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Radios and Range
Old 08-10-2014, 12:08 PM   #1
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Radios and Range

Continuing on this scenario for my book: All electronic devices and electrical power is out east of California. A fast plane from California will deliver a battery-powered short-wave transceiver to the government in Washington DC so that they can communicate with those on the West coast.

That should work, right? Could the president just turn on a transceiver and use it, or would a ham enthusiast be needed to set up a big antenna, etc.?

Is there some more sophisticated communication device that depends on neither intermediate stations nor satellites?

An additional plan is distribute thousands of standard portable radios to towns across the U.S. Then a special high-powered AM station in California would broadcast continuous updates and other information. My understanding is that that would work, since radio signals in that frequency range bounce off the ionosphere, and can reach around the curvature of the earth. Because the special station would have such a high power output, I'm figuring that all those radios would get a clear signal, even in the daytime. Yes?

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Old 08-10-2014, 01:30 PM   #2
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Somebody with more technical smarts will chime in here, but in a nutshell:
- The high-powered AM radio transmitter in California would always be received by those people within line-of-sight of the transmitting antenna (there's a general formula for this, but figure a few hundred miles). Beyond that, the signal primarily depends on a "bounce" off of the ionosphere to reach receivers, and that is a highly variable thing. In general, I don't think it would work well in the daytime. And if whatever EMP effect in your story disrupted comms/equipment in the first place is still going on, it might be disrupting the ionosphere, too.
- The shortwave/HF radio dropped off at the White House: It would require some setting up. For maximum effectiveness the antennas are big, and are "pointed" (physically or electronically) in the direction they need to send/receive. This would require some setup (wires on poles or masts, etc). The White House/national capital region already have some of these antenna farms dedicated to backup/redundant communications. And, again, the skip or bounce off the ionosphere is something that is not always reliable.

- If the EMP phenomenon has subsided, eventually somebody is going to launch some new comms satellites. It might not take as long as we might think.
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Old 08-10-2014, 01:56 PM   #3
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Given the typical president, (s)he would need assistants to explain how to push a microphone transmit button.
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Old 08-10-2014, 02:38 PM   #4
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Originally Posted by TromboneAl View Post
Continuing on this scenario for my book: All electronic devices and electrical power is out east of California. A fast plane from California will deliver a battery-powered short-wave transceiver to the government in Washington DC so that they can communicate with those on the West coast.

That should work, right? Could the president just turn on a transceiver and use it, or would a ham enthusiast be needed to set up a big antenna, etc.?
Cross-country communication is possible almost every day under most radio propagation conditions using a 100 Watt transceiver and a modest antenna, usually on a mid-range shortwave frequency like 20 meters/14 Megahertz. Conditions are often best for this path in the late afternoon/evening on the west coast, three hours later on the east coast, when the sunset line is somewhere between the coasts.

Conditions can vary with solar activity which affects the refraction and absorption of signals in the ionosphere. Alien weapons fire probably has an effect as well.

Someone will need to set up an antenna, but that can be done pretty quickly. There are portable antennas that I've used on this path before.

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Quote:
Is there some more sophisticated communication device that depends on neither intermediate stations nor satellites?
There are different communications MODES that can work well over this path, but without a relay sat or ground stations, you are fundamentally relying on getting a radio signal from here to there. That leaves you with ionospheric refraction("skip") or a couple of novel approaches below.

Some digital communications modes are quite good at getting a signal through where a voice message would be inaudible through natural static.

Digital Data Modes
Weak Signal Modes

There are also some pretty trippy paths that can be used. If the moon is over the horizon, Earth-Moon-Earth reflection of signals can be used to communicate between any two points where the moon is up, day or night. This uses VHF or UHF radio gear, and special directional antennas that are large but can be hand-steered.

Very short burst transmissions can be bounced off the ionization wakes of meteors to do some moderately long-range (but not quite cross-country) communications

Good overview of moonbounce operations, including whacky conditions and limits:
http://www.k4lrg.org/Projects/K4MSG_EME/

Good tech background stuff:
MoonBounce (EME) OperationWeak Signal -- (VHF-DX, Meteor Scatter, EME-Moonbounce)
WSJT Home Page


Quote:
An additional plan is distribute thousands of standard portable radios to towns across the U.S. Then a special high-powered AM station in California would broadcast continuous updates and other information. My understanding is that that would work, since radio signals in that frequency range bounce off the ionosphere, and can reach around the curvature of the earth. Because the special station would have such a high power output, I'm figuring that all those radios would get a clear signal, even in the daytime. Yes?
Maybe. The 'clear channel' broadcasters putting out 50,000 watts on the AM broadcast band with directional antennas to keep their power directed inland can be heard up to about 750 miles away after sunset with standard portable radios using their internal ferrite 'loop' antennas, under the right conditions.

Older stations that were part of the emergency broadcast network had huge transmitters, up to 500,000 watts, that could be used. These stations could be easily heard up to 1200 miles away at night via 'skywave' radio propagation.

Anyone remember "Wolfman Jack" on XERB, an insanely high power Mexican border station?

There's still a hobby activity built around picking up these 'mediumwave' distant stations, called MW DX. Radios used to pick up distant stations are often augmented with a long wire antenna to improve reception. That's nothing fancy, just a few hundred feet of wire tossed up in the trees (via slingshot or tied to a rock), with the end connected to the radio antenna jack if available, or wrapped around the ferrite antenna inside the radio.
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Old 08-10-2014, 03:47 PM   #5
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What about those super cheap itty bitty quartz crystal radios that didn't even use a battery? I'm remembering clipping onto a chain link fence and using an ear piece. Did those receivers have any range? Maybe a chain of listeners with Morse code reading ability and sending on with some crude device? Boy Scouts to the rescue?
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Old 08-10-2014, 04:18 PM   #6
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What about those super cheap itty bitty quartz crystal radios that didn't even use a battery? I'm remembering clipping onto a chain link fence and using an ear piece. Did those receivers have any range? Maybe a chain of listeners with Morse code reading ability and sending on with some crude device? Boy Scouts to the rescue?
That's a crystal radio set. They're powered by the received radio signal, which has to be strong enough to drive the earpiece directly after it gets through the 'detection' process the crystal (really a diode) does. They need a pretty strong signal to work, and typically just pick up local broadcast stations.

You might be able to pair it with a spark gap transmitter for a Morse code station with very limited range, perhaps a few miles. Working large very high voltage transformers will be scarce after that EMP Al used to set up the scenario, but perhaps some old auto ignition coils could be found. Range would be a few miles. (Marconi's 1901 trans-atlantic spark gap transmitter was some 300 kilowatts, powered by three 5 kilovolt generators in series driven by a steam engine. The capacitor for the spark gap was 4 stories high.)
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Old 08-10-2014, 07:37 PM   #7
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That's a crystal radio set. They're powered by the received radio signal, which has to be strong enough to drive the earpiece directly after it gets through the 'detection' process the crystal (really a diode) does. They need a pretty strong signal to work, and typically just pick up local broadcast stations.
Ah, that brought back memories. As a teenager, I made numerous crystal radios. Did you know you can build a crystal radio from a safety razor blade and a safety pin? That's a fun little project.
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Old 08-10-2014, 11:34 PM   #8
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From my observations years ago, AM broadcast band radio stations with omnidirectional antennas at 50 KW ERP (Effective Radiated Power) had a ground-wave reception area out to about ~250 miles. But out at the edges, expect fading and a lot of noise, not really listenable.
To get farther than that, then nighttime sky-wave propagation. But summertime was loaded with lightning static. Wintertime was pretty good. But arc-discharge lamps create a lot of noise for weak signal reception (like fluorescent lights, mercury vapor street lamps, etc.).

I agree on the 14 - 15 Mhz. region for best all-around coast-to-coast transmission. There was, probably still is, a international broadcast band at 15 MHz., the 19 meter broadcast band. That's where the action was during the day. As it got dark, can progress downward to lower frequencies, but static and arc-discharge interference goes up.

As a kid, I used to live with old short-wave radios and AM radios... instead of doing my homework. In winter, I would visit (via radio) exotic places like WWL 870, "broadcasting from the Roosevelt Hotel in New Orleans"' and WBAP in some far-off magic place called Fort-Worth where they must surely be having a good time while rounding up cattle and fighting off indian raids or something like that...

I also loved slowly tuning through the LORAN signals that were just above the AM broadcast band, around 1825-1975 KC. Yup, KC, Kilo Cycles! Long before Hertz was memorialized by renaming the unit of frequency. The LORAN signals had cool phasing effects, many years before phase-shift music boxes like Prophets, etc, came out.

Years earlier I had upgraded my hand-made crystal radio to use a 1N270 small-signal Germanium diode as the detector. Much much better than razor blades or Galena crystals.
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Old 08-11-2014, 12:22 AM   #9
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To give folks an idea of the AM radio range, tonight, using a Kenwood TS-590S radio and moderately large outdoor antenna, I'm getting clear signals in San Francisco from:

KFI, Los Angeles: 50 KW, about 347 miles (very clear)
KTNN, Window Rock, AZ, 50 KW, about 755 miles (All your Navajo nation news!)
KOA, Denver: 35 KW TPO, 950 miles (very clear)
WLW, Cincinnati, 50 KW, 2046 miles (barely legible; Cardinals radio network news)
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Old 08-11-2014, 10:17 AM   #10
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WLW, Cincinnati, 50 KW, 2046 miles (barely legible; Cardinals radio network news)
Interesting piece on WLW history here:
WLW's Big-Arse Transmitter
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Old 08-11-2014, 10:32 AM   #11
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To give folks an idea of the AM radio range, tonight, using a Kenwood TS-590S radio and moderately large outdoor antenna, I'm getting clear signals in San Francisco from:

KFI, Los Angeles: 50 KW, about 347 miles (very clear)
KTNN, Window Rock, AZ, 50 KW, about 755 miles (All your Navajo nation news!)
KOA, Denver: 35 KW TPO, 950 miles (very clear)
WLW, Cincinnati, 50 KW, 2046 miles (barely legible; Cardinals radio network news)
In your experience, how variable is the reception from day to day? I recall that the availability of distant stations varies according to lots of conditions, and that different ones could be available on different nights.

About WLW: From 1942 to 1944, shortwave broadcasts from that station were the predecessors to Voice of America. Hitler called them "the Cincinnati liars." Later, VOA set up a huge shortwave transmitting station not far from Cincinnati, the antennas are gone but the giant pads for the masts and the massive concrete cable anchors give a hint at their size. They are in the process of building a proper museum to highlight the history and contributions of VOA at the Bethany, OH site, more here.
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Old 08-11-2014, 12:11 PM   #12
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In your experience, how variable is the reception from day to day? I recall that the availability of distant stations varies according to lots of conditions, and that different ones could be available on different nights.
It can vary a fair amount from night to night. Some of this is driven by solar activity and geomagnetic storms, which affect the 'skywave' radio path.

Some of the reception issues also come from interference between stations in different parts of the country on the same frequency. Even some of the 'clear channel' frequencies have two stations assigned, often one on the west coast or Alaska, and the other in the eastern half of the country. Add in some of the part-time 250 watt broadcasters that may be on the same frequency, and some distant stations are not audible until others on the same frequency shut down.

The really dedicated DX chasers use things like Beverage antennas to enable directional reception of only the desired signal. For AM broadcast radio, that takes some serious lengths of wire. That won't fit in my back yard...

In Al's scenario, he won't have interference from other stations, and if his protagonists get one of the old 250-500 kilowatt transmitters running, they'll be audible nationwide most nights.
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Old 08-11-2014, 03:23 PM   #13
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Originally Posted by M Paquette View Post
To give folks an idea of the AM radio range, tonight, using a Kenwood TS-590S radio and moderately large outdoor antenna, I'm getting clear signals in San Francisco from:

KFI, Los Angeles: 50 KW, about 347 miles (very clear)
KTNN, Window Rock, AZ, 50 KW, about 755 miles (All your Navajo nation news!)
KOA, Denver: 35 KW TPO, 950 miles (very clear)
WLW, Cincinnati, 50 KW, 2046 miles (barely legible; Cardinals radio network news)
When I was a teenager in NYC, we used to wait until near midnight and listen to WOWO (Ft. Wayne, IN). It came booming in on any car radio, about 650 miles.
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Old 08-11-2014, 07:57 PM   #14
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You could use some surplus AN/TRC-75 radios. The AN/TRC-75 was the work horse for heavy ground communications for the Army and Marines during the Vietnam era. The military may have some stashed away.

Under proper conditions the AN/TRC-75 could easily transmit/receive from West Coast to East Coast.

AN/TRC-75 - RadioNerds
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Old 08-11-2014, 09:30 PM   #15
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You could use some surplus AN/TRC-75 radios. The AN/TRC-75 was the work horse for heavy ground communications for the Army and Marines during the Vietnam era. The military may have some stashed away.

Under proper conditions the AN/TRC-75 could easily transmit/receive from West Coast to East Coast.

AN/TRC-75 - RadioNerds
Al's scenario had an EMP effect take out communications except for on the west coast. I'd suggested that maybe an AN/ARC-5 or similar all-tube command set might survive that. (I bet some ham would have one in the cellar on the East coast.)

I'm not sure the AN/TRC-75's inverter and semiconductors would make it through an EMP unless the radio was buttoned up tight. (The case acts as a Faraday cage.)

It's a nice rig if running OK. Over 300 pounds, though. Oof. I'll stick with my little TS-590S. :-)
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Old 08-12-2014, 06:09 PM   #16
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When this book is finished I want to read it. Sounds very interesting.
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Old 08-12-2014, 07:38 PM   #17
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Assuming the scenario is "today"... how would satellites become unusable?

Broad range of wireless means of communication here...
Wireless - Wikipedia, the free encyclopedia
Free Space wireless is an interesting theoretical concept... for the future.

Also in the future future, am thinking that the GPS system could be used for emergency data packet transmission, but that is beyond me. Interesting aside that the following systems are in process... GLONASS, Galileo, Beidou, COMPASS, RNSS and QZSS, so the limitations could extend beyond the US control.

Interesting proposition. "On the Beach" comes to mind.
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Old 08-15-2014, 01:23 PM   #18
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When I was a teenager in NYC, we used to wait until near midnight and listen to WOWO (Ft. Wayne, IN). It came booming in on any car radio, about 650 miles.
Me, Too! In Upstate NY in Cold Spring. It was just across the Hudson from West Point Military Academy.

Then, at age 14, my world was opened up and my musical taste was formed by saving lawn mowing money and getting a mono FM clock radio from Service Merchandise and tuning it to WNEW-FM, a progressive rock station, which I had heard about from reading the newspaper Rolling Stone. It was really something. I still love that kind of Rock and Roll to this day.

NY Radio Archive - WNEW-FM 102.7

Geez, now I'm all nostalgic!
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Old 08-15-2014, 02:53 PM   #19
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Rosko on WNEW from LI.

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Old 08-15-2014, 03:03 PM   #20
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What about satellite communications. I assume they still have generators east of CA. Also if an electrical/electronics device was off whenever this disruption occurred, it should be safe - no? If that is so, there should be inventory lying around for both generation and communication.

Sorry if the above is explained in another thread.
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