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#1
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Dynamic Tuning VLF antenna tuner
Ran across this:
https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=12681 "Dynamic tuning works by physically changing the antenna tuning network so that it is consistently tuned to the frequency being "transmitted at that instant, allowing for peak efficiency." I'm guessing this means they are sending FSK and retuning for every bit. -- A host is a host from coast to & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
#2
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Dynamic Tuning VLF antenna tuner
On Fri, 23 Aug 2019 14:11:25 +0000 (UTC), David Lesher
wrote: Ran across this: https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=12681 "Dynamic tuning works by physically changing the antenna tuning network so that it is consistently tuned to the frequency being "transmitted at that instant, allowing for peak efficiency." I'm guessing this means they are sending FSK and retuning for every bit. Yep. When working at VLF or ELF (300 Hz to 3 KHz) frequencies, the antennas are very very very very long. If the transmitter or receiver is moving (submarine or airplane) the antenna tuning will change with changes in altitude, depth, water salinity, proximity to mountains, direction of travel, etc. The narrow bandwidths and slow data rates necessitate some manner of continuous transmission communications protocol. Here's an example of 1 character every 5 minutes: "OPERATING ON ELF FREQUENCIES" http://jproc.ca/radiostor/vlfelf.html Just think of ELF as your worst communications nightmare. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#3
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Dynamic Tuning VLF antenna tuner
Jeff Liebermann writes:
Yep. When working at VLF or ELF (300 Hz to 3 KHz) frequencies, the antennas are very very very very long. If the transmitter or receiver is moving (submarine or airplane) the antenna tuning will change with changes in altitude, depth, water salinity, proximity to mountains, direction of travel, etc. Having seen the towers at NAA, I am pretty sure they didn't move much. Nick from navy-radio.com confirmed they changed the antenna tuning between MARK & SPACE via a saturable reactor.... -- A host is a host from coast to & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
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