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Author Topic: Explosives "Resistant"/ Hardened Antennas  (Read 1981 times)

Offline NQC

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Explosives "Resistant"/ Hardened Antennas
« on: May 12, 2021, 1238 UTC »
Hey All,

LONG shot on this one- but :

I am wondering about   pics  I saw MANY,MANY  years ago of an antenna in Israel. (If we could , please leave politics and "current events" out of  any replies- strictly  a technical discussion -thanks).

I believe that the Israelis had a "hardened" antenna  (if I recall correctly)  for AM broadcast. It consisted of  heavy steel I  beams welded in series  stood off on large insulators , very close to the ground (6' up ?) .There may have been protective earthen dikes around it as well.

Probably a miserable  pattern for local ground wave but maybe via NVIS- MAYBE ??  . But if one really cranked up the juice then tuned  and loaded it properly, I suppose it COULD  ground  wave  "radiate" MAYBE enough to cover a limited area ( ie maybe just  around Tel Aviv ?). If nothing else, a fascinating technical concept (re being bomb "resistant"), even if it was a real dog re power in vs. power out.  Transmitter was likely in a bunker.

I can't find a THING about this online and I can only imagine it may be long gone by now.

It also seems that Israel in general  is now completely off of the AM broadcast band for ALL (ALL) outlets and that Kol Yisrael is also long gone off shortwave (  anyone ,any info  ?).

Israeli Army Radio / Galgalatz now seems to be on FM only as well. Not sure if the I beam antenna was theirs or not for civil defense purposes. Also WAY, WAY back in the day, I THINK they were also  on shortwave, maybe using  SSB (anyone, any info,  frequencies used /mode ?).

I have personally seen "a sort of" "hardened" antenna  on the Maginot Line Fortifications near Bitche, France. Large steel brackets on a vertical wall held a  large gauge   long wire antenna on heavy insulators. Certainly  not  nearly as beefy as an I beam antenna, but "tough enough" against small arms fire ( I guess) .

de K
« Last Edit: May 12, 2021, 1353 UTC by NQC »
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline ChrisSmolinski

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #1 on: May 12, 2021, 1250 UTC »
Israeli Army Radio used to be a regular here on 6973, I was sad to see them go. Great propagation beacon, and who could resist Hebrew covers of cheesy 70s pop music?  :)

There's a few logs of them on the SWBC forum here, up to the end of 2012: https://www.hfunderground.com/board/index.php/board,4.0.html

Looks like they moved to 6885 at one point to avoid Chinese jamming.
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Offline NQC

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #2 on: May 12, 2021, 1257 UTC »
  Hey Chris ,

Thanks for the  info.

K
« Last Edit: May 12, 2021, 1355 UTC by NQC »
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline redhat

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #3 on: May 12, 2021, 1832 UTC »
I believe that the Israelis had a "hardened" antenna  (if I recall correctly)  for AM broadcast. It consisted of  heavy steel I  beams welded in series  stood off on large insulators , very close to the ground (6' up ?) .There may have been protective earthen dikes around it as well.

I would wonder if you go to that length, whats to keep someone (with lots of money) from floating an entire building an using that as an antenna?  Maybe a watertower?

During WWII, many domestic AM's that were considered "essential" built fortifications around their tower bases to keep the enemy from shooting out the insulators and bringing the tower down.

+-RH
« Last Edit: May 13, 2021, 1831 UTC by redhat »
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Offline Ct Yankee

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #4 on: May 12, 2021, 1943 UTC »

It also seems that Israel in general  is now completely off of the AM broadcast band for ALL (ALL) outlets and that Kol Yisrael is also long gone off shortwave (  anyone ,any info  ?).


This website indicates KOL stopped broadcasting on shortwave in March 2008 with an exception of a Farsi service transmission to Iran.
http://mt-shortwave.blogspot.com/2008/03/last-days-of-kol-israel-on-shortwave.html

I went through my archives and found Prime Time Shortwave English Broadcast Schedules for B11 which included a WRMI relayed 15 minute broadcast of KOL in English at 0645 utc on 9955am.  WRMI probably streaming (or rebroadcasting podcast) KOL as they do now with RAE and others.
« Last Edit: May 12, 2021, 2010 UTC by Ct Yankee »
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Offline East Troy Don

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #5 on: May 13, 2021, 0010 UTC »
).

I have personally seen "a sort of" "hardened" antenna  on the Maginot Line Fortifications near Bitche, France. Large steel brackets on a vertical wall held a  large gauge   long wire antenna on heavy insulators. Certainly  not  nearly as beefy as an I beam antenna, but "tough enough" against small arms fire ( I guess) .

de K

Well, if it was a hardened antenna on the Maginot Line it was the only thing about that fortification that worked.    :D
Primary: Yaesu FRG-7700  Secondary: ICOM R75 Tertiary: Grundig  750. Tecsun PL-990X, Tecsun PL-880 . Malahit DSP SDR V3,  Alpha Delta  SWL Sloper antenna. : Also, 1940 Mantola am/sw tube. CountyComm GP-5/SSB hand held, Tecsun PL-380 ,et al.  QTH: EAST TROY WI  USA.  Sea Level: + 320 meters .  75 miles (but not far enough) NNW of Chicago


Offline NQC

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #7 on: May 19, 2021, 1213 UTC »
Hey All,

Thanks  for the responses.

NJQA: I had heard about vertically buried / explosive charge activated  "Pop Up " antennas  underneath pineapple field(s) in Hawaii used at "certain facilities "  . Details unknown.

K
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline Ray Lalleu

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #8 on: May 26, 2021, 2050 UTC »
Look for DDR antennas. They are antennas made with a ring of pipe very low above the ground. The simplest form is almost one quater wave long, one end direct to the ground, the other via a VC. Coax connected with a gamma-match near the grounded end.

Designed in the 1950s as SW antennas for war ships. But larger versions seem to have been built on land, to be ready for nuclear war ? (photos on Internet, but not all story is disclosed)

There were versions  for amateur use in HF. Now outdated, lots of drawbacks, including a very narrow bandwidth on low HF. But a 27 or 28 MHz version built on a flat rooftop, simpler without VC, could be interesting.

edit : the acronym is DDRR, but it's a misnomer.
A 7 Mhz version (above a lawn) was in the 1974 edition of the ARRL Antenna Book
 

« Last Edit: May 29, 2021, 1632 UTC by Ray Lalleu »
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Offline ThaDood

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #9 on: May 26, 2021, 2228 UTC »
What y'all describe sound like the 160MHz antennas mounted on the roof of a train, and other type of railcar. Kind of looked like a large handle than an antenna.
I was asked, yet another weird question, of how I would like to be buried, when I finally bite the big one. The answer was actually pretty easy. Face-down, like a certain historical figure in the late 1980's, (I will not mention who, but some of you will get it, and that's enough.) Why??? It would be a burial that will satisfy everyone: (1) My enemies will say that it will show me where to go. (2) On the same point, I can have my enemies kiss my butt. (3) It will temporarily give someone a place to park a bicycle. See??? A WIN / WIN for everyone.

Offline NQC

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #10 on: May 28, 2021, 0133 UTC »
Hey All,

 Ray : DDR design is  interesting , never seen that one.

Dood: I have seen train antennas like that.

Still learning. 

K
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline Molvania Poacher

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #11 on: May 28, 2021, 1208 UTC »
You might look into DOD hardened communications systems such as:

Survivable Low-Frequency Communication System (SLFCS)

Ground Wave Emergency Network (GWEN) (AN/URC-117)

USAF SAC's "Green Pine" Northern Area Ultra High Frequency Radio System (488L)

All reception from this location, radio and antenna.
QTH New Hampshire (70 miles north of Boston).
Tecsun S-8800 and Kenwood R-2000, with about 135 feet of wire thrown up in the trees.
eQSLs most appreciated to molvaniapoacher@gmail.com.

Offline NQC

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #12 on: May 31, 2021, 2301 UTC »
Hey Poacher,

 Very in interesting info especially re SLFCS (which I had not heard of  ) and GWEN which I had heard of and remember when IT was up.

A bit OT , but FWIW, I was assigned to the CSS in Germany, not DIRECTLY involved in SIGINT, but as a support of it.

But there was plenty of "side action". For reasons I do still do not understand , I was allowed to build  my own personal listening post IN the barracks. It included outdoor smaller U/VHF AM/FM, a large  (successful)  "trans Atlantic" VHF low band antenna and HF antennas (on R-71a , R-70 ,etc). It was amazing how much "open mode" traffic there was  - IF you knew where to look.

I was ALSO allowed to do the SAME thing  in the barracks  while at a previous posting in SC ( 100 ft long wire with Rhombic  antennas suspended underneath- for U/VHF/AM FM  "SIGINT" and TV Dx), mostly using the same rigs as above.I was actually able to locate  an intelligence "entity" close by  on my installation that was still using CW ! That's ONE way to "hide"   (I guess ???).

During exercises in SC I   used to set up a hidden UHF aero receiver at work  on our local tower UHF  frequency listening for "hostile" call signs on approach. I'd quietly don my gas mask a full minute before the "surprise" attack. Folks never figured out how I did it :).

All happened a million years ago, I imagine things are different now.

K
« Last Edit: May 31, 2021, 2311 UTC by NQC »
Station main receiver : Bed springs to  blue razor blade detector to 2000 ohm cans to steam  radiator. Grid FN 42

Offline Molvania Poacher

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Re: Explosives "Resistant"/ Hardened Antennas
« Reply #13 on: June 06, 2021, 0500 UTC »
Thanks for sharing NQC...Very interesting. So much for Cold War SIGINT COMSEC, based on your experience! Well played.

Appreciate you posting this thread.
All reception from this location, radio and antenna.
QTH New Hampshire (70 miles north of Boston).
Tecsun S-8800 and Kenwood R-2000, with about 135 feet of wire thrown up in the trees.
eQSLs most appreciated to molvaniapoacher@gmail.com.

 

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