[RadioFan2J3]

That sounds about right. The KUSW log-periodic had a fixed takeoff angle. They never changed target areas.
I'd love to see some of those big curtains. There's a lot of pictures and info in the book, "Radio Antenna Engineering", edited by Edmund LaPorte, that showed those things being built in the 40's and 50's.
Wow!!

After the size of the 4x4 and 6x4 curtains ceases to be something to consider, remember that many of the newer curtain array antennas also have slewable beams, typically five beam patters, the mechanical boresite bearing, 6 degrees to the right, 12 degrees to the right, six degrees to the left or 12 degrees to the left. This is accomplished by changing the phase relationships between the dipole stacks. Some systems also have the ability for vertical slewing, again, all done by changing the phase relationships.

These more capable (and complex) antenna systems have multiple RF switches which switch in different sections of balanced lines (of varying length) behind the dipole elements. Interesting to see.

 

[SomeRadioGuy]

That doesn't mean that transmissions beamed to a certain area can't be heard elsewhere. Those antennas can have significant back and sidelobes. And the luck of geography can help...for instance transmissions from Madagascar to West Africa can put a good signal into North America as we are "in the beam."

Russia closed its shortwave services in 2014, preferring to concentrate on the RT television channel as well as Radio Sputnik distribution to local broadcasters. China still has a few broadcasts to North America via Cuba, but closed its Albanian relay station (that was well heard here) about 18 months ago.

Romania, Turkey, Spain, Cuba, North and South Korea, and Thailand are the only other remaining countries that beam English to North America, and reception can be poor to nonexistent on some of those broadcasts.

The problem for North Korea, Souyth Korea and Thailand is their choice of frequencies, time of day and how they choose to beam.

THailand uses 15590 or 13740/5 at 0000UTC by beaming over the pole. I can hear it in Alaska.. but ive never seen consistent reception of Radio Thailand in english to north america.. by anyone in the lower 48

KBS World Radio from Seoul uses a 15mhz frequency that would be early to mid morning in the US.

North Korea doesnt use the best frequencies or times of day.

I can hear North Korea quite well on SW here too

 

[Radig]

snip...that many of the newer curtain array antennas also have slewable beams, typically five beam patters, the mechanical boresite bearing, 6 degrees to the right, 12 degrees to the right, six degrees to the left or 12 degrees to the left. This is accomplished by changing the phase relationships between the dipole stacks. Some systems also have the ability for vertical slewing, again, all done by changing the phase relationships.

True. The TCI dipole arrays can slew left and right as well as up and down. Furthermore, depending on the size of the array, they can have several transmissions operating independently, in separate dipole combinations but within the same antenna array. Very, very neat!

 

[kenglish]

See this:

Radio New Zealand International Technical | A Gallery from None (National) | RNZ International

www.rnz.co.nz

 

[Mediafrog+]

THailand uses 15590 or 13740/5 at 0000UTC by beaming over the pole. I can hear it in Alaska.. but ive never seen consistent reception of Radio Thailand in english to north america.. by anyone in the lower 48

I've been able to hear the Thai transmissions from time to time here in Texas on 19 or 22 meters...but usually during times of high solar activity. The signal is subject to polar auroral disturbances unless you are on the west coast of North America.

KBS World Radio from Seoul uses a 15mhz frequency that would be early to mid morning in the US.

And that is mostly a night path for the morning transmission to North America. Frequency is too high, resulting in poor to nonexistent reception. Should use either 25 or 31 meters. Many SWLs have complained to KBS about this, but no response.

I can hear North Korea quite well on SW here too

Much easier to hear NK than SK these days. The morning English transmission to North America often has a decent signal into Texas.

 

[RadioFan2J3]

True. The TCI dipole arrays can slew left and right as well as up and down. Furthermore, depending on the size of the array, they can have several transmissions operating independently, in separate dipole combinations but within the same antenna array. Very, very neat!

All depends on how much one is willing to pay.

As for a dipole array having more than one transmission, I don't think any of the TCI curtain dipole systems installed by VOA ever had that as an option, that is, dividing the dipole elements as I think you are suggesting. Greenville VOA has a handful of diplexed antennas, but the diplexing was done right after the switchbay, as best as I remember. Greenville's diplexing had two separate outputs on the switchbay, two feed lines for a short distance, then the diplexing, and then one transmission line out to the antenna.

I don't recall any of the TCI antenna systems in the VOA network having two feedlines all the way to the antenna. What other shortwave broadcasters have done? I'd have no idea.

Thinking about the number of feedlines, at one station, we had two antennas with one feedline, a low band and a high band TCI antenna, side by side. There was a feedline switch near the two antennas which switched the feedline between the two antennas. Other than saving the costs of transmission line and maybe additional cross points on the switchbay, I never understood that logic, because it meant that one of the antenna arrays could not be used if the other one was scheduled.

From a technical standpoint, I don't have a reason to believe it could not be done, using separate dipoles in one antenna array, but by splitting up the dipoles within one antenna, there is a loss of antenna gain on both frequencies.

 

[Radig]

From a technical standpoint, I don't have a reason to believe it could not be done, using separate dipoles in one antenna array, but by splitting up the dipoles within one antenna, there is a loss of antenna gain on both frequencies.

There is an interesting paper authored by TCI and published by the IEEE, 33 years ago, that outlined the many features of the TCI arrays. Can't believe it was that long ago!

IEEE TRANSACTIONS ON BROADCASTING, VOL. 34, NO. 2, JUNE 1988
High-Power, Broad-Bandwidth HF Dipole Curtain Array with Extensive Vertical and Azimuthal Beam Control
by Ronald Wilensky, TCI International

The VOA Greenville site uses their TCI dipole array for the Radio Marti transmissions. The DRM Marti transmitter uses one of their Rhombics.

 

[RadioFan2J3]

There is an interesting paper authored by TCI and published by the IEEE, 33 years ago, that outlined the many features of the TCI arrays. Can't believe it was that long ago!

IEEE TRANSACTIONS ON BROADCASTING, VOL. 34, NO. 2, JUNE 1988
High-Power, Broad-Bandwidth HF Dipole Curtain Array with Extensive Vertical and Azimuthal Beam Control
by Ronald Wilensky, TCI International

The VOA Greenville site uses their TCI dipole array for the Radio Marti transmissions. The DRM Marti transmitter uses one of their Rhombics.

I've not read that article, perhaps not wanting to pay for it?

In the extract, there is a mention of 8x6 array. I wonder how many of those did TCI ever build? We had some 4x6 arrays at Morocco, but I don't recall any 8x6 systems. Probably the norm for the dipole arrays was the 4x4 arrays,

 

[trusty]

OMG...I remember those. I had to be at work at 0530, to sign the station on, and run PTL Club.
I'd turn on the TV at home while I tried to figure out which shoe was which. I remember Bill Tush trying to hurry and finish his newscast, while the crew pushed his set down a long, dark hallway toward the prop room.
Could anybody get away with that stuff tofay?

I remember the "newscasts", but more specifically the long dark (and narrow) hallways of the old Turner ch.17 studios. They were airing live wrestling matches, and I hurriedly rounded a corner of the narrow hallway and collided with Andre the Giant - my nose against his belly button, and I heard this "Excuse me" from somewhere up there. He was a nice guy.

 

[Radig]

In the extract, there is a mention of 8x6 array. I wonder how many of those did TCI ever build? We had some 4x6 arrays at Morocco, but I don't recall any 8x6 systems. Probably the norm for the dipole arrays was the 4x4 arrays,

I believe the largest TCI array was at the VOA Delano, CA site.

 

[kenglish]

I remember the "newscasts", but more specifically the long dark (and narrow) hallways of the old Turner ch.17 studios. They were airing live wrestling matches, and I hurriedly rounded a corner of the narrow hallway and collided with Andre the Giant - my nose against his belly button, and I heard this "Excuse me" from somewhere up there. He was a nice guy.

My cousin and her (now, ex-) husband both worked for Turner, managing the wrestlers.
Those guys are nice, just playing a role for the fans.
At WCWB, we ran studio rasslin' live each week. The local guys would sit in the lunchroom and help each other do their homework, for their night classes.

 

[RadioFan2J3]

I believe the largest TCI array was at the VOA Delano, CA site.

Was there anything bigger than a 4x6 at Delano? I don't have antenna detail for Delano right handy.


Maybe we should clarify "array" here. I consider each antenna as an array, not the entire antenna complex at a site as an array. As an example, Morocco had 21 TCI antenna arrays, some were 4x6, some were 4x4 arrays.

Sometimes, an array is also a term used for a set of the antennas with the same bearing, typically four antennas, two high band, two low band. At some sites, all four antennas could be radiating. At some sites only one of a low-band/high-band pair could be on the air.

 

[Radig]

Was there anything bigger than a 4x6 at Delano? I don't have antenna detail for Delano right handy.

I also don't have that exact information.

Maybe we should clarify "array" here. I consider each antenna as an array, not the entire antenna complex at a site as an array.

Yes, agreed, that is how I view them.

 

[Radig]

I have found one reference:

National Research Council. 1988. Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America. Washington, DC: The National Academies Press.
Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America | The National Academies Press

Specifically this page:
ANTENNA, PROPAGATION, AND MONITORING CONSIDERATIONS FOR HIGH-FREQUENCY BROADCASTING SYSTEMS | Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America | The National Academies Press

"Currently Technology for Communications, International (TCI) is developing two very large curtain arrays for the VOA that are steerable in azimuth and elevation. These arrays, which are high-band and low-band HR/12/6/0.5 antennas, are being installed at the VOA site in Delano, California to improve the VOA services."

The above shows that TCI was "developing" a 12x6 array, but not sure if it was installed.

 

[RadioFan2J3]

I have found one reference:

National Research Council. 1988. Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America. Washington, DC: The National Academies Press.
Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America | The National Academies Press

Specifically this page:
ANTENNA, PROPAGATION, AND MONITORING CONSIDERATIONS FOR HIGH-FREQUENCY BROADCASTING SYSTEMS | Antennas, Satellite Broadcasting, and Emergency Preparedness for the Voice of America | The National Academies Press

"Currently Technology for Communications, International (TCI) is developing two very large curtain arrays for the VOA that are steerable in azimuth and elevation. These arrays, which are high-band and low-band HR/12/6/0.5 antennas, are being installed at the VOA site in Delano, California to improve the VOA services."

The above shows that TCI was "developing" a 12x6 array, but not sure if it was installed.

I wonder if that was really a practical antenna system? I see the sentence in the report, not that I was doubting your quote, but I wonder if that is either a concept proposal or a misunderstanding of what was actually installed at Delano.


If you look at this video, at the 34:30 point:

a fairly good shot of the TCI antennas at Delano, and it looks like the low band antennas, three of them, are 4x6 each, and if they could be fed by the same transmitter, to all three antennas, yea, I guess it could be considered a 12x6. Without looking at the antenna switchbay matrix, I don't know if it was fed that way. My guess, and only a guess, no.

Interestingly, the narrator, at 34:40, calls the low band antennas a medium wave array, and it certainly is not a medium wave antenna system.

For folks wondering about my use of low band and high band, for the short wave antennas, typically the low band side operates about 6 MHz to 12 MHz or so and the high band, 12 MHz to 22 MHz. Don't lock me into those frequency ranges, for I am not quoting test data for any of these antenna.





The Google Earth photo of the site is dated earlier this year, 2021, so maybe the antennas are still in place. The Google Earth Streetview shots are not sharp enough to see the individual dipole elements to count them.

 

[Radig]

... a fairly good shot of the TCI antennas at Delano, and it looks like the low band antennas, three of them, are 4x6 each, and if they could be fed by the same transmitter, to all three antennas, yea, I guess it could be considered a 12x6.

Mechanically, a 12x6 is a very heavy, complex, and long load for a two tower installation. For those reasons they might need to make a 12x6 by combing three 4x6's.

The Delano site was also used for "12MHz ionospheric heating" experiments where a really, really high gain antenna was required.

 

[RadioFan2J3]

Mechanically, a 12x6 is a very heavy, complex, and long load for a two tower installation. For those reasons they might need to make a 12x6 by combing three 4x6's.

I agree.

If nothing else, the catenary sag for the distance between the two towers would probably required 500 foot towers.

As for making a 12x6 that way, unless the switch matrix was designed to put one transmitter on three antennas, highly unlikely one transmitter could feed three antennas (and of course, that would require a power splitter with impedance matching).

Of course, three transmitters could be on the same frequency, feeding the three antennas at the same time. That really makes little sense, to tie up three transmitters, same frequency, where it might be better to run the same program on three different frequencies.


I don't know the timeframe for the TCI installation at Delano. I was never out there, but in looking at a snapshot, the transmitter schedule effective March, 1987, no two transmitters at Delano were on the air at the same time and frequency.

I do recall that Greenville and going out on a limb for memory purposes, did indeed operate two transmitters on the same frequency, two separate antennas, same program (I think the BBC), but that may have been before 1985. Too far back and a 1985 transmission schedule doesn't show that operation at A or B sites.

The Delano site was also used for "12MHz ionospheric heating" experiments where a really, really high gain antenna was required.

I don't know anything about that.

 

[Radig]

As for making a 12x6 that way, unless the switch matrix was designed to put one transmitter on three antennas, highly unlikely one transmitter could feed three antennas (and of course, that would require a power splitter with impedance matching).

Of course, three transmitters could be on the same frequency, feeding the three antennas at the same time. That really makes little sense, to tie up three transmitters, same frequency, where it might be better to run the same program on three different frequencies.

This article, found on an Amateur Radio site, states that the antenna was capable of 30 dB gain. It also mentions co-phasing three transmitters into the array.

 

[RadioFan2J3]

This article, found on an Amateur Radio site, states that the antenna was capable of 30 dB gain. It also mentions co-phasing three transmitters into the array.

Thanks for that link and I see where this is going.

From the linked article:

In 1988 an experimental high-gain, multiple-band curtain array antenna was installed. The antenna operates from 6MHz to 26MHz and has six separate input ports.

Okay, seems I am using the term curtain array antenna differently than the author of the linked article. The author calls the entire structure one antenna, operating from 6MHz to 26MHz with six inputs.

That premise is incorrect, for none of the six inputs can go from 6MHz to 26MHz. I don't know the exact split point, but typically the low band arrays, would go from 6 MHz to somewhere between 12MHz and 15MHz and the high band arrays would go from somewhere between 12MHz and 15MHz to 26MHz.

For the typical naming convention within the IBB network, each of those inputs and the related antenna array, each are one antenna. In other words, six antennas, three for low band frequency use and three for high band frequency use. Yes, I think all six antennas could be air at the same time, but I don't know that for sure.





In its maximum gain configuration this antenna has a gain of 30dB - a power increase in the beam direction of 1,000 times. In this mode the antenna consists of 72 phased folded dipole elements arranged as 6 high 12 wide "Lazy H."

Well, if the antenna is 72 phased dipoles, then it is only three of the arrays. The other three arrays would consist of another 72 phased dipole. From a IBB transmitter and antenna scheduling viewpoint, again, this antenna system would be six antennas.


By co-phasing three transmitters into this antenna, the station has experimentally achieved an effective peak radiated power of 1.125 gigawatts.

I alluded to this earlier, but from a practical standpoint, I am not sure the agency ever used the antenna systems and transmitters at Delano in this manner. From a technical standpoint, yes, it certainly can be done. From a programming standpoint, the difference in signal strength at a given location between one transmitter on one antenna and three transmitters, three antennas, same bearing and frequency, just doesn't seem to offset the advantage of three transmitters, lower ERP, but on three different frequencies, into the same target area.

Yes, and I believe it was Greenville B Site which had the BBC World Service on two transmitters, same frequency, but if I recall correctly, the two antennas used had different antenna bearings. Three transmitters, same frequency, three different antenna systems, same bearing, even the transmission feed line lengths would have to be taken into account for transmitter phasing.

 

[SWL_Observer]

Just a few miscellaneous comments I wanted to add to the thread!

For the last few years I've hosted a program on some U.S based shortwave stations, I know there aren't many listeners these days but I do the show just because it's enjoyable to do. All caveats understood! Most of my work is done on YouTube and Online Podcast Platforms where a large audience is reached, but I still appreciate the more traditional broadcast mediums.

Aside from the already explained reasons for shortwave's decline, one other substantial issue that I have yet to see mentioned is the increase in RF interference. This is a problem that has been getting worse and worse in recent years, to the point where many listeners are even struggling to receive 100 kW stations with a portable radio when they're right in the target area. Sometimes there are ways to lessen the interference but many casual listeners are not going to hunt around to find out which appliance or device is causing interference and then unplug it, just to hear a radio show! The problem is especially bad for listeners in cities who live in high rise buildings, I've heard time and again from listeners who try to do everything right... they can't control what devices the guy next door uses though.

Low power shortwave stations (1 kW for example) may be more cost-friendly but the audience will only be the most dedicated of hobbyists and certainly won't be large enough for any sort of "revival". To put my money where my mouth is, I've used a number of the European low power stations before in an attempt to get a better signal to listeners in the U.K and Ireland. Due to the previously mentioned RF interference issues, not one single listener there was ever able to pick the broadcast up.

I've had the opportunity to broadcast on 300 kW and even 500 kW transmitters to Europe and North America, with that power the interference issues go away and even the cheapest of radios can receive the signal. The airtime costs are exorbitant though so the high-power broadcasts are usually just a one off occurrence here and there.

Despite that, shortwave is still a fun medium and I'm just thankful that I'm able to enjoy whatever's left.