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  #16  
Old 07-12-2006, 04:32 PM
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wa2ise wa2ise is offline
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Quote:
Originally Posted by 3Guncolor
There are still a few AM stations that have tube type transmitters as back up. Some of them work very well indeed they were only sidelined to save money on the electric bill and tube changes. The only problem is I don't know of any stations that have any tube production equipment left.
So if they could fire up the generator and the 40 + year old transmitter they would not have anything to feed it.
The rectifiers in most of those used to be mercury vapor and likely been replaced with solid state rectifiers.

Maybe the old transmitter has an input jack for a microphone. With a tube preamp?

And how many people will have vacuum tube portable AM radios with fresh batteries? I would assume that the poweline would be dead.
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  #17  
Old 07-12-2006, 05:19 PM
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Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
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Most Basic Receiver?

No way I could connect this post to color TV so I'm not even going to try

The most basic non-active non-germanium non-silicon diode receiver I can conjure up is from my youth: a 50-foot length of antenna wire coupled to a hand-wound inductor grounded to a water pipe and feeding a razor blade/graphite detector (pencil 'lead' touching a Gillette razor blade -- Bright Star brand worked best but Gillette's were easier to get) with a single 'high impedance' earphone.

Last edited by Pete Deksnis; 07-12-2006 at 05:22 PM.
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  #18  
Old 07-12-2006, 07:09 PM
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matt_s78mn matt_s78mn is offline
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Quote:
Originally Posted by wa2ise
The rectifiers in most of those used to be mercury vapor and likely been replaced with solid state rectifiers.

Maybe the old transmitter has an input jack for a microphone. With a tube preamp?

And how many people will have vacuum tube portable AM radios with fresh batteries? I would assume that the poweline would be dead.
Judging from a majority of the AM and FM transmitter sites I have visited, if the older transmitters are kept for backup, generally their exciters are replaced by modern solid state equivelants. One of the more interesting AM sites I've been to had three transmitters, all of them still operational. The oldest one was an RCA, it was from the 1930's, and had very cool art deco styled cabinet. It had a door with a small glass window, where you could look in and see the IPA tubes, and their blue glow modulated along with the audio. The second was a mid '60's Gates, and the third, a modern Harris DX-10 solid state transmitter. They brought the RCA transmitter online every couple months or so, just for the fun of it.

Also, I remember a college professor of mine talking about this very issue of what would happen to the solid state equipment, and he stated that equipment could be protected from the pulse if it was enclosed in a "faraday cage," which is a type of RF shielding.
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  #19  
Old 07-12-2006, 09:39 PM
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The way I understand it, an EMP is just an intense pulse of brad spectrum EM radiation that includes RF. Sensiitve semicondictor devices would be burnt out by the high voltages induced (like putting an IC in the microwave). I would imagine that the more ruggid power semiconductors and anything that's well shielded would be fine. Obviously, vacuum tubes should be able to handle a short overload like that.
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  #20  
Old 07-13-2006, 01:59 AM
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colorfixer colorfixer is offline
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Hollow state and EMP Protection

As a communications engineer, I began to look into what might happen to a modern emergency communication system in the event that *something* went down.

I came across a paper at this site which tweaked my interest in EMP:
http://www.fas.org/spp/military/program/asat/haleos.pdf

Here's a reference for EMP protection:
http://www.aussurvivalist.com/nuclear/empprotection.htm

It would be hard to verify if these methods of protection really work though.

I guess my Toyota BJ-73 would probably be dead after something like an EMP. Sigh...
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  #21  
Old 07-13-2006, 02:34 AM
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kx250rider kx250rider is offline
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Quote:
Originally Posted by colorfixer

I guess my Toyota BJ-73 would probably be dead after something like an EMP. Sigh...

I say you'll be FINE!!! The B engine is an all mechanical Diesel, so you would be unaffected

But are you in the USA? If so, how in Sam Hill did you get a BJ-73 in here?????? (jealous)...

Charles
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  #22  
Old 07-13-2006, 04:30 PM
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bgadow bgadow is offline
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I'm a little dumb on this stuff, but...my old '67 Chevy has points/condenser-but how about the survival of the voltage regulator?

There was a bad ice storm around here about 10 years ago-no electric anywhere around. And no gas stations open. But there was an old store with a hand crank kersosene pump and that kept my grandfather from freezing. I tried to give the old storekeeper $20 for a 5 gallon can of kero but he refused to take the bonus.
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  #23  
Old 07-14-2006, 01:20 AM
Keefla Keefla is offline
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Quote:
Originally Posted by bgadow
I'm a little dumb on this stuff, but...my old '67 Chevy has points/condenser-but how about the survival of the voltage regulator?

.
Pretty sure that's got a mechanical voltage regulator on it too so u should be fine there too.
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  #24  
Old 07-15-2006, 01:15 PM
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colorfixer colorfixer is offline
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I'm in BC, Canada. Anything 15 years or older can be imported with little or no problem. Right hand drive Land Cruisers from Japan abound here, but they really suck when going through a drive through or the border...

There are some form of electronic controls on the truck (turbo timer, timing belt alarm, etc), but I haven't had the time to tear into it.
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